The use of mechanical stimulation to obtain the sacral reflex latency: a new technique.

We determined sacral reflex latencies and morphologies in 18 neurologically normal patients and 83 with neurological disease by stimulating the glans penis or clitoris using electrical and a new technique of mechanical stimulation, and recording from the external urethral sphincter. The results with both stimulation techniques were compared among various diagnostic groups. In normal patients the mean sacral reflex latencies were 35.3 +/- 2.5 (standard deviation) msec. with electrical stimulation, and 39.1 +/- 4.0 msec. with mechanical stimulation. The mean reflex latencies in patients with lower motor neuron lesions studied by both methods were statistically longer than in normal subjects, and the mean reflex latencies in patients with upper motor neuron impairment studied by both methods were not statistically different from those in normal subjects. The morphological findings of the reflex tracings suggest that both types of evoked responses follow the same general anatomical pathway and both resemble a special human flexor reflex. The mechanical technique has advantages over the electrical technique because it is less painful and in certain instances it is easier to obtain.