Mapping Referred Sensation In Traumatic Brachial Plexus Injury Patients

Abstract

BackgroundReferred sensation (RS) is described as the sensation evoked in the skin areas other than the stimulated region. The aim of the study was to identify and map RS in traumatic brachial plexus injury (TBPI) patients through a standardised assessment.MethodsIn Experiment 1, 12 patients underwent an RS screening by stimulating 22 skin areas distributed in both upper limbs, neck, and face with a cotton swab. In Experiment 2, a detailed RS mapping employing Semmes-Weinstein monofilament was performed at the reinnervated forearm of three subjects who showed RS in experiment 1 screening. In one of these patients, RS mapping was performed over a time span of 6.3 years.ResultsScreening of TBPI patients submitted to different reconstructive surgeries revealed RS only in the patients who underwent intercostal to musculocutaneous nerve (ICN-MCN) transfer. RS systematic mapping of these patients revealed a unique distribution in the forearm and the chest, without any clear topographic organisation. Longitudinal assessment in one of the tested participants showed a scattered expansion of the RS throughout time.ConclusionsThis is the first study to map systematically the RS in patients with TBPI. RS was identified only after ICN-MCN transfer. A possible explanation for this phenomenon is that the greater distance between the representations of the donor and receptor nerves at the primary somatosensory cortex (S1) could constrain plastic reorganisation and thus limit the disentangling of the forearm and chest sensations.