Urinary continence networks in Parkinson's disease; a resting state functional MRI study

Lower urinary tract symptoms (LUTS) are a common feature of Parkinson's disease (PD), affecting up to 70% of patients [1] and significantly impairing quality of life. Ongoing use of continence aids also represents an economic burden. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been shown to improve LUTS in PD [2] and to have a significant benefit regarding improvement of LUTS compared with DBS of the globus pallidus interna [3]. Two positron emission tomography studies that compared brain activity in PD patients during bladder filling with STN DBS ‘ON’ and ‘OFF’ showed that STN DBS enhanced responses to bladder filling in the insula and posterior thalamus [4], implying improved sensory processing, and reduced blood flow in areas associated with urinary urgency, such as the anterior cingulate cortex and the left lateral frontal cortex [5]. As catheterisation and concomitant brain imaging are not always possible in frail patients with PD, we wanted to understand whether an alternative approach, using resting-state functional MRI (rsfMRI) in patients across two different conditions (full and empty bladder) would be an effective tool to investigate the neural mechanisms underlying urinary symptoms in PD. In order to further explore the mechanism by which the STN is involved in sensory aspects of bladder control circuitry, we undertook an rsfMRI study in DBS-naive PD patients. Our rationale was that, by understanding the wider brain network changes underlying the role of STN DBS on urinary symptoms, we might reveal further avenues for improved treatment of urine storage problems in PD. Our aim was to compare functional connectivity (FC) between the STN and global brain networks in the empty and full bladder state and thus infer the potential role that the STN may play in bladder control.