Evoked potentials in assessment and follow-up of patients with Wilson's disease. Treatment of 9 patients with Wilson's disease was prospectively studied with evoked potentials and magnetic resonance imaging (MRI). Oral penicillamine therapy led to a decrease in auditory brainstem (ABP) and somatosensory (SEP) conduction times in 6 and 4 neurologically symptomatic patients, respectively. ABP and SEP were normal in 3 other symptom-free patients. MRI showed cerebral lesions in 4 of 7 patients. Quantified indices of brain atrophy were unaffected by treatment. ABP and SEP may reveal a reversible component of the disease that cannot be detected by MRI, and may be a more sensitive measure of treatment efficacy. 