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Adult intramedullary spinal cord ependymomas: the result of surgery in 38 patients

Fred J. Epstein, Jean-Pierre Farmer, and Diana Freed

✓ Thirty-eight patients underwent surgery for an intramedullary spinal cord ependymoma. In 37 patients, postoperative magnetic resonance imaging confirmed that the tumor was totally removed. The morbidity of surgery was directly related to the preoperative neurological condition. Patients who were normal or nearly normal preoperatively were rarely worse after surgery, and those who had significant disability preoperatively were at greatest risk of being more impaired after surgery. There has been no tumor recurrence in any patient after a mean follow-up period of 24 months, and radiation therapy has not been employed as a surgical adjunct.

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Brain-stem glioma growth patterns

Fred J. Epstein and Jean-Pierre Farmer

✓ During the last decade, several authors have reported that certain brain-stem gliomas may be associated with a better prognosis than others. In this paper, retrospective correlations between the pathological findings and the magnetic resonance (MR) imaging appearance of 88 brain-stem gliomas are established. The authors propose an anatomical hypothesis that helps identify glioma growth patterns in general and that clarifies why cervicomedullary, dorsally exophytic, and focal tumors have a more favorable prognosis. According to this hypothesis, growth of benign gliomas of the brain stem is guided by secondary structures such as the pia, fiber tracts, and the ependyma, which in turn leads to stereotypical growth patterns that are clearly identified on MR images. The authors believe that this hypothesis, in conjunction with clinical data, may help establish selection criteria for the surgical treatment of specific brain-stem lesions.

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Reliability of intraoperative electrophysiological monitoring in selective posterior rhizotomy

Sandeep Mittal, Jean-Pierre Farmer, Chantal Poulin, and Kenneth Silver

Object. Selective posterior rhizotomy is a well-established treatment for spasticity associated with cerebral palsy. At most medical centers, responses of dorsal rootlets to electrical stimulation are used to determine ablation sites; however, there has been some controversy regarding the reliability of intraoperative stimulation. The authors analyzed data obtained from the McGill Rhizotomy Database to determine whether motor responses to dorsal root stimulation were reproducible.

Methods. A series of 77 patients underwent selective dorsal rhizotomy at a single medical center. The dorsal roots from L-2 to S-2 were stimulated to determine the threshold amplitude. The roots were then stimulated at 2 to 4 times the highest threshold with a 1-second 50-Hz train. A second stimulation run of the entire dorsal root was performed before it was divided into rootlets. Rootlets were individually stimulated and sectioned according to the extent of abnormal electrophysiological propagation. Motor responses were recorded by electromyography and were also assessed by a physiotherapist, and grades of 0 to 4+ were assigned. The difference in grades between the first and second stimulation trains was determined for 752 roots.

Statistical analysis demonstrated a clear consistency in motor responses between the two stimulation runs, both in the electromyographic readings and the physiotherapist's assessment. More than 93% of dorsal roots had either no change or a difference of only one grade between the two trials. Furthermore, the vast majority of dorsal roots assigned a grade of 4+ at the first trial maintained the same maximally abnormal electrophysiological response during the second stimulation run.

Conclusions. This study indicates that currently used techniques are reproducible and reliable for selection of abnormal rootlets. Intraoperative electrophysiological stimulation can be valuable in achieving a balance between elimination of spasticity and preservation of underlying strength.

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Negative-pressure hydrocephalus

Michael Vassilyadi, Jean-Pierre Farmer, and José L. Montes

✓ Two cases of children with closed myelodysplasia, Arnold-Chiari malformation, and shunted hydrocephalus who underwent spinal arachnoid cystopleural shunting are presented. Postoperatively, both patients developed craniovertebral symptomatology accompanied by radiologically documented ventricular dilation in spite of negative intracranial pressure and functional ventriculoperitoneal (VP) shunts. Both patients recovered after the cystopleural shunts were revised to increase the resistance to flow within the system. The authors believe that some communication between the arachnoid cyst and the subarachnoid space existed in both cases and that the negative pleural pressure was transmitted preferentially to the spinal and cerebral convexity subarachnoid spaces with relative sparing of the ventricular system. A transmantle pressure gradient was thereby established, leading to ventricular dilation. The authors further suggest that a craniospinal gradient was possibly established as well, leading to craniovertebral symptomatology in the patients. Return of flow in the VP shunts was obtained by correcting this iatrogenic transmantle pressure gradient.

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Adult intramedullary astrocytomas of the spinal cord

Fred J. Epstein, Jean-Pierre Farmer, and Diana Freed

✓ In this series, 25 adult patients with intramedullary astrocytomas were treated by radical excision alone. Six patients proved to have anaplastic astrocytoma; five of them died within approximately 2 years and the sixth has demonstrated disease progression. The other 19 patients were diagnosed as having low-grade astrocytoma (16 cases) or ganglioglioma (three cases); two of these had advanced preoperative neurological disability and died of medical complications. Fifteen of the remaining 17 patients have no clinical evidence of tumor recurrence after a mean follow-up period of 50.2 months; the other two have a small residual neoplasm that demonstrates no progression. Of these 17 patients, seven had previously received radiation therapy, but had clear evidence of tumor growth subsequently.

This experience suggests that surgery is not beneficial for anaplastic spinal astrocytoma. However, in cases of low-grade tumor, radical excision is associated with minimal morbidity and an excellent long-term prognosis when carried out before significant disability occurs.

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Comparison of syringopleural and syringosubarachnoid shunting in the treatment of syringomyelia in children

Olivier Vernet, Jean-Pierre Farmer, and José L. Montes

✓ Case records from the Montreal Children's Hospital containing the diagnosis of shunted syringomyelia were retrospectively reviewed. From 1984 to 1994, 31 patients had their syrinx treated by either syringopleural (19 cases, Group A) or syringosubarachnoid (13 cases, Group B) shunting. One patient was included in both groups.

Associated diagnoses included: in Group A, two cases of Chiari I and 14 of Chiari II malformations, 14 cases of shunted hydrocephalus, 13 cases of spina bifida aperta, and three cases of spina bifida occulta; Group B, four cases of Chiari I and two of Chiari II malformations, four cases of shunted hydrocephalus, two cases of spina bifida aperta, and five cases of spina bifida occulta. Eight Group A and six Group B patients had undergone prior posterior fossa decompression. Motor deficits predominated in both groups and arachnoiditis was a uniform operative finding.

Neurological follow-up examinations showed 11 Group A patients improved and eight stabilized, whereas on magnetic resonance imaging, 12 cavities appeared to have collapsed, five were markedly reduced, and one had increased. One patient underwent reoperation for pleural effusions and one for shunt displacement. In Group B, one patient improved, eight stabilized, three worsened neurologically, and one was lost to follow-up review. Radiologically, one cavity appeared to have collapsed, six were significantly reduced, two were unchanged, and three had enlarged.

The authors conclude that syringopleural shunting is a valuable option for controlling syringomyelia in patients without Chiari malformation or in patients who have previously undergone a craniovertebral decompression or are otherwise asymptomatic from their Chiari malformation.

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Intraoperative ultrasonography: an important surgical adjunct for intramedullary tumors

Fred J. Epstein, Jean-Pierre Farmer, and Steven J. Schneider

✓ The echographic characteristics of 186 suspected intramedullary spinal cord tumors were reviewed. Ultrasonography was found to be specific in distinguishing the tumor type, the extent of the lesion, and the presence and type of associated cysts. Ultrasonography greatly facilitates the selection of respective sites for the placement of a myelotomy, and for initiation of the resection. Additionally, this indispensable adjunct provides ongoing images that allow the preoperative plan to be precisely followed in a surgical field where anatomical landmarks are limited and the margin for error is minimal.

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Stereotactic transtentorial hiatus ventriculoperitoneal shunting for the sequestered fourth ventricle

Technical note

José L. Montes, David B. Clarke, and Jean-Pierre Farmer

✓ The authors describe a technique of stereotactic transtentorial hiatus ventriculoperitoneal shunting for the treatment of the sequestered fourth ventricle, used successfully in the care of four patients. They recommend it as a safe, effective treatment of patients suffering from an isolated fourth ventricle.

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Omental Transplantation for Epilepsy

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Intractable epilepsy after a functional hemispherectomy: important lessons from an unusual case

Case report

Sandeep Mittal, Jean-Pierre Farmer, Bernard Rosenblatt, Frederick Andermann, José L. Montes, and Jean-Guy Villemure

✓ Residual seizures after functional hemispherectomy occur in approximately 20% of patients with catastrophic epilepsy. These episodes are traditionally attributed to incomplete disconnection, persistent epileptogenic activity in the ipsilateral insular cortex, or bilateral independent epileptogenic activity. The authors report on the case of an 8-year-old boy with an intractable seizure disorder who had classic frontal adversive seizures related to extensive unilateral left hemispheric cortical dysplasia. The initial intervention consisted of extensive removal of the epileptic frontal and precentral dysplastic tissue and multiple subpial transections of the dysplastic motor strip, guided by intraoperative electrocorticography. Subsequently, functional hemispherectomy including insular cortex resection was performed for persistent attacks. After a seizure-free period of 6 months, a new pattern ensued, consisting of an aura of fear, dystonic posturing of the right arm, and unusual postictal hyperphagia coupled with an interictal diencephalic-like syndrome. Electroencephalography and ictal/interictal single-photon emission computerized tomography were used to localize the residual epileptic discharges to deep ipsilateral structures. Results of magnetic resonance imaging indicated a complete disconnection except for a strip of residual frontobasal tissue. Therefore, a volumetric resection of the epileptogenic frontal basal tissue up to the anterior commissure was completed. The child has remained free of seizures during 21 months of follow-up review.

Standard hemispherectomy methods provide extensive disconnection, despite the presence of residual frontal basal cortex. However, rarely, and especially if it is dysplastic, this tissue can represent a focus for refractory seizures. This is an important consideration in determining the source of ongoing seizures posthemispherectomy in patients with extensive cortical dysplasia. It remains important to assess them fully before considering their disease refractory to surgical treatment.