Abnormalities of somatosensory and motor evoked potentials in adrenomyeloneuropathy: comparison with magnetic resonance imaging and clinical findings

We studied 6 patients with adrenomyeloneuropathy (AMN) showing mild signs of central nervous system involvement. All patients underwent brain and spinal magnetic resonance imaging (MRI) and somatosensory (SEP) and motor (MEP) evoked potential study. Whereas SEPs and MEPs were abnormal in all patients, only 1 patient showed brain MRI abnormalities; spinal MRI showed hypotrophy without focal abnormalities in 4 of 6 patients. Median nerve SEPs, which were recorded with noncephalic reference montage, revealed delayed or absent scalp P14 far-field potential in all patients and abnormal spinal N13 in 2. Moreover, tibial nerve SEPs revealed abnormalities of the subcortical P30 response in all 4 patients in whom scalp-to-ear recording was employed. These findings strongly suggest that in the early stages of disease neurological dysfunction is localized in the spinal cord, where it is difficult to assess using MRI. However, SEPs and MEPs, which show a typical pattern of abnormality in these patients, could be useful in disclosing signs of long tract involvement and in monitoring treatment.