Allodynia

Welcome to Arkansas Colleges of Health Education School of Physical Therapy Musculoskeletal 1 Project. This space was created by and for the students at Arkansas Colleges of Health Education School in the United States. Please do not edit unless you are involved in this project, but please come back in the near future to check out new information!!

Original Editors - Abbi Davis, Jessica Bradshaw, & Parker Hall

Overview

Allodynia is defined pain resulting from a stimulus, such as a light touch of the skin, that would not normally provoke pain (2). Allodynia is a type of neuropathic (nerve) pain and is categorized into three types: dynamic (or mechanical) when pain results from an object moving across the skin, thermal which results from mild changes in temperature, and tactile (or static) which results from gentle touch or pressure.

Etiology

The exact etiology behind allodynia is unknown. Allodynia is considered a symptom, not a disease. It may be a patient's chief complaint. Allodynia is the phenomenon of a non-painful stimulus producing a sharp pain response, which implies an error in neuronal conduction. The mechanism behind this also error is unclear. The strongest evidence that exists thus far, suggests that sensory neuronal fibers may stimulate pain pathways, possibly due to an error in long-term potentiation. However, studies exist that suggest that superficial sensory components may also have involvement. There is also evidence that different mental states can affect the perception of allodynia. The use of the analogy of "crisscrossed" fibers, the actual location of the crisscrossing can vary and may be located almost anywhere along the peripheral to the central nervous system tract. Allodynia can involve both the peripheral nervous system and central nervous system via sensitization, and the mechanism behind the inappropriate pain sensations can evolve over time; this might partially explain the existing contradictory studies - they may all be measuring allodynia with neuronal confusion at different locations .

Listed below are some of the most common diseases associated with allodynia:

• Fibromyalgia
• Trigeminal Neuralgia
• Diabetic Neuropathic Pain
• Migraine Associated Allodynia

Differential Diagnoses

Another sensory condition that is often a differential diagnosis to allodynia is hyperalgesia. Hyperalgesia is the condition of having a heightened perception to pain. Patients do not necessarily perceive high pressure as pain, but stimulus that would normally be perceived as low pain is sensed at a higher pain level. Patients respond to pain stimulus in the same way that they would if they did not have the condition, but it is an exaggerated response (1). The cause of both allodynia and hyperalgesia is unknown.

Treatment

References

He, Y., & Kim, P. Y. (2021, September 9). Allodynia. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK537129/

Definition of ALLODYNIA. (2017). Merriam-Webster.com. https://www.merriam-webster.com/dictionary/allodynia

see adding references tutorial.