Search

Background: Dural arteriovenous fistulas (dAVFs) in the foramen magnum region (FMR) are rare entity of dAVFs. There is no established treatment for FMR-dAVFs owing to their rarity and anatomical complexity. Herein, we report cases of high-flow dAVFs located at the posteromedial part of the FMR that were successfully treated by surgical interruption., Methods: We demonstrated the surgical procedures for the interruption of high-flow FMR-dAVF with representative images and videos. In both cases, endovascular transarterial embolization was performed prior to surgical interruption., Conclusion: As this type of FMR-dAVF has high-risk clinical features, curative surgical treatment is highly desirable., Competing Interests: Declarations. Ethical approval: All procedures employed in the present study were in accordance with the ethical standards of the Gifu University Hospital and with the 1964 Helsinki Declaration and its later amendments. Consent to participate: The patients consented to participate. Consent to publication: The patients consented to the publication of their cases in the present study. Conflict of interest: The authors declare no competing interests., (© 2024. The Author(s).)

Background: We describe techniques for safe resection of a Type 3 foramen magnum meningioma with dorsal displacement of the accessory nerve rootlets and vertebral artery which limits ventral access to the tumor., Method: Partial sectioning of the accessory nerve rootlets may help create larger working space. Topical lidocaine placement on the rootlets of the spinal accessory nerve may mitigate trapezius muscle contraction and facilitates further progress throughout tumor resection., Conclusion: Creating safe working corridors between the lower cranial nerves through mobilization or partial sectioning of rootlets in the case of CN XI facilitates tumor resection through a far lateral approach., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background: Chiari I malformation (CM-I) is defined as the extension of brain tissue into the spinal cord. This study aimed to refine the methodology for the acquisition of 3-dimensional measurements of the posterior fossa and introduce occipital keel size as a new marker and its impact in patients with CM., Methods: In this retrospective study, all patients who underwent Chiari decompression surgery at Montefiore Medical Center from April 2012 to April 2022 were included. Perioperative clinical information was obtained in addition to maximal keel thickness (KT), foramen magnum area, and preoperative and postoperative posterior fossa volumes for each patient and age-matched controls. Volumetric measurements were obtained using artificial intelligence-based semiautomated segmentation., Results: A total of 107 patients with CM including 37 males, and 70 females were studied with a mean age of 26.56 ± 17.31 compared with 103 controls without CM. The comparison between the CM and the general population groups demonstrated a significantly increased keel size in Chiari patients. Keel size had a significant relationship with dysphagia, paresthesia, and intraoperative blood loss, while posterior volume change had a significant relationship with sex and early symptomatic improvement. The Foramen magnum area was related to tonsillar descent and more prominent in patients with spina bifida., Conclusions: The Keel of Goodrich is a new anatomical factor that should be taken into consideration when evaluating preoperative symptoms, and intraoperative complications in patients with CM-I. Volumetric analyses demonstrated that posterior fossa volume change had a significant impact on early symptom improvement in patients with Chiari, as did the choice of operative approach. The routine use of semiautomated segmentation of the posterior fossa may help stratify Chiari patients in the future and should be implemented in routine clinical care., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The occipitocervical junction is formed by the foramen magnum (FM) and the adjacent anatomical structures of the C1 and C2 vertebrae. The FM is formed anteriorly by the basilar part of occipital bone. Anterolaterally, it borders the occipital condyles and hypoglossal canal as well as the jugular foramen. Posteriorly, the FM is formed by the squamous part of the occipital bone with the internal occipital crest. In the midline, named landmarks at the anterior margin are the basion and, at the posterior margin, the opisthion. Vital anatomic structures are located in the FM or pass through. Among these are the medulla oblongata, meninges, anterior and posterior spinal arteries, vertebral arteries, and spinal roots of the accessory nerve. The FM is firmly anchored to the cervical canal via strong ligamentous support.Pathologies in this area can be of congenital, acquired, traumatic, neoplastic, or infectious origin, with the respective surgical indications and approaches depending on the nature and location of the pathology. If the pathology is occipitoatlantal, the occiput is usually involved in surgery. On the other hand, if the pathology is only at the level of C1-C2, surgery may be limited to these two vertebrae.In this section, we present the surgical management of exemplary congenital cases, and we discuss the complications and what needs to be done to deal with them., (© 2025. The Author(s).)

We report a fairly rare case of postoperative acute subdural hygromas without concurrent hydrocephalus complicating foramen magnum decompression (FMD) for Chiari malformation type I (CM-I). Full resolution of subdural hygromas was achieved through therapeutic lumbar puncture releasing bloody cerebrospinal fluid which has been scarcely advocated in managing post-FMD subdural hygromas. This outcome suggests that bloody cerebrospinal fluid may be related to the formation of subdural hygromas after FMD for CM-I and therapeutic lumbar puncture may provide an effective treatment modality in such conditions.

Objective: Achondroplasia is associated with foramen magnum stenosis (FMS), which can lead to sudden unexpected death in infants. There is no wide consensus regarding the best management of FMS. This study aimed to analyze the prevalence of FMS in a cohort of children with achondroplasia and to evaluate screening and neurosurgical interventions of FMS regarding its effects and complications., Methods: The authors conducted a retrospective cohort study including all children with achondroplasia assessed or treated at Karolinska University Hospital between September 2005 and June 2020. The severity of FMS was graded using the MRI Achondroplasia Foramen Magnum Score (AFMS). The AFMS was correlated with neurological examinations and polysomnography (PSG) results., Results: Severe FMS (AFMS 3-4) was present in 35% of the 51 children included in the study. As many as 65% of the children in the cohort underwent foramen magnum decompression (FMD). Neurological examination had a high specificity (94%) but a low sensitivity (28%) for severe FMS. Signs of central apnea on PSG did not correlate with severity of FMS (p = 0.735). Surgery improved FMS (p < 0.001) with a nonsignificant trend of decreased central apnea (p = 0.070), but carried a 9% risk of severe surgery- and anesthesia-related complications., Conclusions: This study confirmed previous reports that severe FMS is common in children with achondroplasia, that neurological symptoms may be absent even in severe FMS, and that FMD improves FMS and may improve central apnea. The finding that neurological examination had a low sensitivity for severe FMS supports the recommendation that all children with achondroplasia should undergo early MRI.

Introduction: Foramen magnum stenosis in achondroplasia carries a risk of sudden death. A proportion of these patients benefit from foramen magnum decompression (FMD). The Achondroplasia Foramen Magnum Score (AFMS) was developed to stratify those most at risk. We hypothesise that this score may be reflected in neurophysiological findings., Methods: Patients with achondroplasia who had undergone FMD (n=20) were retrospectively grouped into AFMS 2, 3 and 4. Amplitude from tibialis anterior (TA) and the percentage change in somatosensory evoked potential (SSEP) latency after FMD were reported., Results: Baseline motor evoked potential amplitudes for patients with AFMS=4 were significantly lower left (p=0.0017 and p=0.02 for right and left TA, respectively) compared with AFMS grades 2 and 3. Median reduction (% change) in SSEP latency (ms) after surgery was not significantly different in any of the patients., Conclusions: This short report cross-references AFMS to intraoperative neuromonitoring. Baseline amplitudes were noticeably lower in the most severe AFMS group. This observation supports the notion that AFMS can help risk stratify patients and aid in surgical selection., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Chiari Malformation Type I (CM1) is characterized by the downward displacement of the cerebellar tonsils below the foramen magnum. The standard surgical treatment for CM1 is foramen magnum decompression and atlas laminectomy (FMD-AL). However, there is a growing interest in exploring minimally invasive techniques, such as neuroendoscopically assisted FMD-AL, to optimize surgical outcomes. The aim is to present the results of the less invasive neuroendoscopic-assisted system application as an alternative to decompression surgery in patients with CM-1 with/without syringomyelia., Patients and Methods: A retrospective analysis was conducted on 76 patients with CMI who underwent either neuroendoscopic-assisted FMD-AL (n = 23) or open surgery (n = 53). Preoperative and postoperative assessments were performed, including pain levels, functional assessment, outcome and serum creatinine kinase (CK) levels. Surgical parameters and radiological imaging were also evaluated and compared., Results: Both surgical groups showed improvements in pain levels and increase in postoperative CK levels. There were no statistically significant differences between the groups in terms of postoperative JOA scores, VAS scores, CCOS, or syrinx resolution. However, the neuroendoscopic group had significantly lower CK levels, shorter hospital stays, less blood loss, and shorter operation times compared to the open surgery group, indicating reduced muscle damage and potential benefits of the neuroendoscopic assisted approach., Conclusion: Both neuroendoscopy and open surgery groups can effectively alleviate symptoms and improve outcomes in patients with CM1. The neuroendoscopic assisted technique offers the advantage of reduced muscle damage and shorter hospital stays. The choice of surgical technique should be based on individual patient characteristics and preferences., Level of Evidence: 3 (Retrospective case-control study) according to using the Oxford Centre for Evidence-Based Medicine (CEBM) Table., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Foramen magnum decompression (FMD) is an established technique for patients with Chiari-1 malformation. However, the extent of decompressive surgery is controversial, in particular whether dural opening is undertaken., Objective: In this study, we report outcomes with our technique utilising intraoperative ultrasound (iOU) findings. Decision to proceed for further decompression was based on CSF flow around foramen magnum and visualisation of tip of tonsils., Methods: Review of adults with CM-1 undergoing FMD 2013-2018. Patients underwent a suboccipital craniectomy ± partial C1 superior laminectomy ± duraplasty in a stepwise manner. Favourable iOU findings of CSF flow around the foramen magnum and pulsation of the tonsillar tips were sought at each step. Post-operative outcomes were assessed using the Chicago Chiari Outcome Score (CCOS)., Results: Fifty-seven patients were included. The mean age was 47 years (range 18-77 years). There was a strong female preponderance (48 females to nine males). The mean follow-up was 3.2 years (range 1-5 years). Surgery included: suboccipital craniectomy (52/57, 91%), plus partial C1 superior laminectomy (2/57, 4%), and plus duraplasty (3/57, 6%). Redo surgery was undertaken in 7/57 patients (12%). At final follow-up, 56/57 (98%) patients achieved a good (CCOS 13-16) or satisfactory (CCOS 9-12) outcome based on COSS., Conclusions: A patient centred approach to surgery utilising findings from iOU can achieve favourable outcomes. Dural opening is not routinely required.

Objective: The objective was to identify clinical and radiological factors associated with sleep-disordered breathing (SDB) in children with Chiari type I malformation (CIM) and to evaluate the efficacy of foramen magnum decompression (FMD) in resolving SDB., Methods: A retrospective chart review was conducted for all children evaluated for CIM at a single institution from 2002 to 2022, identifying all children who had undergone nocturnal polysomnography (PSG). Apnea-hypopnea index (AHI) score, sleep apnea type (obstructive, central, mixed, and unspecified), clinical manifestations, and radiological measurements were recorded. SDB was considered present when officially diagnosed in the PSG report. Logistic regression was performed to identify factors correlating with the presence of SDB. For children with SDB who underwent FMD, the Wilcoxon signed-rank test was used to assess AHI improvement., Results: Of the 997 children referred for CIM, 310 completed PSG. SDB was diagnosed in 147 patients (overall prevalence 14.7%, 95% CI 12.7%-17.1%; prevalence among children with PSG 47.4%, 95% CI 41.9%-53%). Specific SDB diagnosis consisted of 33% of patients with central sleep apnea, 27% with obstructive sleep apnea, 9% mixed, and 31% unspecified. Lower cranial nerve (CN) dysfunction (OR 3.891, p = 0.009), tonsillar position (OR 1.049, p = 0.017), Chiari type 1.5 malformation (OR 1.862, p = 0.044), and BMI (OR 1.039, p = 0.036) were significantly associated with presence of SDB. Of the 310 patients who underwent PSG, 47 were originally categorized as asymptomatic: 27 (57%) of these asymptomatic patients were diagnosed with SDB on PSG. Of children diagnosed with SDB, 34 completed PSG before and after FMD. Median AHI score decreased from 6.5 preoperatively to 1.8 postoperatively, with a median (IQR) difference of -2.3 (-11.9 to 0.1) (p = 0.001). Twelve (35%) had resolution of SDB., Conclusions: The authors' findings suggest that the prevalence of SDB in children with CIM is high (15%-47%). Furthermore, lower CN dysfunction, Chiari type 1.5, lower tonsillar position, and higher BMI may be risk factors. Notably, SDB can be present even in the absence of clinical symptoms. This study also demonstrates that surgical intervention has the potential to reduce the severity of SDB. These results could help clinicians identify CIM patients at risk for SDB and those who may benefit from surgical decompression.

The jugular foramen, also known as the foramen magnum, is a highly intricate region of the skull base through which numerous critical blood vessels and nerves traverse. Meningiomas, the most common tumors in neurosurgical pathology, can arise at any location where the meninges are present, posing significant challenges. Meningiomas involving the jugular foramen and sublingual neural tube are particularly notable for their potential to extend from intracranial to extracranial sites, necessitating familiarity with extracranial anatomy, which is not typically encountered in clinical practice. A comprehensive understanding of anatomical characteristics, along with an ample field of view and working space, is crucial for handling the cerebellum, brainstem, and nerves meticulously. The use of surgical support tools such as neuromonitoring and navigation is essential for enhancing the safety of the procedure. Furthermore, preparedness for treatment options, rehabilitation, and adjunctive therapies is vital in the event of neurological symptoms such as those affecting the glossopharyngeal, vagal, or hypoglossal nerves.

Objective: Basilar invagination is one of the most frequently observed abnormalities at the craniovertebral junction, in which the odontoid process of C2 prolapses into the foramen magnum., Methods: The current study included 27 patients who underwent surgery for basilar invagination between October 2013 and January 2023. The study group was divided into 2 groups according to basilar invagination types; type I (the presence of type A atlantoaxial instability and instability is the main pathology) and type II (the presence of type B and C atlantoaxial instability and skull base dysgenesis is the main pathology). Craniometric parameters included in the study were atlantodental interval, posterior atlantodental interval, Chamberlain's line violation, clivus-canal angle, Welcher's basal angle, and Boogaard angle., Results: The mean age of the patients was 24.30 ± 14.36 years (5-57 years). Fourteen patients (51.9%) were female, and 13 patients (48.1%) were male. Ten patients (37%) had type I basilar invagination, and 17 patients (63%) had type II basilar invagination. Preoperative and postoperative atlantodental interval and Boogaard angle were significantly higher in type I basilar invagination, as preoperative and postoperative posterior atlantodental interval and clivus-canal angle were significantly higher in type II basilar invagination. There was a positive strong correlation between Chamberlain's line violation and Boogaard angle. Postoperative Chamberlain's line violation was significantly higher in occipitocervical fixation (P = 0.035). C1 lateral mass screw fixation was found more successful in Chamberlain's line violation correction than occipital plates. Occipitocervical fixation was found to be associated with higher postoperative Nurick scores (P = 0.015) and complication rates (P = 0.020). Cages applied to the C1-C2 joint space were found to be associated with higher fusion rates (P = 0.023) and lower complication rates (P = 0.024)., Conclusions: In the present study, it was found that C1-C2 fixation was more successful in correcting craniometric parameters and had lower complication rates than occipitocervical fixation. In appropriate patients, it was determined that cage application increased the success rates of the operations., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Chiari 1 malformation and hind brain hernia can be associated with skull base and craniocervical anomalies. One of the more recently associated anomalies is a retroverted or retroflexed odontoid process or dens. We conducted a retrospective study of our operated symptomatic and conservatively managed asymptomatic Chiari cohort to assess the impact of dens retroflexion on rate of revision or cerebrospinal fluid diversion following primary foramen magnum decompression (FMD)., Methods: We undertook a retrospective study of all foramen magnum decompression (FMD) cases for Chiari type 1 malformation performed over a 15-year period in a single tertiary paediatric neurosurgical unit. For comparison, non-operated asymptomatic Chiari cases were considered as reference cohort. Information gathered included: demographics, age, sex, length of cerebellar tonsils below McRae's line, pB-C2 distance (a line drawn perpendicular to one drawn between the basion and the posterior aspect of the C2 body), angle of retroflexion (angle formed between a line drawn through the odontoid synchondrosis and its intersection with a line drawn from the tip of the odontoid process) and angle of retroversion (angle formed between the line drawn from the base of C2 and its intersection with a line drawn from the tip of the odontoid process). Grade of retroflexion was measured using pre-operative mid-sagittal MR images and classified as grade 0 (> 90°), grade 1 (85°-89°); grade 2 (80°-84°) and grade 3 (< 80°). The rates for redo surgery or need for cerebrospinal fluid (CSF) diversion were obtained from clinical records and compared in the operated and non-operated groups., Results: One hundred twenty-six Chiari 1 patients were included in this study with adequate imaging. Sixty-five patients were in the non-operated asymptomatic cohort with 61 patients in the operated symptomatic cohort. Mean age of non-operated cohort was 10.2 years with M:F ratio (30:35). Mean cerebellar tonsillar length below McRae's line was 10.3 mm. 7.7% of this cohort had associated syrinx. Mean angles of retroversion and retroflexion were 76 and 78°, respectively. Retroflexion grades included (9.2% grade 1, 35% grade 2 and 52.3% grade 3). pB-C2 distance was 6.8 mm. Mean age of operated cohort was 11.3 years, with M:F ratio (21:40). Mean cerebellar tonsillar length below McRae's line was 15 mm. 45.9% of this cohort had associated syrinx. Mean angles of retroversion and retroflexion were 73 and 74.5°, respectively. Retroflexion grades included (4.9% grade 1, 16.5% grade 2 and 78.6% grade 3). pB-C2 distance was 6.9 mm. No association was identified between retroflexion grade and rate of revision or CSF diversion following primary foramen magnum decompression., Conclusion: The operated Chiari 1 cohort had more retroflexed dens, longer tonsils and associated syrinx compared to the non-operated asymptomatic cohort., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Proximity to critical neurovascular structures can create significant obstacles during surgical resection of foramen magnum meningiomas (FMMs) to the detriment of treatment outcomes. We propose a new classification that defines the tumor's relationship to neurovascular structures and assess correlation with postoperative outcomes., Methods: In this retrospective review, 41 consecutive patients underwent primary resection of FMMs through a far lateral approach. Groups defined based on tumor-neurovascular bundle configuration included Type 1, bundle ventral to tumor; Type 2a-c, bundle superior, inferior, or splayed, respectively; Type 3, bundle dorsal; and Type 4, nerves and/or vertebral artery encased by tumor., Results: The 41 patients (range 29-81 years old) had maximal tumor diameter averaging 30.1 mm (range 12.7-56 mm). Preoperatively, 17 (41%) patients had cranial nerve (CN) dysfunction, 12 (29%) had motor weakness and/or myelopathy, and 9 (22%) had sensory deficits. Tumor type was relevant to surgical outcomes: specifically, Type 4 demonstrated lower rates of gross total resection (65%) and worse immediate postoperative CN outcomes. Long-term findings showed Types 2, 3, and 4 demonstrated higher rates of permanent cranial neuropathy. Although patients with Type 4 tumors had overall higher ICU and hospital length of stay, there was no difference in tumor configuration and rates of postoperative complications or 30-day readmission., Conclusion: The four main types of FMMs in this proposed classification reflected a gradual increase in surgical difficulty and worse outcomes. Further studies are warranted in larger cohorts to confirm its reliability in predicting postoperative outcomes and possibly directing management decisions., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Craniovertebral junction malformation is a congenital malformation located in the foramen magnum and upper cervical spine, including bone and nerve malformation, resulting in motor and sensory disorders, cerebellar and lower cranial nerves, etc. The evaluation methods of clinical symptoms and efficacy of craniovertebral junction malformation are important for the surgical indications and effects, mainly including the evaluation of clinical symptoms and the quality of life. At present, the commonly used methods in clinical work and literature are the Japanese orthopaedic association scores, visual analogue scales, 36-item short-form health survey, etc. Most of these clinical evaluations are not aimed at craniovertebral junction diseases but focus on the description of a certain type of clinical symptoms. Chicago Chiari outcome scale and syringomyelia outcome scale of Xuanwu hospital are dedicated to Craniovertebral junction malformation, but more clinical studies are needed to prove their effectiveness. Based on the literature reports, this article reviewed the previous clinical evaluation methods of craniovertebral junction malformation and discusses their applications and limitations.

Achondroplasia is an autosomal dominant disorder with defect in the ossification of the cartilage of long bones. Many bony abnormalities constitute its clinical features, with craniovertebral junction (CVJ) anomalies being one of most common issues which need to be addressed at the earliest. CVJ anomalies in individuals may cause neurovascular compression, which may warrant an early surgery to prevent catastrophic complications. Posterior circulation strokes secondary to CVJ anomalies are well known. We hereby present an unusual case of posterior circulation stroke in an achondroplastic dwarf who presented to our tertiary care centre. Prospective case study. The present case adds to the existing literature about one of the preventable causes of fatal posterior circulation strokes in the young. A high index of suspicion for neurovascular compression at the foramen magnum and early initiation of treatment in achondroplastic young individuals may have gratifying results., (Copyright © 2024 Copyright: © 2024 Neurology India, Neurological Society of India.)

Achondroplasia is the most common form of dwarfism, caused by a mutation in fibroblast growth factor receptor 3 gene, leading to multiple pathological conditions. Herein, we present a case of an infant with achondroplasia associated with hydrocephalus and severe foramen magnum stenosis. Computed tomography (CT) venography showed prominent suboccipital emissary veins comprising major venous drainage routes and hypoplastic transverse sinuses, which increased the risk of foramen magnum decompression. The infant was initially treated with ventriculo-peritoneal (VP) shunt. After 8 months, CT venography showed regression of suboccipital emissary veins and more prominent transverse sinuses. Subsequently, foramen magnum decompression was safely performed without sacrificing major venous drainage routes., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Knowledge of the normal anatomy of the cerebellar tonsils is a prerequisite in various surgeries of the posterior cranial fossa Clinical conditions, as the Chiari I malformations (CIM) alter the normal position of the cerebellar tonsils., Objective: Therefore, we aim to better elucidate the surgical anatomy of and around the cerebellar tonsils in regard to the CIM., Methods: Fifty formalin-fixed adult cadavers injected with colored latex through vertebral arteries underwent craniotomy and durotomy to expose the cerebellar tonsils and related structures. The tonsils and their surrounding anatomy were then studied., Results: Forty cerebellar tonsils were at or above the foramen magnum. Five specimens presented with CIM with the tonsils below (3-5 mm) the FM with a mean tonsillar decent of 7.9 ± 2.3 mm. Of the cadavers without CIM, in forty-two cases, the thickness of the dura mater was within ±3SD ranges. In three cases, the dura mater was thinner at the CVJ and one case; the dura adhered tightly to the inner aspect of the occipital squama. In five CIM cadavers, the dura mater was markedly thicker at the CVJ. The PICA caudal loop was 5.9 ± 1.6 mm long. In CIM cases, the PICA loop was longer, nearer the dura, 1 mm below the superior border of the C1 posterior arch. The distances from the PICA loop were markedly reduced by 3 mm from the spinal accessory nerve and 2 mm from the first spinal nerve. The DN was significantly closer to the tonsillar peduncle in CIM cases., Conclusion: These data are important for better understanding the intrinsic and extrinsic anatomy of the cerebellar tonsils in patients with and without CIM. Importantly, tonsillectomy/tonsillar coagulation must consider the close relationship of the dentate nucleus to the base of the cerebellar tonsil to avoid iatrogenic injury., (© 2023 American Association of Clinical Anatomists and British Association of Clinical Anatomists.)

Background: Chiari I malformation is defined by tonsillar herniation through the foramen magnum. There is no consensus on the treatment of Chiari malformation. A simple follow-up is recommended for asymptomatic cases. The classic approach is the midline sub-occipital craniotomy., Methods: For four years, we operated on six patients with Chiari malformation I using our endoscopic minimally invasive sub-occipital approach. We compared the results with six other patients operated by the classical sub-occipital approach., Results: Patients operated by endoscopic approach had shorter hospital stays, and wounds healed faster and smoother. Mid-term results were similar in the two groups., Conclusion: This paper proposes a new endoscopic Minimally invasive paramedian sub-occipital approach for Chiari malformation I. Although the number of cases is limited, the results look promising. We need to gather more cases to have significant numbers to perform a global comparison between the two approaches and assess the advantages and disadvantages of each technique., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Objective: Foramen magnum(FM) stenosis can be responsible for acute and chronic damage to the cervicomedullary junction in children with achondroplasia. The bony anatomy and patterns of suture fusion of the FM in this context are incompletely understood, yet becoming increasingly important in the light of novel medical therapies for achondroplasia. The objective of this study was to describe and quantify bony anatomy and fusion patterns of FM stenosis in patients with achondroplasia using CT scans, comparing them to age-matched controls and other FGFR3 craniosynostosis patients., Methods: Patients with achondroplasia and severe FM stenosis, classified as achondroplasia foramen magnum score(AFMS) grades 3 and 4, were identified from a departmental operative database. All had pre-operative CT scans of the craniocervical junction. Measurements obtained comprised sagittal diameter (SD), transverse diameter (TD), foramen magnum area, and opisthion thickness. Anterior and posterior interoccipital synchondroses (AIOS and PIOS) were graded by the extent of fusion. These measurements were then compared with CT scans from 3 age-matched groups: the normal control group, children with Muenke syndrome, and children with Crouzon syndrome with acanthosis nigricans (CSAN)., Results: CT scans were reviewed in 23 cases of patients with achondroplasia, 23 normal controls, 20 Muenke, and 15 CSAN. Children with achondroplasia had significantly smaller sagittal diameter (mean 16.2 ± 2.4 mm) compared to other groups (control 31.7 ± 2.4 mm, p < 0.0001; Muenke 31.7 ± 3.5 mm, p < 0.0001; and CSAN 23.1 ± 3.4 mm, p < 0.0001) and transverse diameters (mean 14.3 ± 1.8 mm) compared with other groups (control 26.5 ± 3.2 mm, p < 0.0001; Muenke 24.1 ± 2.6 mm, p < 0.0001; CSAN 19.1 ± 2.6 mm, p < 0.0001). This translated into a surface area which was 3.4 times smaller in the achondroplasia group compared with the control group. The median grade of the AIOS fusion achondroplasia group was 3.0 (IQR 3.0-5.0), which was significantly higher compared with the control group (1.0, IQR 1.0-1.0, p < 0.0001), Muenke group (1.0, IQR 1.0-1.0, p < 0.0001), and CSAN (2.0, IQR 1.0-2.0, p < 0.0002). Median PIOS fusion grade was also highest in the achondroplasia group (5.0, IQR 4.0-5.0) compared with control (1.0, IQR 1.0-1.0, p < 0.0001), Muenke (2.5, IQR 1.3-3.0, p < 0.0001), and CSAN (4.0, IQR 4.0-4.0, p = 0.2). Distinct bony opisthion spurs projecting into the foramen magnum were seen in achondroplasia patients but not others, resulting in characteristic crescent and cloverleaf shapes., Conclusion: Patients with AFMS stages 3 and 4 have significantly reduced FM diameters, with surface area 3.4 times smaller than age-matched controls. This is associated with premature fusion of the AIOS and PIOS in comparison with controls and other FGFR3-related conditions. The presence of thickened opisthion bony spurs contributes to stenosis in achondroplasia. Understanding and quantifying bony changes at the FM of patients with achondroplasia will be important in the future quantitative evaluation of emerging medical therapies., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise., (© 2023. Crown.)

Indications Corridor and Limits of Exposure: The extreme lateral approach is useful for both extradural and intradural anterior and anterolateral lesions at the lower clivus down to the level of C2., Anatomic Essentials Need for Preoperative Planning and Assessment: The patient is evaluated with MRI, computed tomography (CT), and an angiogram. Special attention is given to vascular (vertebral artery course, dominance, tumor feeders) and bony (occipital condyle, jugular tubercle, foramen magnum and extent of bony involvement) anatomy., Essentials Steps of the Procedure: The patient is positioned lateral with the head flexed and tilted down without axial rotation. A hockey-stick incision is performed, and the myocutaneous flap is raised. A retrocondylar craniectomy is performed. The extradural vertebral artery is exposed for proximal control. A C1 hemilaminectomy is performed. Cephalad/caudal exposure and drilling of the occipital condyle are determined per case. The dura is opened, and the vertebral artery is released at the dural entry point to facilitate the tumor removal. The tumor is debulked and delivered inferoventrally away from the neuroaxis and cranial nerves. After removing the tumor, the dura is closed using an allograft.The patients consented to the procedure and to the publication of their images., Pitfalls/avoidance of Complications: • Cranial nerve deficits• Craniocervical instability• Postoperative hydrocephalus• Postoperative pseudomeningocele., Variants and Indications for Their Use: A transmastoid extension of the craniectomy allows access further rostrally in the clivus. For C1-2 chordomas, the approach is extended inferiorly, and the vertebral artery is mobilized out of the C1-2 transverse foramina. For tumors involving the joints, an occipitocervical stabilization is required.Images in video reused with permission as follows: image at 00:16 from Revuelta Barbero et al, Endoscopic endonasal transclival-medial condylectomy approach for resection of a foramen magnum meningioma: 2-dimensional operative video, Oper Neurosurg , 16(2), 2018, by permission from the Congress of Neurological Surgery; images at 00:30, and top image at 00:52 reused from Wen et al, Microsurgical anatomy of the transcondylar, supracondylar, and paracondylar extensions of the far-lateral approach, J Neurosurg , 87(4), 1997, with permission from JNSPG; bottom images at 00:52 from Muthukumar et al, A morphometric analysis of the foramen magnum region as it relates to the transcondylar approach, Acta Neurochir , 147(8), 2005, by permission from Springer Nature., (Copyright © Congress of Neurological Surgeons 2023. All rights reserved.)

Background: Chiari malformations are a spectrum of posterior cranial fossa anomalies characterized by herniation of the cerebellar tonsils through the foramen magnum. Surgery is the treatment of choice for selected patients with good postoperative outcomes., Methods: We describe foramen magnum decompression (FMD) with dural opening and a "drum skin" duraplasty technique., Conclusions: In our experience, FMD with "drum skin" duraplasty is a safe and effective procedure, reducing the risk of CSF leakage and arachnoidal adhesions and yielding better long-term clinical and radiological outcomes than other traditional techniques., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background and Definition: In recent years thanks to the growing use of radiological assessment, Chiari I malformation became one of the major diseases for a neurosurgeon to deal with. CIM can be classified according to the extent of cerebellar tonsil tip into the foramen magnum being a protrusion over five mm considered pathological. Such a disease is a heterogeneous condition with a multifactorial pathogenetic mechanism that can subdivided into a primary and secondary form. Regardless of the form, it seems that CIM is the result of an imbalance between the volume of the braincase and its content. Acquired CIMs are secondary to conditions causing intracranial hypertension or hypotension while the pathogenesis of primary forms is still controversial., Pathogenesis and Treatment: There are several theories in the literature but the most accepted one implies an overcrowding due to a small posterior cranial fossa. While asymptomatic CIM do not need treatment, symptomatic ones prompt for surgical management. Several techniques are proposed being the dilemma centered in the need for dural opening procedures and bony decompression ones., Conclusion: Alongside the paper, the authors will address the novelty presented in the literature on management, diagnosis and pathogenesis in order to offer a better understanding of such a heterogeneous pathology., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Symptomatic Chiari type 1 malformation (CIM) patients may elect to be treated; however, choosing the optimum surgical method remains problematic: posterior fossa decompression with duraplasty (PFDD) or without duraplasty (PFD). Many studies have compared these surgical methods from several perspectives. We looked at soft tissue density (STD) at the foramen magnum to add another perspective to the comparison of PFD with PFDD., Materials and Methods: Eighty-six patients who underwent surgery in our clinic were included in the study. We examined preoperative and postoperative MR images taken in the 1st year. We obtained the foramen magnum area (FMA) and soft tissue at the level of the foramen magnum. The STD within the foramen magnum was calculated as the percentage ratio of soft tissue area (STA) to FMA. Anteroposterior diameters of the syrinx cavities in sagittal T2 sections were measured preoperatively and at 1-year postoperatively. Measurements were double-blind and were performed by the neurosurgeon and by the neuroradiologist., Results: There was no statistically significant difference between the postoperative FMA increases, STA changes, STD changes in patients who underwent PFD and PFDD. In this study, there was no statistically significant difference between PFD and PFDD in terms of syrinx changes., Conclusions: The medium-term anatomical outcome following craniovertebral decompression for CIM, is no different whether performed PFD or PFDD.

Cerebrospinal fluid overdrainage in long-lasting shunted hydrocephalus is a well recognized complication. It may lead to different clinical syndromes which may occur over time, namely cranioencephalic disproportion and hindbrain herniation. Among the latter, Chiari malformation type 1 classically refers to one of the mildest form. When symptomatic, the patients generally exhibit a chronic, slowly progressive disease course. Although well documented in Chiari type II malformation and hydrocephalus, ventriculo-peritoneal shunt malfunction causing acute neurological deterioration in acquired Chiari malformation type 1 has been described only in three cases. All these patients underwent urgent shunt revision and suboccipital decompression in two of them, achieving good clinical improvement. We report on a 20-year-old woman harboring a previously asymptomatic Chiari malformation type 1, who experienced an acute foramen magnum syndrome with ventriculo-peritoneal shunt malfunction. We performed an endoscopic third-ventriculo-cisternostomy and definite removal of the shunt, obtaining the complete resolution of symptoms and shunt independence at 2 years follow-up. The phisiopathogenetic mechanisms and surgical management are discussed.

Introduction: Achondroplasia is a genetic disorder known for short stature and skeletal abnormalities., Case Report: We present a case of narrowing of the foramen magnum from a large opisthion extending to the spinal canal., Conclusion: Foramen magnum stenosis and cervicomedullary stenosis are potentially life threatening neurological manifestations of achondroplasia.

Foramen magnum stenosis is a serious, and potentially life-threatening complication of achondroplasia. The foramen magnum is smaller in infants with achondroplasia, compared with the general population, and both restricted growth in the first 2 years and premature closure of skull plate synchondroses can contribute to narrowing. Narrowing of the foramen magnum can lead to compression of the brainstem and spinal cord, and result in sleep apnoea and sudden death. There is a lack of clarity in the literature on the timing of regular monitoring for foramen magnum stenosis, which assessments should be carried out and when regular screening should be ceased. The European Achondroplasia Forum (EAF) is a group of clinicians and patient advocates, representative of the achondroplasia community. Members of the EAF Steering Committee were invited to submit suggestions for guiding principles for the detection and management of foramen magnum stenosis, which were collated and discussed at an open workshop. Each principle was scrutinised for content and wording, and anonymous voting held to pass the principle and vote on the level of agreement. A total of six guiding principles were developed which incorporate routine clinical monitoring of infants and young children, timing of routine MRI screening, referral of suspected foramen magnum stenosis to a neurosurgeon, the combination of assessments to inform the decision to decompress the foramen magnum, joint decision making to proceed with decompression, and management of older children in whom previously undetected foramen magnum stenosis is identified. All principles achieved the ≥ 75% majority needed to pass (range 89-100%), with high levels of agreement (range 7.6-8.9). By developing guiding principles for the detection and management of foramen magnum stenosis, the EAF aim to enable infants and young children to receive optimal monitoring for this potentially life-threatening complication., (© 2023. The Author(s).)

Purpose: The aim of this study is to morphometrically and morphologically examine the occipital condyle, which is an important anatomical region in terms of surgery and forensic medicine, and its surrounding structures, to evaluate the change in mean values according to gender and age, and to evaluate the correlation of the measurements obtained., Methods: 180 (90 men, 90 women) CBCT images selected from the archive of Ankara University Faculty of Dentistry. Occipital Condyle length and width, Hypoglossal Canal-Basion distance, Hypoglossal Canal-Opistion distance, Hypoglossal Canal-Occipital Condyle anterior and posterior border distance, Occipital Condyle thickness, Hypoglossal Canal length, the widest diameter of Hypoglossal Canal, the narrowest diameter of the Hypoglossal Canal, the length of the Jugular Tubercle, the width of the Jugular Tubercle, the anterior intercondylar distance, the posterior intercondylar distance, and the Foramen Magnum index were measured. At the same time, the presence of septum or spicule in the hypoglossal canal and protrusion of the occipital condyle were evaluated. The relationship of age, gender, anterior and posterior intercondylar distance, and foramen magnum index measurements with all measurements were examined., Results: In our study, all measurements were repeated 1 month after the first measurements to evaluate the intra-observer agreement, and the agreement between the obtained measurements and the first measurements was evaluated by calculating the intraclass correlation coefficient and 95% confidence intervals. Men's measurements were found to be significantly higher than women's measurements. When the coefficients of concordance in all measurements were examined, it was observed that there was a perfect concordance., Conclusion: When the results of the study are evaluated, it is seen that the values ​​obtained are generally close to the studies related to CT. Considering this, an idea can be gained as to whether CBCT, which has a lower dose and less cost, can be used as an alternative to CT in studies to be conducted with more comprehensive and different methods in skull base surgical planning., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Objective: To present our experience with an individualized surgical approach to treat Chiari malformation type 1., Methods: Based on (1) neurological symptoms, (2) the existence and extent of a syrinx and (3) the degree of the tonsillar descent we performed four types of approaches on a case-by-case basis in 81 patients: (1) foramen magnum decompression (FMD) with dura splitting (FMDds); (2) FMD with duraplasty (FMDdp); (3) FMD with duraplasty and tonsillar manipulation (FMDao); and (4) tonsillar resection/reduction (TR). Patient characteristics, Chiari Severity Index (CSI), fourth ventricular roof angle (FVRA) and Chicago Chiari Outcome Scale (CCOS) were analyzed., Results: CCOS was between 13 and 16 points in 8/11 (73 %) patients after FMDds, 38/45 (84 %) patients after FMDdp, and 24/24 (100 %, one patient lost to follow-up) patients after TR. We experienced an overall complication rate of 13.6 % (11/81) in this series, whereas seven of these eleven complications (64 %) occurred in the FMDao group and the complication rate increased with the invasiveness of the approach (0 % FMDds; 4 % FMDdp; 12 % TR)., Conclusion: Given the clear correlation between the extend of the approach and the complication rate the least invasive approach necessary to achieve clinical improvement should be selected. Due to the high complication rates, FMDao should not be used as a treatment option. The severity of the tonsillar descent, basilar invagination and current CM1 scores could be used to aid in the approach selection., Competing Interests: Declaration of Interests None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Purpose: Malformations of the craniovertebral junction (CVJ) range from mild, asymptomatic conditions to severe forms of instability with basilar invagination. Rarely, there have been accounts of forms of so-called paramedian basilar invagination, with abnormal bone masses invading the lateral portion of the foramen magnum. All these entities have been comprehensively classified both from an anatomical and embryological standpoint., Methods: Here, we report a case of a unique CVJ malformation which is not included in any existing classification framework and could represent a novel pathologic entity. We also provide an overview of the pertinent literature., Results: The patient was a 14-year-old boy with a recent onset of spastic tetraparesis. Radiological studies documented a malformation of the atlas which invaginated through the foramen magnum, causing anterolateral medullary incarceration. Surgical treatment involved posterior decompression with resection of the abnormal bone and occipito-cervical fusion., Conclusion: Our report enriches the panorama of CVJ malformations, showing how anatomical knowledge and embryological insights constitute the basis for the correct assessment and treatment of these complex entities., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Achondroplasia is associated with foramen magnum stenosis. We report a male infant with achondroplasia and centrally mediated obstructive apnoea who underwent two foramen magnum decompression due to bone regrowth. He presented at six weeks of age with breath holding and apnoeic episodes associated with significant desaturation, requiring non-invasive ventilation. Craniospinal imaging revealed a narrow foramen magnum without signal change in the spinal cord. Sleep studies showed obstructive, but not central, apnoea. Respiratory abnormalities persisted and reimaging at two months showed development of significant signal changes at the cervicomedullary junction (CMJ). He underwent emergency foramen magnum decompression with initial clinical improvement. Ten days later he relapsed with further apnoeic episodes requiring respiratory support. After extensive re-investigations including CT and MRI, incomplete initial decompression and foramen magnum restenosis were considered and confirmed with a CT head scan 15 weeks after the initial operation. Repeat decompression of bone and removal of thickened dural bands resulted in complete resolution of the apnoeic episodes. Obstructive sleep apnoea can be centrally mediated and further decompression of foramen magnum stenosis should be considered, especially if significant respiratory compromise persists or recurs.

Background: In patients with Chiari malformation type 1 (CMI) presenting with low intracranial compliance (ICC), foramen magnum decompression (FMD) often fails and the complication rate may be higher. We therefore routinely perform a preoperative assessment of ICC from intracranial pressure measurement. Patients with low ICC are treated with ventriculoperitoneal shunt (VPS) before FMD. In this study, we assess the outcome of patients with low ICC, compared with patients with high ICC treated with FMD alone., Methods: We reviewed the clinical and radiologic data of all consecutive patients with CMI treated between April 2008 and June 2021. ICC was assessed by overnight measurement of the pulsatile intracranial pressure: mean wave amplitude (MWA) above a previously defined threshold for abnormality was considered a surrogate marker for low ICC. The outcome was scored by Chicago Chiari Outcome Scale., Results: Of 73 patients, 23 with low ICC (average MWA 6.8 ± 1.2 mm Hg) received VPS before FMD, whereas 50 with high ICC (average MWA 4.4 ± 1.0 mm Hg) received only FMD. After a mean follow-up of 78.7 ± 41.4 months, 96% of all patients subjectively improved. The mean Chicago Chiari Outcome Scale score was 13.1 ± 2.2. Enlargement of cerebrospinal fluid space in the foramen magnum was achieved in 95% and regression of syringomyelia in 74% of cases. We found no significant difference in outcome between the patients with low and high ICC., Conclusions: By identifying patients with CMI associated with low ICC and tailoring their treatment by VPS before FMD, we achieved favorable clinical and radiologic outcomes comparable to those with high ICC., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

To identify skull-base growth patterns in Crouzon syndrome, we hypothesized premature minor suture fusion restricts occipital bone development, secondarily limiting foramen magnum expansion., Skull-base suture closure degree and cephalometric measurements were retrospectively studied using preoperative computed tomography (CT) scans and multiple linear regression analysis., Evaluation of multi-institutional CT images and 3D reconstructions from Wake Forest's Craniofacial Imaging Database (WFCID)., Sixty preoperative patients with Crouzon syndrome under 12 years-old were selected from WFCID. The control group included 60 age- and sex-matched patients without craniosynostosis or prior craniofacial surgery., None., 2D and 3D cephalometric measurements., 3D volumetric evaluation of the basioccipital, exo-occipital, and supraoccipital bones revealed decreased growth in Crouzon syndrome, attributed solely to premature minor suture fusion. Spheno-occipital (β = -398.75; P  < .05) and petrous-occipital (β = -727.5; P  < .001) suture fusion reduced growth of the basioccipital bone; lambdoid suture (β = -14 723.1; P  < .001) and occipitomastoid synchondrosis (β = -16 419.3; P  < .001) fusion reduced growth of the supraoccipital bone; and petrous-occipital suture (β = -673.3; P  < .001), anterior intraoccipital synchondrosis (β = -368.47; P  < .05), and posterior intraoccipital synchondrosis (β = -6261.42; P  < .01) fusion reduced growth of the exo-occipital bone. Foramen magnum morphology is restricted in Crouzon syndrome but not directly caused by early suture fusion., Premature minor suture fusion restricts the volume of developing occipital bones providing a plausible mechanism for observed foramen magnum anomalies.

Purpose: Anatomical knowledge of the hypoglossal canal is very important in relation to drilling of occipital condyle, jugular tubercle etc. So, this study was conducted to identify various morphometric and morphological features of the hypoglossal canal and its distance from adjacent structures relative to stable and reliable anatomic landmarks., Methods: The study was performed on 142 hypoglossal canals of 71 adult human dry skulls. The parameters measured were the transverse, vertical diameter, depth of the hypoglossal canal. The distances from the hypoglossal canal to the foramen magnum, occipital condyle and jugular foramen were also noted. In addition, the different locations of the hypoglossal canal orifices in relation to the occipital condyle were assessed. The different shapes and types of the hypoglossal canal were also noted., Results: There was significant difference (p < 0.05) in measurements taken on the right and left sides in males and females. The intracranial orifice of hypoglossal canal was present in middle 1/3rd in 100% of occipital condyle for both genders. The extracranial orifice of the hypoglossal canal was found to be in the anterior 1/3rd in 99% and 93.7% for male and female, respectively. Simple hypoglossal canal with no traces of partition was found to be more in males and females. The most common shape noted was oval both in males and females (71.8% and 68.7% respectively)., Conclusion: The results of the dimensions of the hypoglossal canal and its distance from other bony landmarks will be helpful for neurosurgeons to plan which surgical approaches should be undertaken while doing various surgeries in posterior cranial fossa., (© 2023. The Author(s).)

The far lateral approach provides wide surgical access to the lower third of the clivus, pontomedullary junction, and anterolateral foramen magnum and rarely requires craniovertebral fusion. The most common indications for this approach are posterior inferior cerebellar artery and vertebral arteryaneurysms, brainstem cavernous malformations, and tumors anterior to the lower pons and medulla, including meningiomas of the anterior foramen magnum, schwannomas of the lower cranial nerves, and intramedullary tumors at the craniocervical junction. We provide a stepwise description of how we perform the far lateral approach, as well as how to combine the far lateral approach with other skull base approaches, including the subtemporal transtentorial approach, for lesions involving the upper clivus; the posterior transpetrosal approach, for lesions involving the cerebellopontine angle and/or petroclival region; and/or lateral cervical approaches, for lesions involving the jugular foramen or carotid sheath regions., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Chiari type 1 deformity (Ch1) is associated with bony deformity of the skull base and herniation of cerebellar tonsils more than 5 mm below the foramen magnum. Magnetic resonance imaging (MRI) is used for diagnosis and surgery is advised for symptomatic children. We present a case series using MRI including cerebrospinal fluid (CSF) flow, in children with Ch1 to demonstrate a variety of outcomes, both surgical and spontaneous: spontaneous resolution, spontaneous worsening, postsurgical improvement, and postsurgical deterioration., Case: A 2-week-old female newborn underwent brain MRI demonstrating an ectopic neurohypophysis, under opercularization suggesting brain immaturity and a normal craniocervical junction (CCJ). Follow-up (F/U) MRI at 6 years of age showed interval spontaneous development of Ch1 with decreased CSF spaces at CCJ., Case: A 6-year-old girl referred for imaging with short stature and growth hormone deficiency demonstrated incidental findings of Ch1 without syringomyelia. There was 15-mm protrusion of pointed cerebellar tonsils through the foramen magnum and a reduced CSF space at the craniocervical junction. No surgery was performed, and F/U MRI at the age of 7 years demonstrated spontaneous resolution of the tonsillar ectopia (cerebellar tonsils now 3 mm right and 6 mm left) and expansion of the CSF spaces at CCJ., Case: A 7-year-old boy with headaches and staring spells underwent an MRI demonstrating 6-mm protrusion of pointed cerebellar tonsils and CSF space reduction at CCJ. No surgery was performed, and F/U imaging at the age of 9 years demonstrated spontaneous improvement in cerebellar tonsillar position and increased bidirectional CSF flow at CCJ., Case: A 17-month-old boy underwent brain MRI for unsteady gait and poor vestibular response, which showed Ch1 and narrow CSF spaces at the foramen magnum and with reduced CSF flow. At the age of 3 years, after posterior fossa decompression, F/U MRI showed postsurgical improvement of the position of the cerebellar tonsils and increased CSF space at CCJ., Case: A 4-month-old male infant with a history of 34-week prematurity, prior germinal matrix hemorrhage, and neonatal subdural hemorrhage was referred for MRI of the cervical and thoracic spine for evaluation of developmental delay and hypotonia with torticollis. Magnetic resonance imaging of the spine demonstrated mild protrusion of inferiorly pointed cerebellar tonsils up to the foramen magnum, with visible CSF and without retroflexion of the dens. Follow-up MRI scans demonstrated progressive worsening of the Chiari 1 deformity, even after multiple surgeries., Conclusions: It is important to be aware of a variety of different outcomes with Ch1, including spontaneous resolution, spontaneous worsening, improvement with surgery, and even deterioration after surgery. More research is required to determine objective criteria for predicting outcome, which include both anatomic measures and physiologic measures of CSF flow, so that better surgical decisions can be made and for evaluating patients who have undergone surgery., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Chiari malformation type 1 has been traditionally treated with foramen magnum decompression and C1 arch excision with or without duroplasty depending on the surgeon's preference. Each of the various surgical modifications has its advantages and disadvantages., Methods: We describe a minimally invasive tubular retractor-based approach to achieve bony decompression in these cases. We have had good results comparable to the open approach., Conclusions: Strict orientation to the midline using soft tissue landmarks in between the muscles and bony landmarks in the deeper planes is important to achieve good surgical results. Operative time decreases with expertise and is comparable to the open technique. Minimal blood loss and decreased hospital stay and an excellent cosmetic scar make this procedure more appealing., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background: Foramen magnum decompression is a common operation used to treat Chiari malformation. There are different surgical techniques; however, some are anecdotally more effective than others. Our aim was to determine whether there is a superior technique in relation to revision rates, presence of persistent postoperative headache and nausea, and syrinx reduction., Methods: This was a retrospective analysis of foramen magnum decompressions performed between 2012 and 2017 for Chiari 1 in a single institution. Three types of operations were performed: 1) bony decompression alone; 2) bony decompression with durotomy and dura left open; 3) bony decompression with opening of dura and duraplasty. We compared postoperative symptoms and revision rates between these 3 operations., Results: In 168 patients, 185 foramen magnum decompressions were performed. Among the 168 primary operations, in 66 the dura was not opened, in 86 the dura was opened without a duraplasty, and in 16 a duraplasty was performed. Of 185 operations, 17 were revision surgery. For primary procedures, the revision rates were 12 (18%) where the dura was not opened, 4 (5%) where the dura was left open, and 1 (6%) when duraplasty was performed. Severe postoperative headache and nausea occurred in 2 (3%) patients where the dura was not opened, 4 (25%) patients after primary duraplasty, and 64 (74%) patients after primary durotomy., Conclusions: In this study, rate of revision surgery was highest in patients who had bony decompression without dural opening. Rate of postoperative headache and nausea was highest in the durotomy group. Overall duraplasty had the best results., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The foramen magnum approach is always challenging because of the relationships between vital neurovascular structures in this area. Several approaches have been described, among them, the far lateral approach remains a cornerstone for the resection of anterior or anterolateral processes of the foramen magnum. This approach displays two main steps: the first is cervical, whereas the second is cranial.We report the case of a 63 year-old woman admitted for a progressive quadriplegia with swallowing disorders revealing a process of the anterior and anterolateral part of the foramen magnum. A cervical step of a far lateral approach without opening the foramen magnum achieved a near total resection of the process via a trans-tumor corridor and confirmed a dumbbell shape neurofibroma. The postoperative period showed a resolution of swallowing disorders and a progressive improvement of muscular strength. At 8 months follow-up, she was asymptomatic and able to walk with a normal balance. The surgical technique and anatomical correlation of this trans-tumor approach are discussed., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

The term Chiari malformation refers to a heterogeneous group of anatomical abnormalities at the craniovertebral junction. Chiari malformation type 1 (CM1) refers to the abnormal protrusion of cerebellar tonsils through the foramen magnum and is by far the commonest type. Its prevalence is estimated approximately 1%; it is more common in women and is associated with syringomyelia in 25-70% of cases. The prevalent pathophysiological theory proposes a morphological mismatch between a small posterior cranial fossa and a normally developed hindbrain that results in ectopia of the tonsils.In most people, CM1 is asymptomatic and diagnosed incidentally. In symptomatic cases, headache is the cardinal symptom. The typical headache is induced by Valsalva-like maneuvers. Many of the other symptoms are nonspecific, and in the absence of syringomyelia, the natural history is benign. Syringomyelia manifests with spinal cord dysfunction of varying severity. The approach to patients with CM1 should be multidisciplinary, and the first step in the management is phenotyping the symptoms, because they may be due to other pathologies, like a primary headache syndrome. Magnetic resonance imaging, which shows cerebellar tonsillar decent 5 mm or more below the foramen magnum, is the gold standard investigative modality. The diagnostic workup may include dynamic imaging of the craniocervical junction and intracranial pressure monitoring.The management of CM1 is variable and sometimes controversial. Surgery is usually reserved for patients with disabling headaches or neurological deficits from the syrinx. Surgical decompression of the craniocervical junction is the most widely used procedure. Several surgical techniques have been proposed, but there is no consensus on the best treatment strategy, mainly due to lack of high-quality evidence. The management of the condition during pregnancy, restriction to lifestyle related to athletic activities, and the coexistence of hypermobility require special considerations., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

In this study, the authors summarize the current knowledge on epidemiology, demographics, risk factors, and prognostic factors that influence outcomes in patients with adult Chiari malformation type I (CM-I) who underwent posterior fossa decompression surgery with duraplasty. Furthermore, they describe the contribution of their research group to the field of adult CM-I treatment, including association of increased body mass index with severity of CM-I and syringomyelia, relevant surgical anatomy, and surgical technique of 270° microsurgical decompression of foramen magnum. The authors also report on common complications in the literature and describe techniques for prevention of complications., (Copyright © 2022 Elsevier Inc. All rights reserved.)

While intracranial aneurysms rarely develop after neurosurgical procedures, delayed pseudoaneurysm formation after foramen magnum decompression (FMD) has never been reported. A 52-year-old woman presented with an atypical subarachnoid hemorrhage in the posterior fossa 12 years after a FMD for symptomatic Chiari malformation type I was performed. A pseudoaneurysm on a dural-pial anastomosis was identified as the bleeding source and successfully occluded by endovascular means with full clinical recovery of the patient. Injury to the distal posterior inferior cerebellar artery related to surgery and postoperative infection likely caused formation of a dural-pial anastomosis. Additionally, hemodynamic stress or dissection may have contributed to delayed pseudoaneurysm formation and rupture., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)