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Objective: The rostral ventrolateral medulla is thought to serve as a final common pathway for the integration of central cardiovascular information and to be important for the mediation of central pressor responses. An association between essential hypertension and neurovascular compression of the rostral ventrolateral medulla has been reported. This may be mediated by an increase in sympathetic tone., Clinical Presentation: Schwannomas arising from the lower cranial nerves (Cranial Nerves IX-XI) are rare, constituting only 3% of all intracranial schwannomas unassociated with neurofibromatosis. The majority of these tumors present as jugular foramen lesions and, less commonly, they occur along the extracranial course of these nerves. An intracisternal location is extremely rare. Fewer than 15 cases of pathologically proven intracisternal vagal schwannomas in the absence of neurofibromatosis have been reported., Intervention: We report a case of vagal schwannoma in the cerebellomedullary cistern causing distortion of the vagal root entry zone and presenting with refractory neurogenic hypertension. Total microsurgical excision of this tumor, arising from one of the rootlets of the vagus nerve, was achieved. Immediately postoperatively, blood pressure decreased markedly, and despite our effort to maintain the blood pressure with fluids, the patient developed a cerebral infarction in the watershed zone., Conclusion: We discuss the proposed mechanism of hypertension, and the perioperative management, stressing blood pressure control. A review of the literature regarding vagal schwannomas is also presented. To the best of our knowledge, this is the first case report of a cerebellomedullary cistern vagal schwannoma presenting with neurogenic hypertension.

Juhn Wada developed a test while in Montreal designed to definitively confirm hemispheric lateralization of speech in candidates for surgical treatment of epilepsy. By unilateral intra-carotid administration of a bolus of a general anesthetic, classically sodium amobarbital, function can be tested in the non-injected hemisphere, while the injected side is dysfunctional. The test has been expanded to test memory functions in the hemisphere (temporal lobe) contralateral to expected surgery (memory reserve) in the hope of contra-indicating surgery that may result in global amnestic syndromes (patient HM). Conversely, risk of material-specific memory loss following surgery can be assessed by testing memory in the hemisphere/temporal lobe to be operated ("functional adequacy"). Memory dysfunction, when concordant with EEG seizure onset and chosen side of temporal lobe surgery has also been shown to correlate with favourable post-operative seizure outcome. Nevertheless, the test remains invasive, requiring an angiogramme. Non-invasive alternatives such as fMRI and PET and their reported reliability compared to a Wada test are discussed. A world-wide shortage of amobarbital has led to the use of some other anesthetic agents. Overall, the indications for the test and the manner in which it is performed vary greatly from one institution to the next. It is used almost systematically in some institutions and very rarely in others. Future perspectives are discussed.

Neuropsychological testing is an integral part of investigation and management of pharmacologically intractable epilepsy. Patients often complain of cognitive difficulties, in particular memory disturbances. A review of the literature demonstrates that correlations between subjective memory difficulties and objective memory deficits are often poor with mood correlating more consistently with subjective complaints. Nevertheless, objective memory difficulties are often found, especially in patients with temporal lobe epilepsy. Many factors can contribute to cognitive difficulties in patients with pharmacoresistant partial epilepsy. These include brain pathology that may be the cause or the consequence of chronic seizures (or both), physiological brain dysfunction due to epileptic activity and effects of antiepileptic medications. We review some of the abundant relevant literature. Neuropsychological evaluation is routinely used in pre-surgical evaluations of patients and cognitive dysfunction has some degree of correlation with lateralization and localization of epileptic activity, thus helping to determine a surgical strategy. The goal of seizure control is tempered with an assessment of the potential cognitive loss resulting from resective surgery. A number of studies have addressed postoperative neuropsychological findings and it is universally recognized that patients who have high levels of cognitive functioning in the areas targeted for resection (for instance verbal memory in dominant temporal lobe) show the greatest functional loss following surgery. More selective surgery probably results in some level of preservation of cognitive function.

Objective and Importance: Only two cases of primary intracranial myxomas have been described previously in the literature: one patient had a primary intracranial myxoma in the pituitary fossa, and the other patient's myxoma was located in the posterior fossa., Clinical Presentation: A rare case of primary myxoma of the temporal bone in a 17-year-old boy is described. The patient presented with a history of progressive left-sided hearing loss and increasing headaches of a few months' duration., Intervention: An initial draining procedure in the left ear revealed extant mucous material, and further investigation showed a large calcified lesion involving the petrous and temporal bones and filling the middle fossa. At surgery, a large mucoid-appearing tumor was removed. The tumor pathology revealed a primary myxoma with bone and meningeal involvement. No clinical or histopathological evidence that it was a metastatic lesion was found., Conclusion: The features of myxomas on computed tomographic and magnetic resonance imaging, the histopathology, and surgical considerations are discussed.

Epidural hematomas remain at the pinnacle of neurosurgical emergencies, representing approximately 3% to 8% of all serious head injuries. Mortality from this entity is usually prevented once the diagnosis is clear. Although readily recognized on non-contrast head CT, the occasional patient may go on to develop a clinically significant hematoma after an initial negative CT. This phenomenon is appropriately termed delayed epidural hematoma. We present a case in which a 3-year-old boy developed a large epidural hematoma, which was not evident until the second CT, several hours after the injury. We feel that maintaining a high clinical suspicion, coupled with a low threshold for CT scanning, is the key to morbidity prevention in this illness.

Chronic motor cortex stimulation (CMCS) has provided satisfactory control of pain in patients with central or trigeminal neuropathic pain. We used this technique in 3 patients with intractable phantom limb pain after upper limb amputation. Functional magnetic resonance imaging (fMRI) correlated to anatomical MRI permitted frameless image guidance for electrode placement. Pain control was obtained for all the patients initially and the relief was stable in 2 of the 3 patients at 2 year follow-up. CMCS can be used to relieve phantom limb pain. fMRI data are useful in assisting the neurosurgeon in electrode placement for this indication., (Copyright 2002 S. Karger AG, Basel)

THE NATURE OF functional hemispherectomy continues to be misunderstood despite its 20-year history. Recently, we introduced the concept of peri-insular hemispherotomy, a functional hemispherectomy with minimal brain removal (9, 21). To avoid additional confusion, a detailed neuroanatomic account of this operation, which has been performed in 11 patients, is presented. The name of the operative variant presented derives from the central importance of the exposure of the insula as the first surgical landmark. Incising along the circular sulcus that surrounds the insula not only allows access to the dilated ventricular system but also disrupts the entire internal capsule. A parasagittal callosotomy is performed from within the lateral ventricle by incising the medial ventricular roof. Projections through the anterior commissure are disrupted at the time of radical amygdalar resection. The posterior hippocampus need not be radically removed, because its posterior transsection disconnects it. Overall, peri-insular hemispherotomy can be viewed as a radical hemispheric tractotomy, resulting in a completely disconnected hemisphere. Advantages include shorter operative times, a less stormy postoperative course, and better anatomic preservation of the operated hemisphere, thus presumably reducing long-term complications.

There has been a recent surge of interest in chronic animal models of epilepsy. Proper assessment of these models requires documentation of spontaneous seizures by EEG, observation, or both in each individual animal to confirm the presumed epileptic condition. We used the same automatic seizure detection system as that currently used for patients in our institution and many others. Electrodes were implanted in 43 rats before intraamygdalar administration of kainic acid (KA). Animals were monitored intermittently for 3 months. Nine of the rats were protected by anticonvulsants [pentobarbital (PB) and diazepam (DZP)] at the time of KA injection. Between 1 and 3 months after KA injection, spontaneous seizures were detected in 20 of the 34 unprotected animals (59%). Surprisingly, spontaneous seizures were also detected during the same period in 2 of the 9 protected animals that were intended to serve as nonepileptic controls. Although the absence of confirmed spontaneous seizures in the remaining animals cannot exclude their occurrence, it indicates that, if present, they are at least rare. On the other hand, definitive proof of epilepsy is invaluable in the attempt to interpret pathologic data from experimental brains.

In order to evaluate the safety of the new synthetic opioids, alfentanil and sufentanil, in neurosurgical patients, we administered sufentanil 1 microg/kg i.v., alfentanil 50 microg/kg i.v. followed by an infusion of 1 microg/kg/min, or fentanyl 5 microg/kg i.v. to 30 patients with supratentorial tumors anesthetized with nitrous oxide (N2O), 60% in O2. Lumbar cerebrospinal fluid pressure (CSFP) and mean arterial pressure (MAP) responses were recorded for 10 min thereafter, while ventilation was held constant [mean PaCO2 = 36.1 +/- 1.0 mm Hg (SEM)]. There was no change in CSFP after fentanyl. In contrast, both sufentanil and alfentanil caused increases in CSFP, equal to 89 +/- 31 % SE (p < 0.05) and 22 +/- 5% (p < 0.05), respectively. MAP decreased after administration of each opioid. Peak decreases in cerebral perfusion pressure (MAP - CSFP) were 14 +/- 3% after fentanyl, 25 +/- 5% after sufentanil, and 37 +/- 3% after alfentanil. It is concluded that because sufentanil increased CSFP in patients who have brain tumors, it also may be contraindicated in other neurosurgical patients at risk for intracranial hypertension. Alfentanil may share this propensity, since CSFP increased despite a profound reduction in MAP. Among the three opioids evaluated, only fentanyl appears to be appropriate for supplementing N2O-2 anesthesia in patients who have compromised intracranial compliance.