A Multidisciplinary Approach to Neuropathic Pain: Assessing Tactile Sensation and Neuroma Pain Factors

by Luis A. Jr. Pardo
Doctoral thesis
Date of Examination:2023-06-26
Date of issue:2023-07-18
Advisor:Prof. Dr Arndt Schilling
Referee:Prof. Dr Arndt Schilling
Referee:Prof. Dr. Christine Stadelmann-Nessler
Persistent Address: http://dx.doi.org/10.53846/goediss-10002

 

 

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Abstract

English

Neuropathic pain is a complex and often debilitating condition. Distally from the injury site, missing input contributes to deafferentation pain, while proximally, neuroma formation leads to peripheral and central sensitization, increasing pain sensation and lowering pain thresholds. Tactile feedback has been shown to potentially alleviate deafferentation pain by substituting missing afference and restoring sensorimotor incongruence. This thesis establishes a baseline on the perception of mechanical vibration in the healthy arms of ten able-bodied participants. It investigates the effects of sensory loss after peripheral nerve injury (PNI) distal to the injury site when feedback is applied proximal to the injury site in five transradial amputees and, in six subjects with brachial plexus injury when applied distal to the lesion site. It then performs a comparative analysis of various aspects of neuromas forming proximal to the injury site. Here, several inflammation-related and morphological aspects are considered comparing patients with and without neuroma, and patients with and without neuroma pain. Psychometric evaluation tasks were performed to quantify sensation threshold, just noticeable difference, Weber fraction, and perception of dynamically changing vibrotactile stimuli. Additionally, a combination of machine learning and computer vision was used to investigate several aspects of neuromas. Results demonstrated that the sensation capacity on the arm does not differ from the one on a healthy arm proximally from the site of injury, which facilitates the design and accommodation of vibrotactile feedback interfaces. In contrast, if applied distally, the more distal it is applied the sensation capacity drastically decreases. Moreover, inflammation-related cells were not more abundant in the neuroma group, however, patients suffering from pain had a significantly lower amount of organized (healthy) nervous tissue, suggesting the amount of organized tissue to counteract neuroma-evoked pain. The findings presented here contribute to a deeper understanding of neuropathic pain, giving insight into how the lost connection between the receptors and the brain affects sensation proximal- and distally from the injury and, additionally, which further factors decide if a neuroma –if formed– is painful or not, aiding in the development of therapeutic approaches and strategies for its prevention.
Keywords: Neuropathic pain; Neuroma; Tactile Sensation
 
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