Sleep and benign partial epilepsies of childhood: EEG and evoked potentials study.
The electroclinical picture and nosological limits of benign partial epilepsy of childhood with rolandic spikes (BERS) have been better defined by nocturnal sleep records. In all stages of sleep, there is a significant increase in frequency and amplitude of rolandic spikes (RS) without change of their morphology. Another interesting observation is the appearance of independent spike foci in sleep, or brief subclinical spike wave discharges which are limited to the state of drowsiness. More recently, other types of partial epilepsy of childhood with benign evolution have been identified: (a) partial epilepsy with induced spike representing somatosensory evoked potentials; (b) benign psychomotor epilepsy; (c) partial epilepsy with occipital spike waves. In all these forms, the sleep records are essentially similar to those in BERS and have been very helpful in the nosological identification of these forms of epilepsy. For this reason, the sleep records of these special forms are truly informative for the clinician from the diagnostic and prognostic viewpoint. On the other hand, some investigators, have pointed out that, in the initial stage of these benign forms of partial epilepsy, there may be more or less significant intellectual impairment and behavioral disorder, sometimes accompanied by frequent brief absences. From the EEG viewpoint, this condition is characterized by brief discharges of slow spike wave complexes amounting to a pattern of "electrical status epilepticus". This special electroclinical condition mimics the Lennox-Gastaut syndrome but is generally self-limited. Thus, a correct differential diagnosis is very important from the diagnostic viewpoint. There is good evidence that sleep records permit an earlier identification of these conditions and strongly contribute to a correct differential diagnosis. In the benign partial epilepsy the SEPs, during awake and sleep, morphology and latency are normal, while the N60 amplitude is increased. A group of children with benign partial epilepsy shows EEG spikes evoked by tapping, and giant N60 component. This giant component persists during sleep and is not specific for any type of benign partial epilepsy. In conclusion, the results of sleep recordings are conducive to a correct diagnosis and better definition of the nosological delineation of partial epilepsies in childhood; they also provide a better comprehension of their evolution, and thus of their prognosis. The Evoked Potentials seem be a useful tool in the study of benign partial epilepsy.