Surgery for focal epilepsy in the older patient

Eight of the 237 patients who received a surgical procedure for intractable partial epilepsy at the Mayo Clinic during a 3-year period were 50 years of age or older. All patients had disabling partial seizures of several years in duration that were refractory to antiepileptic drug medication. A neuroimaging-identified epileptogenic lesion prompted referral for surgical treatment in three patients. The only clinically significant morbidity associated with surgery in the eight patients was a transient exacerbation of an aphasia in a patient who underwent a left frontal corticectomy. All eight patients had a favorable seizure outcome, and three patients postoperatively are seizure free. Epilepsy surgery may be an appropriate alternate therapy for select patients in the sixth decade of life or older with medically refractory partial seizures.

Epileptiform electroencephalographic abnormalities in liver transplant recipients

We retrospectively studied patients who had undergone orthotopic liver transplantation and who also had electroencephalography to determine whether epileptiform changes were associated with a poor neurological outcome. Study groups were 36 patients who died after transplantation (141 electroencephalograms) and underwent neuropathological examination, 11 who died (18 electroencephalograms) but did not have autopsy, and a third group of 34 (62 electroencephalograms) who remained alive. Epileptiform activity was seen in electroencephalograms of 14 of the patients who died (11 from the autopsy group) and in 2 of those who remained alive. All had multiple epileptiform abnormalities and clinical or subclinical seizures. The incidence of epileptiform activity after orthotopic liver transplantation was fivefold higher in the nonsurvivors. Serious cerebral structural changes were found in 10 of the 11 patients who underwent autopsy. Epileptiform activity in the electroencephalograms of patients who had undergone orthotopic liver transplantation indicates a poor prognosis. It should alert the clinician to investigate further for potentially treatable causes.

Magnetic resonance imaging-based volume studies in temporal lobe epilepsy: pathological correlations

We performed a prospective study correlating magnetic resonance imaging volume measurements of the hippocampal formation with histopathology in 24 patients with intractable partial epilepsy who subsequently underwent an anterior temporal lobectomy for their seizure disorder. Patients with mass lesions verified pathologically were excluded from this study. In 71% of patients, quantitative hippocampal formation atrophy correctly lateralized the temporal lobe of seizure origin; in 29%, the volume study was indeterminant. The severity of the pathological alterations in the hippocampus correlated with the hippocampal formation volume determination. Mesial temporal sclerosis was identified in the surgically excised temporal lobe in 15 patients. The magnetic resonance imaging volume studies indicated hippocampal atrophy in the temporal lobe resected in 14 of the 15 patients. Magnetic resonance imaging-based volume measurements of the hippocampal formation increase the diagnostic yield of magnetic resonance imaging scanning in patients with intractable partial epilepsy related to mesial temporal sclerosis.

Seizure-associated speech arrest in elderly patients

Recurrent, brief episodes of speech arrest associated with bifrontal electroencephalographic seizure activity developed in three ill elderly patients. The seizures ceased after the initiation of antiepileptic drug therapy and the correction of metabolic abnormalities. The cause of the seizure activity remains unknown, but a possible mechanism may be a transient epileptogenic cortical dysfunction that predominantly affects the frontal lobes as a result of concomitant metabolic alterations.

Metabolic and neurologic effects of an intravenous medium-chain triglyceride emulsion

These studies were undertaken to investigate the relationship between medium-chain fatty acid availability, medium-chain fatty acid oxidation, and central nervous system toxicity during infusion of medium-chain triglycerides in dogs. Six dogs received a sequential, stepwise infusion of trioctanoin at three different rates for 80 min each, providing calories below and equal to resting energy expenditure in the species. Ketone body production rates (using a 14C beta-hydroxybutyrate tracer) and plasma concentrations of lactate and octanoate were monitored. Three animals were infused with saline to serve as controls. Blood-brain barrier integrity was assessed with Evans blue dye, and brain samples were taken at the end of the study to quantify brain water. Three animals were studied under anesthesia to obtain good quality EEG and intracranial pressure measurements. Results were (1) plasma octanoate increased to 0.37 +/- 0.13, 0.78 +/- 0.2, and 1.44 +/- 0.41 mmol/liter during the three infusion intervals; (2) emesis, somnolence, and coma were observed at the two highest trioctanoin rates; (3) ketone body concentrations and production increased from 102 +/- 15 to 859 +/- 54 mumol/liter and 3.6 +/- 0.43 to 18.5 +/- 1.7 mumol/kg/min, respectively, at the highest trioctanoin infusion rate; and (4) plasma lactate also increased from 1.3 +/- 0.1 to 4.3 +/- 0.9 mmol/liter at the highest infusion rate. EEG changes were also observed, consisting of high amplitude slowing and reduction in amplitude of faster components. There was no extravasation of Evans blue dye, nor change in brain water or intracranial pressure. The conclusion--medium-chain triglycerides have significant dose-related central nervous system toxicity in dogs. Therefore, caution should be exercised in clinical studies with MCTs, including careful measurement of medium-chain fatty acid concentrations.

Effects of suxamethonium on the cerebrum following disruption of the blood-brain barrier in dogs

We have studied the effects of suxamethonium 1.0 mg kg-1 i.v. on cerebral blood flow (CBF), cerebral metabolic rate (CMRO2), and the electroencephalogram (EEG) in dogs anaesthetized with halothane (1.0 MAC) following blood-brain barrier (BBB) disruption with intracarotid (i.c.) mannitol. The combination produced a transient increase in CBF, while CMRO2 did not change. These responses were similar to those produced by i.c. mannitol plus i.v. saline. Suxamethonium produced desynchronization of the EEG that persisted longer than that produced by saline. In only one of the six animals was the desynchronization sustained (90 min) beyond that found in dogs with a normal BBB. We conclude that disruption of the BBB did not enhance the cerebral stimulating effects of i.v. suxamethonium, and did not increase the likelihood of seizure activity following suxamethonium.

Stereotactic resection of intra-axial cerebral lesions in partial epilepsy

We performed a retrospective study of stereotactic resections of intra-axial brain mass lesions in 30 patients with intractable partial epilepsy. The most common pathologic alterations observed were vascular malformations (11 lesions) and glial neoplasms (11 lesions). The locations of the lesions included the postcentral gyrus in five patients, the precentral gyrus in five, and the deep-seated left posterior temporal region in four, all of which were sites that may have precluded standard craniotomy and cortical resection. Of the 30 medically refractory patients, 26 had at least an 80% reduction in seizure activity at a mean duration of follow-up of 22 months postoperatively. Nineteen of 22 patients with at least 1 year (mean, 28 months) of follow-up and 13 of 15 patients with at least 2 years (mean, 34 months) of follow-up had favorable surgical outcomes. "Lesionectomy" may allow pathologic examination of intracranial lesions and may produce a worthwhile reduction in seizure activity in some patients with intractable partial epilepsy.

EEG scalp electrode projection onto three-dimensional surface rendered images of the brain

A technique is described for generating magnetic resonance-based, surface rendered images of the brain with electroencephalographic (EEG) scalp electrode positions projected onto the cortical surface. This technique (EEG electrode projection) was used in 10 patients who subsequently underwent surgery for medically intractable frontal lobe epilepsy. In most cases of intractable epilepsy, successful surgery entails the resection of electrophysiologically abnormal cortical tissue rather than an identifiable mass lesion. EEG electrode projection is a unique and useful surgical tool because it provides images that spatially correlate the surface anatomy of the brain and the electrophysiologic abnormality recorded at the scalp. Excellent correlation was found between cortical topography delineated by the surface rendered images and cortical anatomy at surgery. Agreement between EEG electrode projection and electrocorticography as to the location of the electrophysiologic abnormality increases confidence that appropriate cortical areas have been identified for resection. The technique provides new and unique insight into important anatomic-electrophysiologic relationships and aids in formulation of surgical strategy.

Temporal lobe seizures: lateralization with MR volume measurements of the hippocampal formation

A retrospective magnetic resonance (MR) imaging study was performed in 41 right-handed patients with presumed mesial sclerosis who underwent surgery for medically intractable, complex partial seizures of temporal lobe origin. The ability of each of five different MR imaging-based tests to lateralize the seizure disorder was determined. In order of decreasing usefulness the tests were (a) hippocampal formation (HF) volume measurements, (b) visual grading of MR images for unilateral HF atrophy, (c) anterior temporal lobe (ATL) volume measurements, (d) visual grading of MR images for unilateral ATL atrophy, and (e) evidence of unilateral medial temporal lobe signal intensity abnormalities on long repetition time MR images. A right-side minus left-side volume (designated DHF) was obtained to quantify unilateral HF atrophy with a single number. Patients with right-sided seizures had a median DHF of -0.4 cm3, while those with left-sided seizures had a median DHF of 0.8 cm3, consistent with atrophy of the HF ipsilateral to the seizure disorder. Conservative volumetric threshold values (-0.2 cm3 and 0.6 cm3), separating individual DHF measurements into right-side abnormal, indeterminate, and left-side abnormal, allowed DHF measurements to be 76% sensitive and 100% specific for correct seizure lateralization.

Anterior temporal lobes and hippocampal formations: normative volumetric measurements from MR images in young adults

Volumes of the right and left anterior temporal lobes and hippocampal formations were measured from magnetic resonance images in 52 healthy volunteers, aged 20-40 years. Subjects were selected by age, sex, and handedness to evaluate possible effect of these variables. Data were normalized for variation in total intracranial volume between individuals. Right-left asymmetry in the volumes of the anterior temporal lobes and hippocampal formations was a normal finding. The anterior temporal lobe of the non-dominant (right) hemisphere was larger than the left by a small (mean right-left difference, 2.3 cm3) but statistically significant amount (P less than .005) in right-handed subjects. No significant effect of age or sex was seen in normalized right or left anterior temporal lobe volume. The right hippocampal formation was larger than the left for all subjects by a small (mean right-left difference, 0.3 cm3) but statistically significant amount (P less than .001). No effect of age, sex, or handedness was seen in normalized hippocampal formation volumes.

Gadolinium-DTPA-enhanced magnetic resonance imaging in intractable partial epilepsy

We performed magnetic resonance imaging (MRI), before and after the administration of gadolinium-DTPA (Gd-DTPA), in 23 patients with medically refractory partial epilepsy who subsequently had surgical treatment for their seizure disorder. In most patients, 61%, unenhanced and enhanced MRI studies were negative. In 26% the unenhanced image was positive, and the abnormality enhanced with Gd-DTPA. In 13% the unenhanced MR image was positive, but the abnormality did not enhance with Gd-DTPA. Gd-DTPA does not appear to increase the diagnostic yield of MRI in the presurgical evaluation of patients with partial epilepsy if the unenhanced MRIs are normal.

Selective posterior cerebral artery injection of amytal: new method of preoperative memory testing

The carotid Amytal test (Wada test) was introduced, in 1948 by Wada, to localize speech function before temporal lobectomy in patients with medically refractory epilepsy, and it remains the standard for that purpose. The same test has also been used since 1962 to evaluate memory function; however, the adequacy of the test in this application has been viewed with increasing skepticism in recent years. Therefore, we developed an alternative to the Wada test. It consists of selective injection of Amytal into the posterior cerebral artery (PCA). This PCA Amytal test is designed to test only memory function (not language). We present several anatomic and functional reasons why this approach should be superior to the Wada test for this purpose. We also present preliminary data in support of this hypothesis. To date, we have had successful results of the PCA Amytal test in 38 of 45 patients (84%), and one major complication has occurred (2%).

Psychologic and social adjustment to epilepsy in Rochester, Minnesota

The psychologic and social aspects of epilepsy have rarely been assessed in community-based samples. We administered the Washington Psychosocial Seizure Inventory in 1985-1986 to 125 nonretarded adults, 18 to 59 years of age, who in 1980 had active epilepsy and resided in Rochester, Minnesota. Individuals having seizures or taking anticonvulsant medications within the past 12 months had somewhat poorer adjustment than those without recent seizures or medications, but even this more severely affected group appeared relatively well adjusted.

Computer simulation of the generation of the electroencephalogram

We have used a computer program for modeling some features of the scalp electroencephalogram (EEG) in terms of the time- and space-dependent interactions of populations of neurons in different hypothetical brain configurations of increasing levels of complexity. The input of the model consists of: (1) geometric and anatomic data characterizing the brain configuration, including interconnecting fiber pathways between neuronal groups; (2) physiologic characteristics of neurons, such as thresholds, driving potentials and conductances of excitatory and inhibitory synapses, synaptic delay times, and rise and fall times of postsynaptic potentials; and (3) functions describing the time-dependent afferent impulses to the brain configuration under study. The output of the model consists of plots of selected intracellular and extracellular potentials, including electrical potentials measured by an array of electrodes on the surface of the head, as a function of time. The objective was to assess how the characteristic frequencies seen in scalp EEG recordings might be determined by characteristics of local neuronal circuits (such as thalamic 'pacemakers') and by global circuit characteristics (such as cortico-cortical and thalamo-cortical interactions). We find that in our model the basic requirement for rhythmic behavior is the existence of local feedback circuits containing inhibitory neurons and that, when parameters of the model are chosen so that sustained rhythmic oscillations in the alpha frequency range are generated, the characteristic frequencies of these oscillations are primarily determined by the local circuit parameters, especially the duration of the inhibitory postsynaptic potentials, and are relatively independent of global circuit parameters such as the ranges of the long interconnecting axons and the propagation velocity of action potentials in these axons.

Use of MR imaging for quantitative evaluation of resection for temporal lobe epilepsy

The postoperative magnetic resonance imaging studies of 40 patients who underwent surgery for medically refractory temporal lobe epilepsy were reviewed. A method for quantifying the resection of four specific medial temporal lobe structures--amygdala, uncus, hippocampal formation, and parahippocampal gyrus--was used to correlate postoperative seizure control with the degree to which those structures had been resected. Satisfactory postoperative seizure control was found to be strongly dependent (P less than .01) on the performance of at least partial resection of all four medial temporal lobe structures. The total amount of tissue removed did not necessarily correlate with the clinical outcome in individual cases, however, as long as some portion of all four medial structures had been resected. Two complicating factors--the presence of posterior or bilateral independent electroencephalographic foci and a history of meningoencephalitis--each negatively influenced surgical outcome (P less than .01). In cases with a complicating factor and inadequate medial resection, the outcome was invariably poor.

Selective posterior cerebral artery Amytal test for evaluating memory function before surgery for temporal lobe seizure

Selective testing for memory function with Amytal (amobarbital) in the posterior cerebral artery (PCA) is a promising modification of that test in the internal carotid artery (ICA). This new technique, performed with a Tracker catheter system, was completed successfully in 17 of 20 patients being examined before planned surgery for refractory temporal lobe seizure. The PCA test overcomes three major problems with the ICA technique. First, with the PCA technique, memory testing is begun immediately after injection, when the drug has its peak effect. Second, when the speech-dominant hemisphere is being tested with the PCA test, patients do not become aphasic. Third, injection into the PCA delivers the drug more effectively to the target, the ipsilateral hippocampal formation.

Anterior temporal lobectomy for the control of partial complex seizures: information for counseling patients

We examined the effect of anterior temporal lobectomy on cognitive function in the treatment of intractable partial complex seizures in a sample of 142 patients. Our current results replicate previous work in this area and clearly establish the presence of differential effects on cognitive function as a consequence of the side of the operation. Learning and memory are most susceptible to impairment postoperatively, although general intellectual abilities are also affected in a small number of patients. The data are further analyzed in a manner that permits determination of the probability of cognitive alterations postoperatively for individual patients. Information is provided to assist health-care professionals in evaluating the risk-to-benefit ratio relative to cognitive abilities as they consider this treatment alternative for their patients who suffer from intractable partial complex seizures.

An electroencephalographic study of glossopharyngeal neuralgia with syncope

In the case described, electroencephalography (EEG) proved valuable for determining the nature of spells of loss of consciousness with brief clonic jerks associated with ear and throat pain. A 70-year-old woman had a history of episodic brief attacks of pain below the right ear and deep in the neck that had started three years previously. The spells became more severe and progressed to loss of awareness associated with clonic jerks of the extremities. Because of a concern that the spells represented seizures, an EEG was performed, with electrocardiographic monitoring. Multiple spells were recorded; they began with profound bradycardia followed by generalized slow-wave activity and then by suppression of all EEG activity correlating with loss of consciousness and clonic jerking. The spells were thought to represent syncopal attacks associated with glossopharyngeal neuralgia.

Effects of atracurium, vecuronium or pancuronium pretreatment on lignocaine seizure thresholds in cats

Among the non-depolarizing neuromuscular blocking drugs, atracurium appears to be unique in its ability to produce cerebral stimulation in lightly anaesthetized animals. This effect is attributed to the atracurium metabolite, laudanosine. The following studies were performed to determine if pretreatments with the non-depolarizing neuromuscular blockers pancuronium, atracurium or vecuronium would differ in their effects on the seizure threshold of lignocaine. Adult mongrel cats were anaesthetized with 1.0 MAC halothane in oxygen and nitrogen. Ventilation, blood-gas tensions, acid-base balance and temperature were controlled. Cats received pancuronium 0.2 mg kg 1 i.v. (n = 7), atracurium 1.0 mg kg-1 i.v. (n = 7) or vecuronium 0.2 mg kg-1 i.v. (n = 7). Ten minutes after the administration of the myoneural blocker, all cats received lignocaine 4 mg kg-1 min-1 i.v. until the onset of EEG evidence of generalized seizure activity. At seizure onset, there were no statistically significant differences among the cumulative lignocaine doses or the serum lignocaine concentrations in cats pretreated with pancuronium, atracurium or vecuronium.

Temporal lobe volume measurement from MR images: accuracy and left-right asymmetry in normal persons

The effect of several magnetic resonance (MR) variables on the accuracy of volume measurements in phantom objects was investigated by use of an off-line automatic border-outlining and internal area pixel-counting computer program, and an optimal set of imaging variables was identified. Measurements were made of the temporal lobe volumes of a gross fixed brain specimen from MR image data. The range in accuracy was from -2 to +7%, and the standard deviation of the difference in right minus left lobe volume measurements obtained from the MR images and those obtained by use of Archimedes' principle was 1 cm3. This volumetric technique was applied to 25 normal persons, most of whom were right-handed. The median ratio of right to left temporal lobe volume was 1.16 (range 0.99-1.23). The nondominant temporal lobe was significantly larger than the dominant. The mean difference (95% confidence interval) between right and left volumes was 7 cm3 (6-9 cm3). This confidence interval was similar to that obtained when the variability within a subject (estimated from the gross fixed brain specimen) was taken into account. Unilateral temporal lobe atrophy, particularly in patients with temporal lobe epilepsy, should be interpreted from MR images with this range of discrepancy in normal left-right size in mind.

Computer simulation of neuronal circuit models of rhythmic behavior in the electroencephalogram

A computer program for modeling some features of the electroencephalogram (EEG) recorded by scalp electrodes in terms of the time- and space-dependent interactions of populations of neurons in different hypothetical brain configurations was developed. The input of the model consists of: (1) geometric and anatomic data characterizing the brain configuration; (2) physiologic features characterizing neurons; and (3) functions describing the time-dependent afferent impulses to the brain configuration under study. The output of the model consists of plots of selected intracellular and extracellular potentials as a function of time. In application of the model to various brain configurations, some configurations were sufficiently compact spatially that propagation times of action potentials between elements were either taken to be constant or were nearly independent of distance within the accuracy of the calculations. Other configurations represented cerebral cortex alone or a combined thalamocortical system in which many elements interacted via global interconnections. The basic requirement for rhythmic behavior is the existence of circuits containing inhibitory neurons. The characteristic frequencies of rhythmic oscillations are primarily determined by the local circuit parameters and are relatively independent of global circuit parameters.

Isoflurane when compared to enflurane and halothane decreases the frequency of cerebral ischemia during carotid endarterectomy

Data from the records of patients who underwent 2223 carotid endarterectomies at the Mayo Clinic between January 1, 1972, and December 31, 1985, were abstracted to compare the effects of isoflurane, enflurane, and halothane on the critical cerebral blood flow (CBF) (i.e., the CBF below which the majority of patients develop EEG ischemic changes within 3 min of carotid occlusion), the incidence of EEG ischemic changes, and the neurologic outcome. In a total of 2196 of these procedures, the patient received one of the three volatile anesthetics and, in 2010 of these, both the EEG and the CBF were monitored. Chronologically, halothane was the primary agent from 1972-1974; enflurane progressively replaced halothane during 1975-1981; and isoflurane was used almost exclusively since 1982. This analysis confirmed a previous study that the critical CBF during isoflurane anesthesia (703 procedures) was approximately 10 ml X 100 g-1 X min-1, as contrasted to that of approximately 20 ml X 100 g-1 X min-1 during halothane anesthesia (467 procedures). This analysis also established that the critical CBF during enflurane anesthesia (840 procedures) was approximately 15 ml X 100 g-1 X min-1. The incidence of EEG ischemic changes was significantly less (P less than 0.001) during isoflurane anesthesia (18%) than during either enflurane (26%) or halothane (25%) anesthesia. This difference occurred despite the fact that the preoperative risk status was greater in the patients given isoflurane. There was no difference in neurologic outcome between the three anesthetics, and none was expected, since all patients with EEG changes were immediately shunted, if possible.(ABSTRACT TRUNCATED AT 250 WORDS)