Giant and absent somatosensory evoked potentials in children with cerebral palsy with and without epilepsy

ABSTRACT

Many studies have reported the relationship between giant somato-sensory evoked potentials [SEP] and myoclonic epilepsy in adults and children. However there are few reports about giant SEP and absent SEP in children with cerebral palsy. To assess the diagnostic significance of giant SEP and absent SEP in children with cerebral palsy with and without epilepsy. The study included 25 children [10 boys and 15 girls] with cerebral palsy, 10 of them with a history of epilepsy. The age of all the CP children was 5.2 +/- 2.3 years. Ten healthy children of matched age, sex and height were included in the study as a control group. SEP to median [N20] and posterior tibial [P40] nerves stimulation was recorded. Giant SEP was defined as that bigger than 3 SD of the mean amplitude in normal children. Inter-ictal EEG recordings were done for all the patient population as well as for the controls. The peak latency of N20 in normal children was 16.2 ms +/- 1.1 ms while its amplitude was 7.5 micro.V +/- 2.6 micro V. The peak latency of P40 in normal children was 31.3 ms +/- 3.2 ms while its amplitude was 4.8 micro V +/- 1.8 micro V. Giant SEP was considered if the amplitude was more than 15.3 micro V for N20 and 10.2 micro V for P40. SEP was absent in 5 CP children without epilepsy [33.3%] and a patient [10%] with epilepsy. All of them were severely handicapped. On the other hand 4 CP children with epilepsy [myoclonic seizures] [40%] showed giant SEP while none of the CP children without epilepsy showed giant SEP. EEG recordings were unremarkable in 10 patients [40%]. Abnormal EEG findings were focal paroxysmal discharges in 5 children [20%], polyspike and slow wave complexes In 4 children [16%] and abnormal background activity in 6 children [24%]. Both groups of CP children [with and without epilepsy] showed significant increase of the SEP latency and significant decrease of the SEP amplitude of the median and posterior tibial nerves compared to the control group. Giant SEP being present in CP children only with epilepsy, suggests that it is related to a state of cortical hyper-excitability. Absent SEP is present in CP children with and without epilepsy, but more in severely handicapped children. So absent SEP is attributed to the severity of neurological disorder