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Purpose: Placement of a subdural drain after burr-hole drainage of chronic subdural hematoma (cSDH) significantly reduces risk of its recurrence and lowers mortality at 6 months. Nonetheless, measures to reduce morbidity related to drain placement are rarely addressed in the literature. Toward reducing drain-related morbidity, we compare outcomes achieved by conventional insertion and our proposed modification., Methods: In this retrospective series from two institutions, 362 patients underwent burr-hole drainage of unilateral cSDH with subsequent subdural drain insertion by conventional technique or modified Nelaton catheter (NC) technique. Primary endpoints were iatrogenic brain contusion or new neurological deficit. Secondary endpoints were drain misplacement, indication for computed tomography (CT) scan, re-operation for hematoma recurrence, and favorable Glasgow Outcome Scale (GOS) score (≥ 4) at final follow-up., Results: The 362 patients (63.8% male) in our final analysis included drains inserted in 56 patients by NC and 306 patients by conventional technique. Brain contusions or new neurological deficits occurred significantly less often in the NC (1.8%) than conventional group (10.5%) (P = .041). Compared with the conventional group, the NC group had no drain misplacement (3.6% versus 0%; P = .23) and significantly fewer non-routine CT imaging related to symptoms (36.5% versus 5.4%; P < .001). Re-operation rates and favorable GOS scores were comparable between groups., Conclusion: We propose the NC technique as an easy-to-use measure for accurate drain positioning within the subdural space that may yield meaningful benefits for patients undergoing treatment for cSDH and vulnerable to complication risks., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The surgical morbidity of brainstem lesions is higher than in other areas of the central nervous system because the compact brainstem is highly concentrated with neural structures that are often distorted or even unrecognizable under microscopic view. Intraoperative neurophysiologic mapping helps identify critical neural structures to avoid damaging them. With the trans-fourth ventricular floor approach, identifying the facial colliculi and vagal and hypoglossal triangles enables incising and approaching the brainstem through the safe entry zones, the suprafacial or infrafacial triangle, with minimal injury. Corticospinal tract mapping is adopted in the case of brainstem surgery adjacent to the corticospinal tract. Intraoperative neurophysiologic monitoring techniques include motor evoked potentials (MEPs), corticobulbar MEPs, brainstem auditory evoked potentials, and somatosensory evoked potentials. These provide real-time feedback about the functional integrity of neural pathways, and the surgical team can reconsider and correct the surgical strategy accordingly. With multimodal mapping and monitoring, the brainstem is no longer "no man's land," and brainstem lesions can be treated surgically without formidable morbidity and mortality., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Meningiomas are the most common intradural extramedullary tumors, followed by nerve sheath tumors that can also grow extradurally. Metastases are the most frequent extradural tumors and most commonly affect the thoracic vertebrae. Spinal fractures with column dislocation and/or instability require surgical fixation. Spine surgery for an extramedullary tumor or fracture usually involves decompression of neural elements and instrumentation for stabilization. These procedures risk spinal cord and nerve root injury. The incidence of nerve root deficits after resection of nerve sheath tumors is particularly high since the tumor grows from the rootlets. Intraoperative neurophysiologic monitoring and mapping techniques have been introduced to prevent iatrogenic neurologic deficits. These include motor and sensory evoked potentials, electromyography, compound muscle action potentials, and the bulbocavernosus reflex. The combination of techniques chosen for a particular procedure depends on the surgical level and the character of the lesion., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Intramedullary spinal cord tumor (ISCT) surgery is challenged by a significant risk of neurological injury. Indeed, while most ISCT patients arrive to surgery in good neurological condition due to early diagnosis, many experience some degree of postoperative sensorimotor deficit. Thus, intraoperative neuromonitoring (IONM) is invaluable for providing functional information that helps neurosurgeons tailor the surgical strategy to maximize resection while minimizing morbidity. Somatosensory evoked potential (SEP), muscle motor evoked potential (mMEP), and D-wave monitoring are routinely used to continuously assess the functional integrity of the long pathways within the spinal cord. More recently, mapping techniques have been introduced to identify the dorsal columns and the corticospinal tracts. Intraoperative SEP decline is not a sufficient reason to abandon surgery, since SEPs are very sensitive to anesthesia and surgical maneuvers. Yet, a severe proprioceptive deficit may adversely impact daily life, and the value of SEPs should be reconsidered. While mMEPs are good predictors of short-term motor outcome, the D-wave is the strongest predictor of long-term motor outcome, and its preservation during surgery is essential. Mapping techniques are promising but still need validation in large cohorts of patients to determine their impact on clinical outcome. The therapeutic rather than merely diagnostic value of IONM in spine surgery is still debated, but there is emerging evidence that IONM provides an essential adjunct in ISCT surgery., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The subtemporal approach provides a narrow operative corridor to the crus cerebrum and adjacent structures of the crural, interpeduncular, and ambient cistern. Addition of a zygomatic osteotomy widens this narrow corridor and spares retraction of the temporal lobe. We investigate and compare the morphometric parameters of the subtemporal approach with versus without zygomatic osteotomy. On each side of four cadaveric heads, a temporal craniotomy was performed to gain access to the crus cerebrum and adjacent subarachnoid cisterns using a subtemporal approach. Operative corridor width and corridor working angle were measured with and without brain retraction on each specimen side. Next, a zygomatic osteotomy was performed followed by full downward reflection of the temporalis muscle and further drilling of the squamous part of the temporal bone. Lastly, operative corridor width and corridor working angle were measured again for comparison. The subtemporal operating corridor was (mean/SD): 5.8/2.6 mm without retraction, 11.4/4.3 mm with retraction, and 13.5/6.5° working angle. After addition of a zygomatic osteotomy, the operative corridor was 8/9.2/4.3 mm without retraction, 14.7/4.5 mm with retraction, 31.8/3.1° working angle. Zygomatic osteotomy significantly increased the operative corridor working angle of the subtemporal approach. Furthermore, we demonstrate a direct approach into the interpeduncular fossa. Clin. Anat. 32:710-714, 2019. © 2019 Wiley Periodicals, Inc., (© 2019 Wiley Periodicals, Inc.)

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez‑Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Background: The combined anterior transpetrosal and subtemporal/transcavernous (atsta) approach to the petroclival junction provides a wide exposure facilitating resection of large tumor lesions such as petroclival mengiomas, chondrosarcomas, or chordomas. In this article we provide technical instructions on the approach with anatomical consideration and a literature review of previous applications of this approach., Methods: The combined approach was performed in two cadaveric specimen and relevant anatomical aspects were studied. Additionally, the authors performed a review of the literature focusing on indications, neurologic outcome, and complications associated with the technique., Results: A combined atsta approach offers a wide exposure of the crus cerebrum, pons, basal temporal lobe, cranial nerves III to VII/VIII, posterior cerebral artery (PCA), superior cerebellar artery (SCA), basilar artery (BA), anterior inferior cerebellar artery (AICA), and posterior communicating artery (Pcom). It has been successfully applied with acceptable morbidity and mortality rates, mainly for (spheno-) petroclival meningiomas., Conclusion: The combined approach studied here is a useful skull base approach to the petroclival junction and can be applied to treat large or complex pathologies of the region. Detailed anatomical knowledge is essential., Competing Interests: There are no conflicts of interest.

Objectives: Anatomical identification of the corticospinal tract (CT) and the dorsal column (DC) of the exposed spinal cord is difficult when anatomical landmarks are distorted by tumour growth. Neurophysiological identification is complicated by the fact that direct stimulation of the DC may result in muscle motor responses due to the centrally activated H-reflex. This study aims to provide a technique for intraoperative neurophysiological differentiation between CT and DC in the exposed spinal cord., Methods: Recordings were obtained from 32 consecutive patients undergoing spinal cord tumour surgery from July 2015 to March 2017. A double train stimulation paradigm with an intertrain interval of 60 ms was devised with recording of responses from limb muscles., Results: In non-spastic patients (55% of cohort) an identical second response was noted following the first CT response, but the second response was absent after DC stimulation. In patients with pre-existing spasticity (45%), CT stimulation again resulted in two identical responses, whereas DC stimulation generated a second response that differed substantially from the first one. The recovery times of interneurons in the spinal cord grey matter were much shorter for the CT than those for the DC. Therefore, when a second stimulus train was applied 60 ms after the first, the CT-fibre interneurons had already recovered ready to generate a second response, whereas the DC interneurons were still in the refractory period., Conclusions: Mapping of the spinal cord using double train stimulation allows neurophysiological distinction of CT from DC pathways during spinal cord surgery in patients with and without pre-existing spasticity., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Objective: The cervical carotid segment is used routinely as donor site for high-flow bypass procedures. The horizontal petrous segment would offer a shorter graft distance, complete graft protection intracranially, and avoid the need for surgical neck exposure. In a morphometric cadaveric study, we aimed to investigate variations of the petrous carotid anatomy, especially the incidence of bony dehiscence of the roof of the horizontal petrous carotid segment canal, which may facilitate exposure of the vessel and thereby potentially lower the morbidity of high-flow bypass procedures., Methods: A subtemporal approach was used to expose the horizontal petrous internal carotid artery (ICA) on each side of 4 alcohol-embedded, silicone-injected human cadaver heads to perform a morphometric analysis of the vessel segment and surrounding bony anatomy., Results: The following measurements were obtained of the horizontal petrous ICA (millimeters): long axis mean 9.6 (standard deviation [SD] 4.4, MIN 4.2, MAX 19.5), diameter mean 4.9 (SD 0.6, MIN 4, MAX 5.7), thickness of canal roof mean 2.1 (SD 1.7, MIN 0, MAX 5), and distance from temporal squama mean 22.5 (SD 6, MIN 17, MAX 35). Dehiscence of the bony roof of the horizontal petrous carotid canal was found in 25% of specimen investigated., Conclusions: A dehiscent bony roof of the horizontal petrous carotid canal potentially facilitates exposure of the vessel for high-flow bypass procedures and was observed in 25% of specimens. This feature could be identified on preoperative high-resolution imaging and thus aid in patient selection., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Introduction: In selected cases, microsurgical clipping remains a valuable treatment alternative to endovascular occlusion of anterior communicating artery (AComA) aneurysms. Their clipping is challenging and carries a risk of postsurgical cognitive impairment. We evaluate the microsurgical anatomy of a new, minimally invasive combined interhemispheric-subfrontal approach to the AComA complex via a medial supraorbital craniotomy., Methods: In this descriptive anatomic study, four alcohol-embedded, silicon-injected human cadaver heads were used. In each of the two cadavers, the AComA complex was approached from either the right or left side. An operating microscope and standard microsurgical instruments were used., Results: After a medial eyebrow incision, a medial supraorbital minicraniotomy was performed. The frontal sinus was opened and cranialized. Following the dural opening, a subfrontal arachnoid dissection was performed to identify the optico-carotid complex. By following the A1 segment, a low-lying AComA complex could be visualized. Shifting the corridor towards the midline enabled an interhemispheric dissection. This dissection resulted in a wide superior-inferior corridor. Higher-lying AComA complexes could also be visualized. The achieved exposure of the AComA complex would allow safe dissection and clipping of low- and high-lying AComA aneurysms, with minimal retraction and preservation of the surrounding anatomical structures, in particular the perforators., Conclusions: We demonstrate the anatomy of a novel approach for surgical clipping of AComA aneurysms. Our study suggests that this approach provides good exposure without concomitant structural and vascular injury and thus might reduce the risk of procedure-related morbidity.

Objective: To provide a summary of the intraoperative monitoring of muscle motor evoked potentials (MEPs) based on the presence-absence concept during neurosurgical operations along the spinal cord., Method: Expert review., Discussion: The measurable parameters of MEPs, such as signal amplitudes and thresholds vary considerably both during a single surgery in a single individual patient as well as between individuals and operations. The presence or absence of responses irrespective of stimulus intensity and response amplitude is much more clearly defined. The correlation of intraoperative MEP data to clinical findings preoperatively and postoperatively so far is best if a presence-absence paradigm is used. The most reliable correlation of postoperative motor deficits is with the disappearance of previously present MEPs, not with the deterioration of amplitudes or the elevation of thresholds. However, in intraoperative decision making an elevation of threshold, without signal loss may still be considered a practical warning sign as it may be a subclinical injury indicator, and may therefore induce a change in surgical strategy. This may be considered a minor warning criterion. A practical concept of the combined use of MEPs with D-wave recordings produced a neurophysiological pattern, which correlates with a reversible motor deficit: Disappearance of MEPs correlates with transient motor deficits if the D-wave amplitude is preserved above an approximate value of 50% of its baseline. Disappearance of the D-wave correlates to paraplegia., Conclusions: To date, the best correlation of muscle MEP data to clinical deficits lies in the assessment of disappearance of a previously present MEP regardless of thresholds or amplitudes. Increase in stimulus thresholds for MEPs or to a lesser degree decrement of signal amplitudes may be considered subclinical injury indicators without correlation to neurological dysfunction and thus is considered a minor warning criterion.

Background and Importance: This is the first report of a primarily intracranial interdigitating dendritic cell sarcoma (IDCS)., Clinical Presentation: A 39-year-old patient with right hemiparesis underwent complete resection of a large parafalcine tumor with subsequent complete recovery of neurological symptoms. Histologically, the tumor was diagnosed as IDCS. Extensive staging did not reveal any extracranial manifestation of this disease. After 1.5 years, the patient remains recurrence free and is being observed closely., Conclusion: IDCS are exceedingly rare tumors and so far have not been found intracranially. On the basis of the limited experience with extracranial occurrence, this tumor is best managed by complete resection and careful oncological observation., Abbreviations: FDCS, follicular dendritic cell sarcomaIDCS, interdigitating dendritic cell sarcomaRTU, ready-to-use kit.

Object: The aim of this study was to provide evidence for the effect of intrathecal morphine application after spinal cord tumor resection., Methods: Twenty patients participated in a prospective open proof-of-concept study. During dural closure, morphine (7 μg/kg) was injected into the subarachnoid space. All patients were monitored in an intensive care setting postoperatively. Pain, additional opioids given, and vital parameters were recorded., Results: Six patients received a mean morphine dose of 365 μg between C-3 and C-7 and 14 patients received a mean dose of 436 μg between T-2 and T-12. In the cervical and thoracic groups, the mean Numeric Rating Scale score was highest upon intensive care unit admission (1.2 and 2.5, respectively) and declined at 12 hours (0.5 and 0.8, respectively). Minimal extra morphine was required. Minor side effects occurred without consequence., Conclusions: Intrathecal morphine for postoperative analgesia after resection of cervical and thoracic spinal cord tumors is effective and safe. These preliminary results require confirmation by larger comparative studies and further clinical experience.

Object: Presently, the best available treatment for intramedullary spinal cord tumors (IMSCTs) in children is microsurgery with the objective of maximal tumor removal and minimal neurological morbidity. The latter has become manageable with the development and standard use of intraoperative neurophysiological monitoring. Traditionally, the perioperative neurological evaluation is based on surgical or spinal cord injury scores focusing on sensorimotor function. Little is known about the quality of life after such operations; therefore, this study was designed to investigate the impact of surgery for IMSCTs on the quality of life in children., Methods: Twelve consecutive pediatric patients treated for IMSCT were included in this retrospective fixed cohort study. A multidimensional questionnaire-based quality of life instrument, the Pediatric Quality of Life Questionnaire version 4 (PedsQL 4.0), was chosen to analyze follow-up data. This validated instrument particularly allows for a comparison between a patient cohort and a healthy pediatric sample population., Results: Of 11 mailed questionnaires (1 patient had died of progressive disease), 10 were returned, resulting in a response rate of 91%. There were 8 low-grade lesions (5 pilocytic astrocytomas, 1 ganglioglioma, 1 hemangioblastoma, and 1 cavernoma) and 4 high-grade lesions (2 anaplastic gangliogliomas, 1 glioblastoma, and 1 glioneuronal tumor). The mean age at diagnosis was 7.5 years, the mean follow-up was 4.2 years, and 83% of the patients were male. Total resection was achieved in 5 patients and subtotal resection in 7. Four patients had undergone 2 or more resections. The 4 patients with high-grade tumors and 2 with incompletely resected low-grade tumors underwent adjuvant treatment (2 chemotherapy and 4 both radiotherapy and chemotherapy). The mean modified McCormick Scale score at the time of diagnosis was 1.7; at the time of follow-up, 1.5. The mean PedsQL 4.0 total score in the low-grade group was 78.5; in the high-grade group, 82.6. There was no significant difference in PedsQL 4.0 scores between the patient cohort and the normal population., Conclusions: In a small cohort of children who had undergone surgery for IMSCTs with a mean follow-up of 4.2 years, quality of life scores according to the PedsQL 4.0 instrument were not different from those in a normal sample population.

Gangliogliomas (GGs) are a small subset of intramedullary spinal cord tumors in children. The anaplastic variant (WHO grade III) appears to be an extreme rarity. A literature research revealed only 15 case reports of intramedullary anaplastic GGs (aGGs) and only 4 pediatric patients. The course of an 18-month-old boy with sudden onset of paraparesis is presented. Spinal MRI revealed a contrast-enhancing intramedullary tumor ranging from T6 to T12. The patient underwent a standard laminectomy/laminoplasty and gross total resection of the lesion. His neurological status remained unchanged postoperatively and he recovered very well during outpatient neurorehabilitation. Neuropathologic examination revealed an aGG of WHO grade III. Because of the high-grade histology, adjuvant radiotherapy and chemotherapy with temozolomide were administered. The patient subsequently recovered to a normal functional status. Clinical and radiographic progression-free survival is now 4 years. Based on an extensive literature review, this is only the fifth pediatric patient with a primary intramedullary aGG and the second with documented progression-free survival of over 4 years. Another 4 primary intramedullary aGGs in adults and 7 patients with spinal dissemination from a cerebral aGG or malignant transformation of a low-grade GG have been reported. In comparison to the published case reports, which often indicate significant neurological dysfunction and rather short survival, the neurological recovery in this patient was favorable, and the oncologic outcome even more so. This is an argument for the use of the aggressive treatment regimen of complete resection followed by radio- and chemotherapy applied here., (Copyright © 2012 S. Karger AG, Basel.)

Purpose: Intraoperative neurophysiological techniques are becoming routine tools for neurosurgical practice. Procedures affecting the lumbosacral nervous system are frequent in adult and pediatric neurosurgery. This review provides an overview of the techniques utilized in cauda and conus operations., Methods: Two basic methodologies of intraoperative neurophysiological testing are utilized during surgery in the lumbosacral spinal canal. Mapping techniques help identify functional neural structures, namely, nerve roots and their respective spinal levels. Monitoring is referred to as the technology to continuously assess the functional integrity of pathways and reflex circuits. For mapping direct electrical stimulation of a structure within the surgical field and recording at a distant site, usually a muscle is the most commonly used setup. Sensory nerve roots or spinal cord areas can be mapped by stimulation of a distant sensory nerve or skin area and recording from a structure within the surgical field. Continuous monitoring of the motor system is done with motor evoked potentials. These are evoked by transcranial electrical stimulation and recorded from lower extremity and sphincter muscles. Presence or absence of muscle responses are the monitored parameters. To monitor the sensory pathways, sensory potentials evoked by tibial, peroneal, or pudendal nerve stimulation and recorded from the dorsal columns with a spinal electrode or as cortical responses from scalp electrodes are used. Amplitudes and latencies of these responses are measured for interpretation. The bulbocavernosus reflex, with stimulation of the pudendal nerve and recording from the external anal sphincter, is used for continuous monitoring of the reflex circuitry. The presence of absence of this response is the pertinent parameter monitored. Stimulation of individual dorsal nerve roots is used to identify those segments that generate spastic activity and which may be cut during selective dorsal rhizotomy. Electromyographic activity can be continuously observed during surgery, and monitoring concepts developed in cranial nerve surgery may be used in the cauda equina as well., Conclusion: A range of intraoperative neurophysiological techniques are available for neurophysiological testing of the neural structures of conus medullaris and cauda equina.

Objective: Resections of intramedullary spinal cord tumors were attempted as early as 1890. More than a century after these primitive efforts, profound advancements in imaging, instrumentation, and operative techniques have greatly improved the modern surgeon's ability to treat such lesions successfully, often with curative results., Methods: We review the history of intramedullary spinal cord tumor surgery, as well as the evolution and advancement of technologies and surgical techniques that have defined the procedure over the past 100 years., Results: Surgery to remove intramedullary spinal cord tumors has evolved to include sophisticated imaging equipment to pinpoint tumor location, laser scalpel systems to provide precise incisions with minimal damage to surrounding tissue, and physiological monitoring to detect and prevent intraoperative motor deficits., Conclusion: Modern surgical devices and techniques have developed dramatically with the availability of new technologies. As a result, continual advancements have been achieved in intramedullary spinal cord tumor surgery, thus increasing the safety and effectiveness of tumor resection, and progressively improving the overall outcomes in patients undergoing such procedures.

Myxopapillary ependymomas, a specific tumor variant of spinal cord ependymomas, occur most commonly in the lumbosacral region. During the study period, 1,013 patients underwent surgery for spinal cord tumors. Fifty-two of the patients had a myxopapillary ependymoma. Forty-eight of these patients underwent surgery at our institutions. There were four patients who came for consultations only. Fourteen pediatric patients were diagnosed with myxopapillary ependymoma. The overall average age at which a patient was diagnosed was 31.8 years. The average age a child was diagnosed was 12.6 years. The adult mean age was 38.7 years. The clinical presentation was of a slow, indolent course, with average symptom duration of 20.8 months. Overall, the pediatric patients had a much more aggressive clinical course with a much higher rate of local recurrence and dissemination of the tumor within the neural axis (64% versus 32%). The median time to disease recurrence was 88 months for the entire group. The overall survival after 11.5 years of follow-up was 94%. The optimal management of patients harboring myxopapillary ependymomas remains somewhat controversial. Excellent outcomes may be obtained, however, with the use of aggressive surgical techniques. No clear benefit for adjunctive chemotherapy, and radiation therapy was demonstrated.

Objective: The optimal management of malignant intramedullary spinal cord astrocytomas remains controversial. Although radiotherapy has become the standard of care, the relationship between extent of resection and survival remains unclear. We report the outcomes of the surgical management of 35 malignant spinal cord astrocytomas and assess the association of extent of resection with survival after aggressive resection of these tumors., Methods: An institutional intramedullary spinal cord tumor database (1990-2002) was reviewed to identify all patients treated for malignant astrocytomas of the spinal cord (anaplastic astrocytoma [AA] or glioblastoma multiforme [GBM]). Length of survival from surgery was charted by Kaplan-Meier plots, and association of extent of resection with survival was assessed via log rank analysis for stratified covariates and Cox proportional-hazards model for continuous covariates., Results: Twenty-seven (77%) and eight (23%) patients underwent resection of AA and GBM, respectively. Mean age was 29 +/-16 years (range, 2-61 yr). Tumor involved six +/- four vertebral levels. For AA cases, radical resection (no residual postoperative magnetic resonance enhancement) was achieved in 12 (44%) patients and subtotal resection (residual postoperative magnetic resonance enhancement) was achieved in 15 (56%). No GBM patients underwent radical resection (mean estimated resection, 70%). After surgery, two (6%) patients improved neurologically by modified McCormick score, 19 (54%) remained stable, and 14 (40%) declined. Median overall survival for AA patients was 72 months (85% at 1 yr; 59% at 5 yr). Median overall survival for GBM patients was 9 months (31% at 1 yr; 0% at 5 yr). Subtotal versus radical resection of AA was associated with decreased overall survival (38 versus 78% at 4 yr, P = 0.028). Postoperative tumor dissemination was associated with decreased survival (P = 0.004). When adjusting for multiple comparisons (P < 0.006 needed for significance), a trend of increased survival was observed with radical resection (P = 0.023)., Conclusion: Neurological function can be preserved with aggressive resection of malignant intramedullary spinal astrocytomas; however, motor decline may be observed in many cases. Radical resection of AA was associated with a trend of increased overall survival in nondisseminated AA cases. Radical surgery and radiotherapy of GBM was associated with poor survival, similar to historical controls of diagnostic biopsy and radiotherapy. A markedly shorter survival may be expected in cases in which AA disseminates along the neuraxis. Biopsy alone may not provide the best outcomes for patients with malignant spinal cord tumors.

Object: Spinal cord tumors represent approximately 10-20% of primary central nervous system tumors. Only 20-30% of primary intradural tumors are intramedullary. The incidence of longitudinally extensive tumors involving the cervical, thoracic, and lumbar spine is very low (<1% of intramedullary lesions); hence, little literature exists on the management of this entity., Materials and Methods: We retrospectively reviewed all patients undergoing surgical resection of longitudinally extensive intramedullary spinal cord tumors involving the majority of the spinal cord between 1990 and 2002. Clinical, radiographic, operative, and outcome variables were retrospectively recorded and reported., Results: Thirteen patients (eight male, five female) were included in the study. Mean age was 15 years (range, 3-45) at the time of the initial resection. Gross total resection was achieved in eight cases and subtotal resection in five cases. Pathology revealed astrocytoma in six cases (two pilocytic, four grade II), gangliogliomas in four cases, oligodendroglioma in two cases (one anaplastic), and lipoma in one case. One (8%) patient died from progression of anaplastic oligodendroglioma, and two (15%) underwent reoperation for recurrent tumor (ganglioglioma, grade II astrocytoma). With a mean of 3.4 years (range, 1-12) after surgery, the modified McCormick score (MMS) had worsened in only two (15%) patients, improved in three (23%) patients, and remained stable in seven (54%) patients compared to preoperative MMS. Five (38%) patients required fusion for progressive spinal deformity., Conclusion: Gross total resection of holocord and longitudinally extensive intramedullary spinal cord tumors can be achieved with preservation of long-term neurological function in many cases. Serial imaging is recommended to guide subsequent resection for tumor recurrence and stabilization of progressive spinal deformity.

During resection of intramedullary spinal-cord tumors intraoperative neurophysiological monitoring has become a true surgical technology. Motor evoked potentials are the most important modality for this purpose. Its use requires neurophysiological expertise from the surgeon, and a monitoring team in place able to handle the necessary equipment. Motor potentials are evoked by transcranial electrical motor cortex stimulation. A "single stimulus technique" evokes D-waves recorded from the spinal cord. The "multipulse (or train) stimulation technique" evokes electromyographic responses in peripheral muscles. These are optimally recorded from the thenar, hypothenar, tibialis anterior, and flexor hallucis brevis muscles, which are known to have strong pyramidal innervation. D-wave monitoring looks primarily at the peak-to-peak amplitude. When monitoring muscle MEPs, the presence or absence of the response irrespective of stimulation intensity is the important parameter. Preparations for neurophysiological monitoring fit quite well into a neurosurgical operating room environment. Recording and interpretation of MEPs is fast and straightforward. Pre- and postoperative clinical motor findings correlate with intraoperative MEP results. Thus correct prediction of the clinical status at a given time during surgery is possible with a very high certainty. The sensitivity of muscle MEPs for postoperative motor deficits is nearly 100%, its specificity is about 90%. Thus MEP data indeed reflect the clinical "reality". Present and stable recordings document intact motor pathways and allow the surgeon to confidently proceed with a tumor resection. Loss of muscle MEPs and/or decrease of the D-wave amplitude constitutes a "window of warning". It reflects a pattern of MEP change indicating a reversible injury to the essential motor pathways. Using this information, the surgical strategy can be adapted before irreversible neurological damage is caused by the surgical manipulation. Such adaptation comprises simply waiting for the recordings to spontaneously improve again, irrigating with warm saline solution to wash out blocking potassium. Other measures include the elevation of mean arterial pressure to improve local perfusion. Even staged resection can be considered if intraoperative measures do not sufficiently improve the recordings.

Objective: To evaluate the efficacy of constant current transcranial electric stimulation (TES) parameters for eliciting muscle motor evoked potentials (MEPs) in the abductor pollicis brevis muscles (APB) and the tibialis anterior muscles (TA). The following parameters were tested intraoperatively: interstimulus interval (ISI), individual stimulation pulse duration within a train of five stimuli. Different montages of stimulating electrodes were assessed for effectiveness and focality. Further, reference values for APB and TA motor thresholds in neurosurgical patients with normal motor status under total intravenous anesthesia were determined., Methods: Motor thresholds of contralateral muscle MEPs were determined at 0.1, 0.2, 0.4, and 0.5 ms pulse duration and ISIs of 2, 3, 4, and 5 ms using a train of five monophasic constant current pulses with C3/C4 (27 patients). The stimulating electrodes were positioned at C1, C2, C3, C4, Cz, and Cz+6 cm. Different montages were used to determine the most effective and the most focal stimulation montages for the APB and TA muscles (30 patients). Eighty-six patients with clinically normal motor function were studied for motor threshold reference values., Results: The prolongation of the pulse duration has the strongest effect to decrease the motor threshold, which proportionally increases the delivered charge. The lowest stimulation threshold to elicit muscle MEPs in the APB and TA muscles is achieved with a train of stimuli consisting of an individual stimulus pulse duration of 0.5 ms. An ISI of 4 ms gave the lowest motor thresholds, but did not reach statistical significance compared to 3 ms. The stimulating electrode montage C3/C4 (C4/C3) allows for the lowest stimulation thresholds, but the vigorous muscle contractions it has is a disadvantage. The most focal stimulating electrode montages for the contralateral APB muscles are C3/Cz and C4/Cz, respectively, and for the TA muscles Cz/Cz+6 cm., Conclusions: In adult neurosurgical patients with a normal motor status under total intravenous anesthesia, an individual pulse duration of 0.5 ms and an ISI of 4 ms provide the lowest motor thresholds. Pragmatically, C1/C2, resp., C2/C1 montage provides monitorable responses in both APB and TA muscles at reasonable stimulation thresholds without inducing movements disturbing surgery and especially microdissection. If the most focal hemispheric stimulation for the distal upper extremity muscles is required, the use of C3 or C4 referenced to Cz is recommended., Significance: The stimulation parameters within a train of five pulses with an individual pulse duration of 0.5 ms and an ISI of 4 ms provide the lowest motor threshold. These data confirm not only studies for D wave recovery but also provide optimal stimulation parameters for intraoperative near threshold stimulation.

Object: Currently, the optimal treatment of children harboring myxopapillary ependymomas of the spinal cord remains somewhat debatable. The authors present a retrospective study in which they evaluated the records of patients in whom resection of these lesions had been performed., Methods: Fourteen pediatric patients who had undergone resection of a spinal cord tumor between September 1982 and July 2004 were identified from the database as having histologically classified myxopapillary ependymomas. There were 10 boys and four girls ranging in age from 7 to 18 years (mean age 12.6 years); 71% of the patients were boys. The clinical presentation of the tumor's course was slow and indolent, and the patients had a mean symptom duration of 19.6 months. Twelve patients, who underwent a total of 16 operations, were available for long-term follow-up review. Thirteen gross-total resections and three subtotal resections were performed. There were no deaths due to surgery. Postoperatively, patients initially remained at their preoperative level of function or improved. Patients who had undergone previous surgery and radiotherapy were treated more conservatively than patients who were undergoing surgery for the first time. Four children experienced significant complications following treatment., Conclusions: As the authors demonstrate in this study, excellent outcomes may be obtained with the use of aggressive surgical techniques with the goal being that of gross-total resection. Despite the best of resections, however, the risk of recurrence remains. Therefore, periodic neuroimaging surveillance of the neuraxis and close clinical follow up are warranted throughout the patient's life. The role for adjunctive chemo- and radiotherapy remains to be defined in the management of myxopapillary ependymomas.

The majority of intramedullary spinal cord tumors in children are low-grade glial tumors. They become symptomatic with pain, neurologic deficits or spinal deformity. The diagnosis is most readily obtained using magnetic resonance imaging. The natural history is significant for slow progression of symptoms. Surgery is the best treatment and is also indicated to confirm the histological diagnosis. In case of a low-grade tumor or a vascular lesion such as hemangioblastoma or cavernoma, a total or near-total resection is attempted. For astrocytomas the resection almost always remains biologically incomplete, but a near-total resection is still associated with a long progression-free survival. Neurologic morbidity is relatively low during long-term follow-up but can be up to 30% for transient motor deficits. The risk for neurologic deterioration is higher for patients with pronounced dysfunction preoperatively. This is an important argument for early surgical resection. Surgery is performed using the spectrum of microsurgical techniques as well as advanced technology, e.g. lasers and intraoperative neurophysiological monitoring with motor evoked potentials. High-grade tumors are resected conservatively and treated with radiation and chemotherapy. The prognosis of high-grade glial tumors remains poor.

Tethered cord syndrome (TCS) is a diverse clinical entity characterized by symptoms and signs which are caused by excessive tension on the spinal cord. The majority of cases are related to spinal dysraphism. TCS can present in any age group, and presentations differ according to the underlying pathologic condition and age, with pain, cutaneous signs, orthopedic deformities and neurological deficits being the most common. Surgical untethering is indicated in patients with progressive or new onset symptomatology attributable to TCS. The surgical strategy aims to release the tethering structure and thus the chronic tension on the cord. Early operative intervention is associated with improved outcomes. Pain relief is accomplished in almost all cases. Realistic surgical goals include relief of pain and stabilization of neurological function, although improvement in function is often seen. Cord untethering can also halt the progression of scoliosis. The benefits of surgery are debated in asymptomatic patients and patients with normal imaging.

Object: Intramedullary cavernous malformations (CMs) account for approximately 5% of all intraspinal lesions. The purpose of this study was to define the spectrum of presentation for spinal intramedullary CMs and the results of microsurgery for these benign but clinically progressive lesions., Methods: Retrospective chart review was performed in 26 patients with histologically diagnosed CMs. All patients had undergone preoperative magnetic resonance (MR) imaging studies. All patients were treated with a laminectomy and microsurgical resection of the malformation., Conclusions: The MR imaging findings are diagnostic for intramedullary CMs; these lesions abut a pial surface and have a characteristic imaging pattern. Spinal intramedullary CMs present with either an acute onset of neurological compromise or a slowly progressive neurological decline. Acute neurological decline occurs secondary to hemorrhage inside the spinal cord. Chronic progressive myelopathy occurs due to microhemorrhages and resulting gliotic reaction to blood products. Surgery and total removal of the lesion tends to halt progression of symptoms.

Our descriptive technical report on 7 children describes the microsurgical laser scalpel as an useful tool for removal of firm and soft lesions from a variety of delicate tissues. It combines precise atraumatic tissue dissection with immediate hemostasis while having no adverse side effects on adjacent and neighbouring tissues even through a limited surgical access.

The traditional treatment for all forms of hydrocephalus has been the implantation of ventricular shunt systems; however, these systems have inherent tendencies toward complications such as malfunction and infection. A significant advance in the treatment of hydrocephalus has been the evolution of endoscopy. The recent technological advances in this field have led to a renewed interest in endoscopic third ventriculostomy as the treatment of choice for obstructive hydrocephalus. Although several different endoscopes are available, the authors favor a rigid one to perform a blunt fenestration of the third ventricle floor. This description of the technique stresses the nuances for successful completion of this procedure.

Object: Intraoperative neurophysiological recording techniques have found increasing use in neurosurgical practice. The development of new recording techniques feasible while the patient receives a general anesthetic have improved their practical use in a similar way to the use of digital recording, documentation, and video technology. This review intends to provide an update on the techniques used and their validity., Methods: Two principal methods are used for intraoperative neurophysiological testing during tethered cord release. Mapping identifies functional neural structures, namely nerve roots, and monitoring provides continuous information on the functional integrity of motor and sensory pathways as well as reflex circuitry. Mapping is performed mostly by using direct electrical stimulation of a structure within the surgical field and recording at a distant site, usually a muscle. Sensory mapping can also be performed with peripheral stimulation and recording within the surgical site. Monitoring of the motor system is achieved with motor evoked potentials. These are evoked by transcranial electrical stimulation and recorded from limb muscles and the external anal sphincter. The presence or absence of muscle responses are the parameters monitored. Sensory potentials evoked by tibial or pudendal nerve stimulation and recorded from the dorsal columns via an epidurally inserted electrode and/or from the scalp as cortical responses are used to access the integrity of sensory pathways. Amplitudes and latencies of these responses are then interpreted. The bulbocavernosus reflex, with stimulation of the pudendal nerve and recording of muscle responses in the external anal sphincter, is used for continuous monitoring of the reflex circuitry. Presence or absence of this response is the pertinent parameter that is monitored., Conclusions: Intraoperative neurophysiology provides a wide and reliable set of techniques for intraoperative identification of neural structures and continuous monitoring of their functional integrity.

Chemical agents routinely used in neurosurgery to achieve intraoperative hemostasis can cause a foreign body reaction, which appears on magnetic resonance (MR) images to be indistinguishable from recurrent tumor. Clinical and/or imaging evidence of progression of disease early after surgical resection or during aggressive treatment may actually be distinct features of granuloma in these circumstances. A series of three cases was retrospectively analyzed for clinical, imaging, surgical, and pathological findings, and the consequences they held for further disease management. All patients were boys (3, 3, and 6 years of age, respectively) and all harbored primitive neuroectodermal tumors. Two tumors were located in the posterior fossa and one was located in the right parietal lobe. Two boys exhibited clinical symptoms, which were unexpected under the circumstances and prompted new imaging studies. One patient was asymptomatic and imaging was performed at planned routine time intervals. The MR images revealed circumscribed, streaky enhancement in the resection cavity that was suggestive of recurrent disease. This occurred 2 to 7 months after the first surgery. At repeated surgery, the resected material had the macroscopic appearance of gelatin sponge in one case and firm scar tissue in the other cases. Histological analysis revealed foreign body granulomas in the resected material, with Gelfoam or Surgicel as the underlying cause. No recurrent tumor was found and the second surgery resulted in imaging-confirmed complete resection in all three patients. Because recurrent disease was absent, the patients continued to participate in their original treatment protocols. All patients remain free from disease 34, 32, and 19 months after the first operation, respectively. During or after treatment for a central nervous system neoplasm, if unexpected clinical or imaging evidence of recurrence is found, a second-look operation may be necessary to determine the true nature of the findings. If the resection yields recurrent tumor, additional appropriate oncological treatment is warranted, but if a foreign body reaction is found, potentially harmful therapy can be withheld or postponed.

Object: The authors describe the results of performing a standard posterior craniovertebral decompression and placement, if indicated, of a syringosubarachnoid shunt for the treatment of patients with Chiari I malformation with and without syringomyelia., Methods: This is a retrospectively analyzed consecutive series of 66 patients (mean patient age 15 years, range 1-53 years). The uniform posterior craniovertebral decompression consisted of a small suboccipital craniectomy, a C-1 laminectomy, microsurgical reduction of the cerebellar tonsils, and dural closure with a synthetic dural graft to increase the cerebrospinal fluid space at the craniocervical junction. The presence of a large syrinx, with significant thinning of the spinal cord tissue and obliteration of the spinal subarachnoid space, particularly when combined with syrinx-related symptoms, was an indication for the placement of a syringosubarachnoid shunt. In 32 patients Chiari I malformation alone was present, and 34 in patients it was present in combination with syringomyelia. Clinical findings included pain, neurological deficits, and spinal deformity. The presence of syringomyelia was significantly associated with the presence of scoliosis (odds ratio 74.4 [95% confidence interval 8.894-622.4]). All patients underwent a posterior craniovertebral decompression procedure. In 22 of the 34 patients with syringomyelia a syringosubarachnoid shunt was also placed. The mean follow-up period was 24 months (range 3-95 months). Excellent outcome was achieved in 54 patients (82%) and good outcome in 12 (18%). In no patient were symptoms unchanged or worse at follow-up examination, including four patients who initially required a second operation for persistent syringomyelia. Pain was more likely to resolve than sensory and motor deficits after decompressive surgery. Radiological examination revealed normalization of tonsillar position in all patients. The syrinx had disappeared in 15 cases, was decreased in size in 17, and remained unchanged in two., Conclusions: Posterior craniovertebral decompression and selective placement of a syringosubarachnoid shunt in patients with Chiari I malformation and syringomyelia is an effective and safe treatment. Primary placement of a shunt in the presence of a sufficiently large syrinx appears to be beneficial. The question of if and when to place a shunt, however, requires further, preferably prospective, investigation.

Objective and Importance: Intraspinal clear cell meningioma is a rare morphological variant of meningioma. Only 13 case reports are found in the literature; therefore, no management strategy has been defined for this tumor type. This article describes two patients, reviews the literature, and proposes a treatment plan for clear cell meningioma., Clinical Presentation: Two female patients, 22 months and 8 years of age, respectively, presented with localized neck and leg pain that limited their ability to walk. Magnetic resonance imaging revealed intradural tumors, a cervical intramedullary neoplasm in the younger patient, and a cauda equina tumor in the older child., Intervention: Both patients underwent radical resection of their intradural tumor. Both tumors, however, recurred shortly (5 and 6 mo) after the initial operation. During the second operation, a radical removal was performed on each patient. Both patients received adjuvant radiotherapy. In addition, the younger patient developed posterior fossa metastasis 20 months after intraspinal surgery., Conclusion: Intraspinal clear cell meningiomas are very uncommon tumors. The clinical course in our two patients supports the reported 40% recurrence rate within 15 months. These tumors also can disseminate within the central nervous system. We recommend serial imaging studies every 3 months. For recurrent tumors, we recommend localized radiation therapy after reoperation.

Objective and Importance: Complications usually occur when they are least expected. We present an unusual case of nerve entrapment after microsurgical discectomy., Clinical Presentation: A patient undergoing uneventful first lumbar microsurgical discectomy developed severe back and leg pain and a progressive neurological deficit during the first postoperative night. Herniation of cauda equina nerve roots had occurred through an unnoticed minimal defect in the dura, which had not caused cerebrospinal fluid leakage. The roots were incarcerated and swollen, and they filled the space of the resected nucleus pulposus. It was presumed that elevation of intra-abdominal pressure and consequent increased intraspinal pressure during extubation led to the herniation of arachnoid and cauda equina roots. The nerve roots were then trapped and incarcerated in the manner of bowel loops in an abdominal wall hernia., Intervention: During reoperation, the nerve roots were repositioned into the dural sac. The patient recovered without further complications and without long-term sequelae., Conclusion: All dural tears that occur during intraspinal surgery, even if they are small and the arachnoid is intact, should be closed with stitches or at a minimum with a patch of muscle or gelatin sponge with fibrin glue. Care should be taken to avoid increased intra-abdominal pressure during extubation. Excessive pain and progressive neurological dysfunction occurring shortly after microsurgical lumbar discectomy or any intraspinal procedure is indicative of possible hemorrhage with subsequent compression of nerve roots. The case reported here provides anecdotal evidence that this situation can also be caused by a herniation of cauda equina nerve roots through a small dural defect that was not evident during the initial operation.

Resection of intramedullary spinal cord tumors carries a high risk for surgical damage to the motor pathways. This surgery is therefore optimal for testing the performance of intraoperative motor evoked potential (MEP) monitoring. This report attempts to provide evidence for the accurate representation of patients' pre- and postoperative motor status by combined epidural and muscle MEP monitoring during intramedullary surgery. The authors used transcranial electrical motor cortex stimulation to elicit MEPs, which were recorded from the spinal cord (with an epidural electrode) and from limb target muscles (thenar, anterior tibial) with needle electrodes. The amplitude of the epidural MEPs and the presence or absence of muscle MEPs were the parameters for MEP interpretation. A retrospective analysis was performed on data from the resection of 100 consecutive intramedullary tumors and MEP data were compared with the pre- and postoperative motor status. Intraoperative monitoring was feasible in all patients without severe preoperative motor deficits. Preoperatively paraplegic patients had no recordable MEPs. The sensitivity of muscle MEPs to detect postoperative motor deficits was 100% and its specificity was 91%. There was no instance in which a patient with stable MEPs developed a motor deficit postoperatively. Intraoperative MEPs adequately represented the motor status of patients undergoing surgery for intramedullary tumors. Because deterioration of the motor status was transient in all cases, it can be considered that impairment of the functional integrity of the motor pathways was detected before permanent deficits occurred.