Aims Uncoordinated reflex contractions of the external urethral sphincter (EUS) are a major component of voiding dysfunction after neurologic injury. Patterned stimulation of sacral afferent pathways can reduce abnormal EUS reflexes after acute SCI; however, effectiveness following chronic SCI is unknown. Methods Four adult male cats were implanted with bilateral extradural sacral root electrodes to allow bladder activation and underwent subsequent spinal transection (T10–12). Nine weeks after SCI urethral and bladder pressures were recorded with and without sacral afferent stimulation. Surface electrodes were applied to sacral and lumbar dermatomes and stimulus amplitude set below the muscle fasciculation threshold. The stimulation pattern was varied by on/off times of fixed frequency at each location. Results Reflexive EUS contractions were observed in all animals after chronic SCI. Patterned sacral dermatome stimulation reduced EUS reflex rate and amplitude in 2 of 4 cats. Suppression was dependent on both the stimulus location and pattern. Sacral locations and a stimulation pattern of (0.75 seconds on, 0.25 seconds off, 20 Hz) were effective in both responder animals. Conclusions Patterned sacral dermatome stimulation can reduce urethral abnormal reflexes following chronic SCI. Reflex suppression is dependent on both the stimulation location and stimulus pattern. Reduction of reflexive EUS activity after chronic SCI with this non-destructive and non-invasive approach may provide an advance for the treatment of detrusor-sphincter-dyssynergia.

Stimulation parameters and locations effective in SCI animals did not suppress reflex sphincter activity in these human subjects. It is likely that a broader set of stimulus patterns and dermatome locations will need to be tested to find the effective combination in humans.