Botulinum Toxin A Injections in Patients With Fowler's Syndrome

Full Title: Open label pilot study to treat women with chronic urinary retention or voiding dysfunction due to a primary disorder of sphincter relaxation (Fowler's syndrome) with outpatient urethral injections of botulinum toxin A (BoNT-A).

Short Title: Botulinum toxin A injections in patients with Fowler's Syndrome Rationale: The department of Uro-Neurology at the National Hospital for Neurology and Neurosurgery attracts approximately 300 new female patients with urinary retention referred from all over the UK a year. A retrospective study showed the commonest diagnosis was a primary abnormality of the striated urethral sphincter or Fowler's syndrome. Fowler's syndrome (FS) is due to an intrinsic muscle disorder causing the muscle to be in a state of constant contraction and is recognized by needle electromyography (EMG) of the striated muscle. In the original description the EMG abnormality was frequently observed in women with clinical features of polycystic ovaries, leading to the hypothesis that the electromyographic abnormality was a consequence of a hormonal abnormality, since it is known that the female urinary sphincter is hormonally dependent. The ongoing abnormal EMG activity is thought to lead to a sustained and involuntary contraction of the sphincter that has a secondary effect of inhibiting detrusor contraction.

A diagnosis of FS is made by finding the characteristic abnormal activity on EMG recording but the findings of an abnormally raised urethral pressure profile and an enlargement of the striated urethral sphincter muscle on ultrasound have been shown to be additional valuable investigations. The only treatment found so far to restore voiding is sacral neuromodulation. This is an expensive, resource intensive surgical intervention, subject to a high revision rate (53%). An alternative management option would be welcomed both by patients and healthcare professionals.

Sphincter injection of botulinum toxin A (BoNT-A) was first used to treat detrusor sphincter dyssynergia following spinal injury when inappropriately timed but qualitatively normal EMG activity occurs in the sphincter with detrusor contraction. However some recent publications have reported a restoration of detrusor function after sphincter injections of botulinum toxin A in women with non-neurological conditions, although insufficient detail is given in those papers to know if the patients had FS. Although, Fowler used sphincter botulinum toxin injections 15 years ago in an attempt to treat that condition it was concluded then that the intervention was not effective. This was possibly because a much lower dose was used compared with the recently reported successful studies, in which 100 U Botox® were used.

Objectives: The aim of this small scale, open label pilot study is to obtain data about the response of women with a definite diagnosis of FS after an injection of 100 U Botox® (BoNT-A) into the striated urethral sphincter. If there is evidence for a positive response the data will form the basis for a future large scale, placebo controlled, grant funded study.

Method: 5 women with complete urinary retention due to the abnormality of sphincter relaxation demonstrated to be characteristic of FS and 5 women with the same sphincter abnormality but with obstructed voiding will be fully studied to document the severity and extent of their sphincter-bladder dysfunction.

Pre-treatment assessment will include the standard investigations appropriate for women with complete urinary retention or obstructed voiding which have been shown to be characteristically abnormal in FS. These are urine flow rate (if voiding), cystometry, urethral pressure profile, sphincter volume. The definitive diagnosis rests on the findings of sphincter EMG and as this test is uncomfortable it will be possible to combine the necessary EMG recording with the injection of the Botox® if the patient consents to enter the study.

The injection treatment will be an outpatient procedure (estimated to take less than 15 minutes): following 1ml of 1% or 2% lignocaine injected either side of the urethral orifice, 100 U Botox® dissolved in 2mls of saline will be injected, 1ml on each side into the striated urethral sphincter under EMG control.

The effect of BoNT-A injected into other striated muscle is known to have an onset within 3-4 days and duration of action of 6 weeks. The patients will therefore be followed up at 1, 4, and 10 weeks following treatment with flowmetry and ultrasound residual volumes and IPSS questionnaire. The pre intervention investigations of cystometry, urine flow rate (if voiding) and residual volume measured by ultrasound, urethral pressure profile will be repeated at 4 weeks. Sphincter EMG will only be repeated in patients who have shown a highly significant response i.e. restoration of detrusor contraction in women who previously had complete urinary retention or elimination of post void residual volume in women with obstructed voiding.

Outcome measures Primary

• Improvement in urinary flow rates (as assessed by uroflowmetry and measured in mL/sec) by more than 50% after botulinum toxin compared to baseline in women with obstructed voiding
• Restoration of voiding (either yes or no) after botulinum toxin for women in complete urinary retention

Secondary

• Improvement of post void residual urine (as assessed by bladder scan and measured in mL) compared to baseline after botulinum toxin. A reduction to less than 100mls would be considered clinically significant.
• Improvement in lower urinary tract symptoms as assessed by an improvement in scores on the IPSS (International Prostate Symptom score) questionnaire