Value of ictal and interictal epileptiform discharges and high frequency oscillations for delineating the epileptogenic zone in patients with focal cortical dysplasia.

OBJECTIVES: There are different neurophysiological markers of the Epileptogenic Zone (EZ), but their sensitivity and specificity for the EZ is not known in Focal Cortical Dysplasia (FCD) patients. METHODS: We studied patients with FCD who underwent stereoelectroencephalography (SEEG) and surgery. We marked in the SEEG: (a) typical and atypical interictal epileptiform patterns, (b) ictal onset patterns, and (c) rates of ripples (80-250 Hz) and fast ripples (FRs) (>250 Hz). High frequency oscillations were marked automatically during one hour of deep sleep. Surgical outcome was defined as good (Engel I) or poor (Engel II-IV). We computed the sensitivity and, as a measure of specificity, the false positive rate to identify the EZ, and compared them across the different neurophysiological markers. RESULTS: We studied 21 patients, 19 with FCD II. Ictal and typical interictal pattern were the markers with highest sensitivity, while the atypical interictal pattern had the lowest. We found no significant difference in specificity among markers. However, there is a tendency that FRs had the lowest false positive rate. CONCLUSION: The typical interictal pattern has the highest sensitivity. The clinical use of FRs is limited by their low sensitivity. SIGNIFICANCE: We suggest to analyze the typical interictal pattern first. FRs should be analyzed in a second step. If, for instance, a focus with FRs and no typical interictal pattern is found, this area could be considered for resection.

Finger snapping during seizures.

We describe two patients who showed snapping of the right hand fingers during invasive intracranial EEG evaluation for epilepsy surgery. We correlated the EEG changes with the finger-snapping movements in both patients to determine the underlying pathophysiology of this phenomenon. At the time of finger snapping, EEG spread from the supplementary motor area towards the temporal region was seen, suggesting involvement of these sites.

EEG-fMRI: adding to standard evaluations of patients with nonlesional frontal lobe epilepsy.

OBJECTIVE: In patients with nonlesional frontal lobe epilepsy (FLE), the delineation of the epileptogenic zone is difficult. Therefore these patients are often not considered for surgery due to an unclear seizure focus. The aim of this study was to investigate whether EEG-fMRI can add useful information in the preoperative evaluation of these patients. METHODS: Nine nonlesional FLE patients were studied with EEG-fMRI using a 3 T scanner. Spike-related blood oxygen level dependent (BOLD) signal changes were compared to the topography of the spikes and to PET and SPECT results if available. The structural MRIs were reviewed for subtle abnormalities in areas that showed BOLD responses. For operated patients, postoperative resection and histology were compared to BOLD responses. RESULTS: Concordance between spike localization and positive BOLD response was found in 8 patients. PET and SPECT investigations corresponded with BOLD signal changes in 6 of 7 investigations. In 2 cases, reviewing the structural MRI guided by EEG-fMRI data resulted in considering a suspicious deep sulcus. Two patients were operated. In 1, the resected cortex corresponded with the suspicious sulcus and fMRI results and histology showed cortical dysplasia. In another, histology revealed an extended microdysgenesis not visible on structural MRI. EEG-fMRI had shown activation just adjacent to the resected pathologic area. CONCLUSIONS: Our study provides different types of support (topography, concordance with PET and SPECT, structural peculiarities, postoperative histology) that EEG-fMRI may help to delineate the epileptic focus in patients with nonlesional frontal lobe epilepsy, a challenging group in the preoperative evaluation.

Different structures involved during ictal and interictal epileptic activity in malformations of cortical development: an EEG-fMRI study.

Malformations of cortical development (MCDs) are commonly complicated by intractable focal epilepsy. Epileptogenesis in these disorders is not well understood and may depend on the type of MCD. The cellular mechanisms involved in interictal and ictal events are notably different, and could be influenced independently by the type of pathology. We evaluated the relationship between interictal and ictal zones in eight patients with different types of MCD in order to better understand the generation of these activities: four had nodular heterotopia, two focal cortical dysplasia and two subcortical band heterotopia (double-cortex). We used the non-invasive EEG-fMRI technique to record simultaneously all cerebral structures with a high spatio-temporal resolution. We recorded interictal and ictal events during the same session. Ictal events were either electrical only or clinical with minimal motion. BOLD changes were found in the focal cortical dysplasia during interictal and ictal epileptiform events in the two patients with this disorder. Heterotopic and normal cortices were involved in BOLD changes during interictal and ictal events in the two patients with double cortex, but the maximum BOLD response was in the heterotopic band in both patients. Only two of the four patients with nodular heterotopia showed involvement of a nodule during interictal activity. During seizures, although BOLD changes affected the lesion in two patients, the maximum was always in the overlying cortex and never in the heterotopia. For two patients intracranial recordings were available and confirm our findings. The dysplastic cortex and the heterotopic cortex of band heterotopia were involved in interictal and seizure processes. Even if the nodular gray matter heterotopia may have the cellular substrate to produce interictal events, the often abnormal overlying cortex is more likely to be involved during the seizures. The non-invasive BOLD study of interictal and ictal events in MCD patients may help to understand the role of the lesion in epileptogenesis and also determine the potential surgical target.

Patterns of hippocampal abnormalities in malformations of cortical development.

OBJECTIVE: To assess whether different types of malformation of cortical development (MCD) are associated with specific patterns of hippocampal abnormalities. METHODS: A total of 122 consecutive patients with MRI diagnosis of MCD (53 males, age range 1-58 years) were included in the study. Hippocampal measurements were made on 1-3 mm coronal T1-weighted MRIs and compared with MRIs of normal controls. RESULTS: A total of 39 patients had focal cortical dysplasia, 5 had hemimegalencephaly, 5 had lissencephaly-agyria-pachygyria, 11 had SLH, 11 had PNH, 12 had bilateral contiguous PNH, 5 had schizencephaly, and 34 had polymicrogyria. The frequency of hippocampal abnormalities in these patients with MCD was 29.5%. A small hippocampus was present in all types of MCD. Only patients with lissencephaly and SLH had an enlarged hippocampus. Abnormalities in hippocampal rotation and shape were present in all types of MCD; however, these predominated in PNH. None of the patients with lissencephaly-agyria-pachygyria or SLH had hyperintense signal on T2 or FLAIR images or abnormal hippocampal internal architecture. CONCLUSION: A small hippocampus was present in all types of MCD; however, the classic MRI characteristics of hippocampal sclerosis were often lacking. Abnormal enlargement of the hippocampus was associated with only diffuse MCD due to abnormal neuronal migration (lissencephaly-agyria-pachygyria and SLH).

Etomidate speech and memory test (eSAM): a new drug and improved intracarotid procedure.

BACKGROUND: The intracarotid amobarbital procedure (IAP) is an important part of comprehensive investigation of patients who are candidates for surgical treatment of epilepsy. Owing to repeated and lengthy shortages of amobarbital, causing delays in elective surgery, attempts have been made to find a suitable alternative anesthetic. The authors report their experience using etomidate, a widely used agent for the induction of anesthesia. METHODS: Sixteen consecutive patients requiring IAP to evaluate memory or to lateralize speech underwent the procedure using etomidate. Prior to the procedure a catheter was placed in the internal carotid artery and an angiogram was performed. EEG was recorded and read online by an electroencephalographer. An anesthetist injected the drug, administered by bolus followed by an infusion, which was maintained until each speech measure had been sampled and new memory items had been introduced. The infusion was then stopped and testing continued as in a standard IAP. RESULTS: In all cases (30 hemispheres) contralateral hemiplegia followed injection. EEG slow waves were observed in every injected hemisphere, with some contralateral slowing anteriorly in 18. Global aphasia with preserved attention and cooperation followed dominant-hemisphere injections. These phenomena remained during infusion, and upon its termination returned gradually to baseline over a period of about 4 minutes. CONCLUSIONS: Etomidate is a viable alternative to amobarbital, and its administration by bolus followed by infusion offers an improvement over the traditional intracarotid amobarbital procedure. Cognitive tests can be performed during an assured hemianesthesia of the injected hemisphere.

Preictal headache in partial epilepsy.

The authors studied clinical characteristics in 11 patients with intractable focal epilepsy and preictal headache (PIHA) using a standardized interview. Headache was frontotemporal, ipsilateral to the focus, in nine patients with temporal lobe epilepsy (TLE) and contralateral in one with TLE and in one with frontal seizures. Migrainous features were found in four. After surgery, all seven seizure-free patients and two with rare seizures were free of PIHA. It may be a useful lateralizing sign in patients with TLE.

Adult-onset epilepsy in focal cortical dysplasia of Taylor type.

Focal cortical dysplasia of Taylor type (FCDT) usually presents with seizures at an early age, whereas adult onset of epilepsy is uncommon. We reviewed the medical records of 213 patients with FCDT. In 21 patients (10%), age at seizure onset ranged from 18 to 55 years (mean 25.3). The outcome of seizures in patients with FCDT and adult-onset epilepsy seems favorable vs childhood-onset seizures.

Posterior quadrantic dysplasia or hemi-hemimegalencephaly: a characteristic brain malformation.

INTRODUCTION: Posterior quadrantic dysplasia (PQD), a developmental malformation involving the temporal, parietal, and occipital lobes of one cerebral hemisphere, leads to intractable epilepsy. OBJECTIVE: To characterize the clinical features of 19 patients with PQD and analyze the postsurgical outcome of those who underwent resection of dysplastic tissue. METHODS: The extent and nature of the malformation were primarily assessed with high-resolution brain imaging. Fourteen patients underwent complete or partial temporoparieto-occipital resection or temporal resection associated with parieto-occipital disconnection. Postoperative follow-up period ranged from 8 months to 7 years. The authors used the Engel classification for postoperative outcome. RESULTS: All patients were sporadic. Clinical features included infantile spasms, partial seizures, mental retardation, mild hemiparesis, and visual field defects. Neuroimaging localized the malformation within the posterior cerebral quadrant contralateral to the neurologic deficit and demonstrated hemi-hemimegalencephaly in 14 of 19 patients and multilobar cortical dysplasia in 5 of 19 patients. The authors observed class I outcome in six patients. Two patients had class II and four patients had class III outcome. Class IV outcome was seen in two patients. After surgery, two patients developed mild hemiparesis, and two developed a visual field defect. CONCLUSIONS: Widespread cortical dysplasia is more frequent in the posterior quadrant. In our series, posterior quadrantic dysplasia represents either hemi-hemimegalencephaly or multilobar cortical dysplasia. Individuals with posterior quadrantic dysplasia share a spectrum of clinical features. The intractable epilepsy in these patients may be alleviated by a large quadrantic temporoparieto-occipital resection.

Intractable temporal lobe epilepsy with rare spikes is less severe than with frequent spikes.

OBJECTIVE: To analyze clinical, electrophysiologic, and neuroradiologic characteristics of a group of patients with nonlesional intractable temporal lobe epilepsy (TLE) and rare or absent interictal epileptiform abnormalities (IEA). METHODS: Between 1990 and 2000, 31 patients (11 men; mean +/- SD age 34.3 +/- 11.7 years) with nonlesional intractable TLE were consecutively selected on the basis of the absence or paucity of IEA (<1/h) on serial scalp EEG recording; these were defined as "oligospikers." The clinical and laboratory characteristics of oligospikers were compared with those of a group of 27 age-matched control subjects (10 men; mean +/- SD age 38.5 +/- 11 years), randomly selected from a pool of patients with nonlesional TLE with frequent IEA. RESULTS: Oligospikers showed a later age at seizure onset (mean +/- SD 19.1 +/- 14.4 versus 10.2 +/- 7.4 years; p = 0.004), lower monthly frequency of complex partial seizures (median 6 versus 12; p = 0.035), lower incidence of secondarily generalized tonic-clonic seizures (10 versus 81%; p < 0.001), and no status epilepticus (0 versus 22%) than control subjects. Also, hippocampal atrophy (HA) was less commonly found in oligospikers (55 versus 96%; p = 0.001). However, there were no differences between the two groups in the frequency of family history of epilepsy, risk factors, febrile convulsions, and type of medication. Twenty-three (74%) oligospikers and 25 (93%) control patients underwent either a selective amygdalohippocampectomy or corticoamygdalohippocampectomy. Excellent surgical outcome (Engel's Class Ia) was found in 14 of 23 (61%) oligospikers and 17 of 25 (67%) control patients. CONCLUSIONS: This study identified a subgroup of patients with nonlesional intractable TLE with no or few IEA. Oligospikers have a later age at seizure onset, less frequent and less severe seizures, besides a lower incidence of HA. The similarity of etiologic factors compared with patients with frequent IEA suggests that the rarity of spikes could reflect a disease not really distinct but less severe, even though still intractable and incapacitating enough to consider surgery. In spite of the absence or paucity of IEA, oligospikers have excellent surgical outcome.

Localizing value of alpha-methyl-L-tryptophan PET in intractable epilepsy of neocortical origin.

BACKGROUND: [(11)C] alpha-methyl-L-tryptophan (alpha-MTrp) has been developed as a tracer for the study of the synthesis of serotonin in the brain with PET. However, it has been shown that in pathologic conditions the tracer may reflect the activation of kynurenine metabolism. Increased levels of serotonin and quinolinic acid have been described in resected epileptogenic cortex, raising the possibility that alpha-MTrp can localize seizure foci in patients with intractable partial epilepsy. The authors assessed the uptake of alpha-MTrp in 18 patients (11 men, mean +/- SD age 27.1 +/- 10.1 years, range 13 to 54) with intractable partial epilepsy to correlate the PET findings with the epileptogenic area defined by electroclinical and neuroimaging data. METHOD: Seven patients with cortical dysplasia (CD) and 11 with partial epilepsy in which conventional MRI and fluorine-18-deoxyglucose ((18)FDG)-PET studies failed to detect any abnormality were studied. All underwent scalp EEG monitoring during the PET scan to exclude ictal events and estimate the interictal epileptic activity. RESULTS: In seven patients (39%; CD four and cryptogenic partial epilepsy three), PET showed focal increased uptake of alpha-MTrp corresponding to the epileptogenic area. alpha-MTrp uptake in the epileptic focus correlated with the frequency of interictal spikes (r = 0.7, p < 0.05). CONCLUSIONS: alpha-MTrp-PET may be of value in the localization of the epileptogenic area not only in patients with visible dysplastic lesions, but also in those with cryptogenic partial epilepsy.

Texture analysis and morphological processing of magnetic resonance imaging assist detection of focal cortical dysplasia in extra-temporal partial epilepsy.

In many patients, focal cortical dysplasia (FCD) is characterized by minor structural changes that may go unrecognized by standard radiological analysis. To increase the sensitivity of magnetic resonance imaging (MRI) for the detection of subtle lesions of FCD, we developed voxel-based image postprocessing methods, including first-order texture analysis and morphological processing modeled on known MRI features of FCD. We selected 16 patients with histologically proven FCD. Image processing features were calculated over a neighborhood for each voxel in the three-dimensional T1-weighted MRI. Three feature maps were generated: (1) gray matter thickness map to model cortical thickening, (2) gradient map to model blurring of the gray matter-white matter junction, and (3) relative intensity map to model the hyperintense signal within the lesion. Two observers detected lesions on conventional MRI in 8/16 and on ratio maps in 14/16 patients. Sensitivity was 87.5% (14/16) for the ratio maps compared to 50% (8/16) for MRI (p < 0.003). Specificity was 95% (19/20) for ratio maps and 100% (20/20) for MRIs. Cohen's kappa was 0.53 for MRIs, indicating moderate agreement, and 0.83 for ratio maps, indicating strong agreement beyond chance between the 2 observers. The image-processing methods developed in this study improve visual detection of FCD, even in cases where no lesion is obvious on MRI. These techniques could increase the number of patients with partial epilepsy who could benefit from surgery.

Repeated neural tube defects and valproate monotherapy suggest a pharmacogenetic abnormality.

Valproate (VPA) is an effective, widely used antiepileptic drug. Unfortunately its use in pregnant women is associated with neural tube defects in the offspring. Although the etiology of neural tube defects is multifactorial, there is evidence that underlying genetic susceptibility plays a part. We describe two women taking moderate doses of VPA who repeatedly bore children with neural tube defects, despite folate supplementation. This suggests a pharmacogenetic susceptibility to the teratogenic effects of VPA.

Entorhinal cortex atrophy in epilepsy patients exhibiting normal hippocampal volumes.

OBJECTIVE: To determine whether MRI volumetric measurement of the entorhinal cortex could detect structural damage and lateralize the seizure focus in patients with temporal lobe epilepsy in whom no measurable hippocampal abnormalities were found. BACKGROUND: A reduction in the volume of the entorhinal cortex ipsilateral to the seizure focus in patients with intractable temporal lobe epilepsy and hippocampal atrophy was recently shown. METHODS: MRI volumetric analysis of the entorhinal cortex was performed using a T1-weighted three-dimensional gradient echo sequence in 24 control subjects and 22 patients with temporal lobe epilepsy and normal hippocampal volumes. Thirteen patients underwent surgery, with a mean postoperative follow-up of 36 months. RESULTS: Group analysis (multivariate analysis of variance) showed a reduction in the volume of the entorhinal cortex ipsilateral to the seizure focus in patients with left (p < 0.0001) and right temporal lobe epilepsy (p < 0.0001). Lateralization of the seizure focus could be done in 14 of 22 patients (64%) based on entorhinal cortex volumetry. CONCLUSION: Entorhinal cortex atrophy ipsilateral to the seizure focus supports the presence of structural damage in the mesial temporal lobe in patients with temporal lobe epilepsy and normal hippocampal volumes and emphasizes the participation of the entorhinal cortex in the pathogenesis of this disorder.

Time course of postoperative recovery of N-acetyl-aspartate in temporal lobe epilepsy.

PURPOSE: To assess the time course of increases in N-acetyl-aspartate/creatine (NAA/Cr), which can be measured using proton MR spectroscopic imaging (1H-MRSI), in patients with intractable nonlesional temporal lobe epilepsy (TLE) after successful epilepsy surgery. METHODS: We performed pre- and postoperative 1H-MRSI in 16 seizure-free (SF) patients and 16 not seizure-free (NSF) TLE patients. We calculated a mixed-design analysis of variance (ANOVA) between SF and NSF groups, ipsi- and contralateral to the side of operation, and pre- and postoperative NAA/Cr measurements. We applied nonlinear regression between pre- and postoperative NAA/Cr differences and the time interval between 1H-MRSI scans to fit a negative exponential model to NAA recovery. RESULTS: Mixed-design ANOVA revealed that (a) postoperative NAA/Cr was significantly higher in SF than in NSF patients (p = 0.02) and that (b) in the SF group, postoperative NAA/Cr values were significantly higher than preoperative values (p < 0.05) and returned to the normal range in most patients. According to our nonlinear regression model, in SF patients, there was a 50% increase relative to preoperative NAA/Cr values after 5.8 months, whereas an improvement of 95% was reached after 25 months. CONCLUSIONS: Our results extend preliminary observations of postoperative NAA recovery of SF patients by characterizing the time course of recovery as an exponential function with a half-time of approximately 6 months. The reversal of neuronal metabolic dysfunction remote from the epileptic focus may underlie the clinical observation of improvement of cognitive dysfunction after successful epilepsy surgery.

Surgery for temporal lobe epilepsy in older patients.

OBJECT: The goal of this study was to evaluate the efficacy of surgery for temporal lobe epilepsy (TLE) in older (> or = 50 years of age) patients. METHODS: The authors conducted a review of all patients 50 years of age or older with TLE surgically treated at the Montreal Neurological Institute and Hospital since 1981 by one surgeon (A.O.). Only patients without a mass lesion were included. Outcome parameters were compared with those of younger individuals with TLE, who were stratified by age at operation. In patients aged 50 years and older, the onset of complex partial seizures occurred 5 to 53 years (mean 35 years) prior to the time of surgery. Postoperatively, over a mean follow-up period of 64 months, 15 patients (83%) obtained a meaningful improvement, becoming either free from seizures or only experiencing a rare seizure. Most surgery outcomes were similar in both older and younger individuals, except for a trend to more freedom from seizures and increased likelihood of returning to work or usual activities in the younger patients. Note that a patient's long-standing seizure disorder did not negatively affect their ability to achieve freedom from seizures following surgery. CONCLUSIONS: Surgery for TLE appears to be effective for older individuals, comparing favorably with results in younger age groups, and carries a small risk of postoperative complications.

Clinical findings, imaging characteristics and outcome in catastrophic post-encephalitic epilepsy.

OBJECTIVES: The aim of this study is to characterize the clinical features and prognostic factors for intractable, post-encephalitic epilepsy. METHODS: We studied retrospectively 42 patients (26 men) evaluated between 1982 and 1999. MRI, neuropsychological findings, interictal and ictal scalp EEG were reviewed for all patients. Fifteen patients had additional stereo EEG (SEEG) studies. RESULTS: The mean age at encephalitis was 17 years (SD = 15.5); etiology was identified in 18 patients. During the acute illness, 79% had status epilepticus (SE) or recurrent seizures and 76% were in coma; mean Glasgow outcome scale (GOS) was 3.6 (SD = 0.8). The mean latency to seizure onset was 0.8 years (SD = 1.9). The majority (72%) presented with complex partial seizures with or without secondary generalization. According to interictal epileptiform findings and the predominant seizure onset pattern as found on scalp EEG, patients were unilateral temporal (UTLE) = 8, bilateral temporal (BTLE) = 12, and extratemporal/multifocal or generalized (ETMFE) = 22 patients. MRI atrophy and/or signal changes were unilateral temporal in 7 (18%), bilateral temporal in 5 (13%), multilobar/diffuse in 20 (51%), and absent in 7 (18%). ANOVA revealed significant differences in mean GOS between UTLE versus BTLE and ETMFE (4.7 versus 3.2 versus 3.6; p < 0.0001), but not in age at encephalitis. Latency to the first unprovoked seizure was shorter in patients with ETMFE compared to UTLE and BTLE (p < 0.01). Surgery was performed in 24 patients. The best outcome was obtained in UTLE (7/8 class I and II). In the others, outcome was poor in the majority (13/16 class III and IV). CONCLUSION: There is a small subgroup of patients with postencephalitic UTLE for whom the outcome is favorable. The majority of our patients had multifocal seizure onset with BTLE and ETMFE, and poor outcome after surgical treatment.

Lateralization of temporal lobe epilepsy (TLE) and discrimination of TLE from extra-TLE using pattern analysis of magnetic resonance spectroscopic and volumetric data.

PURPOSE: To examine whether or not pattern analysis of magnetic resonance volumetric (MRVol) and proton magnetic resonance spectroscopic imaging (1H-MRSI) data would enable (a) the accurate lateralization of temporal lobe epilepsy (TLE) and (b) the discrimination of TLE from extratemporal epilepsy (E-TLE). METHODS: For lateralization analysis, we used data from 150 nonforeign tissue lesional TLE patients [88 left-sided (L-TLE), 46 right-sided (R-TLE), and 16 bilateral (Bi-TLE)]. For the discrimination of TLE from E-TLE, we used data from 174 patients (145 with unilateral TLE, 14 with unilateral E-TLE, and 15 with widespread epileptogenic zones involving both the TL and extra-TL regions-multilobar epilepsy). A series of "leave-one-out" cross-validated linear discriminant analyses were performed using the MRVol and 1H-MRSI data sets to lateralize TLE and discriminate it from E-TLE. RESULTS: Lateralization: The leave-one-out linear discriminant analyses were able to correctly lateralize (with a posterior probability >0.50) 120 (90%) of the 134 L-TLE and R-TLE patients. Imposing higher posterior probability (>0.95) increased accuracy of lateralization to 98%, with only two discordant cases who underwent surgery on the side of electroencephalogram, and both had bad outcome. Discrimination: the leave-one-out linear discriminant analyses were able to correctly classify (with a posterior probability >0.50) 142 (89%) of the 159 TLE and E-TLE patients. Accuracy increased slightly as higher posterior probability cutoffs were imposed, with fewer patients being classified. CONCLUSIONS: Pattern analysis of 1H-MRSI and MRVol data can accurately lateralize TLE. Discriminating TLE from E-TLE was less accurate, probably due to the presence of temporal lobe damage in some patients with E-TLE reflecting dual pathology.

Invasive electrographic recording techniques in temporal lobe epilepsy.

The management of uncontrolled partial epilepsy is a process dependent on a multidisciplinary and analytic approach. It is necessary to understand which lesions are epileptogenic, and if they are indeed responsible for the generation of seizures. In addition to localizing seizure onset, the functional and eloquent areas of the brain need to be identified. As in many other centres, we perform resective surgeries on the basis of combined information derived from seizure semiology, EEG abnormalities, neuroimaging and other tests of cerebral function. If surface EEG recording yields inconclusive or ambiguous results, then invasive intracranial techniques using intracerebral depth or subdural electrodes can be used to improve diagnostic or prognostic accuracy. The indications, principles, results and complications of these recording techniques based on extensive experience at two epilepsy surgery centres are reviewed.

Successful epilepsy surgery in catastrophic postencephalitic epilepsy.

The authors studied prognostic factors for surgical treatment in 22 patients with intractable postencephalitic epilepsy. A small subgroup of patients (9/22) had a positive outcome after resective surgery. They had a higher functional level after encephalitis as measured by Glasgow Outcome Score, a longer time interval between encephalitis and onset of seizures, and localization of ictal EEG to one temporal lobe. The other patients had devastating seizures with poor outcome after surgery.