Estimating bladder pressure from sacral dorsal root ganglia recordings

Abstract

Individuals with dysfunctional bladders may benefit from devices that track the bladder state. Recordings from pelvic and sacral nerve cuffs can detect bladder contractions, however they often have low signal quality and are susceptible to interference from non-bladder signals. Microelectrode recordings from sacral dorsal root ganglia (DRG) neurons may provide an alternate source for obtaining high quality sensory signals for bladder pressure monitoring. In this study, penetrating microelectrode arrays were inserted in the S1 and S2 DRG in two cats to record afferent spiking activity at different bladder pressures. Multivariate linear regression models were used to estimate bladder pressure from the spiking activity of DRG neurons. The best estimates were obtained with populations of 5–10 units primarily from the S2 DRG, with root mean square errors of 3.0–3.2 cm H2O (correlation coefficients of 0.5–0.9). This work demonstrates the feasibility of monitoring bladder pressure from DRG recordings.

Chronic monitoring of lower urinary tract activity via a sacral dorsal root ganglia interface

“…Our interests lie in developing a closed-loop DRG interface for bladder control. Electrodes at one or two sacral DRG allow for the bladder state (pressure) to be observed, via pelvic nerve afferents (figures 4–8) [10,11], and for the bladder state to be driven, by activating pudendal nerve afferents (figure 9) [12]. A single location for both state detection and state control offers significant benefits over approaches that require interfaces at multiple locations.…”

“…Penetrating arrays have also successfully been implanted in the feline dorsal root ganglia (DRG) to record LUT activity and evoke reflex responses [10–12]. There are several reasons why the sacral DRG are an ideal location for accessing information about the LUT.…”

Using the Native Afferent Nervous System to Sense Bladder Fullness: State of the Art

“…DRGs contain the cell bodies of afferent neurons projecting into the spinal cord, and they offer unique access to hundreds of neurons that can be recorded with a higher signal-to-noise ratio (13) •. Large numbers of neurons in DRGs can be isolated and recorded simultaneously, although it remains impossible to definitively know which neurons are being recorded.…”

“…DRG are shielded by the spinal column, which offers protection from mechanical forces compared to peripheral nerves; however, access to DRG requires a laminectomy, making this approach much more invasive. Bruns et al was the first group to demonstrate that DRG neural activity could be used to estimate bladder pressure (13) •. They have since created the first cat model that uses sacral DRG microelectrodes to measure reflex bladder responses that control micturition and continence (14) ••.…”

An Implantable Sacral Nerve Root Recording and Stimulation System for Micturition Function Restoration

“…Consequently, closed-loop feedback system with the ability to monitor the bladder volume and to trigger stimulation is needed. Currently known methods of monitoring the bladder volume change include ultrasound devices, pressure sensors located in the bladder wall [12], [13], body impedance measurement [14], recording electromyogram (EMG) of external urethral sphincter [15], and tracing the bladders activities through its neural pathway [1], [7], [11], [16]. Each one of these techniques has its drawbacks, such as artifacts caused by movements impacting the sensors, electrodes migration and irritation to bladder.…”