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Dennis D. Spencer

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Theodore H. Schwartz and Dennis D. Spencer

Object. Prior reports of seizure control following reoperation for failed epilepsy surgery have shown good results. These studies included patients who presented during the era preceding magnetic resonance (MR) imaging, and the patients were often not monitored intracranially or underwent subtotal hippocampal resections. In this study, the authors hypothesized that reoperation for recurrent seizures following a more comprehensive initial workup and surgery would not yield such good results.

Methods. The authors examined a consecutive series of patients who underwent two operations at Yale—New Haven Hospital for medically intractable epilepsy and in whom there was a minimum of 1-year follow up after the second surgery. All patients were evaluated and treated according to a standard protocol, including preoperative MR imaging, a low threshold for invasive monitoring, and a radical amygdalohippocampectomy when indicated.

Twenty-seven patients were identified (five with mesial temporal sclerosis, 20 with neocortical disease, and two with multifocal sites of seizure onset) of whom six (22%) underwent intentionally palliative second surgery (corpus callostomy or placement of a vagus nerve stimulator [VNS]). Of the remaining 21 patients, only four (19%) became seizure free after a second resective operation. The most common causes of treatment failure were dual pathology, recurrent tumor, limited resection to preserve function, widespread developmental abnormalities, and electrographic sampling error. Successful outcomes resulted from removal of recurrent tumors, completion of a functional hemispherectomy, or repeated invasive monitoring to correct a sampling error. Five (83%) of the six intentionally palliative second operations resulted in more than a 50% decrease in seizure frequency.

Conclusions. If an aggressive preoperative evaluation and surgical resection are performed, reoperation for recurrent seizures has a much lower likelihood of cure than previously reported. Intentionally palliative surgery such as placement of a VNS unit may be considered for patients in whom the initial operation fails to decrease seizure frequency.

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Itzhak Fried, Dennis D. Spencer, and Susan S. Spencer

✓ An aura is generally understood to be the beginning of a seizure. Yet, following successful surgery for intractable epilepsy, patients may have persistent auras even though they are otherwise seizure free. Ninety patients with intractable seizures and auras underwent resective surgery. Forty-three patients had hippocampal sclerosis and 47 had temporal or extratemporal lesions such as glial tumors or vascular malformations. The semiology of the auras was found to have value in localization but not lateralization of the pathology. Epigastric auras as well as gustatory and olfactory auras were significantly more frequent in patients with hippocampal sclerosis than in those with temporal or extratemporal lesions. Auras of vertigo or dizziness were most frequent in patients with extratemporal pathology.

There was a significant difference between the pathology groups in the efficacy of resection in eliminating the auras. Of the patients with hippocampal sclerosis who were rendered seizure free, 18.9% had persistent auras, whereas only one (2.6%) of the patients with temporal or extratemporal lesions who were rendered seizure free had persistent auras. These findings suggest that for patients with hippocampal sclerosis an anatomical dissociation between seizure and aura may occur, whereas this dissociation is not present in patients with lesions. Patients suspected of having hippocampal sclerosis should be counseled preoperatively as to the significant likelihood of persistent auras even if seizures are successfully abolished.

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Kimberlee J. Sass, Robert A. Novelly, Dennis D. Spencer, and Susan S. Spencer

✓ Language impairments were reviewed retrospectively in patients who underwent partial or total corpus callosum section for medically refractory secondary generalized epilepsy. Postoperatively, four of 32 patients had clinically significant language impairments that were not present prior to the operation. All involved primarily verbal output (speech and writing) and spared verbal comprehension. Written language skills (reading and spelling), verbal memory, and verbal reasoning abilities were impaired to varying degrees. These impairments were associated with crossed cerebral dominance. Three patients with severe speech difficulties after surgery were right hemisphere-dominant for speech and were right-handed. One left hemisphere speech-dominant, left-handed patient was agraphic after surgery, but spoke normally.

It is concluded from these data and from other reports in the literature that three syndromes of language disturbance may follow callosotomy. The first, involving speech difficulty but sparing writing, is attributable to buccofacial apraxia. The second involves speech and writing difficulties and occurs in right hemisphere-dominant right-handed patients. The third involves dysgraphia with intact speech and occurs in left hemisphere-dominant left-handed patients.

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Itzhak Fried, Jung H. Kim, and Dennis D. Spencer

✓ The authors examined hippocampal tissue removed during surgical procedures in 17 patients with intractable epilepsy who were found by preoperative magnetic resonance imaging or computerized tomography to have intra-axial masses in the temporal lobe. Neuronal densities in the cornu ammonis (CA) fields of the hippocampus and in the dentate granule cell layer were measured in hematoxylin and eosin-stained sections and were found to be lower compared to a group of 18 autopsy controls. The neuronal densities in all hippocampal fields except CA2 were related to the patient's age at seizure onset. Patients with an earlier onset of seizures had lower neuronal densities. With the exception of CA4, neuronal densities were not significantly related to the duration of the seizure disorder. Cell counts in all fields except CA2 were also related to the location of the lesion in the temporal lobe. Patients with mesial temporal lesions had lower neuronal counts. These results suggest increased vulnerability of hippocampal cytoarchitecture to proximal lesions with early ictal manifestation.

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Albert E. Telfeian, Dennis D. Spencer, and Anne Williamson

Object. The purpose of this study was to determine whether intrinsic neuronal properties and synaptic responses differed between interictally active and inactive tissue removed in neocortical resections from patients undergoing surgical treatment for epilepsy.

Methods. Whole-cell patch recordings were performed in layer 2 or 3 and layer 5 pyramidal cells in neocortical slices obtained from tissue surgically removed from patients for the treatment of medically intractable seizures. Synaptic responses to stimulation at the layer 6—white matter border were used to classify cells as nonbursting if they responded with only a single action potential for all above-threshold stimuli (80%). These responses were usually followed by biphasic inhibitory postsynaptic potentials (IPSPs). Cells were classified as bursting if they fired at least three action potentials in response to synaptic stimulation (20%). These cells typically showed no IPSPs and responded in either an all-or-nothing or graded fashion. Approximately twice as many cells at layer 2 or 3 (29%) than cells at layer 5 (14%) fired synaptic bursts. Synaptic bursting was not associated with an alteration in a cell's response properties to γ-aminobutyric acid. It was notable that, in tissue samples determined by electrocorticography (ECoG) to be either interictally active or not active, the proportion of cells that burst was exactly the same in both groups (24%). We found no cells with intrinsic burst firing.

Conclusions. We conclude that synaptic bursting was characteristic of a small proportion of cells from epileptic tissue; however, this did not correlate with interictal spikes on ECoG.

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Aaron A. Cohen-Gadol, Michael L. DiLuna, and Dennis D. Spencer

✓ The authors describe a patient who experienced stereotypical episodes of dyspnea and presyncopal sensation without loss of consciousness during a 4-month period. Further evaluation established intermittent arterial O2 desaturations associated with this dyspnea. After an extensive cardiopulmonary workup was performed for presumptive diagnosis of pulmonary embolism, a brain magnetic resonance image revealed a right medial temporal lobe lesion. The patient's dyspnea was then suspected to be a symptom of a seizure. His shortness of breath and O2 desaturation resolved with administration of phenytoin. This case, to the authors' knowledge, is the first documented example of simple partial seizures presenting with episodic autonomic cardiopulmonary symptoms in the absence of other ictal behavior. This case may also illustrate one specific limbic autonomic network.

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Gregory McCarthy, Truett Allison, and Dennis D. Spencer

✓ The authors describe a method of localizing the sensory and motor peri-rolandic cortex representing the face and intraoral structures. Somatosensory evoked potentials (SEP's) to stimulation of the chin, lips, tongue, and palate were recorded in 37 patients studied intraoperatively under general anesthesia or following chronic implantation of cortical surface electrodes. Localization by trigeminal SEP recording was validated by SEP localization of the hand area with median nerve stimulation, and by cortical stimulation of the hand and face areas.

The following conclusions were drawn regarding the implementation of face area localization: 1) in general agreement with the results of cortical stimulation in humans and single-unit recordings in monkeys, there is a medial-to-lateral representation in somatosensory cortex of the hand, chin, upper lip, lower lip, tongue, and palate; 2) the chin and lip representations overlap, are adjacent to the hand area, and provide little additional localizing information if the hand area has been identified; 3) stimulation of the tongue and palate evokes reliable, large-amplitude SEP's useful for localization; 4) palatal SEP's allow localization near the sylvian sulcus; 5) for any type of trigeminal stimulation, the largest SEP's are recorded from the somatosensory cortex and provide the most consistent criterion for its identification; and 6) polarity inversion of potentials across the sulcus (a reliable localizing criterion for median nerve SEP's) is a less reliable criterion for trigeminal SEP's.

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Aaron A. Cohen-Gadol, Dennis D. Spencer, and William E. Krauss

✓ Harvey Cushing's refinement of Halsted's meticulous surgical techniques facilitated safe resection of intradural spinal tumors. Although Cushing focused his attention on brain tumors at the Peter Bent Brigham Hospital, his numerous contributions to the treatment of intradural spinal tumors include the description of these tumors' natural histories and their histological classifications. The application of his experienced intracranial techniques to the resection of spinal tumors improved outcomes. The authors review selected operative notes and sketches to demonstrate his technique in the excision of the spinal cord tumors.

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Joan L. Venes, Bennett A. Shaywitz, and Dennis D. Spencer

✓ Fifteen critically ill children with the diagnosis of Reye-Johnson syndrome were treated with techniques developed to maintain adequate cerebral perfusion pressure and levels of circulating blood glucose. One child died, three sustained neurological deficit, and nine children (70%) recovered without significant neurological dysfunction. The techniques developed during the period these children were treated, the indications for their use, and factors that can interfere with maintaining adequate cerebral perfusion in patients with increased intracranial pressure from metabolic encephalopathy are described. The results suggest that neurological damage in this syndrome results from neuronal injury secondary to inadequate cerebral perfusion and/or hypoglycemia, and that neurological dysfunction like hepatic dysfunction should produce minimal mortality and morbidity if cerebral perfusion and adequate levels of circulating blood glucose are sustained during the period of increased intracranial pressure and liver failure.