The effect of Botulinum toxin A injections for overactive bladder on detrusor contractility

Botulinum toxin A (BT-A) causes muscle relaxation when injected intramuscular.
The protein works peripherally and does not cross the blood-brain barrier. In
patients with overactive bladder (OAB) injection with Botulinum toxin A into
the bladder wall has shown to reduce complaints of urgency, frequency and
urge-incontinence. The working mechanism of BT-A in the peripheral tissue, the
muscle itself, is known to some extent. BT-A is believed to act on both the
afferent and the efferent branch of the micturition regulation circuitry. The
effect of the BT-A treatment on the contractility of the detrusor has never
been investigated. This is remarkable, since this factor could provide
information about both the wordking mechanism of BT-A and the predisposing
factors for the need for intermittent catheterisation after the treatment.

The objective is to find out whether injection of Botulinum toxin A into the
wall of the bladder has, besides effects on bladder capacity and urgency
symptoms, any influence on the contractility of the detrusor muscle.

This is a prospective pilot study in which patients with OAB will fill out a
micturition diary and Quality of Life-questionnaire and undergo an urodynamic
investigation before and six weeks after their treatment with BT-A injections.

Before the treatment patients undergo urodynamic measurements to establish the
baseline value of detrusor contractility. Then the Botulinum toxin A is
injected into the detrusor muscle during an endoscopic procedure. Six weeks
after the injection, a second urodynamic investigation is carried out to
establish any changes in the detrusor contractility. Also patients will fill
out a micturition diary Quality of Life-questionnaire before and after the
treatment, to objectify the effect of the treatment on the patients symptoms.

The study is performed in patients who are already planned for the procedure of
Botulinum toxin A injections. Urodynamics before injection of BT-A is part of
the standard procedure. In the case of this research one extra test, a so
called isovolumetric contraction test, is carried out as a part of the
urodynamics. Six weeks after the treatment patients will undergo another
urodynamic investigation.
Before and six weeks after the treatment patients will fill out two
questionnaires, taking 10-15 minutes of their time. After the post-operative
urodynamics, patients will continue in the regular follow-up. The patients will
not directly benefit from this study. However, for the patient group this study
may provide information that predicts the need to start intermittent
catheterisation after treatment with Botulinum toxin A.