Autonomic dysreflexia in response to pudendal nerve stimulation

Study design: Pudendal nerve stimulation in complete spinal cord injury (SCI). Objective: To evaluate the influence of pudendal nerve stimulation on the cardiovascular system in SCI patients in order to assess the underlying neuronal mechanism and the potential risk during stimulation. Setting: Swiss Paraplegic Center, and University Hospital, Zurich. Methods: A total of 22 male patients with a complete SCI were divided into two groups according to the level of lesion: group A (C6-T6, n = 15) and group B (T7-L2, n = 7). A total of 66 stimulations using biphasic rectangular impulses (0.2 ms, 10 Hz) with intensities up to 100 mA were applied to the dorsal penile nerve. Of these, 15 stimulations in five patients were repeated after intravenous application of 7 mg of phentolamine. Heart rate (HR) and blood pressure (BP) were recorded by a Finapres(R) cuff applied to the right index finger. Results: Significant increased diastolic and systolic BP accompanied by significant decreased HR suggested the occurrence of autonomic dysreflexia ( AD) during pudendal nerve stimulation. These cardiovascular changes corresponded with the subjective sensation of AD symptoms in patients of group A. Intravenous phentolamine lowered the resting BP and prevented severe hypertension during stimulation. Patients in group B presented with mild HR and BP changes in response to pudendal nerve stimulation and reported no AD symptoms. Conclusion: Our results show a considerable effect of electrical pudendal nerve stimulation on HR and BP in patients with high SCI. This may indicate that sacral somatic afferent fibers of the pudendal nerve are involved in the neuronal mechanism of AD in SCI patients with high neurological level. Intravenous phentolamine enables pudendal nerve stimulation without the risk of severe hypertension.