Arousal response induced by postural changes in patients with subacute myelo-optico-neuropathy, "SMON".

In reaction time (RT) experiments, shifts of arousal level induced by postural changes were examined in 10 normal subjects and 10 patients with SMON. Vocal RTs were recorded at neutral position (N) and facilitating position of the left arm (FA) or the left leg (FL). RT-ratios between two positions, FA/N and FL/N, were used as variables to estimate the arousing effect of facilitating positions. Also the correlations between these variables and several clinical signs such as patellar tendon reflex (PTR), sensory disturbance and dysesthesia were calculated. The grade of dysesthesia was strongly related to FL/N. It is assumed that proprioceptive input from the lower extremities causes abnormally high arousal response in patients with dysesthesia.