Surgical outcome and predictive factors in adult patients with intractable epilepsy and focal cortical dysplasia

OBJECTIVES

To determine the surgical outcome and prognostic factors in adult patients with intractable epilepsy and focal cortical dysplasia (FCD).

MATERIALS AND METHODS

We retrospectively studied the operative outcome in 21 consecutive adult patients with FCD who underwent surgical treatment for intractable partial epilepsy.

RESULTS

The mean age at surgery was 32.7 years (range, 18-58 years). The median post-operative follow-up was 2.5 years. The FCD was extratemporal in 11 patients, involved the temporal lobe in 10 patients, and was multilobar in eight patients. Eleven patients (52%) were rendered seizure-free, four patients (19%) had >95% reduction in seizures, and two patients (10%) had an 80-94% reduction in seizures. A seizure-free outcome was associated with shorter duration of epilepsy (P = 0.02).

CONCLUSION

Adult patients with FCD may be candidates for surgical treatment of intractable partial epilepsy. Most individuals have neocortical, extrahippocampal seizures and approximately 50% of patients are rendered seizure-free.

Resective reoperation for failed epilepsy surgery: Seizure outcome in 64 patients

OBJECTIVE

To determine the surgical outcome and factors of predictive value in patients undergoing reoperation for intractable partial epilepsy.

METHODS

The authors retrospectively studied the operative outcome in 64 consecutive patients who underwent reoperation for intractable partial epilepsy. Demographic data, results of comprehensive preoperative evaluations, and the seizure and neurologic outcome after reoperation were determined. All patients were followed a minimum of 1 year subsequent to their last operative procedure.

RESULTS

Fifty-three patients had two surgeries, and 11 patients had three or more operations. The first surgery involved a lesionectomy (n = 33), "nonlesional" temporal lobe resection (n = 28), and a "nonlesional" extratemporal resection (n = 3). The mean duration between the first and second procedure was 5.5 years. Fifty-five patients underwent an intralobar reoperation, whereas nine had a resection of a different lobe. After reoperation, 25 patients (39%) were free of seizure, 6 patients (9%) had rare seizures, 12 patients (19%) had a worthwhile improvement, and 21 patients (33%) failed to respond to surgery. Predictors of seizure-free outcome were age at seizure onset >15 years (p = 0.01), duration of epilepsy < or =5 years at the time of initial surgery (p = 0.03), and focal interictal discharges in scalp EEG (p = 0.03). Using a logistic regression model, two significant predictors emerged: duration of epilepsy < or =5 years (odds ratio, 3.18; p = 0.04) and preoperative focal interictal discharge (odds ratio, 4.45; p = 0.02). Complications of reoperation included visual field deficits (n = 9), wound infection (n = 2), subdural hematoma (n = 1), and hemiparesis (n = 1).

CONCLUSION

Reoperation may be an appropriate alternative form of treatment for selected patients with intractable partial epilepsy who fail to respond to initial surgery.

Long-term follow-up of temporal lobectomy in children

Temporal lobectomy is an effective treatment for medically intractable seizures. The change in seizure status with prolonged postoperative follow-up is unclear. The authors followed 37 patients who underwent first time temporal lobectomy during childhood for at least 15 years. This study is the longest follow-up of children who have had a temporal lobectomy for intractable seizures. It demonstrates that seizure recurrence can increase with longer duration of follow-up.

Electroconvulsive Therapy for Depression After Temporal Lobectomy for Epilepsy

Electroconvulsive therapy (ECT) was administered to a 25-year-old woman with major depression with psychotic features who had undergone a left temporal lobectomy for medically intractable partial epilepsy 1 year earlier. Her depressive illness responded to ECT without ill effects to her seizure disorder.

The effects of remifentanil on epileptiform discharges during intraoperative electrocorticography in patients undergoing epilepsy surgery

PURPOSE

High-dose i.v. opioids (e.g., alfentanil, 50 microg/kg bolus) are known to increase the intraoperative reading of epileptiform activity during epilepsy surgery (ES), thereby facilitating localization of the epileptogenic zone (i.e., the site of ictal onset and initial seizure propagation). However, this phenomenon has not been studied with remifentanil (i.e., a novel ultra-short acting opioid). The purpose of the present study was to evaluate the effect of remifentanil on electrocorticography (ECoG) during ES.

METHODS

After Institutional Review Board approval, 25 adult patients undergoing elective ECoG-guided anterior temporal corticectomy were enrolled. At the time of ECoG, anesthesia consisted of inhaled isoflurane < or =0.1% (end-tidal) in 50% N2O, and i.v. fentanyl, 2 microg/kg/h and vecuronium. Patients were maintained at normocapnia and normoxia during ECoG. After acquisition of baseline ECoG, bolus remifentanil, 2.5 microg/kg i.v., was administered. The number of epileptiform spikes occurring 5 min before and after this bolus were compared by using a one-sided sign test; p values < or =0.05 were considered statistically significant.

RESULTS

When compared with baseline ECoG, bolus i.v. remifentanil significantly increased the frequency of single spikes or repetitive spike bursts in the epileptogenic zone while suppressing activity in surrounding normal brain.

CONCLUSIONS

During ES, remifentanil enhanced epileptiform activity during intraoperative ECoG. Such observations facilitate localization of the epileptogenic zone while minimizing resection of nonepileptogenic eloquent brain tissue. Although not specifically evaluated in this study, we speculate that remifentanil's short elimination half-life will facilitate neurologic function testing immediately after ES. Should this be the case, we envision remifentanil has the potential to supplant other opioids (e.g., alfentanil) during ECoG-guided ES.

The relationship between quantitative T2 relaxometry and memory in nonlesional temporal lobe epilepsy

PURPOSE

We investigated the relationship between preoperative quantitative magnetic resonance imaging (MRI) T2 relaxometry and volumetry of the hippocampi and pre- and postoperative verbal memory in temporal lobectomy patients who had nonlesional temporal lobe epilepsy.

METHODS

Pre- and postoperative memory data based on the Logical Memory (LM) subtest of the Wechsler Memory Scale-Revised (WMS-R) and the 30-min delayed recall trial of the Rey Auditory Verbal Learning Test (AVLT) were obtained from 26 left and 15 right temporal lobectomy patients. Coronal MRI T2 maps were generated for these 41 temporal lobectomy patients as well as 61 control patients. Hippocampal T2 relaxation times and hippocampal volumes, converted to z scores using control group data, were correlated with neuropsychological performance in the patients.

RESULTS

In left temporal lobe-onset patients, high T2 in the left hippocampal body predicted higher LM performance after surgery. Asymmetrically high T2 in the left hippocampal body (i.e., the right-minus-left difference), compared with the right hippocampal body, also predicted higher LM performance after surgery. In right temporal lobe-onset patients, high T2 in the left hippocampal body predicted relatively lower AVLT performance after surgery. Multiple regression analysis in left temporal-onset patients revealed that high T2 in the left hippocampal body together with higher preoperative LM performance predict higher postoperative LM performance.

CONCLUSIONS

Our findings suggest that elevated (i.e., abnormal) hippocampal T2 signal is associated with memory ability (or hippocampal functional capacity) independent of MRI-determined hippocampal atrophy. Therefore, our findings support the use of quantitative T2 relaxometry as an independent predictor of verbal memory outcome in both left and right TLE patients who are candidates for temporal lobectomy.

Localization of the epileptic focus by low-resolution electromagnetic tomography in patients with a lesion demonstrated by MRI

Patients with medically intractable partial epilepsy and well-defined symptomatic MRI lesions were studied using phase-encoded frequency spectral analysis (PEFSA) combined with low-resolution electromagnetic tomography (LORETA). Ten patients admitted to the epilepsy monitoring unit with MRI-identified lesions and intractable partial epilepsy were studied using 31-electrode scalp EEG. The scalp electrodes were located in three-dimensional space using a magnetic digitizer and coregistered with the patient's MRI. PEFSA was used to obtain a phase-encoded scalp map for the ictal frequencies. The ictal generators were obtained from the scalp map using LORETA. In addition, the generators of interictal epileptogenic spikes were identified using time-domain LORETA. The LORETA generators were rostral to the MRI lesion in 87% (7/8) of patients with temporal lobe lesions, but all were located in the mesial temporal lobe in concordance with the patients' MRI lesions. In patients with frontal lobe epilepsy, the ictal generators at the time that the spectral power was maximal localized to the MRI lesions. Eight of 10 patients had interictal spikes, of which 4 were bilateral independent temporal lobe spikes. Only generators of the interictal spikes that were ipsilateral to seizure onset correlated with the ictal generators. LORETA combined with PEFSA of the ictal discharge can localize ictal EEG discharges accurately and improve correlation with brain anatomy by allowing coregistration of the ictal generator with the MRI. Analysis of interictal spikes was less useful than analysis of the ictal discharge.

Subtraction peri-ictal SPECT is predictive of extratemporal epilepsy surgery outcome

OBJECTIVES

To determine whether localization of extratemporal epilepsy with subtraction ictal SPECT coregistered with MRI (SISCOM) is predictive of outcome after resective epilepsy surgery, whether SISCOM images provide prognostically important information compared with standard tests, and whether blood flow change on SISCOM images is useful in determining site and extent of excision required.

BACKGROUND

The value of SISCOM in predicting surgical outcome for extratemporal epilepsy is unknown, especially if MRI findings are nonlocalizing.

METHODS

SISCOM images in 36 consecutive patients were classified by blinded reviewers as "localizing and concordant with site of surgery," "localizing but nonconcordant with site of surgery," or "nonlocalizing." SISCOM images were coregistered with postoperative MRI, and reviewers visually determined whether cerebral cortex underlying the SISCOM focus had been completely resected, partially resected, or not resected.

RESULTS

Twenty-four patients (66.7%) had localizing SISCOM, including 13 (76.5%) of those without a focal MRI lesion. Eleven of 19 patients (57.9%) with localizing SISCOM concordant with the surgical site, compared with 3 of 17 (17.6%) with nonlocalizing or nonconcordant SISCOM, had an excellent outcome (p < 0.05). With logistic regression analysis, SISCOM findings were predictive of postsurgical outcome, independently of MRI or scalp ictal EEG findings (p < 0.05). The extent of resection of the cortical region of the SISCOM focus was significantly associated with the rate of excellent outcome (100% with complete resection, 60% with partial resection, and 20% with nonresection, p < 0.05).

CONCLUSION

SISCOM images may be useful in guiding the location and extent of resection in extratemporal epilepsy surgery.

Multifocal periodic lateralized epileptiform discharges (PLEDs): EEG features and clinical correlations

OBJECTIVE

To analyze the clinical and EEG findings of patients with multifocal periodic lateralized epileptiform discharges (PLEDs).

METHODS

EEGs containing multifocal PLEDs (3 or more foci of PLEDs) were reviewed. Thirty-five patients (15 males and 20 females), from 2.5 months to 91 years old, met the criteria for multifocal PLEDs.

RESULTS

The disease processes identified in the patients included vascular lesions in 9, central nervous system infections in 7, metabolic/toxic disorders in 6, exacerbation of a chronic seizure disorder in 6, hypoxic ischemic insults in 3, and fat embolism, paraneoplastic encephalitis, cerebral metastasis, and multiple sclerosis in one each. Twenty patients died. Detection of the spatiotemporal distribution of multifocal PLEDs was facilitated by the use of Laplacian montages.

CONCLUSIONS

Multifocal PLEDs were recorded in 35 patients and were associated with processes resulting in diffuse or multifocal cerebral dysfunction. Multifocal PLEDs indicate a significant disturbance of cerebral function and are associated with a mortality rate of 57%.

Factors predictive of the outcome of frontal lobe epilepsy surgery

PURPOSE

To identify factors that predict the outcome in seizure control after frontal lobe epilepsy surgery (FLES). FLES is the second most frequent type of epilepsy surgery, but the results are generally not as good as those after anterior temporal lobectomy.

METHODS

Our cohort consisted of 68 consecutive patients whose first epilepsy surgery involving the frontal lobe occurred between 1987 and 1994. Clinical history and results of imaging and electroencephalographic studies were reviewed in detail. Excellent outcome was defined as being seizure free or having only nondisabling seizures at last follow up.

RESULTS

Forty of the 68 patients (58.8%) had an excellent outcome; none of the patients with a history of childhood febrile seizures had an excellent outcome, whereas outcome was excellent in 63% of those without that history (p </= 0.01). The other significant presurgical factor was the presence of a potentially epileptogenic lesion in the frontal lobe on neuroimaging (excellent outcome in 72% when present versus 41% when absent, p </= 0.001). The only significant postsurgical factor was early postoperative seizure control in the first year (excellent outcome in 96% with early control versus 25% without, p </= 0.01).

CONCLUSIONS

History of childhood febrile seizures is a poor prognostic factor in FLES patients. It may suggest that the structural basis of all or some of the patients' intractable seizures is mesial temporal sclerosis. On the other hand, neuroimaging detection of a potentially epileptogenic frontal lobe lesion and early postoperative seizure control are associated with subsequent excellent outcome.

Factors predictive of the outcome of frontal lobe epilepsy surgery

PURPOSE

To identify factors that predict the outcome in seizure control after frontal lobe epilepsy surgery (FLES). FLES is the second most frequent type of epilepsy surgery, but the results are generally not as good as those after anterior temporal lobectomy.

METHODS

Our cohort consisted of 68 consecutive patients whose first epilepsy surgery involving the frontal lobe occurred between 1987 and 1994. Clinical history and results of imaging and electroencephalographic studies were reviewed in detail. Excellent outcome was defined as being seizure free or having only nondisabling seizures at last follow up.

RESULTS

Forty of the 68 patients (58.8%) had an excellent outcome; none of the patients with a history of childhood febrile seizures had an excellent outcome, whereas outcome was excellent in 63% of those without that history (p </= 0.01). The other significant presurgical factor was the presence of a potentially epileptogenic lesion in the frontal lobe on neuroimaging (excellent outcome in 72% when present versus 41% when absent, p </= 0.001). The only significant postsurgical factor was early postoperative seizure control in the first year (excellent outcome in 96% with early control versus 25% without, p </= 0.01).

CONCLUSIONS

History of childhood febrile seizures is a poor prognostic factor in FLES patients. It may suggest that the structural basis of all or some of the patients' intractable seizures is mesial temporal sclerosis. On the other hand, neuroimaging detection of a potentially epileptogenic frontal lobe lesion and early postoperative seizure control are associated with subsequent excellent outcome.

Time-frequency mapping of R-R interval during complex partial seizures of temporal lobe origin

BACKGROUND

Activation of autonomic nervous system is common with seizures. No reliable biological markers of impending seizures have been found. Evaluation of autonomic changes might help elucidate the transition from interictal to ictal states.

METHODS

We studied twelve patients (eight females, four males), from 19 to 62 years old with temporal lobe complex partial seizures (CPS). Dynamics of autonomic functions from oscillations in R-R interval (RRI) using time-frequency mapping based upon a Wigner distribution during pre-ictal, ictal and post-ictal periods. Oscillations in RRI at respiratory frequencies (RF) (> 0.1 Hz) are parasympathetically mediated and at nonrespiratory frequencies (NONRF) (0.01-0.09 Hz) are under combined sympathetic and parasympathetic influence.

RESULTS

CPS evoked marked autonomic imbalance and tachycardia. Spectral powers at both RF_RRI and NONRF_RRI increased over the pre-ictal period. RF_RRI power then fell rapidly over the 30 s before seizure onset and remained markedly reduced during seizure (P < 0.004). NONRF_RRI power reached a maximum at seizure onset and declined to a minimum before the seizure cessation (P < 0.05).

CONCLUSION

Time-frequency analysis revealed that autonomic activation hallmarks clinical seizure onset for several minutes. After combined parasympathetic and sympathetic activation, rapid parasympathetic withdrawal occurred approximately 30 s before the seizure, and sympathetic activation peaks at seizure onset. Therefore, the transition from interictal to ictal states is relatively long and associated with subclinical autonomic changes.

Assessment of functional MR imaging in neurosurgical planning

BACKGROUND AND PURPOSE

Presurgical sensorimotor mapping with functional MR imaging is gaining acceptance in clinical practice; however, to our knowledge, its therapeutic efficacy has not been assessed in a sizable group of patients. Our goal was to identify how preoperative sensorimotor functional studies were used to guide the treatment of neuro-oncologic and epilepsy surgery patients.

METHODS

We retrospectively reviewed the medical records of 46 patients who had undergone preoperative sensorimotor functional MR imaging to document how often and in what ways the imaging studies had influenced their management. Clinical management decisions were grouped into three categories: for assessing the feasibility of surgical resection, for surgical planning, and for selecting patients for invasive functional mapping procedures.

RESULTS

Functional MR imaging studies successfully identified the functional central sulcus ipsilateral to the abnormality in 32 of the 46 patients, and these 32 patients are the focus of this report. In epilepsy surgery candidates, the functional MR imaging results were used to determine in part the feasibility of a proposed surgical resection in 70% of patients, to aid in surgical planning in 43%, and to select patients for invasive surgical functional mapping in 52%. In tumor patients, the functional MR imaging results were used to determine in part the feasibility of surgical resection in 55%, to aid in surgical planning in 22%, and to select patients for invasive surgical functional mapping in 78%. Overall, functional MR imaging studies were used in one or more of the three clinical decision-making categories in 89% of tumor patients and 91% of epilepsy surgery patients.

CONCLUSION

Preoperative functional MR imaging is useful to clinicians at three key stages in the preoperative clinical management paradigm of a substantial percentage of patients who are being considered for resective tumor or epilepsy surgery.

Subtraction SPECT co-registered to MRI improves postictal SPECT localization of seizure foci

OBJECTIVE

To determine whether the detection of focal hypoperfusion by subtraction SPECT co-registered to MRI (SISCOM) improves the sensitivity and specificity of postictal SPECT in intractable partial epilepsy.

BACKGROUND

Postictal SPECT injections are easier to perform than are ictal injections, but the images are more difficult to interpret and have been reported to have lower sensitivity and specificity.

METHODS

Thirty-five consecutive intractable partial epilepsy patients who had postictal SPECT studies were evaluated. The following sets of SPECT images were separately interpreted by three blinded reviewers and classified as either localizing to 1 of 16 possible sites in the brain or as nonlocalizing: unsubtracted postictal and interictal images for conventional side-by-side comparison, SISCOM images of hyperperfusion, SISCOM images of hypoperfusion, and both sets of SISCOM hyperperfusion and hypoperfusion images (combined SISCOM evaluation).

RESULTS

Significantly higher proportions of the hyperperfusion SISCOM images (65.7%), the hypoperfusion SISCOM images (74.3%), and the combined SISCOM evaluation (82.9%) were localizing than were the conventional method of side-by-side comparison of unsubtracted images (31.4%; p < 0.0001). Concordance with the discharge diagnosis was higher for the combined SISCOM evaluation than it was for either the hyperperfusion or the hypoperfusion SISCOM images alone (both p < 0.05). For the hypoperfusion SISCOM and the combined SISCOM evaluations, concordance of the localization with the site of epilepsy surgery was associated with a greater probability of an excellent outcome than were nonconcordant/nonlocalizing images (both p < 0.05).

CONCLUSION

The use of SISCOM to detect focal cerebral hypoperfusion, in addition to focal hyperperfusion, improves the sensitivity and specificity of postictal SPECT in intractable partial epilepsy.

Improvement and deterioration of seizure control during the postsurgical course of epilepsy surgery patients

PURPOSE

To determine the factors associated with changes in seizure control during the postsurgical course of epilepsy surgery patients.

METHODS

Evaluation of patients after consecutive temporal and frontal resection whose seizure frequency was scored for each year of postsurgical follow-up. In each cohort, patients with a change in their seizure control after the first postsurgical year were compared with control subjects to determine factors that may be responsible for the change.

RESULTS

Thirty-three (15%) of 214 temporal lobectomy versus 12 (20%) of 59 frontal resection patients experienced a change in seizure control (p>0.05). Ten (5%) of 214 temporal lobectomy versus nine (15%) of 59 frontal resection patients experienced an improvement in seizure control (p = 0.009), but 23 (11%) of 214 temporal lobectomy versus three (5%) of 59 frontal resection patients had a worsening in seizure control (p>0.05). In temporal lobectomy patients, preoperative unilateral temporal epileptiform discharges were associated with improvement (p = 0.03), whereas older age at surgery was associated with worsening of seizure control (p = 0.007). In frontal resection patients, presence of a congenital central nervous system (CNS) anomaly was associated with late improvement in seizure control (p = 0.006).

CONCLUSION

During the postsurgical course, an improvement in seizure control is more common after frontal resection than after temporal lobectomy. Factors associated with improvement are the presence of a congenital CNS abnormality in frontal resection patients, and the occurrence of preoperative unilateral epileptiform discharges in temporal lobectomy patients. Older age at temporal lobectomy may be associated with greater risk of worsening seizure control.

Chronic intracranial EEG monitoring for localizing the epileptogenic zone: an electroclinical correlation

PURPOSE

To evaluate the diagnostic yield and identify predictive factors of the surgical outcome in patients with intractable partial epilepsy undergoing chronic intracranial EEG monitoring (CIEM).

METHODS

The clinical, magnetic resonance imaging (MRI) and electrophysiologic data of 108 patients that underwent CIEM were retrospectively reviewed. The discharge pattern and spatial extent of the initial ictal discharge were determined by blinded visual inspection and computerized analysis.

RESULTS

The main predictive indicator for epilepsy surgery outcome in patients that underwent CIEM was the presurgical MRI findings. Most patients with hippocampal atrophy or complete lesionectomy were rendered seizure free after epilepsy surgery (83 and 80%, respectively), whereas only a small minority of patients with partial lesionectomy or no detected MRI lesion had seizure-free operative outcomes (21 and 22%, respectively). Multifocal independent initiation of the initial ictal discharge was associated with a poor surgical outcome. In contrast, the pattern and local spatial extent of the initial ictal discharge observed with CIEM failed to predict the surgical outcome.

CONCLUSIONS

The main predictor of the surgical outcome in patients that underwent CIEM was the MRI findings, whereas CIEM had only limited use in localizing the epileptogenic zone in the absence of an MRI lesion. The reported findings indicate a low specificity of CIEM in defining the site of seizure onset, which in turn significantly impairs the reliability of CIEM in delineating the epileptogenic zone for epilepsy surgery. Further studies are required to define the indications and patient subpopulations who can benefit from CIEM before epilepsy surgery.

Subclinical rhythmic electrographic discharges of adults (SREDA) revisited: a study using digital EEG analysis

Previous descriptions of the subclinical rhythmic electrographic discharges of adults (SREDA) have been based entirely on visual analysis of analog electroencephalographic (EEG) recordings. The introduction of digital electroencephalograms (EEGs) and advances in digital signal processing provide an opportunity to restudy in more depth the nature of SREDA. We identified nine patients who had SREDA diagnosed on a routine EEG recording since the introduction of digital EEG to our laboratory in August 1995. Following careful rereview using standard montages, six of these patients were determined to fulfill the traditional requirements for the diagnosis of SREDA, whereas three were believed to have other benign discharges. Review with Laplacian montages demonstrated that the site of the SREDA activity was maximal in the parietal region or parietocentrotemporal regions, whereas it was maximal in the temporal or frontotemporal regions in the non-SREDA discharges. Frequency analysis, using both the conventional fast Fourier transform (FFT) and time-frequency mapping with the Wigner FFT variant, demonstrated that the SREDA consisted of a complex mixture of multiple rapidly shifting frequencies which showed little spatial and temporal correlation. In contrast, the non-SREDA all consisted of a single dominant well-organized rhythmic frequency spectrum that remained stable throughout space and time.

Predictors of outcome of anterior temporal lobectomy for intractable epilepsy: a multivariate study

OBJECTIVE

To identify presurgical and postsurgical factors that are independently predictive of the outcome of anterior temporal lobectomy (ATL) for intractable epilepsy.

BACKGROUND

There have been reports of prognostic factors in epilepsy surgery, but little is known about factors that independently predict outcome of ATL.

METHODS

We studied 175 consecutive ATL patients who had at least 2 years of postsurgical follow-up. Significant factors on univariate analyses were subjected to stepwise logistic regression analysis.

RESULTS

On univariate analyses, two presurgical conditions were significantly associated with excellent seizure control at last follow-up: (1) unilateral hippocampal formation atrophy as detected on MRI and (2) all scalp interictal epileptiform discharges concordant with the location of ictal onset (p < 0.05). Three postsurgical factors that occurred during the first year were associated with excellent seizure outcome: the absence of interictal epileptiform discharges at 3 months, complete seizure control, and having only nondisabling seizures for those who did not become seizure free. Logistic regression analysis revealed the following to be independently predictive of excellent seizure control: MRI-detected unilateral hippocampal formation atrophy, concordant interictal epileptiform discharges, complete seizure control during the first postsurgical year, and having only nondisabling seizures during the first postsurgical year for those who did not become seizure free.

CONCLUSIONS

Presurgical identification of unilateral hippocampal formation atrophy, or of interictal epileptiform discharges that are all concordant with the location of ictal onset, predict excellent outcome of ATL. However, the probability of excellent outcome is highest (94%) when both factors are present.

Scalp-recorded EEG localization in MRI volume data

Scalp-recorded EEG is a noninvasive and widely available tool for studying normal and dysfunctional human neurophysiology with unsurpassed temporal resolution. However, scalp-recorded EEG data is difficult to correlate with anatomy, and most current display and neural source estimation algorithms are based on unrealistic spherical or elliptical models of the head. It is possible to measure the positions of electrodes on the patient's scalp, and to register those electrode positions into the space of a high-resolution MRI volume, and to then use the patient-specific anatomy as the basis for display and estimation of neural sources. We use a surface matching algorithm to register digitized electrode and scalp surface coordinates to a three-dimensional MRI volume. This study uses fiducial markers in phantom and volunteer studies to quantitatively estimate the accuracy of the electrode registration method. Our electrode registration procedure is accurate to 2.21 mm for a realistic head phantom and accurate to 4.16 mm on average for five volunteers. This level of accuracy is considered within acceptable limits for clinical applications.

Correlation of regional cerebral blood flow with ischemic electroencephalographic changes during sevoflurane-nitrous oxide anesthesia for carotid endarterectomy

BACKGROUND

Carotid endarterectomy necessitates temporary unilateral carotid artery occlusion. Critical regional cerebral blood flow (rCBF) has been defined as the rCBF below which electroencephalographic (EEG) changes of ischemia occur. This study determined the rCBF50, the rCBF value at which 50% of patients will not demonstrate EEG evidence of cerebral ischemia with carotid cross-clamping.

METHODS

Fifty-two patients undergoing elective carotid endarterectomy were administered 0.6-1.2% (0.3-0.6 minimum alveolar concentration) sevoflurane in 50% nitrous oxide (N2O). A 16-channel EEG was used for monitoring. The washout curves from intracarotid 133Xenon injections were used to calculate rCBF before and at the time of carotid occlusion by the half-time (t(1/2)) technique. The quality of the EEG with respect to ischemia detection was assessed by an experienced electroencephalographer.

RESULTS

Ischemic EEG changes developed in 5 of 52 patients within 3 min of carotid occlusion at rCBFs of 7, 8, 11, 11, and 13 ml x 100 g(-1) x min(-1). Logistic regression analysis was used to calculate an rCBF50 of 11.5 +/- 1.4 ml x 100 g(-1) x min(-1) for sevoflurane. The EEG signal demonstrated the necessary amplitude, frequency, and stability for the accurate detection of cerebral ischemia in all patients within the range of 0.6-1.2% sevoflurane in 50% N2O.

CONCLUSIONS

The rCBF50 of 0.6-1.2% sevoflurane in 50% N2O, as determined using logistic regression analysis, is 11.5 +/- 1.4 ml 100 g(-1) x min(-1). Further, in patients anesthetized in this manner, ischemic EEG changes due to carotid occlusion were accurately and rapidly detected.

Characterization and comparison of local onset and remote propagated electrographic seizures recorded with intracranial electrodes

PURPOSE

To compared the ictal discharge patterns between local onset and remote propagated electrographic seizures recorded with chronic intracranial electrodes.

METHODS

The electrophysiological data from 88 consecutive patients who underwent chronic intracranial EEG monitoring were retrospectively reviewed. The early and late discharge patterns of electrographic seizures at local onset and distant propagated sites were determined by blinded visual inspection and computerized analysis.

RESULTS

Four early and three late electrographic seizure patterns were observed at the local onset sites. The four early patterns consisted of a rhythmic discharge in the beta range ("beta buzz"), rhythmic alpha-theta activity, rhythmic sharp waves in the delta range, and an irregular spike discharge. The three distinct late-discharge patterns consisted of a late beta buzz, rhythmic sharp theta activity, and a rhythmic polyspike and wave discharge. At remote propagated sites, electrographic seizures could be divided into two different types according to their early discharge pattern. The first was unique to remote propagated electrographic seizures and consisted of a rhythmic theta-delta activity correlated with the concurrent activity at the local-onset site. The second remote initiation type consisted of patterns indistinguishable from the earlier discharge patterns recorded at the local onset site.

CONCLUSIONS

The initial ictal discharge pattern recorded with intracranial electrodes can assist in differentiating local onset and remote propagated electrographic seizures, with rhythmic round theta-delta activity being unique to distant propagated sites. Nevertheless, the initial discharge of a subclass of remote propagated electrographic seizures consists of an independent pattern indistinguishable from that observed at local onset sites.

Subtraction ictal SPECT co-registered to MRI improves clinical usefulness of SPECT in localizing the surgical seizure focus

Traditional side-by-side visual interpretation of ictal and interictal single-photon emission computed tomography (SPECT) scans can be difficult in identifying the surgical focus, particularly in patients with extratemporal or otherwise unlocalized intractable epilepsy. Computer-aided subtraction ictal SPECT co-registered to MRI (SISCOM) may improve the clinical usefulness of SPECT in localizing the surgical seizure focus. We studied 51 consecutive intractable partial epilepsy patients who had interictal and ictal scans. The SPECT studies were blindly reviewed and classified as either localizing to 1 of 16 sites in the brain or as nonlocalizing. SISCOM images were localizing in 45 of 51 (88.2%) compared with 20 of 51 (39.2%) for traditional side-by-side inspection of ictal and interictal SPECT images (p < 0.0001). Inter-rater agreement for two independent reviewers was better for SISCOM (84.3% versus 41.2%, kappa = 0.83 versus 0.26; p < 0.0001). Concordance of seizure localization with the more established tests was also higher for SISCOM. Late injection of the radiotracer (> 45 seconds), but not secondary generalization of the seizure, was associated with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with the surgical site were more likely to have excellent outcome than patients with nonconcordant or nonlocalizing findings (62.5% [10/16] versus 20% [2/10]; p < 0.05). On the other hand, seizure localization by the traditional method of SPECT inspection had no significant association with postsurgical outcome. We conclude that SISCOM improves the sensitivity and the specificity of SPECT in localizing the seizure focus for epilepsy surgery. Concordance between SISCOM localization and site of surgery is predictive of postsurgical improvement in seizure outcome.

Health care utilization of patients with psychogenic nonepileptic seizures

Medical records were reviewed for 94 consecutive inpatients diagnosed with nonepileptic seizures. A 122-item follow-up questionnaire was returned by 71 patients (76%). The majority of the subjects reported fewer seizures (73%), their general health as "very good" (20%) or "good" (37), and "improved" quality of life (55%). Many patients had either discontinued (50%) or reduced (17%) use of anticonvulsant medications. The patients most often sought care from primary care providers (46%), followed by psychiatrists/psychologists (41%) and neurologists (31%). Of the 57 patients (80%) advised to seek psychiatric care, 27 individuals (47%) followed this recommendation.

Resection of frontal encephalomalacias for intractable epilepsy: outcome and prognostic factors

PURPOSE

Because focal encephalomalacia is an important cause of medically intractable partial epilepsy and few studies have evaluated the efficacy and the safety of resecting focal-encephalomalacias to improve seizure control, we studied a cohort of 17 consecutive patients who underwent resection of encephalomalacias in the frontal lobes as a treatment of their intractable epilepsy.

METHODS

We evaluated several factors for their value in predicting postsurgical seizure control. Pre- and postsurgical magnetic resonance imaging (MRI) scans were reviewed independently by 2 blinded investigators.

RESULTS

At a median of 3 years of follow-up (range 0.6-7.5 years), 12 patients (70%) were seizure-free or had only rare seizures. The presence of a focal fast frequency discharge (focal ictal beta pattern) at the beginning of seizures on scalp EEG was predictive of seizure-free outcome (p = 0.017), even among patients who had complete resection of their encephalomalacias (p = 0.016). There was no significant differences in outcome with regard to age at the time of the injury that caused encephalomalacia, interval between injury and onset of seizures, duration of presurgical seizure history, presurgical seizure frequency, age at surgery, or the completeness of encephalomalacia resection. The analysis regarding completeness of encephalomalacia resection almost reached significance, suggesting that it may also be an important predictive factor (p = 0.051).

CONCLUSIONS

We conclude that surgery is a very effective treatment for intractable frontal lobe epilepsy (FLE) secondary to encephalomalacias. Patients are more likely to become seizure-free if they have a focal ictal beta discharge on their scalp EEG. Complete resection of the encephalomalacia should be attempted, since our results suggest that this may be a favorable predictive factor. Moreover, the operative strategy for our patients entailed, whenever possible, complete resection of the encephalomalacias and of the adjacent electrophysiologically abnormal tissues.

Factors associated with work outcome after anterior temporal lobectomy for intractable epilepsy

PURPOSE

Whereas the effect of anterior temporal lobectomy on seizure frequency is well recognized, less is known about its impact on work status.

METHODS

One hundred thirty-four of 190 consecutive patients with temporal lobectomy participated in this study. Eligibility criteria were developed to ensure that only patients with the potential of achieving specific outcomes were included in the corresponding analyses.

RESULTS

After surgery, significantly more patients were independent in activities of daily living (p < 0.001) or able to drive (p < 0.001). Income from work also increased (p < 0.01). Nearly one fifth of the patients who were eligible for analysis had either a gain (8%) or a loss (11%) of full- or of part-time work. Univariate analyses revealed the following factors to be associated with full-time work after surgery: student or full-time work within a year before surgery, full-time work experience before surgery, full- or part-time employment experience before surgery, no disability benefits before surgery, low postsurgical seizure frequency, improved postsurgical seizure control, excellent postsurgical seizure control, driving after surgery, and further education after surgery (p < 0.05). Significant factors on multivariate analysis were being a student or having full-time work within a year before surgery [odds ratio, 16.2 (95% CI, 4.3-60.5)], driving after surgery [15.2 (3.2-72.0)], and obtaining further education after surgery [9.2 (2.2-53.0)].

CONCLUSIONS

Anterior temporal lobectomy for intractable epilepsy improves activities of daily living and the ability to drive. Work outcome of this surgery is influenced by presurgical work experience, successful postsurgical seizure control especially to allow driving, and obtaining further education after surgery.

Assessing changes over time in temporal lobectomy: outcome by scoring seizure frequency

Current methods of evaluating seizure outcome after anterior temporal lobectomy (ATL) have major limitations. We evaluated the usefulness of a recently proposed system in our study of the stability of seizure frequency after ATL in 184 patients with intractable epilepsy. Data collection by chart review was supplemented by an intensive program of follow-up by our survey research center through correspondence or phone calls according to a protocol approved by our Institutional Review Board. Seizure frequency during each 12-month period after ATL was scored for each patient. The only statistically significant change in seizure frequency scores during follow-up was between the third and the fourth years (means of 2.61 and 2.11; P < 0.045). Further assessment showed that the change was most likely due to an increase in the proportion of patients who achieved a score of 0 when they successfully stopped taking antiepileptic medications (9.1% in the third year and 22.5% in the fourth year; P < 0.05). There was no statistically significant difference between follow-up years in the proportion of patients achieving excellent outcome (i.e. scores of 0-4). Outcome remained unchanged when follow-up at each year was confined to the same patients throughout their postsurgical course. By using the Seizure Frequency Scoring System, we have demonstrated that seizure outcome remains stable after ATL. The scoring system facilitates the detection of subtle changes in the postoperative course. The advantages and the limitations of the system are discussed.

Epileptiform abnormalities in hepatic encephalopathy

Epileptiform abnormalities are uncommon in patients with hepatic encephalopathy. A review of EEGs in patients with hepatic encephalopathy over a 10-year period identified 18 (15%) with epileptiform abnormalities. Thirteen patients had interictal discharges consisting of focal spike and sharp wave discharges, bilateral independent discharges, and generalized spike and wave discharges. A total of 10 patients had electrographic seizure discharges, focal in 6 and generalized in 5 (some patients had more than one abnormality). Twelve patients had clinical seizures, partial in four and generalized in eight. Neuroimaging failed to provide an etiology for the generation of epileptiform discharges in most patients, including those with focal abnormalities. Most patients with epileptiform discharges died or deteriorated. We conclude that epileptiform can be seen in patients with hepatic encephalopathy, and when present imply a poor prognosis.

Spatial filtering of multichannel electroencephalographic recordings through principal component analysis by singular value decomposition

Principal component analysis (PCA) by singular value decomposition (SVD) may be used to analyze an epoch of a multichannel electroencephalogram (EEG) into multiple linearly independent (temporally and spatially noncorrelated) components, or features; the original epoch of the EEG may be reconstructed as a linear combination of the components. The result of SVD includes the components, expressible as time series waveforms, and the factors that determine how much each component waveform contributes to each EEG channel. By omission of some component waveforms from the linear combination, a new EEG can be reconstructed, differing from the original in useful ways. For example, artifacts can be removed and features such as ictal or interictal discharges can be enhanced by suppressing the remainder of the EEG. We developed a variation of this technique in which the factors that reconstruct the modified EEG from the original are stored as a matrix. This matrix is applied to multichannel EEG at successive times to create a new EEG continuously in real time, without redoing the time-consuming SVD. This matrix acts as a spatial filter with useful properties. We successfully applied this method to remove artifacts, including ocular movement and electrocardiographic artifacts. Removal of myogenic artifacts was much less complete, but there was significant improvement in the ability to visualize underlying activity in the presence of myogenic artifacts. The major limitations of the method are its inability to completely separate some artifacts from cerebral activity, especially when both have similar amplitudes, and the possibility that a spatial filter may distort the distribution of activities that overlap with the artifacts being removed.

Long-term follow-up of patients treated surgically for medically intractable epilepsy: results in 291 patients treated at Mayo Clinic Rochester between July 1972 and March 1985

To assess the long-term outcome in patients who underwent surgical treatment of intractable epilepsy, we retrospectively reviewed the medical records of 291 consecutive Mayo patients treated between July 1972 and March 1985. We also evaluated the responses to a follow-up mailed questionnaire or telephone interview completed in 1992. Of the 291 patients, 245 (94% of the 261 patients known to be alive at the time of the survey) responded to the follow-up questioning. Information on the patients' neurologic status (including frequency of seizures, use of antiepileptic drugs, and self-reported assessment of functional capacity) and their overall satisfaction with the operative procedure and postoperative outcome were evaluated. Two hundred ninety patients survived the operation and were dismissed from the hospital. Of the 245 patients who responded to the follow-up survey, 41% and 58% had been free of seizures since surgical treatment and for 3 years preceding the follow-up survey, respectively. In addition, of the respondent cohort, 36% were successfully weaned off all antiepileptic drugs. Patients reported improvement in their daily functional capacity and quality of life after surgical treatment. For example, in comparison with the preoperative assessment, the patients' ability to obtain a driver's license was significantly increased, and seizure-related driving accidents, falls, and bodily injury significantly decreased. Furthermore, on the basis of current knowledge of the operation and its outcome, 85% reported that they would repeat the operative procedure. Thus, surgical treatment of intractable epilepsy is an effective option that is met with patient satisfaction.

The ictal bradycardia syndrome

PURPOSE

Episodic loss of consciousness presents a diagnostic challenge to the neurologist. A perhaps underrecognized cause of episodic loss of consciousness, which we call the ictal bradycardia syndrome, occurs when epileptic discharges profoundly disrupt normal cardiac rhythm, resulting in cardiogenic syncope during the ictal event. We attempt to determine whether the presence of the ictal bradycardia syndrome provides localizing information regarding the site of seizure onset and to describe the demographics of patients with this syndrome. We also discuss difficulties in diagnosis and treatment.

METHODS

We review 23 cases of the ictal bradycardia syndrome from the literature and present four additional cases. Brief histories are provided for the four previously unreported cases. Where data are available, cases are analyzed with respect to age, sex, and site of seizure onset.

RESULTS

Patients with the ictal bradycardia syndrome ranged from 4 months to 72 years (mean 39 years). There was an approximately 5:1 ratio of males to females. Twenty of the 23 patients (87%) whose site of ictal onset could be localized had temporal lobe epilepsy, although no clear lateralizing predominance was apparent.

CONCLUSIONS

The ictal bradycardia syndrome should be considered in patients with unusual or refractory episodes of syncope, or in patients with a history suggestive of both epilepsy and syncope. It suggests seizure onset in temporal lobe, and is more commonly diagnosed in males. Diagnosis may be aided by ambulatory EEG/ECG monitoring. Cardiac pacemaker implantation along with antiepileptic drug therapy may be necessary to minimize the possibility of death.

Long-term electroencephalographic monitoring for diagnosis and management of seizures

Long-term electroencephalographic (EEG) monitoring is the process of recording an EEG for a prolonged period in order to document epileptic seizures or other episodic disturbances of neurologic function. Indications for long-term EEG monitoring include diagnosis of a seizure disorder (epilepsy), classification of seizure types in patients with epilepsy, and localization of the epileptogenic region of the brain. Methods used for long-term EEG monitoring include prolonged analog or digital EEG, prolonged analog or digital ambulatory EEG, and prolonged analog or digital video-EEG monitoring with telemetry. Each of these methods has distinct advantages and disadvantages, particularly relative to storage, retrieval, and manipulation of data. Long-term EEG monitoring is useful in the management of patients with epilepsy and in the diagnosis of a seizure disorder. For most patients, inpatient long-term EEG monitoring is best performed in a specialized epilepsy-monitoring unit, which can provide a safe environment and both educational and psychosocial support. The choice of the most appropriate method of long-term monitoring for a specific clinical situation is best made by an epileptologist or a neurologist at an epilepsy center.

Movement disorders associated with the use of gabapentin

PURPOSE

We report two cases of unusual movement disorders associated with the use of gabapentin (GBP) in patients being treated for epilepsy who were otherwise neurologically intact.

METHODS

We describe two cases of unusual movement disorders associated with the use of GBP.

RESULTS

There were significant differences in the clinical findings between the two cases. In the first case, movements were very pronounced and the patient was in oculogyric crisis. Movements in the second case were quite subtle but nonetheless problematic for the patient. In each case, discontinuation of GBP led to rapid resolution of the movements, although a single dose of lorazepam was used in the first case.

CONCLUSIONS

Although formal electrophysiologic studies have not been performed, the movements associated with GBP use appear to be dystonic or myoclonic. Discontinuation of GBP led to rapid resolution of the movements. In severe cases, as in patients with oculogyric crisis, small doses of a benzodiazepine (BZD) appear to be efficacious and safe.

Routine EEG and temporal lobe epilepsy: relation to long-term EEG monitoring, quantitative MRI, and operative outcome

PURPOSE

To investigate the relation among routine EEG, long-term EEG monitoring (LTM), quantitative magnetic resonance imaging (MRI), and surgical outcome in temporal lobe epilepsy (TLE).

METHODS

We evaluated 159 patients with intractable TLE who underwent an anterior temporal lobectomy between 1988 and 1993. The epileptogenic temporal lobe was determined by ictal LTM. A single awake-sleep outpatient EEG with standard activating procedures was performed before LTM. EEGs were analyzed by a blinded investigator.

RESULTS

MRI scans showed unilateral medial temporal atrophy (109 patients) or symmetrical hippocampal volumes (50 patients). The surgically excised epileptogenic brain tissue revealed mesial temporal sclerosis, gliosis, or no histopathologic alteration. Routine EEG revealed temporal lobe epileptiform discharges in 123 patients. Routine EEG findings correlated with the temporal lobe of seizure origin (p < 0.0001) and the results of MRI volumetric studies (p < 0.0001). Interictal epileptiform discharges were seen only during LTM in 24 patients. Routine EEG was disconcordant with interictal LTM in another 20 patients. MRI-identified unilateral medial temporal lobe atrophy was a strong predictor of operative success (p < 0.0001). There was no significant relation between the routine EEG findings and operative outcome (p > 0.20).

CONCLUSIONS

Results of this study modified our approach in patients with TLE. Interictal epileptiform discharges localized to one temporal lobe on serial routine EEGs or during LTM may be adequate to identify the epileptogenic zone in patients with MRI-identified unilateral medial temporal lobe atrophy.

Bilateral magnetic resonance imaging-determined hippocampal atrophy and verbal memory before and after temporal lobectomy

We investigated pre- and postoperative verbal memory in temporal lobectomy patients who had volumetrically symmetric hippocampi. Pre- and postoperative verbal memory data based on the Logical Memory subtest of the Wechsler Memory Scale-Revised (WMS-R) were obtained from 15 left and 18 right temporal lobectomy patients. The difference between hippocampal volumes (R/L) was between -0.1 and 0.3 cm3, which is indeterminate for lateralizing hippocampal atrophy. Patients were divided into four groups based on side of operation and combined hippocampal volume expressed as a function of total intracranial volume (R + L volume/total intracranial volume). Patients with a combined hippocampal volume that was smaller than any combined hippocampal value of a normal control group were defined as bilaterally atrophic. Left temporal lobectomy patients demonstrated the expected decrease in verbal memory postoperatively regardless of whether the volumetrically symmetric hippocampi were nonatrophic or atrophic. Left temporal lobectomy patients with bilaterally atrophic hippocampi, however, had the poorest verbal memory before and after operation. Right temporal lobectomy patients tended to have improved verbal memory after operation whether or not the volumetrically symmetric hippocampi were atrophic. We conclude that side of operation is a more potent predictor of verbal memory outcome than is hippocampal atrophy when hippocampi are bilaterally symmetric and that left temporal lobectomy patients with bilateral atrophy may be at risk for greater functional deficits after operation.

Ipsilateral independent periodic lateralized epileptiform discharges

We have identified a previously unreported subtype of periodic lateralized epileptiform discharge (PLED) characterized by periodic discharges arising from ipsilateral independent foci. All 4 patients had acute cerebral lesions, and 3 of them had focal motor seizures with secondary generalization. The site of localization of the PLEDs corresponded to the boundaries of the underlying structural lesion or lesions, and this, together with the variable temporal relationship between them, supports a cortical origin for PLEDs associated with underlying lesions. the spatial and temporal independence of these periodic discharges in combination with their association with (1) acute cerebral lesions. (2) altered consciousness and seizures, and (3) resolution with time leads us to propose the term "IpsiIPs" to describe this subtype of PLEDs.

Pseudoseizures after epilepsy surgery

Seizure surgery for medically intractable partial epilepsy in selected patients usually results in dramatically improved seizure control. However, the authors present six patients who, after surgery for refractory complex partial seizures, postoperatively experienced pseudoseizures (also known as nonepileptic seizures), confirmed with EEG monitoring. Three of these patients also had nonepileptic seizures preoperatively that coexisted with their partial epilepsy. Psychiatric assessment revealed that this patient group had several characteristics in common, which suggests that preoperative psychiatric consultation may help identify those patients at risk for developing nonepileptic seizures. Treatment strategies with anticonvulsant medications and behavioral therapy are reviewed.

Interelectrode coherences from nearest-neighbor and spherical harmonic expansion computation of laplacian of scalp potential

Interchannel coherence is a measure of spatial extent of and timing relationships among cerebral electroencephalogram (EEG) generators. Interchannel coherence of referentially recorded potentials includes components due to volume conduction and reference site activity. The laplacian of the potential is reference independent and decreases the contribution of volume conduction. Interchannel coherences of the laplacian should, therefore, be less than those of referentially recorded potentials. However, methods used to compute the laplacian involve forming linear combinations of multiple recorded potentials, which may inflate interchannel coherences. WE compared 3 methods of computing the laplacian: (1) modified Hjorth (4 equidistant neighbors to each electrode), (2) Taylor's series (4 nonequidistant neighbors), and (3) spherical harmonic expansion (SHE). Average interchannel coherence introduced by computing the laplacian was less for nearest-neighbor methods (0.0207 +/- 0.0766) but still acceptable for the SHE method (0.0337 +/- 0.0865). Average interchannel coherence for simulated EEG (random data plus a common 10 Hz signal) was less for laplacian than for referential data because of removal of the common referential signal. Interchannel coherences of background EEG and partial seizure activity were less with the laplacian (any method) than with referential recordings. Laplacians calculated from the SHE do not demonstrate excessively large interchannel coherences, as have been reported for laplacians from spherical splines.

Electrocorticography and temporal lobe epilepsy: relationship to quantitative MRI and operative outcome

We investigated the relationship between electrocorticography (ECoG), quantitative magnetic resonance imaging (MRI), and surgical outcome in 165 patients with intractable nonlesional temporal lobe epilepsy (NLTLE). A standard mesial temporal resection was performed in all patients. Patients with an operative follow-up < 1 year were excluded from the study. The extent of the lateral temporal neocortex resection (LCR) was guided by ECoG and the side of surgery. The extent of the LCR was not predictive of seizure outcome in patients with or without hippocampal formation atrophy (p > 0.5). Patients undergoing a right anterior temporal lobectomy had a larger LCR (p < 0.0001), but the side of surgery was not of predictive value in determining seizure outcome (p > 0.1). The topography of the acute intracranial spikes did not correlate with operative outcome (p > 0.5) and was independent of hippocampal volumetric studies (p > 0.5). The postexcision ECoG was also shown not to be of prognostic importance (p > 0.5). Our results indicates that the extent of the lateral temporal cortical resection and the ECoG findings are not important determinants of surgical outcome in patients with NLTLE.

Bilaterally symmetric hippocampi and surgical outcome

This study investigates the relationship between hippocampal volume and seizure control following temporal lobectomy in patients with volumetrically symmetric hippocampi. Forty-six patients who underwent temporal lobectomy for nonlesional temporal-lobe-onset seizures, and in whom the volumes of the two hippocampi were roughly equal (ie, the difference of the right minus the left hippocampal volume fell between -0.1 and 0.3 cm3), were included. We graded postoperative seizure control on a four-point scale according to criteria defined by Engel. We found no relationship between the hippocampal sum (sum of the right plus left hippocampal volumes normalized for cranial size) and operative outcome. A satisfactory operative outcome is possible in patients with bilaterally symmetric mesial temporal sclerosis by MRI criteria.

Nimodipine as an add-on therapy for intractable epilepsy

OBJECTIVE

To analyze the effect of nimodipine in patients with intractable epilepsy.

DESIGN

We conducted a double-blind placebo-controlled crossover study in 95 patients.

MATERIAL AND METHODS

The dihydropyridine calcium antagonist nimodipine was used as add-on therapy (60 mg four times a day) in a 1-year placebo-controlled crossover study in 71 patients with localization-related epilepsy and 24 with generalized seizure disorders. Of the 95 patients, 81 were receiving two or more antiepileptic drugs. Patients diaries were used to record the number of seizures and any side effects.

RESULTS

Nimodipine seemed to be well tolerated during the study; only two patients were unable to complete the study because of probable adverse effects. The trial demonstrated no significant crossover effect and no significant effect of nimodipine on either the mean or the median number of seizures or seizure days. The peak median serum nimodipine level was less than 5 ng/mL in the 78 patients who completed the study.

CONCLUSION

This clinical trial found no beneficial effect with use of nimodipine as add-on therapy for intractable epilepsy. Potential reasons for the absence of efficacy of nimodipine may be the inclusion of patients with very refractory seizure disorders or the relatively low serum nimodipine concentrations related to the pharmacokinetic effect of concurrent antiepileptic medication.

Depth electrode studies in temporal lobe epilepsy: relation to quantitative magnetic resonance imaging and operative outcome

We performed a retrospective study of 30 patients with presumed intractable temporal lobe epilepsy (TLE) who underwent chronic intracranial EEG monitoring (CIEM). Multicontact depth electrodes were stereotactically implanted through the medial occipital lobe into amygdala and hippocampus. All patients had previously undergone extracranial ictal EEG monitoring that proved inadequate to localize the epileptogenic zone. No morbidity was associated with CIEM in the 30 patients. Twenty-five patients were shown to have exclusively or predominantly unilateral temporal lobe seizures, and 5 patients had bitemporal seizures without unilateral predominance; 24 patients subsequently underwent an anterotemporal lobe cortical resection. Twenty-one patients have been followed a minimum of 1 year postoperatively. Nine patients (43%) had a class I outcome (seizure-free, auras only, or provoked seizures), 3 patients (14%) had a class II outcome (> or = 95% seizure reduction), 4 patients (19%) had a class III outcome (> or = 50% seizure reduction); and 5 patients (24%) had a class IV outcome (< 50% seizure reduction or no change). A prolonged interhemispheric propagation time (p < 0.01) and magnetic resonance imaging (MRI)-identified hippocampal atrophy (p < 0.01) correlated with a favorable surgical outcome. Results of this study may prove useful in counseling patients who undergo CIEM before temporal lobe surgery.

Gender differences in post-temporal lobectomy verbal memory and relationships between MRI hippocampal volumes and preoperative verbal memory

Thirty-three men and 42 women who underwent left, and 26 men and 24 women who underwent right temporal lobectomy (TL) were studied retrospectively to determine if there were sex differences in (1) verbal memory outcome, and (2) relationships between verbal memory and magnetic resonance imaging (MRI) hippocampal volumes. All patients were left hemisphere language dominant. The surgical specimen and MRI were consistent only with mesial temporal sclerosis (MTS). Verbal memory was evaluated by Logical Memory percent retention (LMPER) from the Wechsler Memory Scale-Revised (WMS-R). Women experienced a significant improvement while men experienced a significant decline in postoperative LMPER. The difference between right and left hippocampal volumes predicted verbal memory outcome in both men and women. Preoperative LMPER was positively correlated with both the left and right hippocampal volumes in left TL women only. No verbal memory sex differences or correlations between LMPER and MRI data were found in the right TL group. The data support the presence of human neurocognitive sexual dimorphism. Verbal memory abilities supported by the hippocampus are less lateralized in women with left temporal lobe epilepsy and mesial temporal sclerosis. Women appear to have greater verbal memory plasticity following early left mesial temporal lobe insult.

Low-grade glial neoplasms and intractable partial epilepsy: efficacy of surgical treatment

We performed a retrospective study of 51 consecutive patients who underwent operation for intractable partial epilepsy related to low-grade intracerebral neoplasms between 1984 and 1990. All patients had medically refractory partial seizures and a mass lesion identified on neuroimaging studies. Lesionectomy was performed on 17 patients, and 34 had lesion resection and corticectomy. Mean postoperative follow-up was 4.4 years (range 2-8 years). Sixty-six percent of patients were seizure-free, and 88% experienced a significant reduction in seizure frequency. In 16 patients (31%), antiepileptic drugs (AEDs) were successfully discontinued. Twenty-five of 31 (81%) eligible patients obtained a driver's license after successful operation. Patients with complete tumor resection and no interictal epileptiform activity on postoperative EEG studies had the best operative outcome. Epilepsy surgery can result in long-term improvement in seizure control and quality of life (QOL) in selected patients with intractable tumor-related epilepsy. Our results should be useful to clinicians considering treatment options for patients with intractable seizures related to low-grade intracerebral neoplasms.

Extratemporal cortical resections and lesionectomies for partial epilepsy: complications of surgical treatment

Fifty patients with medically refractory extratemporal seizures underwent epilepsy surgery at our institution between 1988 and 1992. Twenty-nine patients (group I) had an extratemporal (mainly frontal lobe) corticectomy, and 21 patients (group II) had an epileptogenic lesion extirpated without resection of the epileptic brain tissue. Comprehensive neurologic evaluation was performed preoperatively, soon after operation, and approximately 3 months postoperatively to assess operative outcome. Magnetic resonance imaging (MRI) in group I patients usually showed no abnormality or a large destructive lesion. Neuroimaging showed a foreign tissue lesion in most group II patients. Thirteen of the 29 patients who underwent corticectomy had at least one adverse event (AE) potentially related to operation at the time of initial assessment. Four of the 13 patients required a surgical procedure to treat the operative complication, but only 1 of the 13 patients had a persistent neurologic deficit at follow-up examination. Three of the 21 patients who received lesionectomy had acute and persistent neurologic morbidity. Patients undergoing cortical resection remained intubated longer postoperatively (p < 0.005), and required longer hospitalization after operation (p < 0.001) and in the intensive care unit (p < 0.001) as compared with the lesionectomy group. Results of this study may prove useful in counseling patients regarding neurologic outcome after extratemporal surgery.

Diagnosis of mesial temporal sclerosis with conventional versus fast spin-echo MR imaging

PURPOSE

To test the accuracy of fast spin-echo (FSE) imaging versus that of double-echo conventional spin-echo (CSE) imaging in identification of the increased hippocampal signal intensity associated with mesial temporal sclerosis (MTS).

MATERIALS AND METHODS

Thirty-four subjects who subsequently underwent anterior temporal lobectomy for intractable seizures and in whom the presence or absence of MTS was ascertained with certainty were imaged with CSE and FSE. Three blinded reviewers evaluated the first and second CSE images (CSE1 and CSE2) and the FSE images.

RESULTS

CSE1 imaging had lower accuracy than FSE (P = .038) and CSE2 (P = .006) imaging. CSE2 imaging was slightly more accurate than FSE imaging (P = .048). Contrast-to-noise ratios were lower for CSE1 imaging than for CSE2 or FSE imaging (P < .001).

CONCLUSION

The FSE sequence evaluated was more time efficient than CSE imaging but slightly less accurate. Therefore, substitution of this sequence for a CSE sequence seems unwarranted.

Intractable nonlesional epilepsy of temporal lobe origin: lateralization by interictal SPECT versus MRI

We performed a retrospective study of 53 consecutive "nonlesional" temporal lobectomy patients to assess the relative utility of MRI versus interictal single-photon emission computed tomography (SPECT) in this patient population. We compared the seizure lateralizing properties of MRI and SPECT using multiple blinded expert reviewers for both SPECT and MRI with a test-retest reviewer paradigm and measurements of hippocampal volume from MRI. The criterion standard for seizure lateralization was satisfactory postoperative seizure control (n = 43). The rate of correct seizure lateralization was significantly greater for MRI than for SPECT (p < or = 0.01), and the rate of incorrect lateralization was significantly less for MRI than for SPECT. The most accurate MRI measure was hippocampal volume measurements, which correctly lateralized the seizures in 86.0% of cases. The correct lateralization rate for SPECT was 45.4%. The MRI and SPECT studies tended to be noncomplementary with respect to seizure lateralization, and SPECT was likely to give an incorrect or indeterminate result in patients who were not lateralized by MRI. Concordant MRI-EEG lateralization was a strong predictor of satisfactory postoperative seizure control, while no relationship between postoperative seizure control and SPECT findings was present.

Prognostic value of myoclonus status in comatose survivors of cardiac arrest

Generalized myoclonus status is common in comatose patients after cardiac resuscitation, but its prognostic value is uncertain. We studied the clinical, radiologic, and pathologic findings in 107 consecutive patients who remained comatose after cardiac resuscitation. Myoclonus status was present in 40 patients (37%). Features more prevalent in patients with myoclonus status were burst suppression on electroencephalograms, cerebral edema or cerebral infarcts on computed tomography scans, and acute ischemic neuronal change in all cortical laminae. All patients with myoclonus status died. Of 67 patients without myoclonus, 20 awakened. We conclude that myoclonus status in postanoxic coma should be considered an agonal phenomenon that indicates devastating neocortical damage. Its presence in comatose patients after cardiac arrest must strongly influence the decision to withdraw life support.