Optimized Measurement Parameters of Sensory Evoked Cortical Potentials to Assess Human Bladder Afferents - A Randomized Study

Intra-epidermal evoked potentials: A promising tool for spinal disorders?

OBJECTIVES

To test the robustness and signal-to-noise ratio of pain-related evoked potentials following intra-epidermal electrical stimulation (IES) compared to contact heat stimulation in healthy controls, and to explore the feasibility and potential added value of IES in the diagnosis of spinal disorders.

METHODS

Pain-related evoked potentials induced by IES (custom-made, non-invasive, concentric triple pin electrode with steel pins protruding 1 mm from the anode, triangularly separated by 7-10 mm respectively) and contact heat stimulation were compared in 30 healthy subjects. Stimuli were applied to four different body sites. Two IES intensities, i.e., high (individually adapted to contact heat painfulness) and low (1.5 times pain threshold), were used. Additionally, a 40-year-old patient with unilateral dissociated sensory loss due to a multi-segmental syringohydromyelia was assessed comparing IES and contact heat stimulation.

RESULTS

Both IES and contact heat stimulation led to robust pain-related evoked potentials recorded in all healthy subjects. Low intensity IES evoked potentials (14.1-38.0 µV) had similar amplitudes as contact heat evoked potentials (11.8-32.3 µV), while pain ratings on the numeric rating scale were lower for IES (0.8-2.5, compared to 1.5-3.9 for contact heat stimulation). High intensity IES led to evoked potentials with higher signal-to-noise ratio than low intensity IES and contact heat stimulation. The patient case showed impaired pain-related evoked potentials in segments with hypoalgesia for both IES modes. IES evoked potentials were preserved, with delayed latencies, while contact heat evoked potentials were abolished.

CONCLUSION

IES evoked robust pain-related cortical potentials, while being less painful in healthy controls. The improved signal-to-noise ratio supports the use of IES for objective segmental testing of nociceptive processing. This was highlighted in a spinal syndrome case, where IES as well as contact heat stimulation reliably detected impaired segmental nociception.

Lower urinary tract electrical sensory assessment: A systematic review and meta-analysis

Objectives

To summarize the current literature on lower urinary tract electrical sensory assessment (LUTESA), with regard to current perception thresholds (CPTs) and sensory evoked potentials (SEPs), and to discuss the applied methods in terms of technical aspects, confounding factors, and potential for lower urinary tract (LUT) diagnostics.

Methods

The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) statement. Medline (PubMed), Embase and Scopus were searched on 13 October 2020. Meta‐analyses were performed and methodological qualities of the included studies were defined by assessing risk of bias (RoB) as well as confounding.

Results

After screening 9925 articles, 80 studies (five randomized controlled trials [RCTs] and 75 non‐RCTs) were included, comprising a total of 3732 patients and 692 healthy subjects (HS). Of these studies, 61 investigated CPTs exclusively and 19 reported on SEPs, with or without corresponding CPTs. The recording of LUTCPTs and SEPs was shown to represent a safe and reliable assessment of LUT afferent nerve function in HS and patients. LUTESA demonstrated significant differences in LUT sensitivity between HS and neurological patients, as well as after interventions such as pelvic surgery or drug treatments. Pooled analyses showed that several stimulation variables (e.g. stimulation frequency, location) as well as patient characteristics might affect the main outcome measures of LUTESA (CPTs, SEP latencies, peak‐to‐peak amplitudes, responder rate). RoB and confounding was high in most studies.

Conclusions

Preliminary data show that CPT and SEP recordings are valuable tools to more objectively assess LUT afferent nerve function. LUTESA complements already established diagnostics such as urodynamics, allowing a more comprehensive patient evaluation. The high RoB and confounding rate was related to inconsistency and inaccuracy in reporting rather than the technique itself. LUTESA standardization and well‐designed RCTs are crucial to implement LUTESA as a clinical assessment tool.

Detrusor sphincter dyssynergia: can a more specific definition distinguish between patients with and without an underlying neurological disorder?

Study design

Cross-sectional study.

Objectives

To evaluate if specific definitions of detrusor sphincter dyssynergia (DSD) might distinguish between individuals with spinal cord injury (SCI) and those with no underlying neurological disorder (NO ND).

Setting

Single tertiary university SCI center.

Methods

A series of 153 individuals, 81 with traumatic SCI and 72 with NO ND, were prospectively evaluated and included in this study. All individuals underwent a clinical neuro-urological examination, a neurophysiological work-up and a video-urodynamic investigation and were diagnosed with DSD as defined by the International Continence Society (ICS). We determined the DSD grades/types according to the classifications by Yalla (grade 1–3), Blaivas (type 1–3) and Weld (type 1–2). Distribution of the DSD grades/types were compared between SCI and NO ND individuals. Associations between the various DSD grades/types and clinical parameters, such as risk factors for upper urinary tract damage (all individuals) or lower extremity motor scores, SCI injury levels and severity scores (only SCI group), were assessed.

Results

The distribution of all DSD types were similar between groups (p > 0.05). None of the DSD classifications allowed risk assessment for upper urinary tract damage. A significant association between DSD type and other clinical parameters could not be found (p > 0.05).

Conclusions

None of the investigated DSD definitions can distinguish between patients with SCI and with NO ND. The more complex DSD classifications by Yalla, Blaivas or Weld cannot compete with the ICS binary yes-no definition which is pragmatic and straightforward for managing patients in daily clinical practice.

Sponsorship

None.

Scalp Topography of Lower Urinary Tract Sensory Evoked Potentials

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.