Hypothesis / aims of study
Advances in neural imaging studies have improved our understanding of the complex processes that occur within the central nervous system (CNS) during the micturition cycle.
It is accepted that bladder emptying is a reflex, facilitated by the spinobulbospinal pathway that passes through the pontine micturition centre (PMC), located in the pons (brainstem). Excitation of the PMC results in external urethral sphincter relaxation followed by activation of the sacral parasympathetic outflow leading to detrusor contraction, increasing the intravesical pressure sufficiently to generate flow of urine.
Therefore, it is widely accepted that patients with suprapontine (superior to pons) brain lesions will have detrusor overactivity (DO) without detrusor sphincter dyssynergia (DSD). Whereas patients with suprasacral infrapontine (between pons and the sacrum) lesions could have DO and DSD.
Recent advances in neural imaging techniques have allowed researchers to determine that the coordination of multiple brain areas in asymptomatic participants is required to facilitate efficient bladder emptying. A meta-analysis of neural imaging studies during bladder emptying identified six clusters of brain activation that were consistent between nine studies involving 91 asymptomatic participants. The six areas identified include: thalamus, insula, anterior cingulate cortex, inferior frontal gyrus, pons and cerebellum(1).
Patients who have suffered a cerebrovascular accident (CVA) present a unique research opportunity to correlate precise areas of brain impairment with the LUT dysfunction. This study aims to compare area of brain infarct with LUT dysfunction identified during video urodynamic (VUDS) studies.
Study design, materials and methods
We retrospectively compared the VUDS data of 19 patients with the area of brain infarct identified using magnetic resonance imaging (MRI). The inclusion criteria were patients > 18 years old with a cerebral infarct confirmed on brain MRI who underwent VUDS investigation to evaluate their LUT function since 2020. Patients with other neurological diseases were excluded.
All urodynamic studies were conducted in accordance with the ICS Good Urodynamics Practice Document. UDS parameters evaluated included the presence of DO, bladder compliance, maximum cystometric capacity (MCC), voided volume, maximum detrusor pressure during voiding (max.Pdet), maximum flow rate (Qmax), detrusor pressure at maximum flow (PDet.Qmax) and post void residual (PVR). Fluoroscopic imaging was used to evaluate the location of bladder outlet obstruction (BOO). If the membranous urethra was observed to be non-relaxing throughout the voiding phase, anatomical BOO was excluded via flexible cystoscopy.
Results
The age of patients ranged from 26-93 years of age (median 65 years) with 15 males and 4 female patients. Table 1 details the presence of DO, urinary incontinence (UI), grade of vesico-ureteric reflux (VUR) and the presence of any voiding dysfunction (VD) and the location of the cerebral infarct. 16 patients had DO identified during VUDS, with max.Pdet ranging from 17-137cmH2O (median 52cmH2O). 4 patients were diagnosed with DSD, 10 patients had anatomical BOO, all benign prostatic obstruction (BPO) and 1 patient was diagnosed with detrusor underactivity (DU).
Interpretation of results
Of the four patients who presented with DSD during VUDS, the locations of cerebral infarcts included: the cerebellum, thalamus and the posterior cerebral artery (PCA). During voiding the thalamus has been hypothesised to coordinate the decision to void with the relaxation of the EUS. While the cerebellum is known to have important roles in motor control, it is thought to be the modulatory centre for coordinating relaxation of the EUS and contraction of the detrusor muscle during voiding. One of the regions the PCA supplies oxygen to in the brain is the thalamus, therefore an infarct in the PCA could result in impaired functionality of the thalamus.
Five patients identified with infarcts in the thalamus, cerebellum or PCA did not demonstrate overt DSD. However, all of these patients were diagnosed with BPO. Simultaneous BPO and DSD may be present in these patients, but due to insufficient contrast beyond the prostatic urethra, it was not possible to evaluate the presence of DSD.
The insula, anterior cingulate cortex and inferior frontal gyrus are believed to be responsible for the transition from bladder storage to the initiation of voiding and therefore infarcts in these areas may result in a diagnosis of DO and/or DU rather than DSD. No patient in this study had an infarct identified in the pons (an infarct in the pons would be presumed to result in DSD).