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  • Author or Editor: Christopher Michael x
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Alan Diamond, Christopher Kenney, Michael Almaguer and Joseph Jankovic

✓The authors present a unique case of hyperhidrosis as a side effect of a misplaced deep brain stimulation (DBS) electrode near the ventrointermedius (Vim) nucleus in a patient with essential tremor. Magnetic resonance imaging of the brain showed electrode placement in the left anterior thalamus traversing the hypothalamus. High-frequency electrical stimulation possibly resulted in unilateral activation of the efferent sympathetic pathways in the zona incerta. Although a rare complication, hypothalamic dysfunction may occur as a stimulation-related side effect of Vim-DBS.

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Michael G. Muhonen, Scott C. Robertson, Jeffrey S. Gerdes and Christopher M. Loftus

✓ Serotonin (5-HT) produces constriction of peripheral collateral blood vessels. Using an animal model, the authors tested the hypothesis that 5-HT constricts collateral vessels in the cerebrum. A branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally in anesthetized dogs. Blood flow to the area at risk for infarction was detected by perfusing the cannulated MCA branch with microsphere-free blood during systemic injection of radioactive microspheres (shadow flow technique). Blood flow to collateral-dependent and normal cerebrum was measured during intravenous infusion of 5-HT (10 and 40 mg/kg/minute). Serotonin produced a dose-related reduction of blood flow to collateral-dependent cerebrum, increased collateral vessel resistance in large cerebral arteries and collateral vessels, and decreased cerebral artery perfusion pressure. In contrast, blood flow to normal cerebrum was not altered because a decrease in small vessel resistance effectively compensated for a decrease in MCA perfusion pressure. These findings indicate that 5-HT produces constriction of collateral vessels in the cerebrum. This response is clearly different from normal small cerebral vessels, which dilate during 5-HT infusion.

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Rudolf Fahlbusch, Oliver Ganslandt, Michael Buchfelder, Werner Schott and Christopher Nimsky

Object. The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non—hormone-secreting intra- and suprasellar pituitary macroadenomas.

Methods. Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery.

Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%).

Conclusions. Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.

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Arjun S. Chandran, Michael Bynevelt and Christopher R. P. Lind

The subthalamic nucleus (STN) is one of the most important stereotactic targets in neurosurgery, and its accurate imaging is crucial. With improving MRI sequences there is impetus for direct targeting of the STN. High-quality, distortion-free images are paramount. Image reconstruction techniques appear to show the greatest promise in balancing the issue of geometrical distortion and STN edge detection. Existing spin echo- and susceptibility-based MRI sequences are compared with new image reconstruction methods. Quantitative susceptibility mapping is the most promising technique for stereotactic imaging of the STN.

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Christopher B. Michael, Andrew G. Lee, James R. Patrinely, Samuel Stal and J. Bob Blacklock

✓ The authors present a case of visual loss associated with fibrous dysplasia of the anterior skull base and the surgical management of this case. Preoperative computerized tomography scanning in this patient demonstrated a patent optic foramen and a rapidly growing cystic mass within the orbit, which was responsible for the patient's visual loss. A literature review revealed that this case is typical, in that cystic mass lesions of various types are frequently responsible for visual loss associated with fibrous dysplasia. The authors did not find significant evidence in the literature to support the notion that visual loss associated with fibrous dysplasia is the result of progressive optic canal stenosis, thus raising questions about the value of prophylactic optic canal decompression. Instead, as demonstrated by this case and those uncovered in the literature review, most instances of visual loss result from the rapid growth of mass lesions of cystic fibrous dysplasia, mucoceles, or hemorrhage. Findings of the literature review and the present case of fibrous dysplasia of the anterior skull base support a role for extensive surgical resection in these cases and indicate a need for additional prospective analysis of a larger number of patients with this disease.

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Christopher B. T. Adams, Michael R. Fearnside and Sean A. O'Laoire

✓ Serial postoperative angiograms were performed in 28 patients with intracranial aneurysms, 26 of whom had presented with a subarachnoid hemorrhage. The clinical state and intracranial pressure (ICP) were also measured. Angiograms were performed in the ward using a cannula, which was passed into the proximal external carotid artery via the superficial temporal artery. Measurements of the vessel diameters were made, with the preoperative angiogram as a baseline. Patients could be placed into one of five groups depending on the presence or absence of significant arterial spasm, the clinical state of the patient, and the normality or otherwise of the ICP. No patient's condition deteriorated without an elevated ICP and/or significant arterial spasm. The study shows that this spasm is usually associated with a poor clinical state if it reaches a maximum 8 to 12 hours after the operation, although the clinical deterioration is not apparent for a further 6 to 12 hours. Knowledge of the natural history of postoperative arterial spasm may allow earlier treatment of the spasm, which may be more successful than delaying treatment until clinical deterioration has occurred. The worth of the varied drugs proposed for the treatment of spasm may be assessed using this type of protocol.

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Ravikant S. Palur, Caglar Berk, Michael Schulzer and Christopher R. Honey

Object. There is an active debate regarding whether pallidotomy should be performed using macroelectrode stimulation or the more sophisticated and expensive method of microelectrode recording. No prospective, randomized trial results have answered this question, although personnel at many centers claim one method is superior. In their metaanalysis the authors reviewed published reports of both methods to determine if there is a significant difference in clinical outcomes or complication rates associated with these methods.

Methods. A metaanalysis was performed with data from reports on the use of unilateral pallidotomy in patients with Parkinson disease (PD) that were published between 1992 and 2000. A Medline search was conducted for the key word “pallidotomy” and additional studies were added following a review of the references. Only those studies dealing with unilateral procedures performed in patients with PD were included. Papers were excluded if they described a cohort smaller than 10 patients or a follow-up period shorter than 3 months or included cases that previously had been reported. The primary end points for outcome were the percentages of improvement in dyskinesias and in motor scores determined by the Unified PD Rating Scale (UPDRS). Complications were categorized as mortality, intracranial hemorrhage, visual deficit, speech deficit, cognitive decline, weakness, and other.

There were no significant differences between the two methods with respect to improvements in dyskinesias (p = 0.66) or UPDRS motor scores (p = 0.62). Microelectrode recording was associated with a significantly higher (p = 0.012) intracranial hemorrhage rate (1.3 ± 0.4%), compared with macroelectrode stimulation (0.25 ± 0.2%).

Conclusions. In reports of patients with PD who underwent unilateral pallidotomy, operations that included microelectrode recording were associated with a small, but significantly higher rate of symptomatic intracranial hemorrhage; however, there was no difference in postoperative reduction of dyskinesia or bradykinesia compared with operations that included macroelectrode stimulation.

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Christopher B. Shields and Michael West

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Aaron A. Cohen-Gadol, Christopher C. Bradley, Anne Williamson, Jung H. Kim, Michael Westerveld, Robert B. Duckrow and Dennis D. Spencer

Object. The syndrome of medial temporal lobe epilepsy (MTLE) may occur in patients in whom magnetic resonance (MR) images demonstrate normal findings. In these patients, there is no evidence of hippocampal sclerosis on neuroimaging, and histopathological examination of the resected hippocampus does not reveal significant neuron loss. In this paper the authors describe the distinct clinical features of this MTLE subtype, referred to as paradoxical temporal lobe epilepsy (PTLE).

Methods. The authors selected 12 consecutive patients with preoperative findings consistent with MTLE in whom MR imaging did not demonstrate any hippocampal abnormality. Onset of hippocampal seizure was confirmed by long-term intracranial monitoring. There were six female and six male patients with a mean age of 32 ± 11 years (mean ± standard deviation [SD]) at presentation. These patients' seizure histories, available hippocampal volumetric measurements, and hippocampal cell densities in different subfields were reviewed. Sharp electrode recordings from dentate granule cells that had been maintained in hippocampal slices provided a measure of excitation and inhibition in the tissue. We compared these data with those of a cohort of 50 randomly selected patients who underwent anteromedial temporal resection for medial temporal sclerosis (MTS) during the same time period (1987–1999). The durations of follow up (means ± SDs) for the PTLE and MTS groups were 51 ± 59 months and 88 ± 44 months, respectively.

A history of febrile seizure was present less frequently in the PTLE group (8%) than in the MTS group (34%). Other risk factors for epilepsy such as trauma, meningoencephalitis, or perinatal injuries were present more frequently in the PTLE group (50%) than in the MTS cohort (36%). In patients in the PTLE group the first seizure occurred later in life (mean age at seizure onset 14 years in the PTLE group compared with 9 years in the MTS group, p = 0.09). Ten patients (83%) in the PTLE cohort and 23 patients (46%) in the MTLE cohort had secondary generalization of their seizures. Among patients with PTLE, volumetric measurements (five patients) and randomized blinded visual inspection (seven patients) of the bilateral hippocampi revealed no atrophy and no increased T2 signal change on preoperative MR images. All patients with PTLE underwent anteromedial temporal resection (amygdalohippocampectomy, in five patients on the left side and in seven on the right side). Electrophysiological studies of hippocampal slices demonstrated that dentate granule cells from patients with PTLE were significantly less excitable than those from patients with MTS. The mean pyramidal cell loss in the CA1 subfield in patients in the PTLE group was 20% (range 0–59%) and that in patients in the MTS group was 75% (range 41–90%) (p < 0.001). Maximal neuron loss (mean loss 38%) occurred in the CA4 region in six patients with PTLE (end folium sclerosis). At the last follow-up examination, six patients (50%) in the PTLE group were seizure free compared with 38 patients (76%) in the MTS group.

Conclusions. Clinical PTLE is a distinct syndrome with clinical features and surgical outcomes different from those of MTS.