Abstracts

Rationale: In the classification of photoparoxysmal response (PPR), only type 4 (generalized spikes and wave or polyspike wave) is thought to be of clinical significance. More specifically, a PPR type 4 in the very young has been reported to be pathognomonic of certain aetiologies. Study aims at evaluating the clinical significance of PPR in children <5 years of age. Methods: Retrospective review of case notes and EEG characteristics of patients under the age of 5 years with a history of seizures who demonstrated type 4 PPR following intermittent photic stimulation during routine EEG performed between 2003-2010 . Results: Type 4 PPR was demonstrated in 41/6627 (0.6%) children (19 girls) less than 5 years. Age at the onset of epilepsy (0.3 to 56 months, mean: 22.6 m) was categorised into two groups: (A) 0-24 m and (B) 25-60 m. In Group A (n=25, mean age onset 9.4m) 6 (24%) had a definitive syndrome diagnosis (SMEI/Dravet s syndrome). Of the 19 with no syndrome diagnosis, 18 were associated with generalised seizures and one with focal seizures. In group B (n=16, mean age onset 44m), 10 (62.5%) had a distinct epilepsy syndrome diagnosis of which 5 (50%) had childhood absence epilepsy (CAE), 3 myoclonic absence, 1 myoclonic atonic and 1 Lennox Gastaut Syndrome. A history of status epilepticus (11/41; 27%) was found only in Group A ,(11/25; 45.8%). There was an associated clinical correlate with PPR in 33/41 (80%). Conclusions: In children presenting with epilepsy < 24m, early PPR is confirmed as a feature of SMEI, but there are few other currently recognised syndrome associations. However, there is a strong association with status epilepticus. With older onset of presentation, a recognised syndrome diagnosis is more likely. The significance of PPR<24m requires further evaluation.