Study of brain stem auditory-evoked potentials (BAEPs) and visual-evoked potentials (VEPs) in leprosy

A study of brain stem auditory-evoked potentials (BAEPs) and visual-evoked potentials (VEPs) was done on 25 newly diagnosed patients with leprosy whose diagnosis was confirmed by skin biopsy. The results were compared with 25 age- and sex-matched healthy controls. In BAEPs the important observations were the prolonged latency of wave V in 13 (52%), delayed interpeak latency (IPL) of wave I-III in 5 (20%) cases, of wave III-V in 12/25 (40%), suggesting a conduction abnormality of the VIII cranial nerve in its peripheral part, in its nucleus and in its connection in the brain stem. In VEPs, a delayed peak latency of major positive potential (P100) was seen in 20 cases (80%; 11/13, 84.6% TT; 7/10, 70% LL; 2/2, 100% BL), suggestive of subclinical optic nerve involvement. The BAEPs and VEPs were both abnormal in 10 cases (40%; 3/13, 23% TT; 5/10, 50% LL; 2/2, 100% BL). Conduction abnormalities of the central nervous system (CNS) were observed more frequently in lepromatous leprosy, as in other forms of peripheral neuropathy such as hereditary motor sensory neuropathy type I (HMSN I). There is a fair possibility of similar multiple demyelinating lesions in the CNS also, as is seen in leprous peripheral neuropathy. This hypothesis requires further strengthening by an extensive study of multimodality evoked potentials with magnetic resonance imaging in the patients. Histopathological and immunofluorescent studies of autopsy material of the brain can also contribute significantly to solve the dilemma.