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Michael M. Haglund, George A. Ojemann and Gary G. Blasdel

✓ In order to better understand the degree of cortical activation that occurs during bipolar surface stimulation, the authors stimulated monkey visual cortex while monitoring the degree of activation with optical imaging. Optical imaging of intrinsic signals in monkey visual cortex during visual stimulation resulted in functional maps of ocular dominance and orientation selectivity. After functional maps of ocular dominance and orientation preference were obtained, bipolar surface stimulation was applied to activate just the cortical areas around the bipolar electrodes. Graded responses to changes in the stimulation intensity and duration were found. These findings demonstrate the reliability of bipolar cortical surface stimulation in localizing functional regions of cortex. The area of activation, at least in the region around the bipolar stimulating electrodes, did not appear to activate nearby ocular dominance columns or orientation patches. Intraoperative bipolar surface stimulation continues to be a consistently reliable technique for localizing rolandic cortex and essential language sites.

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Mitchel S. Berger, Saadi Ghatan, Michael M. Haglund, Jill Dobbins and George A. Ojemann

✓ Adults and children with low-grade gliomas often present with medically refractory epilepsy. Currently, controversy exists regarding the need for intraoperative electrocorticography (ECoG) to identify and, separately, resect seizure foci versus tumor removal alone to yield maximum seizure control in this patient population. Forty-five patients with low-grade gliomas and intractable epilepsy were retrospectively analyzed with respect to preoperative seizure frequency and duration, number of antiepileptic drugs, intraoperative ECoG data (single versus multiple foci), histology of resected seizure foci, and postoperative control of seizures with or without antiepileptic drugs.

Multiple versus single seizure foci were more likely to be associated with a longer preoperative duration of epilepsy. Of the 45 patients studied, 24 were no longer taking antiepileptic drugs and were seizure-free (mean follow-up interval 54 months). Seventeen patients, who all had complete control of their seizures, remained on antiepileptic drugs at lower doses (mean follow-up interval 44 months); seven of these patients were seizure-free postoperatively, yet the referring physician was reluctant to taper the antiepileptic drugs. Four patients continued to have seizures while receiving antiepileptic drugs, although at a reduced frequency and severity. In this series 41% of the adults versus 85% of the children were seizure-free while no longer receiving antiepileptic drugs, with mean postoperative follow-up periods of 50 and 56 months, respectively. This difference was statistically significant (p = 0.016). Therefore, based on this experience and in comparison with numerous retrospective studies involving similar patients, ECoG is advocated, especially in children and in any patient with a long-standing seizure disorder, to maximize seizure control while minimizing or abolishing the need for postoperative antiepileptic drugs.

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Kim J. Burchiel, Hadley Clarke, Michael Haglund and John D. Loeser

✓ Forty patients were followed for an average period of 8½ years after 44 consecutive suboccipital craniotomies for trigeminal neuralgia. Among these patients, 36 had microvascular decompression (MVD) of the nerve, four had repeat trigeminal rhizotomy after MVD was not successful in controlling their pain, and four had primary trigeminal rhizotomies. Of the 36 patients undergoing MVD, 17 (47%) experienced recurrent postoperative neuralgic pain: in 11 (31%) pain recurrence was major, and in six (17%) it was minor. Among the eight patients undergoing rhizotomy, four (50%) had major pain recurrences and one (13%) had a minor recurrence, for a 63% total recurrence rate. There was a strong statistical relationship between an operative finding of arterial cross-compression of the nerve and long-term complete pain relief. Patients with other compressive pathology (related to veins or bone structures) did not on the average fare as well. Despite this, there appeared to be no point in time in the postoperative interval when the patient could be considered “cured.” Major recurrences averaged 3.5% annually, and minor recurrences averaged 1.5% annually. The implications of these findings for the treatment of trigeminal neuralgia and the current understanding of the mechanism of MVD for this disorder are discussed.

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Renee M. Reynolds, Elizabeth Boswell, Christine M. Hulette, Thomas J. Cummings, Michael M. Haglund, Elizabeth Boswell, Christine M. Hulette, Thomas J. Cumm ings and Michael M. Haglund

In this paper the authors describe the rare disorder of diffuse leptomeningeal oligodendrogliomatosis in a patient with an oligodendroglioma of the cauda equina who died suddenly. Reviewing this uncommon pathological entity is important so that it can be recognized and treated appropriately. This young, otherwise healthy woman with initial symptoms of low-back pain had a mass lesion of the cauda equina. During a workup, profound refractory intracranial hypertension suddenly developed despite aggressive surgical and medical intervention. Autopsy revealed a spinal cord oligodendroglioma with diffuse leptomeningeal oligodendrogliomatosis of the brain and spinal cord. Given the unforeseen outcome in this patient, this entity, although rare, should be considered in patients with similar presentations and addressed early to prevent similar outcomes. A review of the details of this case as well as the literature is presented below.

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Sandra Serafini, Sridharan Gururangan, Allan Friedman and Michael Haglund

✓A bilingual pediatric patient who underwent tumor resection was mapped extraoperatively using cortical stimulation to preserve English and Hebrew languages. The authors mapped both languages by using 4 tasks: 1) English visual naming, 2) Hebrew visual naming, 3) read English/respond Hebrew, and 4) Hebrew reading. Essential cortical sites for primary and secondary languages were compared, photographically recorded, and plotted onto a schematic brain of the patient. Three types of sites were found in this patient: 1) multiuse sites (multiple tasks, both languages) in frontal, temporal, and parietal areas; 2) single-task sites (1 task, both languages) in postcentral and parietal areas; and 3) single-use sites (1 task, 1 language) in frontal, temporal, and parietal areas. These results lend support to the concept that bilingual patients can have distinct cortical representations of each language and of different language tasks, in addition to overlapping or shared sites that support both languages and multiple tasks.

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Charles L. Branch Jr., Frederick Boop, Michael M. Haglund and Robert J. Dempsey

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John H. Sampson, Michael M. Haglund, Allan H. Friedman and Matthew G. Ewend

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Shervin Rahimpour, Michael M. Haglund, Allan H. Friedman and Hugues Duffau

Lesion-symptom correlations shaped the early understanding of cortical localization. The classic Broca-Wernicke model of cortical speech and language organization underwent a paradigm shift in large part due to advances in brain mapping techniques. This initially started by demonstrating that the cortex was excitable. Later, advancements in neuroanesthesia led to awake surgery for epilepsy focus and tumor resection, providing neurosurgeons with a means of studying cortical and subcortical pathways to understand neural architecture and obtain maximal resection while avoiding so-called critical structures. The aim of this historical review is to highlight the essential role of direct electrical stimulation and cortical-subcortical mapping and the advancements it has made to our understanding of speech and language cortical organization. Specifically, using cortical and subcortical mapping, neurosurgeons shifted from a localist view in which the brain is composed of rigid functional modules to one of dynamic and integrative large-scale networks consisting of interconnected cortical subregions.

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Guy M. McKhann II, Julie Schoenfeld-McNeill, Donald E. Born, Michael M. Haglund and George A. Ojemann

Object. Among the variety of surgical procedures that are performed for the treatment of medically refractory mesial temporal lobe epilepsy (TLE), no consensus exists as to how much of the hippocampus should be removed. Whether all patients require a maximal hippocampal resection has not yet been determined.

Methods. At the University of Washington, all TLE operations are performed in a tailored fashion, guided by electrocorticography (ECoG). The amount of hippocampal resection is determined intraoperatively by the extent of interictal epileptiform abnormalities on ECoG recorded from that structure, resulting in a hippocampal resection that is individualized for each patient. Using this approach, the authors prospectively observed 140 consecutive patients who underwent surgery for mesial TLE with pathological diagnoses of either mesial temporal sclerosis with neuronal loss (MTS group) or mild gliosis without neuronal loss (non-MTS group) to determine whether the extent of hippocampal resection correlates with outcome when a tailored approach is used. Additionally, the authors analyzed whether the presence of residual interictal epileptiform activity on ECoG following mesial temporal resection predicts poorer seizure control.

With at least 18 months of clinical follow up, 67% of the 140 patients were seizure free or had only a single postoperative seizure. There was no correlation between the size of the hippocampal resection and seizure control in the group as a whole or when stratified by pathological subtype. Using an intraoperatively tailored strategy, individuals with a larger hippocampal resection (> 2.5 cm) were not more likely to have seizure-free outcomes than patients with smaller resections (p = 0.9). Additionally, both MTS and non-MTS patients, in whom postoperative ECoG detected residual epileptiform hippocampal (but not cortical or parahippocampal) interictal activity following surgical resection, had significantly worse seizure outcomes (p = 0.01 in the MTS group; p = 0.002 in the non-MTS group).

Conclusions. Intraoperative hippocampal ECoG can predict how much hippocampus should be removed to maximize seizure-free outcome, allowing for sparing of possibly functionally important hippocampus.

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Michael M. Haglund, Mitchel S. Berger, Dennis D. Kunkel, JoAnn E. Franck, Saadi Ghatan and George A. Ojemann

✓ The role of specific neuronal populations in epileptic foci was studied by comparing epileptic and nonepileptic cortex removed from patients with low-grade gliomas. Epileptic and nearby (within 1 to 2 cm) nonepileptic temporal lobe neocortex was identified using electrocorticography. Cortical specimens taken from four patients identified as epileptic and nonepileptic were all void of tumor infiltration. Somatostatin- and γ-aminobutyric acid (GABAergic)-immunoreactive neurons were identified and counted. Although there was no significant difference in the overall cell count, the authors found a significant decrease in both somatostatin- and GABAergic-immunoreactive neurons (74% and 51 %, respectively) in the epileptic cortex compared to that in nonepileptic cortex from the same patient. It is suggested that these findings demonstrate changes in neuronal subpopulations that may account for the onset and propagation of epileptiform activity in patients with low-grade gliomas.