A PET STUDY ON BRAIN CONTROL OF MICTURITION IN HUMANS

Although the brain plays a crucial role in the control of micturition, little is known about the structures involved. Identification of thes e areas is important because their dysfunction is thought to cause urg e incontinence, a major problem in the elderly. In the cat, three area s in the brainstem and diencephalon are specifically implicated in the control of micturition: the dorsomedial pontine tegmentum, the periaq ueductal grey, and the preoptic area of the hypothalamus. PET scans we re used to test whether these areas are also involved in human micturi tion. Seventeen right-handed male volunteers were scanned during the f ollowing four conditions: (i) 15 min prior to micturition during urine withholding; (ii) during micturition; (iii) 15 min after micturition; (iv) 30 min after micturition. Ten of the 17 volunteers were able to micturate during scanning. Micturition was associated with increased b lood flow in the right dorsomedial pontine tegmentum, the periaqueduct al grey, the hypothalamus and the right inferior frontal gyrus. Decrea sed blood flow was found in the right anterior cingulate gyrus when ur ine was withheld. The other seven volunteers were not able to micturat e during scanning, although they had a full bladder and tried vigorous ly to do so. In this group, during these unsuccessful attempts to mict urate, increased blood pow was Sound in the right ventral pontine tegm entum, which corresponds with the hypothesis, formulated from results in cats, that this area controls the motor neurons of the pelvic poor Increased blood pow was also found in the right inferior frontal gyrus during unsuccessful attempts at micturition, and decreased blood pow in the right anterior cingulate gyrus was found during the withholding of urine. The results suggest that, as that of the cat, the human bra instem contains specific nuclei responsible for the control of micturi tion, and that the cortical and pontine micturition sites are predomin antly on the right side.