ID 375 – Abnormal recovery functions of somatosensory evoked potentials in HTLV-1-associated myelopathy

Abstract

Objectives To evaluate the inhibitory function of the cerebral sensory cortex in HTLV-1 associated myelopathy (HAM) patients by analyzing high-frequency oscillations (HFOs) and somatosensory evoked potential recovery functions (SEP-Rs), the combination of which could detect slight abnormalities in the cerebral cortex and the white matter. Method Eight HAM patients were enrolled. HFOs were obtained by digitally filtering raw SEPs from 500 to 1000 Hz. We measured amplitudes of the N20 onset-peak (N20o-p), N20 peak–P25 peak (N20p–P25p), P25 peak-N33 peak, and the early and late HFOs. For recovery function study, paired-pulse stimuli at various interstimulus intervals (ISI; 20–200 ms) were given. Results Neither early nor late HFO showed any significant differences between HAM patients and normal controls. In recovery function study, the HAM group showed significantly disinhibited recovery pattern of N20o-p and hyperinhibited one of N20p–P25p compared with normal control group ( P = 0.013 and P = 0.03, respectively). Conclusions (1) HAM patients may demonstrate mild subcortical dysfunction as previously found on MRI, and (2) sensory cortical function may also be disturbed without any imaging findings. Key message HAM could damage both cerebral cortex and white matter.