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Background and Objectives: Patients with basilar invagination (BI) can be treated with several surgical options, ranging from simple posterior decompression to circumferential decompression and fusion. Here, we aimed at examining the indications and outcomes associated with these surgical strategies to devise a staged algorithm for managing BI., Methods: We conducted a retrospective cohort study in 2 neurosurgical centers and included patients with a BI, as defined by a position of the dens tip at least 5 mm above the Chamberlain line. Other craniovertebral junction anomalies, such as atlas assimilation, platybasia, and Chiari malformations, were documented. C1-C2 stability was assessed with a dynamic computed tomography scan., Results: We included 30 patients with BI with a mean follow-up of 56 months (min = 12, max = 166). Posterior decompression and fusion (n = 8) was only performed in cases of obvious atlanto-axial instability (eg, increased atlanto-dental interval or hypermobility on flexion/extension), while anterior decompression (transoral or transnasal) was reserved to patients with lower cranial nerves deficits (eg, swallowing dysfunction) and irreducible anterior compression (n = 9). Patients with posterior signs (eg, Valsalva headaches) or myelopathy but without C1-C2 instability nor anterior signs were managed with an isolated foramen magnum decompression, with or without duraplasty (n = 13). Complications were more frequent for combined procedures, including neurological deterioriation (n = 4) and tracheostomy (n = 2), but reinterventions were more likely in patients undergoing posterior decompression alone (n = 3)., Conclusion: Patient selection is key to determine the appropriate surgical strategy for BI: In our experience, combined approaches are only needed for patients with irreducible and symptomatic anterior compression, while fusion should be restricted to patient with obvious signs of atlanto-axial instability. Other BI patients can be managed by foramen magnum decompression alone to minimize surgical morbidity., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Objective: We compared the diameter of the jugular foramen (JF) between normal individuals and those with a diagnosis of craniovertebral junction abnormalities, such as Chiari malformation type I (CMI) and/or basilar invagination (BI)., Methods: This cross-sectional analytical study measured the diameter of the right and left JF on magnetic resonance imaging scans of patients divided into 4 groups: 68 with combined CMI and BI (CMI+BI), 42 with isolated BI, 45 with isolated CMI, and 102 control cases. The t test determined sex differences, and univariate analysis of variance with Tukey's post hoc test assessed JF differences between groups., Results: Considering all combinations of laterality and sex, the CMI+BI group had a JF narrower than their respective control groups. The JF was bilaterally narrower in the BI group than in the control group only in the women. Regardless of laterality, the CMI group had a wider JF than did the CMI+BI group in men and did not differ from that of the control group. In the female patients with CMI, the right JF did not differ from that of the controls and was wider than that in the CMI+BI group. Also, the left JF was narrower than that in the control group and did not differ from that in the CMI+BI group., Conclusions: JF narrowing is associated with CMI and BI when combined in the same patient. When CMI or BI are detected separately, they do not imply evident changes in JF morphometry. It is expected that these findings could bring empiric substrate to support theories that claim a possible role of intracranial pressure disturbances as a triggering factor for CMI., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objectives and Background : To present a novel technique of treatment for a patient with basilar invagination. Basilar invagination (BI) is a congenital condition that can compress the cervicomedullary junction, leading to neurological deficits. Severe cases require surgical intervention, but there is debate over the choice of approach. The anterior approach allows direct decompression but carries high complication rates, while the posterior approach provides indirect decompression and offers good stability with fewer complications. Materials and Methods : A 15-year-old boy with severe myelopathy presented to our hospital with neck pain, bilateral upper limb muscle weakness, and hand numbness persisting for 4 years. Additionally, he experienced increased numbness and gait disturbance three months before his visit. On examination, he exhibited hyperreflexia in both upper and lower limbs, muscle weakness in the bilateral upper limbs (MMT 4), bilateral hypoesthesia below the elbow and in both legs, mild urinary and bowel incontinence, and a spastic gait. Radiographs revealed severe basilar invagination (BI). Preoperative images showed severe BI and that the spinal cord was severely compressed with odontoid process. Results : The patient underwent posterior surgery with the C-arm free technique. All screws including occipital screws were inserted into the adequate position under navigation guidance. Reduction was achieved with skull rotation and distraction. A follow-up at one year showed the following results: Manual muscle testing results and sensory function tests showed almost full recovery, with bilateral arm recovery (MMT 5) and smooth walking. The cervical Japanese Orthopedic Association score of the patient improved from 9/17 to 16/17. Postoperative images showed excellent spinal cord decompression, and no major or severe complications had occurred. Conclusions : Basilar invagination alongside Klippel-Feil syndrome represents a relatively uncommon condition. Utilizing a posterior approach for treating reducible BI with a C-arm-free technique proved to be a safe method in addressing severe myelopathy. This novel navigation technique yields excellent outcomes for patients with BI.

Introduction: Cranio-cervical anomalies are significant complications of osteogenesis imperfecta (OI), a rare bone fragility disorder that is usually caused by mutations in collagen type I encoding genes., Objective: To assess cranio-cervical anomalies and associated clinical findings in patients with moderate-to-severe OI using 3D cone beam computed tomography (CBCT) scans., Methods: Cross-sectional analysis of CBCT scans in 52 individuals with OI (age 10-37 years; 32 females) and 40 healthy controls (age 10-32 years; 26 females). Individuals with a diagnosis of OI type III (severe, n = 11), type IV (moderate, n = 33) and non-collagen OI (n = 8) were recruited through the Brittle Bone Disorders Consortium. Controls were recruited through the orthodontic clinic of the University of Missouri-Kansas City (UMKC)., Results: OI and control groups were similar in mean age (OI: 18.4 [SD: 7.2] years, controls: 18.1 [SD: 6.3] years). The cranial base angle was increased in the OI group (OI: mean 148.6° [SD: 19.3], controls: mean 130.4° [SD: 5.7], P = .001), indicating a flatter cranial base. Protrusion of the odontoid process into the foramen magnum (n = 7, 14%) and abnormally located odontoid process (n = 19, 37%) were observed in the OI group but not in controls. Low stature, expressed as height z-score (P = .01), presence of DI (P = .04) and being male (P = .04) were strong predictors of platybasia, whereas height z-score (P = .049) alone was found as positive predictor for basilar impression as per the Chamberlain measurement., Conclusion: The severity of the phenotype in OI, as expressed by the height z-score, correlates with the severity of cranial base anomalies such as platybasia and basilar impression in moderate-to-severe OI. Screening for cranial base anomalies is advisable in individuals with moderate-to-severe OI, with special regards to the individuals with a shorter stature and DI., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Secondary basilar invagination or basilar impression is an anomaly at the craniovertebral junction where the odontoid process prolapses into the foramen magnum with the risk of compressing adjacent structures and obstructing the proper flow of cerebrospinal fluid (CSF). The incidence is less than 1% in the general population and occurs mainly in the first three decades of life when it is associated with malformations of the neuroaxis. In older age, the main aetiologies are diseases that alter bone mineral density. The clinical course is usually progressive and the most common symptoms are asthenia, cervical pain and restricted movement, but also dysphonia, dyspnoea and dysphagia. It is a progressive disease which, if left untreated, can cause severe neurological damage and death. We report the case of a 79-year-old woman with osteoporosis and progressive dysphagia leading to severe malnutrition, which conditioned the decision not to intervene due to the high perioperative risk., (Copyright © 2024 SEEN and SED. Published by Elsevier España, S.L.U. All rights reserved.)

Sleep apnoea is common in patients with Basilar Invagination with Arnorld Chiari Malformation (ACM). Various studies have shown its incidence in the range of 60-70% among such patients. Most of the studies have shown improvement in sleep disturbances after decompressive surgeries for Chiari Malformations. There is no report of postoperative deterioration due to sleep apnoea in these patients. Authors report two cases of basilar invagination associated with ACM and Platybasia, who deteriorated probably due to worsening of pre-existing sleep disorders on 3rd and 7th postoperative days after their surgeries, despite clinico-radiological improvements during their early post-operative courses. Authors discuss literature related to sleep apnoea in basilar invagination associated with Chiari Malformations and share precautions, which are relevant and should be undertaken in such patients especially during early post-operative periods to avoid alarming complication which may occur even in experienced hands.

Objective: To analyze the anatomical changes of the IV ventricle and cisterna magna in the Chiari malformation I (CMI) and basilar invagination (type B)., Methods: This is a controlled study with 161 exams of magnetic resonance imaging (MRI) of adults grouped into control (n = 37), basilar invagination (BI; n = 31), Chiari malformation I (CMI; n = 37), and CMI+BI (n = 56). The MRIs were analyzed using the visualization software Osirix (Pixmeo, Bernex, Geneva, version 3.8.2). The morphometric variables were: distance from the obex to the McRae line; length of the IV ventricle floor; and the area and volume of the cisterna magna. The univariate ANOVA followed by Tukey's post-hoc test was applied to evaluate the difference between the groups. The difference between sexes was evaluated by the t test for each group., Results: Alterations in the cisterna magna and IV ventricle were more evident only in the CMI and CMI+BI groups. For both sexes, the CMI and CMI+BI groups showed: a reduction in the CSF space (P < 0.001), cisterna magna with volume reduction (P < 0.001), low position of the obex (P < 0.001), and IV ventricle more elongated (male P = 0.007 and female P < 0.001). The BI group had no significant change in the analysis by sex., Conclusions: The CMI (isolated and associated with BI) showed a low obex position and elongation of the IV ventricle due to traction towards the spinal canal. The reduction of cisterna magna volume added to the occupation of the cerebellar tonsils can impact in the cerebrospinal fluid dynamics. The BI when isolated was not related to alterations in the parameters of cerebrospinal fluid spaces studied., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Objective: Craniocervical junction (CCJ) pathologies with ventral neural element compression are poorly understood, and appropriate management requires accurate understanding, description, and a more uniform nomenclature. The aim of this study was to evaluate patients to identify anatomical clusters and better classify CCJ disorders with ventral compression and guide treatment., Methods: A retrospective review of adult and pediatric patients with ventral CCJ compression from 2008 to 2022 at a single center was performed. The incidence of anatomical abnormalities and compressive etiologies was assessed. Surgical approach, radiographic data, and outcomes were recorded. Association rules analysis (ARA) was used to assess variable clustering., Results: Among 51 patients, the main causes of compression were either purely bony (retroflexed dens [n = 18]; basilar invagination [BI; n = 13]) or soft tissue (degenerative pannus [n = 16]; inflammatory pannus [n = 2]). The primary cluster in ARA was a retroflexed dens, platybasia, and Chiari malformation (CM), and the secondary cluster was BI, C1-2 subluxation, and reducibility. These, along with degenerative pannus, formed the three major classes. In assessing the optimal treatment strategy, reducibility was evaluated. Of the BI cases, 12 of the 13 patients had anterolisthesis of C1 that was potentially reducible, compared with 2 of the 18 patients with a retroflexed dens (both with concomitant BI), and no pannus cases. The mean C1-2 facet angle was significantly higher in BI at 32.4°, compared with -2.3° in retroflexed dens and 8.1° in degenerative pannus (p < 0.05). Endonasal decompression with posterior fixation was performed in 48 (94.0%) of the 51 patients, whereas posterior reduction/fixation alone was performed in 3 patients (6.0%). Of 16 reducible cases, open posterior reduction alone was successful in 3 (60.0%) of 5 cases, with all successes containing isolated BI. Reduction was not attempted if vertebral anatomy was unfavorable (n = 9) or the C1 lateral mass was absent (n = 5). The mean follow-up was 28 months. Symptoms improved in 88.9% of patients and were stable in the remaining 11.1%. Tracheostomy and percutaneous G-tube placement occurred in 7.8% and 11.8% of patients, respectively. Reoperation for an endonasal CSF leak repair or posterior cervical wound revision both occurred in 3.9% of patients., Conclusions: In classifying, one cluster caused decreased posterior fossa volume due to an anatomical triad of retroflexed dens, platybasia, and CM. The second cluster caused pannus formation due to degenerative hypertrophy. For both, endonasal decompression with posterior fixation was ideal. The third group contained C1 anterolisthesis characterized by a steep C1-2 facet angle causing reducible BI. Posterior reduction/fixation is the first-line treatment when anatomically feasible or endonasal decompression with in situ posterior fixation when anatomical constraints exist.

Background:  There is evidence that Chiari malformation (CM) and basilar invagination (BI) are largely due to disproportion between the content and volume of the posterior fossa. A recent study identified an increased association between brachycephaly and BI. In several types of craniosynostosis, the posterior fossa volume is smaller than normal, and this is more pronounced in coronal synostosis. The aim of this study is to evaluate the association between CM and BI., Methods:  The cephalic index (CI) measured on magnetic resonance imaging (MRI) from a sample of patients with craniocervical malformation was compared with that of normal subjects., Results:  The average CI in the craniovertebral junction malformation (CVJM) group was significantly higher in BI patients than in normal subjects. The BI patients also had the highest CI among the whole sample of patients ( p  = 0.009)., Conclusions:  In this study, BI patients had the highest CI among patients with CVJM and a significantly higher CI than those in the control group. Our data confirm the association between BI and brachycephaly., Competing Interests: None declared., (Thieme. All rights reserved.)

Objective: Patients with Chiari malformation (CM) associated with atlantoaxial dislocation (AAD) and basilar invagination (BI) may present with a small posterior cranial fossa, but data on the volumetric analysis are lacking. Additionally, whether additional foramen magnum decompression (FMD) is needed together with atlantoaxial fusion remains controversial. This study evaluated the volumetric alterations of the posterior cranial fossa in these patients and analyzed the radiological and clinical outcomes after posterior C1-C2 reduction and fixation plus C1 posterior arch resection., Methods: Thirty-two adult CM patients with AAD and BI (CM-AAD/BI group) and 21 AAD and BI patients without CM (AAD/BI-only group) who received posterior atlantoaxial fusion plus C1 posterior arch resection were retrospectively studied. The clinical and radiological outcomes and volumetric measurements of the posterior cranial fossa were evaluated., Results: The majority of CM-AAD/BI patients (94%) improved clinically and radiologically at 12 mo postoperatively, and none required additional FMD. Morphological analysis revealed a significant reduction in the bony posterior cranial fossa volumes of the CM-AAD/BI group (P < 0.01) and the AAD/BI-only group (P < 0.01) relative to those of the CM group. No significant differences were observed between the CM-AAD/BI and AAD/BI groups., Conclusions: Compared with patients with simple CM, patients with AAD/BI with or without CM demonstrated a considerably and equally reduced bony posterior cranial fossa volume. No additional FMD is needed in the treatment of CM-AAD/BI patients after posterior reduction and fusion plus C1 posterior arch resection., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: To assess the clinical impact of direct two-step distraction reduction (TSDR) for basilar invagination (BI) with atlantoaxial dislocation (AAD). Methods: Retrospective analysis was conducted on the clinical data of patients who underwent TSDR and occipitocervical fusion in West China Hospital between October 2013 and March 2021. Depending on whether the preoperative decrease was greater than 50% on preoperative hyperextension X-rays, the patients were split into two groups. The neurological function [Japanese Orthopedic Association (JOA) score], atlantodens interval (ADI), the distance of odontoid process beyond McRae Line (ML) and Wackenheim Line (WL), cervicomedullary angle (CMA), O-C 2 angle (OC2A), and complications incidence were compared between two groups preoperatively and postoperatively. Results: There were 12 men and 23 women among the 35 patients with BI and AAD, and the age ranged from 28 to 71 years, with an mean age of (52.0±13.4) years. In the preoperative reduction ≥50% group, there were 4 males and 9 females with an average age of (54.0±13.8) years; in the preoperative reduction <50% group, there were 8 males and 14 females with a mean age of (50.9±13.4) years. All the patients were followed-up for a mean time of (23.3±13.4) months. There was no significant difference in age, gender, bleeding, length of hospital stay and follow-up time between the two groups (all P >0.05). The JOA score, ADI, WL, ML and CMA of 35 patients were significantly improved when compared with those before operation (all P <0.05). The reduction degree of ADI, ML and WL was more than 80% in 31 cases (88.57%), 30 cases (85.71%) and 31 cases (88.57%), respectively. There was no significant difference in postoperative ADI, ML and WL between the two groups (all P >0.05). All patients had no incision infection, no loosening or breakage of the internal fixators. Dysphagia occurred in 3 patients, non-fusion happened in 1 patient, but no instability in X-ray of cervical dynamic position was found, no loosening or displacement occurred in internal fixators, and partial spontaneous fusion occurred between atlantoaxial lateral mass joints. Conclusions: For BI with AAD without atlantoaxial bony connection or serious atlantoaxial facet joint inclination, TSDR could obtain satisfactory reduction degree. The reduction degree on preoperative hyperextension X-ray doesn't affect the degree of intraoperative reduction.

Background: Treatments for symptomatic or unstable basilar invagination (BI) include posterior decompression, distraction/fusion, trans-nasal or trans-oral anterior decompression, and combined techniques, with the need for occipitocervical fusion based on the degree of craniocervical instability. Variations of the far lateral transcondylar approach are described in limited case series for BI, but have not been widely applied., Methods: A single-institution, retrospective review of consecutive patients undergoing a far lateral transcondylar approach for odontoidectomy (± resection of the inferior clivus) followed by occipitocervical fusion over a 6-year period (1/1/2016 to 12/31/2021) is performed. Detailed technical notes are combined with images from cadaveric dissections and patient surgeries to illustrate our technique using a lateral retroauricular incision., Results: Nine patients were identified (3 males, 6 females; mean age 40.2 ± 19.6 years). All patients had congenital or acquired BI causing neurologic deficits. There were no major neurologic or wound-healing complications. 9/9 patients (100%) experienced improvement in preoperative symptoms., Conclusions: The far lateral transcondylar approach provides a direct corridor for ventral brainstem decompression in patients with symptomatic BI. A comprehensive knowledge of craniovertebral junction anatomy is critical to the safe performance of this surgery, especially when using a lateral retroauricular incision., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Background: Treatment of Chiari malformation (CM) is controversial, especially when it coexists with "stable" or Type II basilar invagination (CM + II-BI). Precise evaluation of craniovertebral junction (CVJ) stability is crucial in such patients; however, this has never been validated. This study aimed to dynamically evaluate atlanto-condyle and atlantoaxial stability by kinematic computed tomography (CT) and report its surgical treatment., Methods: The study recruited 101 patients (control, CM, and CM + II-BI groups: 48, 34, and 19 patients, respectively). During kinematic CT, the CVJ stability-related parameters were measured and compared between the 3 groups. The surgical strategy for treating CM + II-BI was based on these results. Preoperative and postoperative images were acquired, and functional scores were used to assess the outcome., Results: Among the 3 groups, the length of the clivus and the height of the condyle were the shortest in the CM + II-BI group, which was accompanied by the greatest rotation of the atlas and atlanto-condyle facet movement on cervical flexion and extension. Moreover, in such patients, increased Chamberlain's baseline violation indicated the aggregate invagination of the odontoid in the flexed position, and asymmetric displacement of atlantoaxial facets was observed. Seventeen CM + II-BI patients underwent surgical treatment with atlantoaxial distraction and occipitocervical fusion. The syringomyelia width and tonsillar herniation decreased significantly, and functional scores indicated symptom relief and good outcomes., Conclusions: CVJ instability, especially the ultramovement of atlanto-condyle facets, commonly exists in II-BI as evaluated using kinematic CT. The surgical strategy of atlantoaxial distraction and occipitocervical fusion should be considered to treat such patients., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Osteogenesis imperfecta (OI) is a rare bone disease due to an abnormal synthesis of 1-type collagen. OI is frequently associated with basilar impression (BI), defined by the elevation of the clivus and floor of the posterior fossa with subsequent migration of the upper cervical spine and the odontoid peg into the base of the skull. Bone intrinsic fragility leading to fractures and deformity, brainstem compression and impaired CSF circulation at cranio-vertebral junction (CVJ) makes the management of these conditions particularly challenging. Different surgical strategies, including posterior fossa decompression with or without instrumentation, transoral or endonasal decompression with posterior occipito-cervical fusion, or halo gravity traction with posterior instrumentation have been reported, but evidence about best modalities treatment is still debated. In this technical note, we present a case of a 16-years-old patient, diagnosed with OI and BI, treated with halo traction, occipito-cervico-thoracic fixation, foramen magnum and upper cervical decompression, and expansive duroplasty. We focus on technical aspects, preoperative work up and postoperative follow up. We also discuss advantages and limitations of this strategy compared to other surgical techniques., (© 2022. The Author(s).)

Background: The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks., Objective: To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach., Methods: A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements., Results: The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion., Conclusion: Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: The craniovertebral junction is an anatomically well-defined transitional zone located between the skull and the cervical spine. Multiple malformations can affect this region with the most prominent being basilar invagination (BI) and Chiari malformation (CM). Despite numerous studies, the origin, pathophysiology, and classification of these pathologies remain controversial. The objective of this study was to evaluate the implication of cranial base flexion angle and clivus length in the development of these conditions., Methods: Midline tomography and magnetic resonance imaging of normal subjects and patients diagnosed with BI (types I and II) and Chiari malformation were evaluated. A craniometric study of the skull base was performed. Linear and angular measurements were used for comparisons between groups., Results: 109 images from patients with craniovertebral junction malformation and controls were evaluated. Seventeen had BI-I, 26 had BI-II, 36 had CM, and 30 were normal subjects. Demographic data for the two groups were not significantly different. Craniometric analysis of images revealed a gradation in linear and angular variables from controls to CM, BI-I, and BI-II patients. Clivus length was significantly smaller in BI-II patients compared with other groups, while basal angle was greater. Moderate or strong correlations were noted among all variables analyzed., Conclusion: Data suggest that clivus length and basal angle may play a role in pathophysiology of BI and CM.

Basilar invagination (BI) and Chiari malformation type I (CM-I) are very important anomalies that introduce instability and compression in the occipitocervical transition region and have complex clinical characteristics. These anomalies vary according to the affected structures. The present study revises current knowledge regarding the anatomy, anatomo-physiology, clinical manifestations, and radiological findings of these entities and the associated surgical treatment approaches. A bibliographic survey was performed through a search in the Medline, PubMed, SciELO, Science and LILACS databases. When associated, these craniovertebral malformations result in neurological deficits due to neural parenchyma compression; however, the presence of microtraumas due to repetitive lesions caused by the bulb and cervical marrow instability has been highlighted as a determinant dysfunction. Surgical treatment is controversial and has many technical variations. Surgery is also challenging due to the complex anatomical characteristics and biomechanics of this region. Nevertheless, advances have been achieved in our understanding of related mechanisms, and compression and atlantoaxial instability are considered key elements when selecting the surgical approach.

Basilar invagination (BI) and Chiari malformation type I CM-I) are the most common adult craniovertebral junction malformations, and they are frequently associated with each other and present synchronously. The relationship between BI and CM-I has remained incompletely understood, and the choice of surgical strategy has remained controversial. This brief review focuses on the different aspects of BI and CM-I, and further discusses the relationship between these two concomitant pathologies on the basis of the concepts proposed over the last three decades.

Competing Interests: There are no conflicts of interest

Background: Basilar invagination (BI) is an abnormality characterized by a superior projection at the craniovertebral junction (CVJ). The high prevalence of BI in Northeastern Brazil associated with brachycephaly, which is measured by the cranial index (CI), has been widely reported by several neurosurgeons and radiologists from that region since the 1950s. However, strong evidence for this relationship is still pending. The aim of this study is to investigate whether there is a relationship between BI and CI in a sample with participants from Northeastern Brazil., Methods: The study used magnetic resonance images (MRIs) from 34 patients with BI and 92 controls. These participants had the CI correlated with radiological measurements used in BI diagnosis: Welcker's basal angle (WBA), clivus-canal angle (CCA), apex distance of the odontoid process to Chamberlain's line (DOCL), and Boogaard's angle (BOA). Craniometry was performed using the software Osirix, version 3.9.2 and statistical analysis by SPSS. We used Pearson's test for correlation analysis and the ROC curve was used for depicting CI accuracy related to BI diagnosis. All tests were calculated at the 95% confidence interval., Results: The BI group showed a moderate correlation between CI and CVJ measurements (P < 0.05). The control group had a weak correlation between CI and DOCL, and no statistical significance was verified for other correlations (P > 0.05). The area under the ROC was 0.659 and a CI greater than 86 had a specificity of approximately 80% for BI (P = 0.002)., Conclusions: The results indicated a greater cephalic projection of the CVJ in patients with high CI in the BI group. Moreover, a CI above 86 has a good diagnosis specificity for BI, showing evidence of a relationship between hyperbrachycephaly and CVJ anomalies in Northeastern Brazil., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To evaluate vertebral artery anomaly at the craniovertebral junction (CVJ) in patients with basilar invagination (BI) by computed tomographic angiography (CTA), and to discuss the prevention strategy of vascular injury., Methods: The primary axial, multiple planar reconstruction and volume-rendering cervicocranial CTA images of 39 BI patients were analysed to evaluate vertebral artery anomaly at the CVJ: persistent first intersegmental artery (PFIA), fenestrated vertebral artery (FEN), and extracranial C1/2 origin of posterior inferior cerebellar artery (PICA), high-riding vertebral artery, side-to-side asymmetry and irregular midline carotid artery loop was determined by subjective vision. 100 patients who underwent CTA for reasons other than CVJ deformity were enrolled as normal controls to evaluate the prevalence of vertebral artery anomaly in a normal population. Chi-square test was utilized for comparing the prevalence of vertebral artery anomaly between these two groups., Results: The incidence of PFIA was 25.6% (10/39), FEN was 7.7% (3/39), PICA was 5.1% (2/39), and the total incidence of extraosseous anomalous course of vertebral artery was 38.5% (15/39), significantly higher than that of control group, 7.0% (7/100) (P < 0.01). The incidence of high-riding vertebral artery and side-to-side asymmetry were 61.5% (24/39) and 30.8% (12/39), respectively. An irregular midline carotid artery loop was observed in five patients (12.8%)., Conclusion: Vertebral artery anomaly, which can be clearly depicted by CTA, is more frequent in BI patients. Preoperative CTA should be performed for this patient population to prevent vascular injury. These slides can be retrieved under Electronic Supplementary Material.

The congenital and acquired deformities of the craniovertebral junction (CVJ), such as basilar invagination, basilar impression, or platybasia, can present in the form of slowly progressive or acute neurologic deterioration. In many cases, an insidious headache is the only symptom and can be a diagnostic challenge for the neurologist. Proper imaging studies as well as recognizing often associated neurologic or systemic conditions are required for early diagnosis and effective therapy. In the current report, the primary focus will be on clinical aspects of these CVJ abnormalities; the pathologic and radiologic aspects, such as developmental and pathophysiologic background or radiographic analysis, will be discussed briefly, confined to clinically relevant data.

Background: Neck pain is one of the most common musculoskeletal disorders in clinical practice. However neck pain may mask more serious pathology. Although uncommon in most musculoskeletal physiotherapy practices, it is possible to encounter rare and extremely life-threatening conditions, such as craniovertebral congenital anomalies. Basilar invagination is an abnormality where the odontoid peg projects above the foramen magnum and is the commonest malformation of the craniocervical junction. Its prevalence in the general population is estimated to be 1%. Furthermore, it is a well-recognised cause of neck pain insomuch as it can be easily overlooked and mistaken for a musculoskeletal disorder. Diagnosis is based on the patient's symptoms in conjunction with magnetic resonance imaging (MRI). If life-threatening symptoms, or pressure on the spinal cord are present, the recommended treatment is typically surgical correction., Case Presentation: This case report describes the history, relevant examination findings, and clinical reasoning used for a 37 year old male who had the chief complaint of neck pain and occipital headache. After the history and the physical examination, there were several key indicators in the patient's presentation that appeared to warrant further investigation with diagnostic imaging: (1) the drop attack after a triggering event (i.e., heading a football), (2) several episodes of facial numbness immediately and shortly after the trauma, (3) the poorly defined muscle upper extremity muscle weakness, and (4) the modification of symptoms during the modified Sharp-Purser test. Therefore, the decision was made to contact the referring neurosurgeon to discuss the patient's history and his physical examination. The physician requested immediate cervical spine MRI, which revealed a "basilar impression"., Conclusion: This case report highlights the need for more research into a number of issues surrounding the prevalence, diagnosis, and the central role of primary care clinicians such as physiotherapists. Furthermore it underlines the importance of including Basilar invagination in the differential diagnosis. Physiotherapists working within a direct access environment must take a comprehensive history and be capable of screening for non-musculoskeletal medical conditions (on a systems, not diagnosis level) in order to avoid providing potentially harmful musculoskeletal treatments (e.g., cervical mobilization or manipulation, stretching, exercise) to patients with sinister medical pathologies, not benign musculoskeletal disorders.

Odontoidectomy is the treatment of choice for irreducible ventral cervical-medullary compression. The endonasal endoscopic approach is an innovative approach for odontoidectomy. The aim of this article is to identify in which conditions this approach is indicated, discussing variants of the technique for selected cases of craniovertebral malformation with platybasia. We believe that the technical difficulties of this approach are balanced by the advantages for patients. Some conditions related to the patient and to the anatomy of the craniovertebral junction may favor adoption of the endoscopic endonasal approach, which should be considered complementary and not alternative to standard approaches., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Object: Chiari I malformation is the most common craniocervical malformation. Its combination with basilar invagination in a significant proportion of patients is well established. This study presents surgical results for patients with Chiari I malformation with and without additional basilar invagination., Method: Three hundred twenty-three patients underwent 350 operations between 1985 and 2013 (mean age 43 ± 16 years, mean history of symptoms 64 ± 94 months). The clinical courses were documented with a score system for individual neurological symptoms for short-term results after 3 and 12 months. Long-term outcomes were analyzed with Kaplan-Meier statistics. The mean follow-up was 53 ± 58 months (the means are expressed ± SD)., Results: Patients with (n = 46) or without (n = 277) basilar invagination in addition to Chiari I malformation were identified. Patients with invagination were separated into groups: those with (n = 31) and without (n = 15) ventral compression by the odontoid in the foramen magnum. Of the 350 operations, 313 dealt with the craniospinal pathology, 28 surgeries were undertaken for degenerative diseases of the cervical spine, 3 were performed for hydrocephalus, and 6 syrinx catheters were removed for cord tethering. All craniospinal operations included a foramen magnum decompression with arachnoid dissection, opening of the fourth ventricle, and a duraplasty. In patients without invagination, craniospinal instability was detected in 4 individuals, who required additional craniospinal fusion. In patients with invagination but without ventral compression, no stabilization was added to the decompression. In all patients with ventral compression, craniospinal stabilization was performed with the foramen magnum decompression, except for 4 patients with mild ventral compression early in the series who underwent posterior decompression only. Among those with ventral compression, 9 patients with caudal cranial nerve dysfunctions underwent a combination of transoral decompression with posterior decompression and fusion. Within the 1st postoperative year, neurological scores improved for all symptoms in each patient group, with the most profound improvement for occipital pain. In the long term, late postoperative deteriorations were related to reobstruction of CSF flow in patients without invagination (18.3% in 10 years), whereas deteriorations in patients with invagination (24.9% in 10 years) were exclusively related either to instabilities becoming manifest after a foramen magnum decompression or to hardware failures. Results for ventral and posterior fusions for degenerative disc diseases in these patients indicated a trend for better long-term results with posterior operations., Conclusions: The great majority of patients with Chiari I malformations with or without basilar invagination report postoperative improvements with this management algorithm. There were no significant differences in short-term or long-term outcomes between these groups. Chiari I malformations without invagination and those with invaginations but without ventral compression can be managed by foramen magnum decompression alone. The majority of patients with ventral compression can be treated by posterior decompression, realignment, and stabilization, reserving anterior decompressions for patients with profound, symptomatic brainstem compression.

Introduction: Klippel-Feil syndrome (KFS) is a congenital cervical vertebral union caused by a failure of segmentation during abnormal development and frequently accompanies conditions such as basicranial malformation, atlas assimilation, or dens malformation. Especially in basilar invagination (BI), which is a dislocation of the dens in an upper direction, compression of the spinomedullary junction from the ventral side results in paralysis, and treatment is required., Clinical Presentation: We present the case of a 38-year-old male patient with KFS and severe BI. Plane radiographs and computed tomography (CT) images showed severe BI, and magnetic resonance image (MRI) revealed spinal cord compression caused by invagination of the dens into the foramen magnum and atlantoaxial subluxation. Reduction by halo vest and skeletal traction were not successful. Occipitocervical fusion along with decompression of the foramen magnum, C1 laminectomy, and reduction using instruments were performed. Paralysis was temporarily aggravated and then gradually improved. Unsupported walking was achieved 24 months after surgery, and activities of daily life could be independently performed at the same time. CT and MRI revealed that dramatic reduction of vertical subluxation and spinal cord decompression were achieved., Conclusion: Reduction and internal fixation using instrumentation are effective techniques for KFS with BI; however, caution should be exercised because of the possibility of paralysis caused by intraoperative reduction.

Objective: To investigate the surgical outcome and its influencing factors in patients of congenital basilar invagination (BI) with atlanto-axial dislocation (AAD)., Methods: From May 2004 to August 2010, 120 patients who had BI with AAD were surgically treated with direct posterior intraoperative distraction-reduction and fixation technique, 93 patients were successfully followed up by means of questionnaire survey, telephone and clinical evaluation. Pre- and postoperative dynamic cervical X-rays, computed tomographic scans, 3-dimentional reconstruction views and magnetic resonance imaging were performed. Pre- and postoperative Japanese Orthopaedic Association (JOA) score, distance between odontoid tip and Chamberlain's line and atlantodental interval were measured to evaluate the surgical result. Statistical analysis was performed by means of paired t test and Pearson Correlation analysis., Results: There were 93 cases were followed up for 24-99 months with an average of 46.5 months. Until the final follow-up, clinical symptoms were improved in 79 patients (84.9%), and were stable in 7 patients (7.5%) and deteriorated in 4 patients (4.3%). Three patients died postoperatively (3.2%). Patients without intramedullary signal intensity change (ISIC) had better surgical outcome. Patients with compression from anterior odontoid tip and posterior bone margin of occipital foramen had the worst surgical outcome (F = 3.987, P < 0.01). Overall, good decompression and bone fusion were shown on postoperative image in 87 patients (93.5%). There were 3 deaths in this series because of basilar artery thrombosis, posterior fossa hematoma and unknown reasons each., Conclusions: The direct posterior intraoperative distraction-reduction and fixation technique is an effective simple and safe method for the treatment of BI with AAD. Anterior compression from odontoid tip and posterior compression from bone margin of occipital foramen-atlantal posterior arch play important roles in its developing mechanism. ISIC on MRI is a predictive factor for the worse surgical outcome.

A teenage girl presented with progressively worsening neck and occipital pain since 8 months ago that was associated with restriction of neck movements, low to moderate grade fever, anorexia and weight loss followed by gradually progressive quadriparesis since 3 months ago. Neurological examination revealed spastic quadriparesis without cranial nerve palsy. MRI of the cervical spine revealed prevertebral and paravertebral abscess from clivus to C2/C3 level, which extended into the anterior epidural space at C1-C3 level, causing atlantoaxial dislocation. There was evidence of basilar invagination. The dislocated dens caused compression over the cervicomedullary junction. On this basis, a diagnosis of craniovertebral junction Pott's disease was made. The patient was given neck immobilisation with cervical collar, and antitubercular treatment was started. She showed significant improvement in her neurological deficit during follow-up.

A case is presented of a 35-year-old woman diagnosed with platybasia associated with Klippel-Feil syndrome type I. She was admitted to University Department of Neurology for clinical examination because of walking difficulties, dizziness, and intermittent vision disturbances. Neurological examination revealed a predominance of cerebellar symptomatology. Relevant diagnostic work-up included craniogram, cervical spine x-ray, computed tomography (CT) of the brain and craniocervical junction, magnetic resonance imaging of the brain, electroencephalography, ophthalmologic examination, urinary tract ultrasonography, laboratory tests, and psychological testing. CT of the craniocervical junction showed platybasia, congenital fusion of the second and third cervical vertebrae, and basilar invagination of dens axis. Platybasia is leveling of the angle between the floor of the anterior cranial fossa and posterior cranial fossa in the area of sella turcica, which is normally at 115-140 degrees. Basilar impression or invagination is moving up of the basis of the occiput and occipital condyles into the cranium, which means that the borders of the foramen magnum, condyles and adjacent bone are invaginated into the posterior fossa. Klippel-Feil syndrome type II is massive fusion of two of seven cervical vertebrae associated with short neck and low hair line.

A case is reported of a 72-year-old woman who presented with severe vertigo, vomit, and mild neck and occipital pain. She had a medical history of hypertension, angina pectoris, cholelithiasis, gastric ulcer, pyelonephritis and periodical mild dizziness. Neuroimaging revealed right vertebral artery occlusion, right cerebellar stroke and basilar impression. The therapeutic approach chosen in our patient was conservative, with non-steroid anti-inflammatory drugs and neck collar. Although our patient's prior risk factors for stroke supported a diagnosis of vertebrobasilar stroke, it is possible that the vertebral artery occlusion was the result of changes in the atlantoaxial anatomy and that cerebellar infarction was secondary to craniocervical anomaly. Although the presence of vertebral artery occlusion, cerebellar stroke and basilar impression in our patient may have been coincidental, we suggest that patients with basilar impression and craniocervical anomalies in general may be at an increased risk of vertebrobasilar vascular disease and vertebrobasilar stroke.

Study Design: This retrospective study was conducted to analyze the radiographic and clinical results in seven patients with primary basilar invagination who accepted a combination of continuous cervical traction before operation and posterior screw/rod system reduction together with occipitocervical fusion., Objective: To evaluate the radiographic and clinical outcomes of this treatment regimen in combination of continuous cervical traction and posterior instrumented reduction with pedicle screw/rod system., Summary of Background Data: Primary basilar invagination poses considerable difficulties in the surgical management regarding surgical approach, reduction, and decompression. A variety of methods have been described to treat primary basilar invagination and all methods existed limits., Methods: There were four male and three female patients, and the ages ranged from 12 to 40 years (average age, 22.3 yr). Six patients presented neurologic deficits. The Nurick scale was from 1 grade to 4 grades (average, 2.7 grades). The distance of the odontoid tip in relation to Wackenheim line, atlantodental interval, Klaus height index, craniospinal angle, modified Omega angle, and cervicomedullary angle were measured pretreated and after surgery. When the tip of odontoid process was inferior or approximate to Wackenheim line and McRae line after cervical traction, the operation of reduction and fixation should be accepted., Results: After surgery, the mean Wackenheim value and atlantodental distance were reduced 9.3 mm and 2.0 mm, respectively. The mean Klaus height index, craniospinal angle, Omega angle, and cervicomedullary angle improved 6.5 mm, 17.0°, 11.6°, and 27.4°, respectively. All postoperative data had a significance compared with pretreatment data (P < 0.05). There was a tendency that younger patients were able to obtain more ideal reduction than adults. Of six patients with neurologic symptoms, five patients were normal or nearly normal. All patients achieved solid fusion., Conclusion: This case series demonstrates a safe, easy, and effective treatment regimen for the patients with primary basilar invagination.

Objective: This case study describes a patient with long-standing rheumatoid arthritis of the cervical spine who presented with significant bone destruction, gross joint derangement, and a potentially life-threatening complication, basilar invagination with brain stem compression. The pathophysiology, clinical presentation, imaging, and surgical management are discussed., Clinical Features: A 67-year-old female presented to a chiropractic clinic with chronic neck pain of 30 years of duration complicated by rheumatoid arthritis. Her neck pain had recently exacerbated and was radiating into her trapezius muscle and shoulders. She also reported a recent onset of mild dysphagia. The patient was referred to a neurosurgeon for consultation and management., Intervention and Outcome: Computed tomography and magnetic resonance imaging of the cervical spine demonstrated significant bone destruction, gross joint derangement, and basilar invagination. There was moderate stenosis of the foramen magnum secondary to basilar invagination with significant brain stem compression. The patient underwent surgical stabilization fusion from the occiput to T2 using a posterior approach. Her pain severity was lessened after surgery, and the dysphagia had not progressed suggesting stabilization of brain stem compression., Conclusion: Patients with long-standing rheumatoid arthritis of the cervical spine often present with chronic neck pain. Cervical spine instability may arise from rheumatoid osteolysis and is also secondary to horizontal or vertical subluxation of the atlantoaxial and occipitoatlantal regions, respectively. High-velocity, low-amplitude manipulation of the upper cervical spine is an absolute contraindication in cases of atlantoaxial instability. A timely diagnosis and favorable surgical outcome provided relief from a potentially life-threatening disorder. This case exemplifies the clinical caution necessary for managing patients with chronic cervical spine pain complicated by rheumatoid arthritis.

A 27-year-old woman presented with bilateral weakness of her all extremities for 5 years. She had a spastic gait and was unable to ambulate without assistance. Neurologic examination revealed increased deep tendon reflexes and positive pathologic reflexes. Radiographs showed occipitalization of the atlas, C2-C3 congenital fusion and fixed atlantoaxial dislocation with an atlanto-dental interval of 10 mm. MRI demonstrated cervicomedullary junction (CMJ) compression from the odontoid, a Chiari type I malformation, and syringomyelia extending from the foramen magnum to C5. The patient underwent transoral atlantoaxial release followed by posterior internal fixation from the occiput to the axis, which resulted in a significant improvement in motor function in all extremities. Post-operative images showed anatomical reduction of the atlantoaxial joint. However, an MRI performed 8 days following surgery showed a new retro-odontoid pannus had developed that was compressing the spinal cord at CMJ. A follow-up CT scan performed at 6 months post-operatively demonstrated a solid bony fusion between the occiput and C2, while an MRI at that time showed complete resolution of the retro-odontoid soft tissue mass with correction of the Chiari I malformation, and resolution of the syringomyelia. Final follow-up at 2-years revealed an excellent clinical outcome.

Introduction: The vascular compression of a nerve is known to be the most important cause of idiopathic trigeminal neuralgia (ITN) by most authors. However, several cases of skull base deformities in patients with ITN have been reported in our bibliographic review. AIM. To compare the existence of platybasia between a group of patients with ITN and a randomized control group., Subjects and Methods: Twenty-five patients with ITN and twenty-five control subjects were X-rayed and their basal angles were measured and compared., Results: The basal angle measured to investigate the existence of platybasia is significantly greater in the ITN group than in the control group. Platybasia was found in 10 patients with ITN. However, only two cases of platybasia were reported in the control group. Therefore in our study we have found that the incidence of platybasia in patients with ITN is significantly increased., Conclusion: Our data demonstrated that platybasia has an important role in the pathogenesis of the ITN by altering the normal anatomy of the nerves and vessels within the posterior fossa.

The Chiari malformation (CM) is characterized by variable herniation of one or both cerebellar tonsils, associated or not with displacement of the hindbrain structures into the vertebral canal. This is a retrospective study of 29 patients with CM submitted to surgical procedure between 1990 and 2003. There were 14 females and 15 males whose ages ranged from 16 to 65 years. There were seven patients with isolated CM, 12 associated with syringomyelia (SM), three associated with basilar impression (BI) and seven associated with SM and BI. The surgery was based on posterior fossa decompression. In seven patients a catheter was introduced from the subarachnoid space into the III ventricle and five were submitted to tonsillectomy. Twenty-one patients improved, one worsened, one remained unchanged, four missed follow up and two died. We conclude that the best results with CM surgery are obtained by an effective posterior fossa decompression. Those CM cases associated with other abnormalities, such as SM and BI, probably need complementary techniques which will be the theme for new prospective studies.

Objective: A novel method of treatment of basilar invagination that involves distraction of the atlantoaxial joint using specially designed spiked spacers is described. Bone graft that is additionally placed within the appropriately prepared atlantoaxial joint and posterior to the arch of atlas and lamina of C2 provides bony fusion., Materials and Methods: Between December 2002 and April 2007, 11 patients underwent the discussed method of fixation at the Department of Neurosurgery, King Edward Memorial Hospital in Mumbai, India. All 11 patients had "congenital" basilar invagination and the symptoms were progressive in nature., Results: The mean follow-up period was 21 months (range 8-40 months). Neurological improvement and successful distraction with atlantoaxial stabilization and ultimate bone fusion was achieved in all the patients and was documented with dynamic radiography. There were no neurological, vascular, or infective complications., Conclusions: We conclude that the described method of atlantoaxial joint distraction and fixation provides an alternative treatment strategy for cases with basilar invagination. "Joint distraction" as a stand-alone method could provide reduction of basilar invagination and firm stabilization in such cases.

The clinical and radiological manifestations of suboccipital tuberculosis have been analyzed in 7 patients aged 7 to 35 years. A case of this condition accompanied by extensive vertebral destruction, abscesses, and basilar impression is described in a 7.5-year-old child. A radical stabilizing operation was successfully performed using the currently available technologies.

The transoral approach provides a safe exposure to lesions in the midline and the ventral side of the craniovertebral junction. The advantages of the transoral approach are 1) the impinging bony pathology and granulation tissue are accessible only via the ventral route; 2) the head is placed in the extended position, thus decreasing the angulation of the brainstem during the surgery; and 3) surgery is done through the avascular median pharyngeal raphe and clivus. We analyzed the clinical effects of odontoidectomy after treating 38 patients with basilar invagination. The anterior transoral operation to treat irreducible ventral compression in patients with basilar invagination was performed in 38 patients. The patients ages ranged from 34 to 67 years. Fourteen patients had associated Chiari malformation and eight had previously undergone posterior decompressive surgery. The main indication for surgery was significant neurological deterioration. Symptoms and signs included neck pain, myelopathy, lower cranial nerve dysfunction, nystagmus and gait disturbance. Extended exposure was performed in 24 patients. The surgery was beneficial to the majority of patients. There was one death within 10 days of surgery, due to pulmonary embolism. Postoperative complications included two cases of pneumonia, three cases of oronasal fistula with regurgitation and one cerebrospinal fluid leak. In patients with marked ventral compression, the transoral approach provides direct access to the anterior face of the craniovertebral junction and effective means for odontoidectomy.

Symptomatic irreducible basilar invagination has traditionally been approached through a transoral-transpharyngeal route with resection of the anterior portion of C-1 and the odontoid. Modification of this exposure with either a Le Fort osteotomy or a transmandibular osteotomy and circumglossal approach has increased the access to pathological conditions in this region. These traditional routes all require traversing the oral cavity and accepting the associated potential complications. The authors have developed a novel surgical approach, an endoscopic transcervical odontoidectomy, which allows access for resection of the odontoid and for brainstem and spinal cord decompression without traversing the oral cavity. In this paper they describe the technique and its advantages and present three cases in which patients underwent the endoscopic transcervical odontoidectomy for basilar invagination. Three consecutive patients (age range 42-74 years) who had irreducible basilar invagination underwent the endoscopic transcervical odontoidectomy. All were symptomatic and had neck pain and myelopathy. All were evaluated preoperatively and postoperatively with computed tomography and magnetic resonance imaging. In all cases the procedure resulted in complete decompression. There were no serious complications. No patient required prolonged intubation, tracheostomy, or enteral tube feeding. One patient had an intraoperative cerebrospinal fluid leak, which had no postoperative sequelae. The authors present an alternative surgical approach for treating ventral compression of the brainstem and spinal cord. The technique is safe and effective for decompression and provides a surgical route that can be added to the armamentarium of treatments for pathological conditions in this region.

Background: Vascular compression of the trigeminal nerve is generally accepted as the primary source causing TN. To date, skull base bone deformity associated with ITN has been reported in only a number of case reports. The aim of the present study was to investigate one such skull base deformity, platybasia, in ITN patients in comparison with a randomized control population., Methods: Basal angle values reflecting the development of platybasia were measured in 25 patients with ITN and compared with the measurements in 25 control subjects., Results: Basal angle measured to investigate the existence of platybasia was found significantly wider in the ITN group (t = 3.90; P < .001), although platybasia was present in only 10 patients. Moreover, the average angle was also greater in the study group than in the control group, and the difference was statistically significant. Platybasia was found in 10 patients, whereas it was detected in only 2 control individuals; difference in platybasia incidence between the 2 groups was also statistically significant (chi(2) = 7.01; P < .01)., Conclusion: Our data demonstrated that platybasia affecting the bony walls of the posterior fossa may play an important role in the pathogenesis if vascular abnormalities causing TN.

We report on a 48 years-old man with basilar impression without syringohydromyelia, in which the cisterna magna was impacted by the cerebellar tonsils. Six months after posterior fossa decompression there was the disappearance of nuchal rigidity, vertigo, spastic paraparesis and improvement of balance. Nevertheless hyperreflexia and diminished pallesthesia of the lower limbs persisted.

Study Design: The authors report a case of a patient with diffuse idiopathic skeletal hyperostosis (DISH) associated with basilar impression resulting in tetraparesis., Objective: To describe neurologic compromise associated with DISH., Summary of Background Data: Neurologic deficits due to DISH are very rare, and only 1 case of basilar impression associated with DISH has previously been reported in the literature., Methods: Diagnosis was confirmed by radiograph and MRI, which demonstrated basilar impression associated with a hyperintense signal in the spinal cord on T2-weighted sequences. Transoral resection of the dens associated with posterior occipitocervical fixation was performed during the same anesthesia., Results: Postoperative outcome demonstrated regression of the pyramidal signs without recovery of unassisted walking., Conclusion: Early MRI should be performed in the evidence of spinal cord suffering in patients with DISH. Transoral approach allowed a good decompression of the spinal cord.

Twelve selected patients, eight males and four females aged 14 to 50 years, with syringomyelia associated with congenital craniovertebral bony anomalies including basilar invagination and fixed atlantoaxial dislocation, and associated Chiari I malformation in eight, were treated by atlantoaxial joint manipulation and restoration of the craniovertebral region alignment between October 2002 and March 2004. Three patients had a history of trauma prior to the onset of symptoms. Spastic quadriparesis and ataxia were the most prominent symptoms. The mean duration of symptoms was 11 months. The atlantoaxial dislocation and basilar invagination were reduced by manual distraction of the facets of the atlas and axis, stabilization by placement of bone graft and metal spacers within the joint, and direct atlantoaxial fixation using an inter-articular plate and screw method technique. Following surgery all patients showed symptomatic improvement and restoration of craniovertebral alignment during follow up from 3 to 20 months (mean 7 months). Radiological improvement of the syrinx could not be evaluated as stainless steel metal plates, screws, and spacers were used for fixation. Manipulation of the atlantoaxial joints and restoring the anatomical craniovertebral alignments in selected cases of syringomyelia leads to remarkable and sustained clinical recovery, and is probably the optimum surgical treatment.

Study Design: The issue of progression of congenital basilar invagination is evaluated on the basis of 3 clinical cases. The rationale of treatment of basilar invagination in general and, particularly, in the complex clinical situation encountered in the presented cases, by the authors' technique of atlantoaxial joint distraction, reduction of basilar invagination, and direct lateral mass plate and screw fixation is discussed., Objective: The subject of progression of congenital basilar invagination and recurrent craniocervical cord compression after an initial transoral decompression is analyzed, and an alternative surgical treatment involving craniovertebral bone realignment is suggested., Summary of Background Data: This is a review of 3 cases of basilar invagination treated earlier by transoral decompression. No fixation procedure was performed. The patients presented with recurrent symptoms of high cervical cord compression. Investigations revealed a progression of basilar invagination and cord compression. The treatment of such a complex clinical situation by atlantoaxial joint distraction is discussed., Methods: Between September 2001 and January 2004, we treated 3 patients with congenital basilar invagination who underwent transoral odontoidectomy but did not undergo any posterior atlantoaxial or occipitoaxial fixation. The patients had postoperative improvement but worsening of their neurologic condition after an average duration of 26 months after transoral surgery. Repeat investigations revealed that basilar invagination and the craniovertebral alignments worsened during the period, and there was recurrent cervicomedullary cord compression. These patients were treated by atlantoaxial facet distraction, and attempts were made toward reduction of the basilar invagination and craniovertebral junction bony realignment, and atlantoaxial fixation by the technique recently described by us., Results: During the average follow-up of 25 months, all 3 patients have had a neurologic recovery., Conclusions: The probable cause of basilar invagination and its progression is a congenital malformation ofalignment of the facets of the atlantoaxial joint. Distraction of the facets and direct interarticular atlantoaxial fixation presents a unique opportunity of reduction of the basilar invagination and fixation of the region.

Posterior fossa decompression utilizing suboccipital craniectomy and duraplasty remains the standard surgical treatment for Chiari-associated syringomyelia. In the presence of basilar invagination, anterior decompression, typically transoral odontoidectomy, or posterior decompression may be performed. We report two cases in which anterior and posterior (circumferential) decompression of the foramen magnum was used to treat cervical syringomyelia successfully. These cases demonstrate that circumferential decompression of the foramen magnum may be necessary in some cases of cervical syringomyelia associated with basilar invagination and Chiari malformation.