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Objective: We describe the evolution of the electroclinical picture of patients with different types of self-limited epilepsy of childhood (SLEC) occurring at the same or at different times with or without atypical evolutions as well as patients with SLEC associated with childhood absence epilepsy (CAE)., Material and Methods: A multicenter, retrospective, descriptive study was conducted evaluating patients with SLEC who had focal seizures of different types of SLEC including atypical evolutions as well as SLEC associated with absence epilepsy seen at eight Argentinian centers between April 2000 and April 2019. Of 7705 patients with SLEC, aged between 2 and 14 years (mean, 7.5 years), of whom 2013 were female and 5692 male (ratio, 1:2.8), 5068 patients had SLECTS, 2260 patients had self-limited childhood occipital epilepsy Panayiotopoulos type (SLE-P), 356 had self-limited childhood occipital epilepsy Gastaut type (SLE-G), and 21 had self-limited epilepsy with affective seizures (SLEAS). Electroclinical features typical of more than one SLEC syndrome were recognized in 998 (13 %) children., Results: We recognized three well-defined groups of patients. The most frequent association was SLE-P and SLECTS, the paradigmatic type, but associations of SLE-P and SLE-G, SLECTS and SLE-G, and SLEAS and SLE-P or SLECTS were also recognized. The second-most-common association was SLEC and an atypical evolution. In this group, the most frequent combination was SLECTS with its atypical evolution, opercular status epilepticus, epileptic encephalopathy with continuous spike-and-waves during slow sleep, or Landau-Kleffner syndrome. SLE-P and SLE-G associated with an atypical evolution were also identified. The third, less-frequent group had SLECTS, SLE-P, or SLE-G associated with CAE. These cases support the concept that the different types of SLEC are part of a self-limited childhood seizure susceptibility syndrome., Conclusion: Our study demonstrated that 13 % of our patients with SLEC have with different types of SLEC occurring at the same or at different times with or without atypical evolutions - i.e. CSWSS - as well as patients with SLEC associated with CAE, supporting the concept of the self-limited childhood seizure susceptibility syndrome., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Objective: Here we present cases of focal epilepsy with affective symptoms analyzing seizure characteristics, EEG pattern, treatment, and outcome., Methods: A multicenter, descriptive, retrospective study was conducted evaluating 18 patients with self-limited epilepsy who presented with seizures with affective symptoms seen between April 2000 and April 2018 at eight Argentinian centers., Results: Eighteen patients had focal seizures with affective symptoms; all of them had affective symptoms characterized by sudden fright or terror and screaming. Seizures started with manifestations of sudden fright or terror manifested by a facial expression of fear; consciousness was mildly impaired in 15/18 patients. Eleven of the patients also had autonomic manifestations, such as pallor, sweating, and abdominal pain. In addition, four of these 11 patients had ictus emeticus and one also presented with unilateral deviation of the eyes and head. Speech arrest, salivation, glottal noises, and chewing or swallowing movements were observed in 2/18 patients at the onset of the affective seizures. Two others also had mild asymmetric dystonic seizures involving both hands and arms. Three patients had tonic deviation of the mouth involving the lips and tongue as well pharyngeal and laryngeal muscles, resulting in anarthria and drooling. Two patients had brief hemifacial focal clonic seizures., Conclusion: Affective manifestations associated or not with motor and/or autonomic manifestations and associated with typical EEG features of the idiopathic focal epilepsies of childhood is a particular presentation of self-limited focal epilepsy in childhood., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Purpose: The aim of this study is to analyze the electroclinical features, treatment, and evolution of patients with Rasmussen syndrome (RS)., Materials and Methods: We conducted a retrospective, descriptive study in 32 consecutive patients with RS followed between 1990 and 2012., Results: Twenty boys and 12 girls were included in the study. The mean and median ages at onset of the seizures were 6.5 and 7 years, respectively. Twenty-eight cases had epilepsia partialis continua that had started at a mean age of 9.5 years. Fixed hemiparesis occurred within the first two years after seizure onset in 26 patients. The ictal EEG showed a multifocal origin, but confined to the affected hemisphere in all patients. Mild focal atrophy involved the temporo-insular region associated with enlargement of the ipsilateral horn and Sylvian fissure. An abnormal cortical and/or subcortical hyperintense signal was observed in T2 and Flair images in 25 and 17 patients, respectively. T2 hyperintensity and atrophy in the basal ganglia was documented in five patients. Corticosteroids associated with immunoglobulins were used in 25 patients. Surgical treatment was performed in 25 patients. After a mean follow-up of 13 years (range, 2-20) good surgical outcome-- Engel class I--was observed in 23 of 25 patients operated., Conclusion: Corticosteroid and intravenous immunoglobulin treatment should be considered in the early stages of the disease. Patients with RS had a good response to surgical excision of the affected hemisphere., (Copyright © 2013 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

Purpose: In children with symptomatic or idiopathic focal epilepsies, their disease may evolve into an epileptic encephalopathy related to continuous spike and wave during slow sleep (CSWS) or electrical status epilepticus during slow sleep (ESES). ESES syndrome implies serious risks of neuropsychologic impairment, and its treatment has frequently been disappointing. The aim of this study is to present our experience using sulthiame as add-on treatment in 53 patients with ESES syndrome that was refractory to other antiepileptic drugs (AEDs)., Methods: Neurologic examinations, cerebral magnetic resonance imaging (MRI), and repeated prolonged sleep electroencephalography (EEG) studies were performed in all cases. Data about school achievements and or neuropsychological evaluations were obtained repeatedly during the follow-up of 1.5-16 years. Sulthiame was added in doses ranging between 5 and 30 mg/kg/day., Key Findings: Since add-on of sulthiame, 10 of 28 patients in the symptomatic group became seizure free: 4 patients with normal EEG studies and 6 with residual spikes. Nine of 28 patients showed a significant reduction in number of seizures and presented spikes but no ESES on EEG. The other nine cases showed neither clinical nor EEG improvement. A striking result was that 3 of 11 children with unilateral polymicrogyria and ESES syndrome became seizure free, and in another six a significant improvement in frequency of seizures and in EEG abnormalities seemed to be related to the add-on of sulthiame. Twenty-one of the 25 patients in the idiopathic group became seizure free and without ESES in <3 months after add on of sulthiame. In two of the patients the changes were seen in a few days., Significance: We understand that sulthiame may be effective as add-on treatment in children with ESES syndrome., (Wiley Periodicals, Inc. © 2012 International League Against Epilepsy.)

Objective: In this study we report the clinical outcomes of hemispherectomy for epilepsy in pediatric patients with special emphasis on the epileptic syndromes and their etiologies., Material and Methods: We retrospectively studied 45 patients with medically refractory epilepsy with hemispheric lesions who underwent hemispherectomy at the "Hospital de Pediatría Prof. Dr. Juan P. Garrahan", Buenos Aires, Argentina between February 1990 and February 2010. Patients had been assessed using a standard protocol involving clinical, neuroradiological, neurophysiological, and neuropsychological teams., Results: Twenty-seven males and 18 females with a mean age of 8.5 years (range, 2 months to 18 years) who underwent epilepsy surgery for refractory epilepsy were assessed. The mean time of follow-up was 9.5 years (range, 1 to 16 years). The following epileptic syndromes were recognized: West syndrome in 15 patients (33.5%), Rasmussen syndrome in 13 (29%), focal symptomatic epilepsy in 8 (17.5%), startle epilepsy in 6 (13.5%), Lennox-Gastaut syndrome in 2 (5%), and continuous spikes and waves during slow sleep in 1 (2%). The surgical specimens revealed malformations of cortical development in 18 patients (40%), Rasmussen encephalitis in 13 (29%), porencephalic lesions in 10 (22%), gliosis in 2 (4.4%), tumor in 1 (2.2%), and Sturge-Weber syndrome in 1 (2.2%)., Conclusion: The outcome of hemispherectomy in pediatric patients is good for those with refractory epilepsies, such as West syndrome, Lennox-Gastaut syndrome, epileptic encephalopathy with continuous spikes and waves during slow sleep, and startle epilepsy arising from a hemispheric lesion associated with hemiplegia.

Unlabelled: In this study, we present the electroclinical features and evolution of patients with epileptic spasms (ES) in clusters without hypsarrhythmia and with or without focal or generalized paroxysmal discharges on the interictal EEG. We also discuss how to nosologically define these cases., Methods: Between February 1, 1990, and December, 2009, sixteen patients met the electroclinical diagnostic criteria of ES in clusters without hypsarrhythmia., Results: ES were cryptogenic in thirteen patients and symptomatic in three. Age at onset of ES was between 4 months and 30 months, with a mean age of 9 months and a median age of 7 months. Seven patients had seizures before the onset of ES. Focal spikes were observed in seven patients, bilateral spikes and spikes and waves in five, multifocal spikes in two, and two patients had a normal EEG. The ictal EEG recording showed diffuse high-amplitude slow waves in ten patients, diffuse slow waves followed by voltage attenuation in four patients, and diffuse fast rhythms in two. ES were cured in five patients. Mean follow-up was 6 years. Neuropsychological development has been normal in the five latter patients. Eleven patients continue with seizures refractory to antiepileptic drugs after a mean follow-up of 10 years. Of these eleven patients, five have severe mental retardation, three have moderate mental retardation, and two have mild mental retardation. All of them show behavioral disturbances., Conclusion: The patients in this series may be considered to have a variant of West syndrome rather than an electroclinically distinct epileptic syndrome., (Copyright © 2010 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

Purpose: We present the electroclinical features, treatment, and evolution of patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS)., Material and Methods: We analyzed the charts of forty-two patients who met the diagnostic criteria of MTLE-HS. The mean follow-up after seizure onset was 10.5 years., Results: According to age, we defined three groups. The first group included nine patients that started with seizures before 2 years of age. Motor seizures were the hallmark clinical manifestation. All patients of this group also presented with motor arrest and oro-alimentary automatisms. In three of them, the interictal EEG recordings showed bilateral paroxysms predominantly in anterior regions, in addition to focal abnormalities, and two had an apparently generalized ictal pattern. The second group included 17 patients that started with seizures between 2 and 10 years of age. In this group the automatisms were also oroalimentary, but more complex and the patients had less motor manifestations. The interictal EEG recordings showed temporal abnormalities. The ictal EEG recordings showed lateralized abnormalities with a maximum in the temporal electrodes. The third group included 16 patients that started with seizures between 10 and 16 years of age. The most common clinical manifestation was abdominal aura followed by oroalimentary, gestural, and verbal automatisms. The interictal and ictal EEG recordings showed well-localized abnormalities in temporal lobes. Thirty-eight patients underwent surgical treatment. Thirty-five patients are seizure free., Conclusion: MTLE-HS represents a well-defined and distinct symptomatic epileptic syndrome. Surgical treatment was successful in most patients., (Copyright © 2010 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

Objective: To analyze the electroclinical features and evolution of seven infants with benign infantile focal epilepsy with midline spikes and waves during sleep (BIMSE)., Material and Methods: Seven patients were examined at our department between February 2003 and February 2009, with onset of seizures between six and 13 months of age (mean, 10.2 months; median, 11 months). Patients with cryptogenic and symptomatic focal epilepsies were excluded. Sex, age, familial history, type of seizures and AED treatment were noted and EEG monitoring, MRI and CT scanning, and developmental and psychomotor evolution were investigated., Results: Patients included five males and two females. All patients suffered from seizures during wakefulness. Two of the patients (29%) did not have a recurrence. Five (71%) had sporadic seizures (ranging between two and five). One of the seven patients (14%) presented with seizures in clusters. During seizures, staring was observed in six (86%), motion arrest in five (71%), stiffening in five (71%), cyanosis in three (42%), automatisms in one (14%) and lateralizing signs in four (57%). Two patients (29%) had secondary generalisation. The duration of the seizures ranged between 30 seconds and five minutes. No status epilepticus was observed. The interictal EEG recording during sleep showed low-voltage unilateral or bilateral spikes located in the central and vertex regions, followed by slow waves in all patients. Outcome was excellent in all patients., Conclusion: We believe that BIMSE is a new syndrome rather than an early presentation of benign epilepsy of childhood with centrotemporal spikes, Panayiotopoulos syndrome, or a late presentation of benign focal infantile seizures.

We present a patient with cryptogenic focal epilepsy and another with Dravet syndrome, who experienced seizure aggravation and negative myoclonus, associated with continuous spikes and waves during slow sleep, induced by levetiracetam. For both patients levetiracetam was discontinued, and there was significant improvement of this particular electroclinical picture.

Purpose: To analyze the electroclinical features, aetiology and outcome in patients with normal neurological examination and psychomotor development who presented seizures during a mild gastroenteritis (MG)., Patients and Methods: Evaluation of the clinical charts of 22 patients who were assessed in the Neurology Department, Hospital Nacional de Pediatría Prof. Dr. JP Garrahan between 1999 and 2007., Results: Twelve patients were boys and 10 were girls, the age of onset ranged from 5 to 26 months, and the median age was 10 months. Rotavirus antigen test in stool was positive in 9 of 18 studied patients. The seizures were brief, focal with secondary generalization in 15 patients (68.5%), apparently generalized in 5 (22.5%) and focal in two (9%). Seven of the patients (35%) had more than one seizure in 24h. The interictal EEG was normal in all patients. Neuroradiological studies were performed in 19 patients with a normal result. No patient was put on long-term treatment with antiepileptic drugs. Four patients had subsequent mild gastroenteritis and two of them presented convulsions during the disease. After between 12 and 67 months of follow-up, all patients had normal psychomotor development and neurological examination., Conclusions: In this study we confirmed the association of benign infantile seizures (BIS) and MG with or without rotavirus. The identification of this entity allows avoiding unnecessary complementary studies and treatment with antiepileptic drugs.

Purpose: We present a series of nine patients with early-onset hydrocephalus who had seizures and continuous spikes and waves during slow sleep (CSWS) associated with neurocognitive and motor deterioration., Methods: Six boys and three girls aged 9-16 years (mean 11.3 years) were studied. [Correction added after online publication 12-Apr-2008: Number of girls and boys has been updated.] All patients underwent clinical examinations, electroencephalographic evaluations, neuroradiological imaging and neuropsychological assessment at first examination. Antiepileptic drugs (AEDs) were given in all cases and changed according to clinical and EEG evolution., Results: Onset of epilepsy occurred from age 8 to 60 months (mean 19.6 months and median 14 months) with focal seizures with or without secondary generalized tonic-clonic seizures. Between ages 6 and 13 years (mean 10.4 years and median 8 years), hyperkinesia, aggressiveness, and poor socialization appeared in all nine cases. Reduced attention span, deterioration of language, and temporospatial disorientation were found in three of them. Negative myoclonus was found in two patients. The EEG showed CSWS. Response to change in treatment was good in all patients. None of the patients had relapses, seven of them have remained seizure free, and two continued having sporadic focal motor seizures during 2-5 years (mean 3 years) of follow-up., Conclusion: In children with early-onset hydrocephalus, particularly with behavioral and language disturbances and/or motor deterioration, CSWS should be considered. Periodic EEG recordings during sleep should be done in these children. The early identification of this particular electroclinical picture is crucial to start adequate treatment to avoid progressive cognitive deterioration.

Objectives: To characterize the electroclinical features and evolution of Panayiotopoulos Syndrome (PS)., Methods: Children with electroclinical criteria of PS were prospectively identified and followed-up clinically, and with sleep and awake EEGs between February 1990 and 2006., Results: We identified 192 patients with PS. In the same length of time 398 children with benign childhood epilepsy with centro-temporal spikes (BCECTS) were registered. PS had a peak age at onset of 5 years. Autonomic manifestations were one of the most common ictal event. Ictal deviation of the eyes and progression to generalized convulsions were also quite frequent. Approximately one third had partial status epilepticus. In all patients except five, the seizures occurred during sleep. One-third also had fits while awake. Sixteen children had concomitant symptoms of rolandic epilepsy and eight developed rolandic seizures after remission of PS seizures. Prognosis was excellent. Eighty-four (44.2%) had a single seizure, 79 (41.2%) had 2-5 fits, and 28 (14.6%) had frequent seizures., Conclusion: PS is less common than BCECTS, but is well defined and easily recognizable by clinical and EEG features, with autonomic manifestations as one of the most common ictal event.

Spasms are defined as epileptic seizures characterized by brief axial contraction, in flexion, extension or mixed, symmetric or asymmetric, lasting from a fraction of a second to 1-2s, and are associated with a slow-wave transient or sharp and slow-wave complex, followed or not by voltage attenuation. Epileptic spasms usually appear in clusters and are age-dependent. This type of epileptic spasms associated with the particular EEG pattern, hypsar rhythmia, constitutes the basis for the diagnosis of West syndrome. The question is, how to nosologically define those patients who clearly present epileptic spasms in clusters without modified or typical hypsarrhythmia and with or without focal paroxysmal discharges on the interictal EEG. In the present series, the four patients show that epileptic spasms in clusters may occur in infancy, without hypsarrhythmia. They all presented the following features: normal neuropsychological development before onset of epileptic spasms, clusters of epileptic spasms, focal clinical and/or EEG abnormalities, normal neuroradiological imaging, neurometabolic investigations and karyotypes. In three of the patients, seizures were refractory to AEDs. Epileptic spasms in clusters without hypsarrhythmia that start in the first year of life represent a subtype of infantile spasms that generally are refractory to AEDs. It is not yet clear whether it should be considered as a variant of West syndrome or not [Published with Video sequence].

We report, on two, school-age girls with clinical and electroencephalographic features of early onset childhood epilepsy with occipital paroxysms (CEOP) of the "Panayiotopoulos type" that showed atypical evolution. Neurological examination and brain imaging were normal in both. One child presented at age 2.5 years episodes of oculocephalic deviation, and ictal vomiting during nocturnal sleep. The EEG showed left occipital spikes during wakefulness and sleep. One year later, frequent inhibitory seizures appeared in the lower limbs causing, "pseudoataxic gait". At the same time she presented with behavioral disturbances and aphasia. EEG showed bilateral spike-waves while awake and continuous spike-waves during slow sleep (CSWSS). After switching AEDs to benzodiazepines, control of seizures along with improvement of behavior, and partial restoration of cognitive functions were achieved. The CSWSS disappeared and the last EEG at age 8 years only showed only isolated right occipital spikes. The other girl had a personal and familial history of febrile seizures. At 4 years of age she presented the first non-febrile seizures during sleep, with oculocephalic deviation and ictal vomiting, followed by a generalized tonic-clonic seizure. Partial control of seizures was obtained with antiepileptic drugs. At age 7, the child began to have weekly episodes of oculocephalic version, occasionally with secondary generalization. Repeated inhibitory seizures and absences also appeared. EEG showed frequent bilateral spikes occupying predominantly the posterior regions while awake, and CSWSS. At 7.5 years the same electro-clinical picture persisted. Ethosuximide was added to sodium valproate and clobazam. Fifteen days later, the seizures disappeared and the EEG showed less frequent bilateral occipital spikes. She is now 9 years old and she has been seizure-free for 18 months. Her present neuropsychological profile shows mild mental retardation. The two children with typical electroclinical features of "Panayiotopoulos Type" CEOP developed an atypical evolution which, to our knowledge, has not been described previously.

The syndrome of benign familial infantile convulsions (BFIC) is an autosomal dominant epileptic disorder that is characterized by convulsions, with onset at age 3-12 mo and a favorable outcome. BFIC had been linked to chromosome 19q, whereas the infantile convulsions and choreoathetosis (ICCA) syndrome, in which BFIC is associated with paroxysmal dyskinesias, had been linked to chromosome 16p12-q12. BFIC appears to be frequently associated with paroxysmal dyskinesias, because many additional families from diverse ethnic backgrounds have similar syndromes that have been linked to the chromosome 16 ICCA region. Moreover, one large pedigree with paroxysmal kinesigenic dyskinesias only, has also been linked to the same genomic area. This raised the possibility that families with pure BFIC may be linked to chromosome 16 as well. We identified and studied seven families with BFIC inherited as an autosomal dominant trait. Genotyping was performed with markers at chromosome 19q and 16p12-q12. Although chromosome 19q could be excluded, evidence for linkage in the ICCA region was found, with a maximum two-point LOD score of 3.32 for markers D16S3131 and SPN. This result proves that human chromosome 16p12-q12 is a major genetic locus underlying both BFIC and paroxysmal dyskinesias. The unusual phenotype displayed by one homozygous patient suggests that variability of the ICCA syndrome could be sustained by genetic modifiers.

This 9-year-old boy was admitted at the age of 2 with a diagnosis of congenital hemiparesis while the rest of physical and neurological examination was normal. His score in the Wechsler intelligence scale was 80. Right fronto-parietal cortical dysplasia with hemisphere atrophy was evident by computerized tomography scanning and magnetic resonance imaging. The latter, also disclosed abnormal thick cortex which was interpreted as polymicrogyria or pachygyria. Karyotype was normal. He had a hemifacial motor seizure at the age of 7. At the age of 8 frequent atonic or inhibitory seizures were presented. Asymmetric bilateral spike discharges with high voltage in the right hemisphere during the EEG recording were found. His mother, a 35-year-old woman (Full scale; Adult intelligence scale: 85) also had congenital hemiparesis. She never had seizures and her EEG was normal. Magnetic resonance imaging disclosed right fronto-parietal cortical dysplasia with ipsilateral hemisphere atrophy. Karyotype was normal. Our cases should be interpreted as a familial presentation of the anomaly, probably with autosomal-dominant transmission.

This is a prospective study designed to evaluate the efficacy and safety of vigabatrin as first-choice monotherapy in infants with West syndrome. One hundred sixteen patients with newly diagnosed West syndrome were studied in Argentina, from June 1994 to April 1998. The follow-up ranged from 17 to 40 months (mean, 23 months). Vigabatrin was administered upon diagnosis, starting with a 50-mg/kg/day dose and increasing 50 mg/kg every 48 hours to reach a maximum dose of 200 mg/kg/day. Twenty-nine percent of cases were considered to be cryptogenic or idiopathic West syndrome, while 70.7% were symptomatic. Response to vigabatrin treatment was measured according to five categories: (1) seizures free: 61.8% of cases for cryptogenic and 29.3% for symptomatic West syndrome, (2) more than 75% reduction in the number of infantile spasms: 14.7% for cryptogenic and 26.8% for symptomatic West syndrome, (3) from 50% to 74% reduction in the number of infantile spasms: 11.8% for cryptogenic and 24.4% for symptomatic West syndrome, (4) poor or null response: 11.8% for cryptogenic and 18.3% for symptomatic West syndrome, and (5) increase in the number of infantile spasms: one symptomatic case (1.2%). All seizure-free cryptogenic cases showed normal neuropsychic development. The most effective dose of vigabatrin was 150 mg/kg of body weight per day. The most frequent adverse events were somnolence in 19 cases and irritability in 15 cases, but none required treatment interruption.

Purpose: Polymicrogyria (PMG) is often associated with symptomatic focal epilepsy and neurologic dysfunction. We investigated the clinical and laboratory features of a group of children with congenital hemiparesis, unilateral polymicrogyria on magnetic resonance imaging (MRI), and a peculiar epileptic syndrome., Methods: Twelve patients (seven girls and five boys) with a mean age of 7.8 years (range, 5-13 years) were studied. All patients underwent clinical evaluation, computed tomography (CT) and MRI scanning, and neuropsychological assessment at initial examination. Patients were followed up from 1 to 7 years (mean, 4.5 years)., Results: Partial motor seizures with secondary generalization with onset between age 1 and 6 years (mean age, 2 years) were recorded in all patients. The course of epilepsy was similar in all patients with development of atypical absences, negative myoclonus, and gait difficulties. EEG recording demonstrated continuous spike-wave or bilateral abnormality throughout. Frequent relapses of the atonic and myoclonic seizures were seen in seven patients. However, during follow-up, seven patients were seizure free, and the others have not developed this particular seizure pattern. A single case underwent cortical resection 23 months ago and has had no seizures since then. Mental retardation was mild in nine and moderate in three patients., Conclusions: Children with unilateral polymicrogyria may develop a syndrome of negative myoclonus seizures that appears to be age specific and responsive to antiepileptic drug (AED) treatment. Despite limited follow-up time, a good outcome was observed in most cases.

We identified 5 of 44 consecutive children (11%) with Guillain-Barré syndrome who had electrophysiologic evidence of severe reduction of the mean amplitude of the compound motor action potentials (mean CMAP amplitude < 10% of lower limit of normal). EMG studies revealed profuse fibrillation activity in distal and proximal muscles after 2 weeks of onset. We compared this group with 16 consecutive children with GBS prospectively evaluated over 1 year, all of whom presented a mean CMAP amplitude > 10% of lower limit of normal. Children in the first group were more likely to require assisted ventilation (60% vs. 6.2%) and were more frequently quadriplegic at the peak of their disability (80% vs. 18.7%). They also required longer periods to improve one functional grade (mean 63.6 days vs. 16.6 days) and to become ambulatory (mean 156 days vs. 17.6 days). Moreover, only the children in the first group had distal atrophy of four limbs after 1 year of follow-up. Severe reduction of the mean amplitude of the CMAPs in children with GBS identifies a subgroup of patients with axonal damage that produces more severe weakness and delayed recovery.