S-100 protein concentration in the cerebrospinal fluid of patients with Creutzfeldt-Jakob disease

We evaluated S-100 levels in paired cerebrospinal fluid (CSF) and serum samples in a group of 135 patients referred to the German Creutzfeldt-Jakob disease (CJD) surveillance unit from June 1993 to May 1995. The patients were seen in a prospective case control study. The diagnosis of probable CJD during life was made in any patient presenting with rapidly progressive dementia of less than 2 years' duration, typical periodic sharp wave complexes (PSWCs) in the EEG and at least two of the following findings: myoclonus, visual/or cerebellar symptoms, pyramidal and/or extrapyramidal signs and/or akinetic mutism. Patients presenting with the above clinical signs and symptoms but without PSWCs were classified as possible, while those with a dementia of a duration exceeding 2 years and without PSWCs were classified as other. S-100 was determined in paired CSF and serum samples by a commercially available enzyme-linked immunosorbent assay. In a group of 76 patients with definite and probable CJD, S-100 concentration (median 25 ng/ml, range 2-117) in CSF was significantly higher (P < 0.0001) than in 32 patients diagnosed as other (median 4 ng/ml, range 1-19). Serum levels of S-100 were below 0.5 ng/ml in all groups. At a cut-off of 8 ng/ml an optimum sensitivity of 84.2% with a specificity of 90.6% for the diagnosis of CJD by the determination of S-100 in CSF is obtained. S-100 levels exceeding 8 ng/ml in CSF support the diagnosis of CJD in any patient presenting with rapidly progressive dementia.     

Electroencephalographic findings and occurence of seizures after surgery of the Gasserian ganglion

The results of EEG investigations after Spiller-Frazier's operation for trigeminal neuralgia in 112 patients are reported. Follow-up EEGs were recorded within 1-8 years after surgery; two to three follow-up tracings were available in 53 patients. Two distinct phases of EEG alterations were noted: 1) The immediate postoperative phase characterized by bilateral delta waves of maximal distribution in the frontal-precentral area and in the temporal area on the side of surgery. Such alterations are supposedly due to postoperative edema or associated metabolic disturbances. 2) Several months after surgery focal abnormalities of the temporal lobe develop, which consist of high amplitude alpha-, beta- or theta-waves, sharp waves, spikes and occasional stypical spike-and-wave complexes. These abnormalities are reflected on the contralateral side in approximately one third of the case. Repeated EEGs confirmed the consistency of degree and location of these findings with the exception of a less constant incidence of spikes and sharp waves. Severity of EEG abnormalities and incidence of potentially epileptogenic discharges increases with age. In spite of the precarious location of such focal abnormalities in the temporal lobe only 3 of 112 patients (2.7%) reported seizures with temporal lobe features. The age of the three patients was below the average age of 59.1 years. Seizures occurred sporadically beginning approximately 2 years after surgery. The low incidence of seizures may in our opinion be due to the advanced age of most patients.     

Merosin-negative congenital muscular dystrophy, occipital epilepsy with periodic spasms and focal cortical dysplasia. Report of three Italian cases in two families

We report clinical, EEG and neuroimaging findings of three patients in two Italian families with merosin-negative congenital muscular dystrophy (CMD), drug-resistant occipital epilepsy, diffuse persistent cerebral white matter changes and focal cortical dysplasia. Clinical and epilepsy histories, EEG and neuroimaging findings were very similar in all patients. Seizures started in childhood and mainly consisted of periodic spasms, a particular type of partial seizure characterized by clusters of epileptic spasms. The motor expression of the spasms was very mild so that they had been frequently missed or misinterpreted as non-convulsive generalized absence seizures. Interictal EEG showed occipital spike-waves and bilateral synchronous slow spike-wave discharges. Ictal EEG showed prolonged periodic sequences of slow waves with associated fast rhythm complexes, characteristic of periodic spasms. Two patients had normal intelligence, one patient presented moderate mental retardation. Focal cortical dysplasia in the posterior areas of the brain, in addition to marked diffuse white matter alterations, was detected in the magnetic resonance images of all patients. Findings in these patients indicate that in merosin-negative CMD brain involvement can include cortical dysplasia, in addition to white matter changes. In such cases the brain damage can lead to a childhood-onset localization-related symptomatic occipital epilepsy. Epileptic seizures and cortical dysplasia can be, however, difficult to detect in CMD. The clinical semiology of epileptic seizures may in fact be modified because of muscular weakness. This implies that epilepsy may be misdiagnosed or even missed and EEG-polymyographic recordings may be necessary to identify it. Similarly, cortical dysplasia may be very localized and visible by neuroimaging only if it is carefully investigated on the basis of epileptological and EEG-polymyographic findings.     

Electroencephalogram

Electroencephalographic (EEG) changes are generally prominent in patients with encephalitis. In most of acute encephalitis, the EEG is characterized by non-specific diffuse slow activity. However several diseases such as herpes simplex encephalitis, slow virus infection or prion disease often show periodic EEG abnormalities, such as periodic synchronous discharges (PSD) and periodic lateralized epileptiform discharges (PLED). These findings are sometimes diagnostic, although the abnormality is not disease specific. EEG is often helpful in following up the clinical course of illness and in evaluating therapeutic effects.     

A field application of the ASAM placement criteria in a 12-step model of treatment for chemical dependency

Various CNS side effects have been reported since interferon (IFN) was introduced for the treatment of chronic active hepatitis C (CAHC) patients. Most reports of EEG changes after IFN therapy were inspective, and there is no report of quantitative EEG analysis. In this study, changes in quantitative EEG and biogenic amines after IFN therapy were studied to enable identification of CNS side effects early in CAHC patients. Before and 7 days after IFN therapy, EEG records and plasma and urinary amines were examined in 36 CAHC patients (46.9 +/- 12.3 years, 29 men and 7 women) who were hospitalized for the IFN therapy. After IFN therapy, no notable change in biogenic amines was recognized. On EEG, 13 patients (39.4%) showed increased slow wave activities and 2 patients (6.1%) showed paroxysmal discharges after IFN therapy. On quantitative EEG, the patients showed significantly increased absolute power in slow alpha, theta and delta bands and decreased absolute power in fast beta band (paired-T test). After IFN therapy, 4 of 36 patients developed psychiatric disorders; 2 patients developed depressive symptoms and 2 other patients developed manic states. One depressive patient and one manic patient had 6 Hz spike and slow waves before IFN therapy. On quantitative EEG, the other manic patient had shown significantly increased absolute power in slow alpha and decreased power in fast alpha and beta bands, and the other depressive patient had shown significantly increased absolute power in fast theta band and decreased power in fast beta band before the development of the psychiatric disorders. These results suggest that the changes of quantitative EEG, between before and 7 days after IFN therapy, can be useful in assessing the risk for the development of psychiatric symptoms induced by IFN therapy. It also suggests that patients with slight EEG abnormality such as a 6 Hz spike and slow waves before IFN therapy need careful observation.     

Spectral analysis in cyclic changes of human sleep evaluation

In this study cyclic changes of human sleep structure were examined. For whole-night polysomnograms of 35 healthy volunteers of both sexes, manual hypnograms were created and divided into NREM-REM cycles. EEG signals from C3-A2 derivation were analysed by computer using a Fast Fourier Transform (FFT). For consecutive NREM-REM cycles of individual sleep stages, EEG power density contents for delta, theta, alpha, sigma and beta waves were analysed. For consecutive sleep cycles, a clear decrease in NREM sleep duration, especially slow wave sleep duration, was obtained. In addition, a decrease in power density of delta waves was observed. For consecutive sleep cycles, increases in REM sleep duration and in power density of theta and alpha waves were obtained. In consecutive sleep cycles, high amplitude delta slow waves are replaced by higher frequency and lower amplitude waves. Thus stages of NREM sleep are replaced by stages of REM.     

Neonatal encephalopathy following fetal distress. A clinical and electroencephalographic study

Twenty-one neonates of over 36 weeks' gestation suffered perinatal asphyxia but not chronic hypoxia. Three clinical stages of postanoxic encephalopathy were distinguished. Stage 1 lasted less than 24 hours and was characterized by hyperalertness, uninhibited Moro and stretch reflexes, sympathetic effects, and a normal electroencephalogram. Stage 2 was marked by obtundation, hypotonia, strong distal flexion, and multifocal seizures. The EEG showed a periodic pattern sometimes preceded by continuous delta activity. Infants in stage 3 were stuporous, flaccid, and brain stem and autonomic functions were suppressed. The EEG was isopotential or had infrequent periodic discharges. Infants who did not enter stage 3 and who had signs of stage 2 for less than five days appeared normal in later infancy. Persistence of stage 2 for more than seven days or failure of the EEG to revert to normal was associated with later neurologic impairment or death.     

Chronic herpes simplex encephalitis initially presenting with persistent myoclonus

A 59-year-old female patient with atypical chronic herpes simplex encephalitis was reported. Initial symptom was persistent myoclonus involving the trunk and limb muscles, and later lateral gaze palsy to the left side, cerebellar ataxia, consciousness disturbance and other brainstem symptoms including absence of corneal and gag reflex and vocal cord palsy developed. The patient was successfully treated with high dose of acyclovir. Electroencephalogram was normal in the initial stage but later showed diffuse slow waves. Although CT scan and MRI showed no abnormal finding in the cerebral cortex, brainstem lesion was observed on PD weighted image of MRI. Lumbar puncture yielded a clear cerebrospinal fluid, with slightly elevated protein, increased lymphocytes, and elevated titer of herpes simplex virus type I. The serological data, albumin ratio (10.3), antibody index (12.3) and antibody ratio (7.1) were consistent with herpes simplex encephalitis. Ten days' administration of acyclovir, 1,200 mg a day and repeated three times, was prominently effective for the myoclonus and consciousness disturbance. A diagnosis of chronic herpes simplex encephalitis initially presenting with brainstem encephalitis was made. Judging from the clinical and EEG findings, the brainstem lesion was initially thought to be a cause of myoclonus in this case. However, somatosensory evoked potential (SPE) of both upper and lower extremities revealed enlarged amplitude (giant SEP), and long loop reflex was enhanced (C-reflex) on the left. Giant SEP and C-reflex imply cerebral cortex as the origin of the myoclonus. Brainstem inflammatory lesion might have involved the ascending inhibitory system, thus disinhibiting the cortical sensorimotor area and causing cortical myoclonus.     

A light microscopic and ultrastructural examination of calcified dental tissues of horses: 1. The occlusal surface and enamel thickness

Sleep is normally a time of motor quiescence. Motor disorders may, however, arise during the different phases of sleep. Nocturnal myoclonus or periodic leg movements in sleep usually occur during light sleep and may be considered the motor accompaniment of the cyclic fluctuations in excitability typical of such stages. Nocturnal frontal lobe epilepsy also occurs during NREM sleep and may be misdiagnosed as parasomnia. REM behavior disorders are instead dissociated episodes of REM sleep without atonia, often associated with or even heralding Parkinson's disease or multiple system atrophy.     

Difficulty in eye opening following left hemispheric infarction-- causative lesion and pathophysiology of abnormalities of the eye and eyelids movements]

Creutzfeldt-Jakob disease (CJD) is a transmissible disease of the nervous system causatively related to the presence of an abnormal prion protein, with dementia, myoclonic jerks, and periodic EEG activity. Fourteen patients (7 females and 7 males) ranging from 26 to 76 years of age (median 59 years) were evaluated between 1974 and 1995 at the Neurologic Clinic of S?o Paulo University School of Medicine. The average duration of the disease was 12 months (3.5-34 months). Early clinical findings were: behaviour changes in 7 patients, dementia in 4, visual disturbances in 4, vertigo in 2, tremor in 9, and dystonia in one. Advanced symptoms were dementia and myoclonus in all patients. Pyramidal tract dysfunction was found in 6, cerebellar ataxia in 2, seizures in 3, nystagmus and vertigo in 4, and peripheral nervous system involvement in 2. Atypical clinical forms were found in 5 patients. Periodic EEG activity was found in 10 patients. Cerebrospinal fluid evaluation showed pleocytosis in 1 patient, higher protein content in 2, and higher gamma globulin level in 2. In 10 patients anatomopathological evidence in the central nervous system confirmed the clinical diagnosis by presenting with status spongiosus. All except one patient presented with the sporadic form of the disease.     

Epileptiform electroencephalographic patterns

Electroencephalography (EEG) is the most useful test for assessment of patients with epilepsy. It can help establish the diagnosis of epilepsy and determine the type of seizure disorder and its site of origin. Epileptiform abnormalities in the EEG tracing may be focal or generalized. The main types of focal epileptiform discharges arise from the temporal, frontal, occipital, centroparietal, centrotemporal, and midline regions of the brain. Generalized epileptiform discharges consist of the 3-Hz spike-and-wave, slow spike-and-wave, atypical spike-and-wave, paroxysmal fast activity, and hypsarrhythmic patterns. Status epilepticus is manifested by continuous epileptiform discharges or recurrent seizure activity without interim recovery, which can occur in a generalized or focal manner. Benign epileptiform variants unassociated with seizures can also be present in the EEG. Included in this category are the "14 & 6" positive bursts, small sharp spikes, wicket waves, 6-Hz spike-and-wave discharges, and rhythmic temporal theta activity. The EEG findings should be interpreted in the context of the overall clinical picture.     

Behaviour-related effects of nicotine on slow EEG waves in basal nucleus-lesioned rats

The basal magnocellular nucleus is assumed to play a crucial role in cholinergic activation of the cortical EEG. The aim of this study was to establish whether intraperitoneally applied nicotine may counteract the power asymmetry of the slow waves in the cortical EEG of both hemispheres after an unilateral lesion in the basal nucleus. In 17 rats the basal nucleus (substantia innominata/ventral pallidum) was unilaterally lesioned by ibotenic acid. The lesion produced unilateral power increases of all frequencies up to 20 Hz in the frontal EEG that increased with higher arousal level. Additionally, synchronized spike and wave discharges appeared in the frontal EEG. The results indicate that the basal nucleus suppresses especially the delta EEG waves in the frontal motor cortex during motor active behaviour. Nicotine (0.1 and 1 mg/kg) partially counteracts the power asymmetry of frontal slow waves (2-6 Hz) only during exploratory sniffing but not during grooming and waking immobility. Physostigmine (1 mg/kg) was also effective during exploratory sniffing. The results may indicate a role of nicotinic mechanisms in the information input component of exploratory behaviour.     

Visual and quantitative ictal EEG predictors of outcome after temporal lobectomy

PURPOSE: We investigated whether visual and quantitative ictal EEG analysis could predict surgical outcome after anteromesial temporal lobectomy (AMTL) in which mesial structures, basal, and temporal tip cortex were resected. METHODS: We retrospectively reviewed 282 presurgical scalp-recorded ictal EEGs (21- to 27-channel) from 75 patients who underwent AMTL. We examined the pattern of seizure onset (frequency, distribution, and evolution) and estimated the principal underlying cerebral generators by using a multiple fixed dipole model that decomposes temporal lobe activity into four sublobar sources (Focus 1.1). We correlated findings with a 2-year postoperative outcome. RESULTS: Sixteen patients had seizures with a well-lateralized, regular 5 to 9-Hz rhythm at onset, that most often had a temporal or subtemporal distribution. All patients became seizure free after surgery. In 51 patients, seizure onset was remarkable for lateralized slow rhythms (<5 Hz), which sometimes appeared as periodic discharges, were often irregular and stable only for short periods (<5 s), and had a widespread lateral temporal distribution. Among these a favorable surgical outcome was encountered in patients with seizures having prominent anterior-tip sources ( 16 of 17 seizure free), whereas those with dominant lateral or oblique sources had a less favorable outcome (three of 14 and 13 of 18, respectively). Irregular, nonlateralized slowing characterized seizure onsets in eight patients. Three patients became seizure free after surgery. CONCLUSIONS: Both visual and quantitative sublobar source analysis of scalp ictal EEG can predict surgical outcome in most cases after AMTL and complement non-invasive presurgical evaluation.     

Assessment of digital EEG, quantitative EEG, and EEG brain mapping: report of the American Academy of Neurology and the American Clinical Neurophysiology Society

A. Digital EEG is an established substitute for recording, reviewing, and storing a paper EEG record. It is a clear technical advance over previous paper methods. It is highly recommended. (Class III evidence, Type C recommendation). B. EEG brain mapping and other advanced QEEG techniques should be used only by physicians highly skilled in clinical EEG, and only as an adjunct to and in conjunction with traditional EEG interpretation. These tests may be clinically useful only for patients who have been well selected on the basis of their clinical presentation. C. Certain quantitative EEG techniques are considered established as an addition to digital EEG in: C.1. Epilepsy: For screening for possible epileptic spikes or seizures in long-term EEG monitoring or ambulatory recording to facilitate subsequent expert visual EEG interpretation. (Class I and II evidence, Type A recommendation as a practice guideline). C.2. OR and ICU monitoring: For continuous EEG monitoring by frequency-trending to detect early, acute intracranial complications in the OR or ICU, and for screening for possible epileptic seizures in high-risk ICU patients. (Class II evidence, Type B recommendation as a practice option). D. Certain quantitative EEG techniques are considered possibly useful practice options as an addition to digital EEG in: D.1. Epilepsy: For topographic voltage and dipole analysis in presurgical evaluations. (Class II evidence, Type B recommendation). D.2. Cerebrovascular Disease: Based on Class II and III evidence, QEEG in expert hands may possibly be useful in evaluating certain patients with symptoms of cerebrovascular disease whose neuroimaging and routine EEG studies are not conclusive. (Type B recommendation). D.3. Dementia: Routine EEG has long been an established test used in evaluations of dementia and encephalopathy when the diagnosis remains unresolved after initial clinical evaluation. In occasional clinical evaluations, QEEG frequency analysis may be a useful adjunct to interpretation of the routine EEG when used in expert hands. (Class II and III evidence as a possibly useful test, Type B recommendation). E. On the basis of current clinical literature, opinions of most experts, and proposed rationales for their use, QEEG remains investigational for clinical use in postconcussion syndrome, mild or moderate head injury, learning disability, attention disorders, schizophrenia, depression, alcoholism, and drug abuse. (Class II and III evidence, Type D recommendation). F. On the basis of clinical and scientific evidence, opinions of most experts, and the technical and methodologic shortcomings, QEEG is not recommended for use in civil or criminal judicial proceedings. (Strong Class III evidence, Type E recommendation). G. Because of the very substantial risk of erroneous interpretations, it is unacceptable for any EEG brain mapping or other QEEG techniques to be used clinically by those who are not physicians highly skilled in clinical EEG interpretation. (Strong Class III evidence, Type E recommendation).     

Regulation of the septal pacemaker theta rhythm by the cervical nuclei of the midbrain

Neuronal activity in the medial septal region (the medial nucleus and the diagonal band nucleus, MN-DBN) was recorded along with hippocampal EEG traces in conscious rabbits with stimulatory electrodes implanted in the median cervical nucleus (MCN) and the reticular formation (RF) of the midbrain and pons. In all animals with electrodes in the MCN, the background theta activity frequency was low (4.6 +/- 0.15 Hz) as compared with intact rabbits or those with electrodes implanted only in the RF (5.2 +/- 0.19 Hz, p < 0.5). Stimulation of the MCN with weak low-frequency impulses reduced theta volleys from MN-DBN cells, reducing their frequency and regularity and inducing the appearance or strengthening of low-frequency delta modulation. The number of spikes in a volley decreased, and the duration of inter-volley intervals increased. Stimulation of the MCN led to a gradual decrease in the frequency and amplitude of theta waves, induced irregular delta waves and spindles of 12 Hz in the hippocampal EEG. Stimulation of the RF produced the opposite changes in volley activity in the MN-DBN and hippocampal EEG, with increases in theta and decreases in delta components. These results support a role for the midbrain cervical nuclei as structures limiting the generation of theta activity by the reticular-septal system, but do not support the existence of an MN-DBN-independent high-frequency serotoninergic theta rhythm. It is proposed that the effect of the MCN may be important for suppression and switching of attention.     

New trends in glass-ionomer chemistry

Carbamazepine (CBZ) is an effective anticonvulsant agent. Current literature reports describe several cases of seizure exacerbation and/or EEG worsening due to CBZ with a high prevalence in children and adolescents; we report 10 new cases. Nine patients had epilepsy; one showed delayed psychomotor development and frequent EEG paroxysmal abnormalities. Four patients were on monotherapy, six on polytherapy. All but one had therapeutic CBZ plasma concentrations. Seizures increased in frequency in nine, and in eight patients new seizure types appeared, mostly absences. Cognitive functions/behaviour worsened in eight; EEG recordings showed slowing background activity and increased paroxysmal abnormalities, in six cases diffuse/generalized spike waves were seen and in two continuous spike wave discharges. The mean time of clinical EEG worsening was 1-2 days after introduction of CBZ at therapeutic doses. After CBZ withdrawal clinical EEG improvement was evident in a few days. The underlying pathogenetic mechanism is not yet understood. However, the pathophysiology of seizure exacerbation might be related to the interaction between age-related alterations in the balance of excitation and inhibition in the developing thalamocortical circuitry and the essential activity of CBZ that tends to induce interictal discharges.     

The ictal electroencephalogram as a marker for the efficacy of electroconvulsive therapy

The question of how to define a therapeutically adequate electroconvulsive therapy (ECT) has been under discussion since the early days of ECT. Although convention has asserted a demand for minimum seizure times, the complex electrophysiological conditions involved in developing a generalized seizure make it problematic for therapeutic efficacy of ECT to be linked only with seizure duration. Within the framework of an open clinical study of 40 patients, selected parameters of the ictal electroencephalogram (EEG) have now been examined with respect to differentiation between therapeutically effective and ineffective treatments. For this purpose a rating scale covering both quantitative and qualitative features of the ictal EEG was used. Although this study recorded no correlations between seizure duration and clinical improvement, correlations were established between clinical improvement, on the one hand, and the frequency of epileptic discharges and their slowing during the spike-wave phase as well as the stereotypy of the discharge or a "stable" pattern of rhythmic spike-wave or sharp wave complexes, on the other. The results suggest that several of these EEG parameters might be combined to form a marker for therapeutically adequate ECT, and that treatment might be controlled accordingly.     

Efficient gene transfer to human squamous cell carcinomas by the herpes simplex virus type 1 amplicon vector

We determined the diagnostic value of the EEG in young children with Angelman syndrome (AS) and Rett syndrome (RS). EEGs, recorded before 5 years of age, of 10 patients with AS, 10 with RS and 10 with mental retardation of other origin were studied blindly by two examiners for the presence of the following items: (A) 4-6 Hz rhythmic activity of over 200 microV; (B) 2-3 Hz frontal activity of 200-500 microV; (C) posterior spikes; (D) triphasic frontal waves; (E) central and/or centro-temporal spike-wave complexes; and (F) other epileptic discharges. Based on these items the EEGs were scored as AS (A-D); RS (E-F); or other. Examiners never made a mistake between AS and RS. One examiner labeled 6 of 10 AS cases correctly, the other 5; 4 (5) were characterized as 'other.' In RS cases 5 were labeled as 'other' by the first examiner and 3 by the second one. We conclude that EEG patterns of AS and RS are sufficiently different to help differentiate between AS and RS at a young age, which has a bearing on genetic counseling.     

Enhanced expression of hepatic acyl-coenzyme A synthetase and microsomal triglyceride transfer protein messenger RNAs in the obese and hypertriglyceridemic rat with visceral fat accumulation

PURPOSE: To assess the diagnostic yield of magnetic resonance (MR) imaging in patients with symptoms and signs related to the trigeminal nerve. MATERIALS AND METHODS: Medical records and MR imaging studies in 112 consecutive patients referred for MR imaging over 5 years were evaluated. MR images were independently reviewed by two neuroradiologists unaware of the clinical findings. Signs and symptoms at presentation were associated with either a positive or negative MR imaging outcome. Logistic regression analysis was performed to identify clinical variables related to imaging results. RESULTS: Sixty-eight (61%) patients had positive MR imaging findings related to symptoms and signs. Trigeminal neuralgia was correlated with a negative MR imaging outcome (P < .001). Numbness (P < .01), impaired sensation (P < .001), other neurologic symptoms and signs (P < .01), progression of symptoms and signs (P < .001), and duration of symptoms of less than 1 year (P < .001) corresponded to a positive MR imaging outcome. Two regression models, each with three clinical parameters (progression, duration < 1 year, and trigeminal neuralgia or impaired sensation), had comparable accuracy for prediction of the MR imaging outcome. CONCLUSION: Clinical findings can be used to identify groups in which a high or a low yield of MR imaging is correlated with symptoms and signs related to the trigeminal nerve.     

Variability in visual cortex activation during prolonged functional magnetic resonance imaging

OBJECTIVE: To review the EEG features of ring 20 syndrome in two patients and determine the characteristic pattern of this syndrome. The features of our cases and 24 patients reported in the literature will be discussed. SUBJECTS AND METHODS: Report of two patients and review of literature. RESULTS: The two patients had intractable epilepsy since childhood. Their clinical seizures were mostly complex partial seizures. Often the patients seizures were of prolonged duration. Ictal EEG revealed characteristic slow waves, and sharp waves. The slow waves were (1) usually synchronous high-voltage slow waves with or without a spike component predominantly in the frontal and frontopolar areas, (2) sometimes showed a change in frequency every several seconds, (3) continued for a long period, and (4) easily spread diffusely. The sharp waves were 5-6 Hz irregular and diffuse discontinuous sharp waves, and sometimes appeared predominantly in the centroparietal area. The clinical seizure pattern and EEG findings were similar in the 24 published cases. CONCLUSIONS: These EEG findings may be a characteristic feature of ring 20 syndrome and thus may be useful as a diagnostic clue.