EEG and clinical studies of the development of alumina cream epileptic focus in split-brain cats

Alumina cream epileptic focus was established in the right sensorimotor cortex in 20 split-brain cats (partial or complete). EEG and behavioral observations were made in a period ranging from 24 to 836 days. Four types of EEG changes after alumina cream injection were differentiated. These types could be related to the direct effects of brain damage and to development of epilepsy. Spikes and sharp waves and paroxysmal discharges (focal and multifocal) were observed in about 60% of the cats. Clinical seizures developed in about the same percentage of the animals. These values are below those reported for cats with intact interhemispheric commissures. Diphenylhydantoin (DPH) was given orally in a daily dose of up to 15 mg/kg body weight in 9 animals with developed epileptic EEG activity. Five of them had epileptic seizures. DPH was introduced not earlier than 1.5 months after intracortical alumina cream injection. The plasma level of DPH varied between 7-20 mug/ml. This dose produced chronic symptoms of intoxication. Neither EEG changes nor clinical seizures were entirely controlled by this drug. Additional doses of Relanium (diazepam), and phenobarbital were necessary to stop generalized seizures or status epilepticus.     

Idiopathic generalised epilepsy in adults manifested by phantom absences, generalised tonic-clonic seizures, and frequent absence status

OBJECTIVES: To describe the clinical and EEG features of adult patients with very mild absences, late onset generalised tonic clonic seizures, and frequent absence status. METHODS: Patients were referrals to a clinic for epilepsies. They all had clinical assessment and EEG, video EEG, or both for documentation of absences. RESULTS: Of 86 adults with idiopathic generalised epilepsies and EEG/video-EEG documented absences, 13 patients showed similar clinico-EEG features with: (a) "phantom absences" consisting of mild ictal impairment of cognition associated with brief (3-4 s), generalised 3-4 Hz spike/multiple spike and slow wave discharges; (b) infrequent, mainly late onset, generalised tonic clonic seizures, and (c), absence status which occurred in six of them either in isolation or terminating with generalised tonic clonic seizures. None of the patients had myoclonic jerks or photosensitivity. Two patients were father and daughter and another patient had a family history of infrequent generalised tonic clonic seizures. CONCLUSION: It seems that this is an idiopathic generalised epilepsy syndrome in adults which has not been previously recognised.     

Problematic standards: improving organizational performance through the assess and improve phases

Since 1987, we have diagnosed 10 patients, 4 males and 6 females, aged 2-11 years at the last evaluation, who all met the following criteria of severe myoclonic epilepsy in infancy (SMEI): generalized or unilateral long-lasting febrile clonic seizures in the first year of life; the subsequent appearance of myoclonic seizures and other types of seizure (partial seizures, atypical absences and convulsive status epilepticus); and neuropsychological deterioration for a certain period. Family histories of epilepsy and febrile seizures could be traced in 1 and 3 cases, respectively. None of them had previous personal history of brain insult. Electroencephalographic (EEGic) recordings in febrile seizure stage were normal; and continuous prophylaxis with phenobarbital failed to prevent the recurrence of febrile seizures. EEG studies in myoclonic stage showed generalized spike-and-waves, polyspike-and-waves, focal abnormalities and/or photosensitivity. The seizures were highly resistant to antiepileptic drugs. Our experiences suggested that comedication of valproic acid, clonazepam and carbamazepine may be most effective in treatment of the diverse seizures including myoclonic seizures, myoclonic-tonic-clonic seizures, atypical absences and partial seizures. Myoclonic seizures and atypical absences diminished in parallel to a clear-cut decrease in generalized abnormalities on EEG in 4 cases aged more than 7 years. However, the partial seizures, secondarily generalized seizures and status epilepticus were still present. Further investigations should aim to identify the underlying etiology and to search more effective treatment.     

Imaging epileptogenic tubers in children with tuberous sclerosis complex using alpha-[11C]methyl-L-tryptophan positron emission tomography

Several reports have indicated that cortical resection is effective in alleviating intractable epilepsy in children with tuberous sclerosis complex (TSC). Because of the multitude of cortical lesions, however, identifying the epileptogenic tuber(s) is difficult and often requires invasive intracranial electroencephalographic (EEG) monitoring. As increased concentrations of serotonin and serotonin-immunoreactive processes have been reported in resected human epileptic cortex, we used alpha-[11C]methyl-L-tryptophan ([11C]AMT) positron emission tomography (PET) to test the hypothesis that serotonin synthesis is increased interictally in epileptogenic tubers in patients with TSC. Nine children with TSC and epilepsy, aged 1 to 9 years (mean, 4 years 1 month), were studied. All children underwent scalp video-EEG monitoring, PET scans of glucose metabolism and serotonin synthesis, and EEG monitoring during both PET studies. [11C]AMT scans were coregistered with magnetic resonance imaging and with glucose metabolism scans. Whereas glucose metabolism PET showed multifocal cortical hypometabolism corresponding to the locations of tubers in all 9 children, [11C]AMT uptake was increased in one tuber (n=3), two tubers (n=3), three tubers (n=1), and four tubers (n=1) in 8 of the 9 children. All other tubers showed decreased [11C]AMT uptake. Ictal EEG data available in 8 children showed seizure onset corresponding to foci of increased [11C]AMT uptake in 4 children (including 2 with intracranial EEG recordings). In 2 children, ictal EEG was nonlocalizing, and in 1 child there was discordance between the region of increased [11C]AMT uptake and the region of ictal onset on EEG. The only child whose [11C]AMT scan showed no regions of increased uptake had a left frontal seizure focus on EEG; however, at the time of his [11C]AMT PET scan, his seizures had come under control. [11C]AMT PET may be a powerful tool in differentiating between epileptogenic and nonepileptogenic tubers in patients with TSC.     

Ictal and interictal technetium-99m-bicisate brain SPECT in children with refractory epilepsy

Identification of epileptogenic foci in patients with refractory epilepsy remains a significant diagnostic challenge. Magnetic resonance imaging studies frequently fail to reveal an anatomic origin for the seizures, and scalp electroencephalography is often limited to identification of the involved hemisphere. Functional imaging modalities such as PET and SPECT are more promising tools for this application because they reflect the functional pathology associated with the seizure. These changes are more pronounced ictally, but until recently, no radiopharmaceutical was available that could be used routinely for ictal SPECT. The present study was therefore undertaken to determine whether 99mTc-bicisate could be used in ictal SPECT in pediatric patients with refractory epilepsy, to compare the patterns of ictal and interictal blood flow in these patients and to compare the localization information provided by ictal SPECT with that available from other techniques. METHODS: Technetium-99m-bicisate/SPECT was compared prospectively with scalp EEG for its ability to identify a possible seizure focus in pediatric patients with refractory epilepsy. Ictal and interictal SPECT studies were performed in 10 patients (3-19 yr old, mean age 10.9 +/- 4.3 yr; 7 female, 3 male) in whom MRI scans revealed no lesions that might be responsible for the seizures. RESULTS: Ictal SPECT was performed in all patients, and all ictal studies revealed focal perfusion abnormalities. By comparison, four of the interictal SPECT studies showed regional hypoperfusion that corresponded to the regions of hyperperfusion in the ictal studies, and three showed regional hyperperfusion corresponding to the hyperperfused regions in the ictal studies. Three interictal studies revealed no abnormal perfusion. Scalp EEG provided localization information in five patients. CONCLUSION: These initial results suggest that ictal SPECT with 99mTc-bicisate is a more promising tool for the identification of epileptogenic foci than interictal SPECT or scalp EEG in patients without focal abnormalities on MRI.     

Dynamic cerebral autoregulation during sevoflurane anesthesia: a comparison with isoflurane

OBJECTIVE: To study the incidence and pattern of epilepsy in patients with periventricular leukomalacia (PVLM) in two specialty clinic settings. BACKGROUND: Motor and cognitive deficit as well as epilepsy are common in patients with PVLM. With modern imaging techniques, PVLM is now easily recognized. METHODS: Epileptic seizures and syndromes as well as motor and cognitive deficits were correlated with MRI findings. Two patient populations were studied: Group A-children with cerebral palsy and PVLM presenting to a center for children with motor disability (n = 19); and Group B-epileptic patients with PVLM presenting to a tertiary epilepsy center (n = 12). A single patient with PVLM and epilepsy who underwent extensive investigations, including intracranial EEG telemetry, is reported. RESULTS: In Group A, 47% of patients had epilepsy (9/19). PVLM was found in 1.27% of patients investigated for epilepsy at a tertiary epilepsy center (12/942). The majority of patients in both groups had multiple seizure types, with complex partial seizures being most common. Of patients with seizures (Groups A and B), 85.7% had intractable epilepsy (18/21). Intracranial EEG in the illustrative case demonstrated a multifocal epileptic process with occipitotemporal predominance. CONCLUSIONS: PVLM was an uncommon underlying cause in patients presenting with epilepsy (Group A); however, patients presenting with motor disability and PVLM (Group B) had a high incidence of seizures. PVLM in epileptic patients is associated with multiple seizure types and medically refractory disease.     

Aspiration: a potential complication to vagus nerve stimulation

PURPOSE: Vagus nerve stimulation (VNS) is reported to reduce the frequency of seizures in children and adults without causing serious side effects. However, clinical observation of swallowing difficulties in 2 children treated with VNS made further investigation necessary. METHODS: Seven patients aged 4-18 years and treated with VNS for 6-14 months were investigated with videoradiography during barium swallow. The children performed 5-30 barium swallow investigations with the VNS device turned off, running as programmed, or set at continuous stimulations. The degree of aspiration was scored from 0 to 3. RESULTS: In 5 of 7 children, of whom reported transient swallowing difficulties, no change in the degree of aspiration was noted. The 2 children with swallowing difficulties, however. showed increased aspiration score when the stimulator was set at continuous stimulations. In 1 the score also appeared to increase with the VNS running as programmed (p > 0.05). Both children had severe mental and motor disabilities. CONCLUSIONS: Before and during VNS treatment patients should be evaluated with regard to swallowing problems. There needs to be an easy way to turn the device on and off to avoid aspirations, a hazardous and potentially life-threatening complication of VNS.     

Multilobar polymicrogyria, intractable drop attack seizures, and sleep-related electrical status epilepticus

BACKGROUND AND OBJECTIVE: Patients with cortical malformations often have intractable seizures and are candidates for epilepsy surgery. Within an unselected series of patients with various forms of cortical malformation, nine patients with multilobar polymicrogyria had electrical status epilepticus during sleep (ESES) accompanied by infrequent focal motor seizures. Eight patients also had intractable atonic drop attack seizures. Because ESES usually is accompanied by a good long-term seizure prognosis, the objective of this study was to examine ESES outcome among patients with a structural lesion that is usually highly epileptogenic and has a low seizure remission trend. METHODS: The nine patients had follow-up periods lasting 4 to 19 years. All underwent brain MRI, serial sleep EEG recordings, and cognitive testing during and after ESES. RESULTS: ESES and drop attack seizures appeared between the ages of 2 and 5 years (mean, 4 years) and ceased between the ages of 5 and 12 years (mean, 8 years). At the last visit patients were 8 to 23 years of age (mean, 14.5 years) and were either seizure free or had very infrequent focal motor seizures during sleep. Three patients were free from antiepileptic drugs. In no patient was definite cognitive deterioration apparent after ESES in comparison with earlier evaluations. CONCLUSIONS: Age-related secondary bilateral synchrony underlying ESES may be facilitated in multilobar polymicrogyria. The good seizure outcome contrasts with that usually found in the presence of cortical malformations. For children with polymicrogyria and drop attack seizures, surgical treatment of the epilepsy should be considered cautiously, and sleep EEG recordings should be performed systematically.     

Status epilepticus related to alcohol abuse

We reviewed the case records of 249 adult patients with generalized convulsive status epilepticus (SE) examined in San Francisco General Hospital between 1977 and 1989 and identified 27 patients (10.8%) in whom alcohol abuse was the only identifiable precipitating cause of SE. In 12 patients (44% of the study group), SE was the first presentation of alcohol-related seizures. Seizures with focal features were observed in 11 patients (40.1%), but there was little correlation with localized computed tomography (CT) or EEG abnormalities. SE was controlled with phenytoin (PHT), with or without a benzodiazepine (BZD), in 18 patients (66.7%). Twenty-two patients (81.5%) were discharged with no new neurologic deficits, but time to recovery of baseline mental status was prolonged (> 12 h) in 24 patients. With regard to alcohol abuse history, study patients did not differ from a comparison group with isolated alcohol withdrawal seizures. The results indicate that alcohol abuse is a common cause of SE and that SE may be the first presentation of alcohol-related seizures. Furthermore, the outcome of patients with alcohol-related SE compares favorably with that of patients with SE due to other causes, but recovery of these patients may be complicated by a prolonged postictal state.     

Neurocysticercosis--experience at the teaching hospitals of the University of Cape Town

In the 15 years 1975-1989, 239 patients attending the associated teaching hospitals of the University of Cape Town have been identified retrospectively as having neurocysticercosis. One hundred and twenty-three (51.46%) were children 12 years of age or younger, 14 (5.86%) were adolescents aged 13-19 years, and 102 (42.68%) were adults 20 years of age or older. Two hundred and twelve (88.7%) of these patients were black, almost exclusively Xhosa-speakers originating from the eastern Cape homeland regions of Transkei and Ciskei. Although the clinical features of neurocysticercosis are protean, these patients could be divided into three clinicoradiological groups--a group with seizures, a group with raised intracranial pressure, and an asymptomatic group. One hundred and ninety patients (79.5%) presented with seizures, either alone or in combination with other neurological deficits. Eighty-six patients (36%) presented with features of raised intracranial pressure, due to hydrocephalus in 32 cases, to focal space-demanding lesions in 4 and to multifocal cysticercal encephalitis in 50. Of interest is the significant difference in the abnormality causing the raised intracranial pressure in the children as opposed to the adults--44 children had multifocal cysticercal encephalitis while only 6 had hydrocephalus, and 26 adults had hydrocephalus while only 6 young adults (including 2 adolescents) had multifocal encephalitis. In the other 4 adults the raised intracranial pressure was caused by space-demanding mass lesions. Ten adult patients (4.1%) were 'asymptomatic' and a computed tomography scan for investigation of head injury revealed neurocysticercosis.     

Electroencephalography and computerized transaxial tomography in epilepsy diagnosis

Over a 6-month period 89 patients with epileptic seizures were systematically examined by EEGs and CT. Forty-two percent of all cases showed pathological findings in CT compared to 89% with abnormal EEGs. CT is very useful in identifying organic lesions in the epileptic patient. CT identified 11 cases of supratentorial tumour which were correctly localized by EEG. In patients with seizures after trauma or encephalitis the EEG abnormalities were more than could be detected by CT. The EEG and CT findings in cerebrovascular disorders, alcoholism and other diseases are discussed. A remarkable result is the relatively high percentage of hydrocephalus (23%) in the group of cryptogenic epilepsy. Positive EEG findings as to epilepsy could be seen in 62% of the cases.     

Can the age limit for endoscopy be increased in dyspepsia patients who do not have alarm symptoms?

We studied the interictal EEG of 50 epileptic patients (28 males, 22 females) who had parenchymal neurocysticercosis, diagnosed by CAT/MRI of the brain, positive immunological reaction for cysticercosis in cerebral spinal fluid or both. Age ranged from 5 to 61 years old; the mean age of onset was 24.2 +/- 12.2 years. Thirty-six patients had generalized seizures, 13 partial seizures with secondarily generalized seizures, and 1 had complex partial seizures. Twenty-two patients had parenchymal calcifications (inactive form); 21 had parenchymal cysts (active form) and 7 had both. EEG was abnormal in 14 patients (28%): 8 had focal slowing, 3 had focal sharp or spike activity, and 3 had both. The EEG was normal in patients with inactive forms of neurocysticercosis. The EEG was abnormal in 50% of patients with active and mixed forms of neurocystercosis and in 48% of patients with active form only. We conclude that the active forms of neurocysticercosis should be suspected when the EEG is found to be abnormal. In additional, EEG abnormality does not depend on the number of lesions, but rather on location and viability of the cysts, and on host response.     

The role of somatosensory evoked potentials in spinal dysraphism--do they have a prognostic significance?

Somatosensory evoked potentials (SEP) are not routinely used in spinal dysraphism. In this study 38 patients (29 children and 9 adults) with spinal dysraphism were prospectively studied with the objective of evaluating whether SEPs were a prognostic tool that could be used to predict clinical improvement after repair of a spinal dysraphic lesion. For all patients, preoperative SEP and postoperative SEP (within 1 week of operation) were recorded. Fifteen of these patients also had follow-up postoperative SEP recordings taken within 3 months of operation. A clinical examination was performed at the time of each SEP. Thirty patients had tethered cord, 12 had diastematomyelia and 15 had intra- and/or extradural tumours, which included lipomas and dermoid and epidermoid tumours. Twenty-one children and all adults had abnormal preoperative SEPs. Sixteen children and 4 adults had improved SEPs postoperatively. All these children and 2 of the 4 adults also experienced clinical improvement. Improvement in SEPs preceded clinical improvement in 12/20 patients. We observe that SEPs have a good prognostic value.     

Factors affecting growth and urease production by Trichophyton spp

BACKGROUND: Two to four percent of epileptics have their seizures triggered by flickering light, an effect which may be wavelength-dependent. We evaluated a patient with a long-standing history of light-induced petit mal seizures to determine if the seizures were triggered more effectively by a particular range of wavelengths and to determine whether this information could be used in the optometric management of such patients. METHODS: Flickering lights of different wavelengths but equal luminance were presented while the patient's electroencephalogram (EEG) and subjective reports were monitored. RESULTS: The EEG results were not significantly different for different wavelengths, but the patient reported that longer wavelength light induced stronger seizures more consistently. Based on these results we concluded that the patient might benefit from spectacles tinted to exclude transmission of red light. The patient was given 4 pairs of 85% transmission spectacles, which differed only in lens tint (red, yellow, green, and blue), to try over a period of time. The patient felt that the tinted lenses were not dark enough to decrease his seizures effectively and he has opted to wear standard sunglasses. CONCLUSIONS: We feel this case shows that patients with light-induced seizures can benefit from optometric consultation. Because the patient's subjective report identified the clearest wavelength effect, we feel that it is reasonable for the general practitioner to suggest deeply tinted lenses to reduce the frequency of seizures in these patients.     

The p21Rac/Cdc42-activated kinases (PAKs)

PURPOSE: Purely subjective events, identified as "seizures" by patients but not accompanied by any clinical or EEG changes, commonly occur during evaluation of patients for intractable epilepsy. We wished to determine the significance of such events. METHODS: We analyzed the frequency of subjective episodes in 379 adults who underwent EEG video monitoring as part of their evaluation for intractable epilepsy and the relationship of these experiences to epileptic and psychogenic nonepileptic (NES) seizures. We examined the results of tests of mental ability and of emotional, psychosocial, and quality of life (QOL) adjustment to determine if individuals with subjective events alone could be distinguished from those with epileptic seizures only, NES only, or no events, by these measures. RESULTS: We noted subjective events in 39% (147 of 379) of the patients. Of patients with subjective episodes, 52% also had epileptic seizures, 7% had NES, 1% had both epileptic seizures and NES, and 40% had subjective events alone. As a group, patients with subjective events alone were slightly more intelligent and less impaired neuropsychologically than people in the other groups, but they performed more poorly on several important measures of adjustment. CONCLUSIONS: The identification of persons with purely subjective episodes apart from all other episodes is important both phenomenologically and from a practical viewpoint.     

Continuous source imaging of scalp ictal rhythms in temporal lobe epilepsy

PURPOSE: We wished to determine whether continuous EEG source imaging can predict the location of seizure onset with sublobar accuracy in temporal lobe epilepsy (TLE). METHODS: We retrospectively analyzed the earliest scalp ictal rhythms, recorded with 23- to 27-channel EEG, in 40 patients with intractable TLE. A continuous source analysis technique with multiple fixed dipoles (Focus 1.1) decomposed the EEG into source components representing the activity of major cortical sublobar surfaces. For the temporal lobe, these were basal, anterior tip, anterolateral, and posterolateral cortex. Ictal EEG onset was categorized according to its most prominent and leading source component. All patients underwent intracranial EEG studies before epilepsy surgery, and all had a successful surgical outcome (follow-up >1 year). RESULTS: Most patients with ictal rhythms having a predominant basal source component had hippocampal-onset seizures, whereas those with seizures with prominent lateral source activity had predominantly temporal neocortical seizure origins. Seizures with a prominent anterior temporal tip source component mostly had onset in entorhinal cortex. Seizures in some patients had several equally large and nearly synchronous source components. These seizures, which could be modeled equally well by a single oblique dipole, had onset predominantly in either entorhinal or lateral temporal cortex. CONCLUSIONS: Multiple fixed dipole analysis of scalp EEG can provide information about the origin of temporal lobe seizures that is useful in presurgical planning. In particular, it can reliably distinguish seizures of mesial temporal origin from those of lateral temporal origin.     

Need for electroencephalogram video confirmation of atypical absence seizures in children with Lennox-Gastaut syndrome

Children with childhood epileptic encephalopathy (Lennox-Gastaut syndrome) frequently have both multiple seizure types and nonepileptic stereotyped events that are difficult to differentiate. We hypothesize that electroencephalogram (EEG) video monitoring is essential for correct identification of atypical absence seizures in this population. All video/EEG monitoring records on patients with confirmed Lennox-Gastaut syndrome between September 1992 and December 1996 were reviewed for clinical events and EEG changes. A subset of patients with suspected atypical absence seizures during the video/EEG formed the cohort for analysis. Thirty-eight patients had 48 monitoring periods ranging from 1 to 4 days (mean, 2.2 days). Twenty-six monitoring periods captured suspected atypical absence seizures and formed the study cohort. Suspected atypical absence seizures were epileptic seizures in only 27% (7 of 26) of the study cohort. By contrast, parents reliably and correctly identified tonic, atonic, and tonic-clonic seizures in the study cohort. Reliable diagnosis and subsequent counting of atypical absence seizures in patients with Lennox-Gastaut syndrome cannot be made on the basis of observation and/or history alone. Future outpatient studies of investigational anticonvulsant medications for patients with Lennox-Gastaut syndrome should consider parental counts of atypical absence seizures unreliable. We recommend that video/EEG monitoring be done on all Lennox-Gastaut syndrome patients with suspected atypical absence seizures not controlled by medication.     

Relationship between EEG and test intelligence: A critical review.

Literature on the relationship of EEG to test intelligence scores is reviewed. Evidence for the relationship between these 2 variables seems strongest for samples of children, institutionalized geriatric patients, mental deficients, and brain-injured persons; and weakest for samples of normal adults. EEG indices seem to be more strongly related to MA than to IQ. Criticisms of the previous research are directed at insufficient attention to the measurement of intelligence, failure to control for sex, too restricted placements of leads, too restricted an employment of EEG indices, and the assessment of EEG performance under inappropriate conditions. (2 p. ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incidence of photosensitive epilepsy: a prospective national study

We undertook a prospective nationwide study to determine the incidence of photosensitive epilepsy (PE). Virtually all EEG departments in Great Britain (providing approximately 90% coverage of all EEGs performed on people with newly diagnosed seizures) screened cases referred to them over a 3 month period and identified all new cases of epilepsy (defined as one or more recognised seizures) whose first EEG showed a photoparoxysmal response (PPR) on intermittent photic stimulation (IPS). 191 cases were identified, 143 of whom had type 4 PPRs (generalised spike and wave on IPS) on their first EEG. The annual incidence of cases of epilepsy with type 4 PPRs on their first EEG was conservatively estimated to be 1.1 per 100,000, representing approximately 2% of all new cases of epilepsy. When restricted to the age range 7-19 years, the annual incidence rose to 5.7 per 100,000-approximately 10% of all new cases of epilepsy presenting in this age range. To ascertain if there was a significant seasonal variation in PE, 5 EEG departments (which together contributed 15% of cases in the first study period) were visited during a second 3 month study period to identify all new cases of epilepsy with type 4 PPRs on their first EEG. No significant seasonal variation in incidence between summer and winter was found.     

Spectral EEG during short-term discontinuation of antiepileptic medication in partial epilepsy

The effect of short-term discontinuation of antiepileptic drugs (AEDs) on spectral analysis of EEG background activity (spectral EEG) was studied in patients undergoing preoperative evaluation for epilepsy surgery. We also wished to clarify whether AED discontinuation would provide lateralizing evidence in spectral EEGs of patients with temporal lobe epilepsy (TLE). Spectral EEGs were performed in 15 patients receiving their regular medication regimen and again after a 1-week period during AED withdrawal. A subgroup of 9 patients who had previously undergone temporal lobectomies (TLE group) was studied separately. In this group, we evaluated the effect of preceding seizures on spectral EEG derived from temporal neocortical areas. In all patients, spectral EEG changes were detected even after a short-term AED withdrawal. The total amount of absolute delta activity was reduced and occipital peak frequency and relative alpha activity were increased as compared with baseline values. In TLE patients with habitual seizures occurring < 20 h before the spectral EEG recording, lateralization was correctly identified by the greater amount of absolute delta activity ipsilateral to the epileptogenic focus. Epileptic seizures are accompanied by subtle focal slowing in spectral EEG for a much longer period than has been assumed. In addition, postictal spectral EEG over the temporal lobes may have lateralizing value. Further studies in larger numbers of patients are needed to evaluate the role of spectral EEG in the preoperative evaluation of patients for temporal lobe surgery.