Abstracts

Angelman syndrome (AS) results from deletion (DEL), uniparental disomy,imprinting anomalies or UBE3A mutations. Patients determined by DEL have a severer phenotype. In 95% of AS patients caused by DEL,two main classes are found: Class I with breakpoints at BP1 (proximal) and BP3 (distal), and Class II with breakpoints at BP2 (proximal) and BP3 (distal).The remaining 5% have the distal breakpoint at BP4 and BP5.We formerly described that BP1-BP3 patients are more severely affected,on clinical grounds,than BP1-BP2 patients. The study of electroclinical data in these distinct groups of DEL patients has not been done. Therefore, we aimed to evaluate the importance of breakpoint on the electroclinical phenotype in patients with DEL., The authors evaluated 18 DEL patients (6 were Class I; 10 were Class II and 2 were Class III and IV). Diagnosis was made by methylation pattern analysis of exon 1 of the SNRPN-SNURF gene and by microsatellite profiling of loci within and outside the 15q11-q13 region. We characterized epilepsy by history obtained with a questionnaire including:occurrence of epilepsy;age of onset;seizure type;epilepsy aggravated by fever;severity of epilepsy determined by:daily seizures; disabling/ injurious seizures;more than 3 seizure types;[italic]status epilepticus [/italic](SE) and;history of refractory epilepsy. These data were corroborated by medical records, personal contact with previous physicians, and video-EEG monitoring. Patients underwent a mean of 2.6 EEGs. Suggestive EEG patterns for AS were classified according to Boyd et al.and were studied as to morphology, duration, occurrence, frequency, amplitude and distribution., Class I had more daily and disabling seizures They also presented a higher frequency of [italic]SE[/italic] . Both groups had similar rates of epilepsy aggravated by fever (p 0.5879); however, in Class I these events evolved to [italic]SE[/italic] Polytherapy was more frequent in Class I , associated with the refractoriness observed in this group.No statistical difference was observed as to age of onset, age of seizure control, seizure type and diversity of seizures presented by these patients.
Background abnormalities, interictal and ictal epileptiform discharges were similar in both groups. Suggestive EEG patterns of AS were high in both groups. Occurrence of prolonged and frequent runs of these patterns did not show statistical differences., Epilepsy was more severe and refractory to treatment in patients with large deletions. Therefore, deletion is not a homogeneous group and breakpoint is predictive for epilepsy severity in AS, representing an important factor in parents[apos] counseling. On the other hand, EEG patterns of AS seem to be reliable for diagnosis, despite the breakpoint., (Supported by FAPESP.)