Correlation of right frontal hypoperfusion and urinary dysfunction in iNPH: a SPECT study.

OBJECTIVES

To elucidate the pathophysiology of urinary dysfunction in idiopathic normal-pressure hydrocephalus (iNPH) by single-photon emission computed tomography (SPECT) and statistical brain mapping.

METHODS

Urinary symptoms were observed and N-isopropyl-p-[(123)I]-iodoamphetamine (IMP)-SPECT imaging was performed in 97 patients with clinico-radiologically definite iNPH. The patients included 56 men and 41 women; mean age, 74 years. The statistical difference in normalized mean tracer counts was calculated and visualized between patients with urinary dysfunction of severer degrees (>grade 2/4) and milder degrees (<grade 1/4) according to the urinary subscales of the iNPH grading scales.

RESULTS

There was a significant decrease in tracer activity in the right-side-dominant bilateral frontal cortex and the left inferior temporal gyrus in the severe urinary dysfunction group (P < 0.05). In order to minimize the effects of gait and cognitive dysfunction, we performed similar analysis among subjects with little or no such dysfunction, and obtained the same results (P < 0.05) as described above.

CONCLUSIONS

Urinary dysfunction was found to be closely related with right frontal hypoperfusion in iNPH using [(123) I]-IMP SPECT. This right frontal area is one of the critical areas for regulating micturition. While secondary incontinence can result from gait disturbance or dementia, there may also be a neurogenic mechanism underlying urinary dysfunction, which is a significant burden in patients with iNPH and their caregivers.