Abstracts

Nonconvulsive status epilepticus(NCSE) is a heterogenous entity, often associated with subtle clinical signs. There are few reports on the electroencephalographic(EEG) patterns in such patients of pediatric age range. NCSE can be further subdivided into 2 groups: complex partial and generalized.
Electroencephalograms(EEGs) are known to have a fairly high degree of sensitivity and specificity for identifying NCSE.Some of the patterns previously described in association with NCSE in the pediatric patients include: generalized synchronous discharges, alpha coma, burst suppression pattern.
We describe an unusual pattern that was observed in three of our patients that presented with mental status(MS) changes and were diagnosed with NCSE. Three patients(age 3-8 years) who presented with MS changes and decreased responsiveness were evaluated at the University of Michigan Hospital. Clinical features(age at presentation, previous history of any kind of seizures, duration of symptoms) and EEGs were assessed. Other diagnostic tests were obtained in each of the patients, according to the clinical presentation.
The EEGs were performed with a number of standard bipolar and referential montages, according to the international 10-20 system of electrode placement.
All three patients were loaded with antiepileptic drugs, and two of them required antibiotic treatment as well. In two of the patients, the background activity was characterized by very high amplitude([gt]250uV) delta activity(1-2Hz) and which was diffusely distributed. This was at times rhythmic, but without clear evolution. In one patient, there were multifocal independent sharp waves noted, with no specific hemisphere predominance. In the other patient, independent right/left frontal sharp waves were present.
The third patient EEG was notable for a very high amplitude delta activity(1-2Hz) over the right hemisphere and loss of faster frequencies within the same region. Bursts of high amplitude rhythmic 2.5 Hz spike and wave activity, up to 15 seconds in duration, were present over the left frontal region and less often over the left temporal region. No distinct clinical events were noted, other than the MS changes.
All EEG patterns improved in paralel with the clinical symptoms, with gradual return of the MS to the previous baseline status. The very high amplitude rhythmic delta activity, whether focal or generalized, is an unusual and not previously described EEG pattern in NCSE. All our patients were younger than 10 years at the time of onset, which raises the question of an age dependent underlying pathophysiologic mechanism responsible.
More EEG studies of patients in NCSE will need to be observed in order to confirm how prevalent this EEG pattern might be and to better characterize its clinical associations(e.g.age, etiology).
This may also contribute to the better and early identification of this category of patients and rapid institution of treatment.