Somatosensory evoked potentials with high cortical amplitudes: clinical data in 31 children.

Between 1989 and 1993, somatosensory evoked potentials (SEP) were recorded as part of the diagnostic work-up in 282 children with different neurologic disorders. In thirty-one children with N20/P25/N35 amplitudes were enhanced compared to our control group (highest amplitude 14.1 microV). Four children had amplitudes > 40 microV ("giant"), fifteen between 20-39.9 microV ("elevated") and twelve between 14-19.9 microV ("borderline"). Enhanced cortical SEPs were seen in all patients with neuronal ceroid lipofuscinosis (5 late-infantile NCL > 20 microV, 1 juvenile NCL 14.7 microV). In addition, five of six NCL children showed bilaterally prolonged cervico-cortical conduction times, otherwise only seen in a 4-month-old child following hypoxia. "Borderline" and "elevated" SEPs occurred in patients with heterogeneous neurologic disorders. Follow-up recordings showed inconsistent results: seven children had amplitudes > 14 microV in all recordings, six only at the first examination, and six only at follow-up. In six children with hemiparesis enhanced SEPs were recorded over both (n = 2) or only over the unaffected hemisphere (n = 4). Myoclonic seizures were observed only in five children with NCL. Similar to other SEP parameters, enhanced amplitudes are an unspecific indicator of an ongoing neurologic disorder. However, in neuronal ceroid lipofuscinosis, enhanced SEP amplitudes may be a useful diagnostic criterium.