Somatosensory evoked response abnormalities in high-risk newborns

In a previous study from our laboratory, the prognostic significance of the auditory brainstem evoked response was assessed in high-risk neonates. An abnormal auditory brainstem evoked response predicted neurologic deficits at age 1 year; however, a normal result did not predict a normal outcome. In order to evaluate the prognostic utility of examining other sensory pathways, somatosensory evoked responses were elicited following median nerve stimulation. Testing was performed at 37-44 weeks conceptional age (defined as gestational age plus chronologic age) and at 2 and 6 months conceptional ages. Those patients studied included 34 high-risk neonates and 18 healthy, term infants as controls. Ten of the 34 patients had abnormal somatosensory evoked responses. Abnormalities included increased absolute (N19, P22) and interwave (N13-N19, N19-P22) latencies and flat potentials, alone or in combination. Three children with flat potentials demonstrated a persistence of this abnormality on subsequent examination and they later presented clinically with spastic quadriparesis. Four infants with increased latencies manifested normal responses on subsequent examination. Recently, these 4 patients exhibited tone abnormalities and mild developmental deficits; developmental outcome, however, will be assessed in a blind study at 1 year of age as part of this ongoing prospective study. Preliminary results suggest that somatosensory evoked responses may be valuable as an electrophysiologic predictor of outcome.