Cognitive event-related potentials and brain magnetic resonance imaging in HTLV-1 associated myelopathy (HAM).

Auditory and visual cognitive event-related potentials (ERPs) were investigated in 14 patients with HTLV-1 associated myelopathy (HAM) and in 36 normal controls. In the HAM patients, the latencies of P300 and N200 by the auditory tone method were significantly delayed, and N100 by the auditory click method was significantly delayed in latency. No abnormal ERP components were observed with visual methods. While these auditory abnormal ERPs were present in the HAM patients, there was no evidence of visual abnormal ERPs. Abnormal lesions on the white matter were evident at magnetic resonance imaging (MRI) in 6 (75%) of 8 patients. There was no correlation between MRI lesions and the abnormalities of ERPs, but there was a significant correlation between bifrontal index on MRI and P300 amplitudes at Cz and Pz sites by auditory tone method. In one patient, atrophy of bilateral parietal lobes was seen on MRI and P300 latencies delayed using various methods. Therefore, the possibility that electrophysiological cognitive impairment in patients with HAM is related to brain atrophy rather than to white matter lesions requires attention.