Studies on sacral-evoked potentials

The bulbocavernosus reflex may be evoked electrically with a latency of approximately 35 msec. in normal male subjects. We have studied the sacral-evoked response in 116 individuals, 10 of whom were normal controls. For each study ipsilateral and contralateral responses were obtained from each side, resulting in 4 latency values. We herein describe the abnormalities in 54 patients with a variety of documented neurologic lesions. Our investigation reveals that the bulbocavernosus reflex has the characteristics of a cutaneous polysynaptic bilateral flexor response. The use of bilateral stimulation and recording techniques permits more effective localization of neurologic lesions involving the conus medullaris or cauda equina roots.