A functional magnetic resonance imaging study of the effect of sacral neuromodulation on brain responses in women with Fowler's syndrome.
METHODS
Aetiology (case series).


METHODS
4.


OBJECTIVE
To examine brain responses to bladder filling in young women with Fowler's syndrome (FS, a sphincter abnormality manifested by impaired voiding and bladder sensation), treated with sacral neuromodulation (SNM).


METHODS
Six women, aged 18-39 years with FS underwent functional brain magnetic resonance imaging (fMRI) immediately after SNM and when untreated (baseline). Data were collected at four sessions: after SNM with an empty and a full bladder, and at baseline with an empty and a full bladder. In each session, 280 whole-brain scans were acquired while repeatedly infusing and withdrawing 50 mL of saline, using push-buttons to report changing desire to void. Data were analysed using Statistical Parametric Mapping.


RESULTS
At baseline with an empty bladder, extensive responses (contrast = infusion-withdrawal) were almost exclusively negative ('deactivations'), e.g. in the right insula, seat of visceral sensation. Increased bladder volume and/or SNM treatment reduced deactivations and strengthened normal (positive) responses, e.g. in the periaqueductal grey (PAG) terminus of ascending spinal afferents. At baseline, there was significant correlation of brain responses with maximum urethral closure pressure.


CONCLUSIONS
These data show that brain responses to bladder filling are abnormal in FS. The explanation for this that best explains the evidence is that the primary abnormality is an overactive urethra that generates abnormally strong inhibitory afferent signals, so effectively blocking bladder afferent activity at the sacral level and deactivating the PAG and higher centres, with consequent loss of bladder sensation and ability to void. Apparently, a normal mechanism for suppression of incontinence involving the striated urethral sphincter becomes exaggerated in FS and prevents voiding. SNM seems to act at the sacral level, by blocking inhibition by urethral afferents.
Kavia
Rajesh
R
Department of Uro-Neurology, National Hospital for Neurology and Neurosurgery, London, UK.
Dasgupta
Ranan
R
Critchley
Hugo
H
Fowler
Clare
C
Griffiths
Derek
D
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008160:Lumbosacral Plexus / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D012677:Sensation; D013577:Syndrome; D001743:Urinary Bladder / Q000502:physiology; D016055:Urinary Retention / Q000503:physiopathology*; D014563:Urodynamics / Q000502:physiology; D055815:Young Adult