Several studies have reported brain activation and functional connectivity (FC) during micturition using fMRI and concurrent urodynamics (UDS) testing [1,2]. However due to the invasive nature of UDS procedure, non-invasive resting state fMRI is being explored as a potential alternative. To evaluate the feasibility of this approach, we compared FC in brain regions belonging to the voiding network [1] during the following states: ‘full urge’, ‘initiation of voiding/or attempt of voiding’, and ‘voiding or attempt of voiding’ with FC during rest in female multiple sclerosis (MS) patients.

Subjects: Six female patients diagnosed with stable MS and voiding dysfunction (age 53.5±15.5). Voiding dysfunction was defined as having post-void residual volume ≥20% of their maximum cystometric capacity, or belonging in the lower 10 percentile of the Liverpool nomogram for women.
Urodynamics testing: Prior to scanning, an MRI compatible lumen catheter was inserted into the patients’ bladder. During fMRI scanning, the patients’ bladder was filled and permission to void was given 30 sec after cessation of filling. Residual of urine was manually aspirated. Patients communicated their progress using a response grid indicating: “full urge”, “initiation of voiding”, or “voiding”. This urodynamic testing was repeated 3-4 times for each patient.  
Data acquisition: MR images were acquired on an FDA-approved human 7T scanner (Siemens MAGNETOM Terra). Each session included the following scans: 3D T1-weighed anatomical scan (isotropic 0.7mm spatial resolution) and T2*-weighted blood oxygen level-dependent (BOLD) fMRI scans in a resting state (8 min) and during urodynamics testing (TR=2500ms, isotropic spatial resolution 1.4mm). 
Data analysis: MRI data was preprocessed in standard steps (slice time correction, motion correction, spatial normalization, and spatial smoothing). 13 regions-of-interest (ROIs) previously associated with voiding located in the inferior/medial/superior frontal gyrus, superomedial primary motor cortex, supplementary motor area (SMA), and dorsolateral prefrontal cortex. Average fMRI time series were computed across each region and functional connectivity (Pearson’s correlation coefficient) between region pairs was computed for each state and compared to the resting state. The similarity between connectivity matrices was quantified with the 2D correlation coefficient.

The SMA exhibited highest connectivity strength while the bilateral motor regions for pelvic floor construction showed lowest (Fig. 1, Table 1). The highest correlations were observed between resting state and the ‘voiding’ state (Fig. 1). Additionally, figure 2 shows high correlations within the 13 ROIs across all subjects during voiding and in a resting state (Fig. 2).

Results from figure 1 suggest that the FC between the ROIs closely resembles resting state only during voiding, thereby indicating the resting state FC’s potential for assessing the voiding process. The high correlations within the 13 ROIs across all subjects during voiding as shown in figure 2 strongly suggests that voiding is consistently achieved through similar network activations independent from the activations required for ‘full urge’, ‘initiation of voiding’, and ‘voiding’. An observed high inter-subject correlation in the resting state (Fig. 2) supports consistency within the individual intrinsic voiding networks.

Brain regions within the voiding network are highly correlated only during voiding and not during full urge or initiation. Additionally, the task-related voiding network closely resembles the resting state intrinsic network only during voiding. These results were found to be consistent across all six subjects and suggests that resting state fMRI can be potentially utilized to reflect voiding-related brain networks during the voiding process but not the other states. Concurrent urodynamic testing is still necessary for studying the effects of full urge and initiation of micturition.

Shy, M., Fung, S., Boone, T.B., Karmonik, C., Fletcher, S.G. and Khavari, R. (2014), ‘Functional magnetic resonance imaging during urodynamic testing identifies brain structures initiating micturition’, The Journal of urology, vol. 192, no. 4, pp. 1149-1154.
Schrum, A., Wolff, S., Van der Horst, C. and Kuhtz-Buschbeck, J.P. (2011), ‘Motor cortical representation of the pelvic floor muscles’, The Journal of urology, vol. 186, no. 1, pp. 185-190.