Auditory brain-stem responses and MRI findings in patients with olivo-ponto-cerebellar (Dejerine-Thomas)-type and cerebello-olivary (Holmes)-type spino-cerebellar degeneration.

Auditory brain-stem responses (ABRs) and magnetic resonance imaging (MRI) findings were investigated in 10 patients with olivo-ponto-cerebellar atrophy (OPCA: Dejerine-Thomas type) and in 5 patients with Holmes-type cerebello-olivary degeneration. In patients with OPCA, (1) the III-V interpeak latency (IPL) was shortened significantly (P < 0.05) as compared with normal subjects when the decrease in longitudinal distance of the pons was within 20% of that of normal controls, (2) the I-III IPL was elongated (P < 0.05), the III-V IPL was shortened (P < 0.01), and the amplitude of the V wave was reduced (P < 0.05) when the decrease in longitudinal distance of the pons was more than 20% of that of normal controls. Patients with Holmes-type degeneration showed no significant difference in any component of ABRs or in the size of any part of the brain-stem, as compared with normal subjects. We conclude that abnormalities in the I-III IPL or the III-V IPL in patients with OPCA were produced by changes in the volume conduction in the pons and midbrain. This study also suggests that differences of IPL appear between OPCA and Holmes-type degeneration.