Evoked potentials in rats with misonidazole neurotoxicity. II. Somatosensory evoked potentials.

Spinal and cortical somatosensory potentials were recorded weekly in rats treated with misonidazole at a dose of 300 mg/kg/day until clinical signs of severe neurotoxicity developed. After sacrifice, the brains, spinal cords and sciatic nerves were examined. All treated rats developed necrotic brain stem lesions identical to those previously described by Griffin and by us. Two rats had mild demyelination of spinal cord white matter tracts, but only one of these rats had changes in the SEPs. Interestingly, changes in the cervical and cortical SEP from this rat were only transient. We conclude that misonidazole neurotoxicity in the rat predominantly affects the brain stem nuclei adjacent to the fourth ventricle without involving the lemniscal pathways that are situated ventromedially in the brain stem. Therefore, somatosensory evoked potentials (SEPs) are not useful for the diagnosis of MISO neurotoxicity.