 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. 