Evaluation of cortical neuroexcitation in urinary urgency using simultaneous near infrared spectroscopy of the brain and bladder with quantification of sensation

Background: Overactivity of the bladder (OAB) affects 20% of people globally, causing urgency to void and incontinence of urine (UI)). OAB has a multi-factorial causation. Problematically current tests are invasive and provide limited information. Recent advances in NIRS technology now offer non-invasive evaluation of brain neuroexcitation and bladder hemodynamics/oxygenation related to micturition. We tested the hypothesis that brain and bladder parameters can be monitored simultaneously with patient-controlled quantification of bladder sensation, and that brain-mediated control impacts UI in OAB. Methods: A symptomatic patient (OAB) and asymptomatic control were monitored during spontaneous bladder filling to capacity with fNIRS of the anterior cortex and continuous wave NIRS of the bladder while using a validated patientcontrolled sensory meter. Changes in oxygenated, de-oxygenated and total hemoglobin in brain and bladder were recorded, and sensory events (bladder fullness/urgency to void) documented. Results: In the asymptomatic control fNIRS-derived neuroexcitation was evident when the bladder filled to capacity, increased at decision to void, was most intense during voiding, and waned thereafter. The OAB subject showed progressive increase in neuroexcitation from documenting a desire to void, to recording sensing urgency (imminent UI). At this point a distractor stimulus occurred (unexpected phone call), the sensation of urgency waned and an abrupt decrease in cortical oxyhemoglobin concentration was evident. Conclusion: Simultaneous brain fNIRS, bladder NIRS and sensation quantification is feasible and adds to OAB evaluation. fNIRS-derived neuroexcitation occurs in association with sensed voiding events. The attenuation of urgency/UI by a distractor stimulus implies brain-mediated mechanisms are integral to OAB.