Does patterned afferent stimulation of sacral dermatomes suppress urethral sphincter reflexes in individuals with spinal cord injury?

AIMS: Dyssynergic contractions of the external urethral sphincter prevent efficient bladder voiding and lead to numerous health concerns. Patterned electrical stimulation of the sacral dermatomes reduces urethral sphincter spasms and allows functional bladder emptying in cats after chronic SCI. Reflex suppression in animals is strongly dependent on stimulus location and pattern. The purpose of this study was to determine whether the stimulation patterns and locations effective in animals suppress urethral sphincter spasms in humans with SCI.

METHODS

Ten subjects with chronic SCI underwent bladder filling to elicit distention-evoked contractions. During reflex contractions patterned electrical stimulation was applied to the S2 or S3 dermatome in random 25-sec intervals. Bladder and sphincter pressures were simultaneously recorded and compared between control and afferent stimulation periods.

RESULTS

Six of the 10 subjects demonstrated both reflex bladder and sphincter contractions with bladder filling. No significant reduction in urethral pressure was observed during stimulation for any stimulus locations and patterns tested.

CONCLUSIONS

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.