Effect of single botulinum toxin a injection to the external urethral sphincter for treating detrusor external sphincter dyssynergia in spinal cord injury

Objective: To evaluate the effect of a single cystoseopic injection of botulinum toxin to the external urethral sphincter in treating detrusor external sphincter dyssynergia. Design: An open treatment trial with pre- and post-treatment evaluations. Subjects: A total of 20 suprasacral spinal cord injured patients with pure detrusor external sphincter dyssynergia. Methods: A single dose of 100 IU botulinum toxin A was applied into the external urethral sphincter via cystoscopy. Outcome measurements included maximal detrusor pressure, maximal urethral pressure, detrusor leak point pressure, integrated electromyography, and maximal pressure on static urethral pressure profilometry obtained 4 weeks post-treatment. Post-voiding residuals were checked pre- and post-injection. Results: There were significant reductions in integrated electromyography and static and maximal urethral pressure, but not in maximal detrusor pressure and detrusor leak point pressure after treatment. Post-voiding residuals were significantly decreased at all evaluation periods. In the sub-group analysis, patients who showed good effects of treatment had significantly lower baseline integrated electromyography (p < 0.05). Conclusion: This study demonstrates the effect of a single cystoscopic injection of botulinum toxin in detrusor external sphincter dyssynergia. Integrated electromyography is a good evaluation tool for the net effect and dosage of botulinum toxin. Patients with severe spasticity over the external urethral sphincter may require repeated injections or higher doses.