# Evaluation of Over-the-Counter Cutaneous Lidocaine Cream for Temporary Deafferentation in Upper Limb Rehabilitation: A Cross-Sectional Study

## TL;DR

This study shows that over-the-counter lidocaine cream can temporarily block nerve signals in the arm, which may help improve rehabilitation for neurological injuries.

## Contribution

Demonstrates that OTC lidocaine can achieve temporary deafferentation in 60 minutes for upper limb rehabilitation.

## Key findings

- TD was achieved after 60 minutes with OTC lidocaine, affecting normal and light touch most significantly.
- Age and sex were the most significant demographic factors influencing the level of TD achieved.
- A 4.56 weighted von Frey hair test reliably detected TD after 60 minutes.

## Abstract

Introduction: Topical or cutaneous methods of temporary deafferentation (TD) have shown potential as a tool to augment the effects of rehabilitative approaches for neurological conditions. TD has been suggested to achieve such effects due to its ability to suppress activity from afferent input that may be inhibitory to rehabilitative processes. However, most approaches to date have utilized prescription-grade anesthetic agents, which may be difficult to translate to routine outpatient rehabilitation or in remote settings. Here, we sought to evaluate whether TD could be achieved with readily available over-the-counter (OTC) 5% lidocaine topical anesthetic. We targeted the biceps brachii for TD, since previous work has suggested excessive afferent input from this muscle may limit triceps recovery following neurological injury.

Methods: Eighteen volunteers without any history of neurological disorders participated in a single-session, cross-sectional study design. TD was applied to the biceps brachii using 5% lidocaine cream (Ebanel). We assessed the loss of normal, diminished light touch, diminished protective sensation, and loss of protective sensation during TD using von Frey hair filaments (VFHT) for up to 75 minutes. Demographic factors (e.g., sex, age, fat percentage, and arm circumference) were evaluated as confounds for the level of achieved TD.

Results: Overall, TD was achieved after a minimum of 60 minutes following the application of OTC lidocaine, with normal and light touch showing the most significant loss in sensation. Age and sex were found to most significantly affect the level of achieved TD. We also found that the 4.56 weighted VFHT could be used to reliably determine if TD was achieved in 60 minutes.

Conclusions: Our results suggest that the use of OTC lidocaine can be used to achieve TD in as little as 60 minutes. While demographic factors were found to influence the level of TD, this approach offers a practical and economical solution for studies seeking to utilize TD outside of traditional healthcare or research facilities.