Abstracts

RATIONALE: EEG may have a cardinal importance in the diagnosis of Angelman syndrome (AS) patients with a milder phenotype, as infants and patients without Chr deletion.Recent reports have agreed with the presence of a suggestive EEG, but there are many discrepancies among their descriptions. This study aimed to: (i) evaluate the sensibility of EEG; (ii) verify the age of onset of suggestive EEG and; (iii) study EEG patterns, analyzing possible variations and comparing our findings with descriptions and nomenclature used in other reports, in an attempt to organize and compile the distinct descriptive terms previously used.
METHODS: 70 EEG and 15 V-EEGs of 26 patients were analyzed and suggestive EEG patterns of AS were classified according to Boyd et al. (1988):1.Delta pattern (DP): runs of generalized, rhythmic delta activity, usually with frontal emphasis, and of high amplitude; 2.Theta pattern (TP): high amplitude, 4-6 Hz activity, generalized or over posterior regions; 3.Posterior Discharges (PD): spike and sharp waves mixed with high amplitude 3-4 Hz activity, over posterior regions, triggered by eye closure. Generic terms, as delta pattern, were preferred instead of lengthy descriptions.
RESULTS: EEG patterns of AS were observed in 25 patients(96.2%) . DP occurred in 22 patients and presented variations, classified as: 1. Hypsarrhythmic-like variant: resembling a hypsarrhytmic pattern with predominance of slow waves over epileptiform discharges (ED); 2. Slow variant: high amplitude, generalized, delta activity with no or rare ED.; 3. Poorly-defined slow spike and wave variant: regular, high amplitude, generalized delta activity with superimposed ED forming a complex characterized by a slow wave, with notched appearance; 4. Triphasic-like variant: monomorphic, rhythmic, moderate amplitude delta waves over anterior regions with low amplitude ED, on the descending phase of the slow wave. None of the DP variants presented changes during sleep. TP was observed in 8 patients and presented a variable distribution, being observed as generalized in 3 patients, and over the posterior regions, in 8 patients (3 asymmetric). Morphology, distribution, frequency and occurrence were not related to sleep/wake cycle, and not blocked by eye-opening. PD were seen in 19 patients and were observed as: runs of rhythmic 4-6 Hz sharp waves in 13 and runs of high amplitude slow waves, with superimposed ED in 16 patients. DP and PD were observed in all ages, and in all genetic groups. TP was age-related (up to 8 years), and only in patients with DEL. In the 22 patients with genetic confirmation, EEG patterns preceded the genetic diagnosis in 16 (72.7%). In all patients without genetic confirmation, EEG was able to corroborate the diagnosis
CONCLUSIONS: Although every author describes EEG findings of AS in a slightly different manner, there is obviously a common denominator. In this context, EEG seems to be a sensitive method for the diagnosis of AS, anticipating this diagnosis. On the other hand, we do not believe that these patterns may be accounted as specific, except for the delta pattern, which seems to be extremely unusual in other syndromes. Other EEG patterns observed in AS, such as theta activity, and posterior discharges, occur in a wide variety of disorders.
[Supported by: FAPESP]