Abnormal trigeminocervical response in patients with spinal and bulbar muscular atrophy

Objective: To investigate the value of the trigeminocervical response (TCR) for revealing bulbar involvement in patients with spinal and bulbar muscular atrophy (SBMA). Methods: Thirty patients with SBMA and 30 healthy male controls were included in this study. In all of the normal controls, stimulation of the infraorbital nerve on one side produced bilateral short latency waves consisting of a positive/negative wave, p19/n31, the mean latency of which was measured. The mean square root of the ratio between the amplitude of p19/n31 and the mean rectified surface electromyography (EMG) activity preceding the stimulus, the A value, was estimated. The parameters of the TCR were compared between the two groups. Results: Among the patients with SBMA, 21 (70.0%) had delayed latencies of p19/n31 (P < 0.01) and all (100%) had reduced A values (P < 0.01) relative to the normal controls. Conclusions: All parameters of the TCR were significantly different between the patients with SBMA and the normal controls. The TCR is helpful for revealing abnormal lower brainstem reflex integration in patients with SBMA.