H-Reflex and physiologic measures of ejaculation in men with spinal cord injury

Objective: To investigate the various physiologic parameters characterizing and predicting ejaculation. Design: Single case-control study. Setting: A referred care center and university setting. Participants: Two men with spinal cord injury (SCI) and 2 control subjects. Intervention: Subjects were asked to self-stimulate with a Ferticare vibrator to induce ejaculation over 5 to 8 independent sessions. Main Outcome Measures: Penile tumescence, blood pressure, heart rate, electromyographic activity of the bulbocavernosus muscles, abdominal muscles, soleus H-reflex, and occurrence of ejaculation. Results: Changes on all measures were observed, with penile tumescence being more stable in control subjects. Blood pressure increased in both groups, whereas tachycardia was observed in controls and bradycardia in subjects with SCI. H-reflex dropped slightly in controls but increased in subjects with SCI. Muscular patterns differed on ejaculatory success or failure. Conclusions: Physiologic changes on all measures can be observed in men with SCI as a function of ejaculation. Changes include hypertension and bradycardia, characteristic of hyper-reflexia, and tachycardia in controls. The neural mechanisms underlying these patterns are discussed. H-reflex showed increased spinal cord excitability in subjects with SCI after ejaculation, which suggests spasticity. The results support investigation of the H-reflex to predict ejaculatory success or failure in men with SCI, along with specific analysis of muscular patterns.