Cerebral activation during withholding urine with full bladder in healthy men using 99mTc-HMPAO SPECT

The aim of this study was to identify the brain areas that control urinary continence in healthy men by 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) SPECT.

SPECT scans were performed on 15 right-handed healthy male volunteers, 24-45 y old. Each subject was scanned twice without movement in a supine position, and 444 and 555 MBq 99mTc-HMPAO were separately injected intravenously during the following 2 conditions: resting state with an empty bladder and urine-withholding state with a full bladder. The final image during urine withholding was obtained by subtracting the first scan data from the second scan data. The images were analyzed by statistical image analysis software and displayed on Z-score images at a significance threshold of P < 0.05 with correction for multiple comparisons.

In the urine-withholding state, as compared with resting, there was a significant increase in tracer activity in the bilateral inferior frontal gyri and the right superior and the middle temporal gyri. Among the regions, the right inferior frontal gyrus was distinctly prominent. When the threshold value was decreased to P < 0.005 without correction, there was a vast network of cortical and subcortical regions involved during urine withholding.

Our results suggest that the right inferior frontal gyrus plays an important role in brain control of urinary continence. This study also suggests that brain control of continence can be confirmed by statistical image analysis software using SPECT.