Electrophysiological studies in five cases of abetalipoproteinemia.

Auditory brainstem responses (ABRs), visual and somatosensory evoked responses (VEPs and SEPs) and nerve conduction studies were conducted in 5 patients with abetalipoproteinemia. The ABRs were normal in all cases. The VEPs were of normal amplitude but of increased latencies in two patients. The four eldest patients had delayed cortical SEPs but normal peripheral sensory nerve conduction studies. The peripheral motor conduction velocities were normal in all cases. The peripheral sensory studies showed normal velocity when a response was seen; however, the amplitude of the response was often reduced or it was absent. The electrophysiological studies reported here support a model of axonal loss of large myelinated fibres with secondary demyelination in abetalipoproteinemia.