Scalp Topography of Lower Urinary Tract Sensory Evoked Potentials

Abstract

Impaired lower urinary tract (LUT) afferents often cause LUT symptoms. Assessment of LUT afferent pathways is possible using bipolar cortical sensory evoked potential (SEP) recordings with the active electrode at the vertex during electrical stimulation in the LUT. This study aimed to investigate the topographical distribution and microstates of lower urinary tract sensory evoked potentials (LUTSEPs) using different stimulation frequencies. Ninety healthy subjects (18–36 years old, 40 women) were randomly assigned to one of five stimulation locations [bladder dome; trigone; proximal, membranous (men only) or distal urethra]. Cycles of 0.5 Hz/1.1 Hz/1.6 Hz electrical stimulation were applied using a custom-made catheter. Cortical activity was recorded from 64 surface electrodes. Marker setting was performed manually on an individual subject-level for the P1, N1, and P2 components of vertex recordings. N1 and P2 topographies presented with central negativities and positivities around the vertex. Regarding topographical distribution, Randomization Graphical User interface (RAGU) analyses revealed consistent frequency effects and microstates for N1/P2. Higher stimulation frequencies resulted in decreasing map strength for P1, N1, and P2. LUTSEP topographies suggest central generators in the somatosensory cortex, which are not detectable in a bipolar set-up. The observed frequency effect indicates fiber refractoriness at higher frequencies. The multichannel approach allows more comprehensive assessment of LUTSEPs and might therefore be sensitive to pathological changes. Examinations in patients with LUT symptoms are needed to further investigate this biomarker.

How brain diseases affect the lower urinary tract function?

“…This 'electrosensation' can be measured in the cerebral cortex by several methods, e.g., by measuring somatosensory evoked potentials (SSEP) [65] and by obtaining a magnetoencephalogram [66] by electrical stimulation of the LUT. Electrosensation was first described in experimental animals [67] and then it was applied in humans.…”

“…[68] The area where evoked potentials are recorded are just around the medial motor cortex (Brodmann's Area 4) where the feet and viscera are located [66]. Recent SSEP studies compared the LUT stimulation frequencies by 0.5, 1.1, and 1.6 Hz, and showed that the lower the stimulation frequency was, the better the map strength might be, like CPT [65]. In contrast to electrical stimulation of the nerves innervating limbs, evoked responses from the thalamus are not clearly obtained by electrical stimulation in the LUT.…”