Objective

EPC is a variant of focal motor status epilepticus persisting for minimum of 60 minutes.  Multiple aetiologies including structural, inflammatory and neurometabolic have been reported.  We aimed to evaluate the underlying aetiologies of all patients presenting with EPC to guide diagnostic work-up.

Methods

Children were retrospectively identified from the neurophysiology database. The diagnosis of EPC was made using established criteria. Clinical, neuroimaging and electrophysiological features were reviewed.

Results

Thirty-six children with neurophysiological diagnosis of EPC were identified (median age at onset 7yrs, IQR5-10.7), 61% female. Clear EEG/EMG correlation for the EPC was detected in 21/36(58.3%) and 34/36(94.4%) had hemispheric or bilateral background EEG disturbances. 18/ 36(50%) had a diagnosis of Rasmussen’s encephalitis (RE); 8(22.2%) had a mitochondrial disorder, including 4 with mutation in polymerase gamma(POLG); 5 had structural brain lesions; 3 had lesion-negative epilepsy that resolved with medication; cause yet unknown in 2 children. Children with mitochondrial disorders (n=8) presented with EPC at a younger age than children with RE (median 1.5yrs vs 7.2yrs, p=0.0001, Mann-Whitney). Presentation with EPC was reported in 2/18(11.1%) of children with RE compared to 6/8(75%) of children with mitochondrial disorders (p=0.0028, Fisher’s exact).

Conclusions

In this large cohort of children presenting with EPC, RE was the most common aetiology but was the presenting symptom in a very small number; majority presented with focal onset seizures. The second commonest cause was mitochondrial disorders in which children presented at a younger age with EPC as the presenting symptom.