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Pain classifications pt. 3 - neuropathic pain

By Elliott Perkins


Continuing our discussion of pain, we arrive at neuropathic pain. Neuropathic pain is often difficult to both diagnose and manage. It typically requires a more in-depth assessment, due to the nature of the symptoms. Sometimes someone can have referred pain that appears neuropathic, but responds to mechanical stimuli, making it appear to have nociceptive characteristics. For example, a patient can be diagnosed with Carpal Tunnel Syndrome – a known nerve-related condition. However, if this patient responds to mechanical stressors like wrist exercises and carpal mobilization, it would be classified as nociceptive. Treat the person, NOT the diagnosis.


Neuropathic pain is defined as is “pain caused by a lesion or disease of the somatosensory nervous system” (Smart, 2012). A lesion can be caused by a mechanical trauma to a nerve – a traction injury or a compression injury, and a disease can include conditions like Multiple Sclerosis, Herpes Zoster, or metabolic neuropathies. Different types of nerve damage can contribute to different symptoms, contributing to the difficulty of diagnosis.


People with neuropathic pain may report a history of an injury, or a pathology (e.g. diabetes). The pain is typically experienced in a dermatomal or cutaneous nerve distribution. Dermatomes (an area of the skin supplied by a single spinal nerve root) have a wide variance from person to person, so our ability to identify a dermatomal distribution clinically is limited (Downs, 2011). In addition to a physical exam, a full neurological exam is essential to identify the nuances of their experience. Pain may be accompanied by other sensory changes, including burning, shooting pain, prickling paraesthesias, numbness (anaesthesia) or spontaneous pain. It may present with hyper or hyposensitivity, motor weakness, atrophy, or asymmetrical reflexes, is often worse at night and provoked by anything that moves, loads and compresses nerves. (Colloca, 2017)


How do we treat neuropathic pain?


Poorly. Neuropathic pain typically has a poorer prognosis and may not fully recover. Pain management and self-efficacy is important, so that individuals can remain functional and be able to take part in meaningful activities. Changing our goal from pain abolition (often not practical) towards increasing function is a much more pragmatic approach to helping these people. (Smart, 2012)


When it comes to pain management, our goal is to desensitize the involved tissue. We do so by de-loading, and progressively reloading the tissue. Managing stress (both physical and emotional) and dosing physical activity is essential.


A note about stress


When we are experiencing stress, the levels of stress hormones (e.g. cortisol, adrenaline, noradrenaline etc.) increase. This produces a sympathetic response, or a ‘fight-or-flight’ reaction. When exposed to chronic mechanical stress, nerves adapt by developing receptors for adrenaline/noradrenaline. This physiological response causes nerves to become more sensitive and have a reduced threshold for noxious stimulation in the presence of stress. Chronic stress can contribute to a process where the brain (amygdala, more specifically) integrates stress-related information with nociception. This is why people with neuropathic pain are typically aggravated more by stress. (Li, 2017) Desensitization involves managing both physical load on the tissue as well as stress load on the person. Sometimes this warrants referral to an appropriate healthcare provider.


Education and reassurance


Education and reassurance is essential for the management of neuropathic pain. Ensure that the patient understands the ins and outs of their condition, what to do to manage their symptoms, and how to interpret what they feel. Reassure them that movement and exercise is safe, not harmful, and teach them how to autoregulate their activity level based on what they feel. The Traffic Light Analogy is absolute money for this and is my go-to on a daily basis. Exercise prescription should be based on the injury, as well as the person’s goals and experiences. The type of exercise often does not matter, but rather the meaning attached to the exercise and the dosage.





It is important to describe the condition in clear, plain language and stress the importance of movement and activity. Here is an example that might be used in a clinical setting:


"Nerves are incredibly strong, but also very sensitive. When a nerve is injured, it can cause symptoms like shooting pain, tingling and numbness. It can even increase how sensitive we are to touch and certain movements that would normally be pain free. Sensitivity or irritation may present itself in a random fashion. What we need to do is create an optimal condition for the nerve to heal. We do this by moving it, sliding it, tensioning it to desensitize it, and increase blood flow to the nerve through exercise. This may cause some pain in the short term but that’s ok! It’s all part of the process”.


On the topic of neurodynamics


You may have heard of nerve flossing, sliders, or gliders. These are exercises that are used to get nerves moving. The theory behind these exercises is that they increase the fluid dispersal within the nerve and increase neuronal blood flow. The efficacy of these exercises is far from conclusive, and in many cases do not provide better results than any other form of exercise (Ellis, 2008). That being said, in some individuals they can be a helpful starting point to introduce movement. They are a tool, not a panacea.


Neuropathic pain is difficult to manage and often requires an interdisciplinary approach. Always remember to stay in your scope, and refer to other healthcare providers for further treatment or diagnostics.



References:


1. Colloca L, Ludman T, Bouhassira D, et al. Neuropathic pain. Nat Rev Dis Primers. 2017;3:17002. Published 2017 Feb 16. doi:10.1038/nrdp.2017.2


2. Ellis, R. F., & Hing, W. A. (2008). Neural mobilization: a systematic review of randomized controlled trials with an analysis of therapeutic efficacy. The Journal of manual & manipulative therapy, 16(1), 8–22. https://doi.org/10.1179/106698108790818594


3. Smart KM, Blake C, Staines A, Thacker M, et al. “Mechanisms-Based Classifications of Musculoskeletal Pain: Part 1 of 3: Symptoms and Signs of Central Sensitisation in Patients With Low Back (± Leg) Pain.” Manual Therapy, Aug. 2012, doi:10.1016/j.math.2012.03.013.


4. ---. “Mechanisms-Based Classifications of Musculoskeletal Pain: Part 2 of 3: Symptoms and Signs of Peripheral Neuropathic Pain in Patients With Low Back (± Leg) Pain.” Manual Therapy, Aug. 2012, doi:10.1016/j.math.2012.03.003.


5. ---. “Mechanisms-Based Classifications of Musculoskeletal Pain: Part 3 of 3: Symptoms and Signs of Nociceptive Pain in Patients With Low Back (± Leg) Pain.” Manual Therapy, Aug. 2012, doi:10.1016/j.math.2012.03.002.


6. Smart KM, Blake C, Staines A, and Doody C. “The Discriminative Validity of ‘Nociceptive,’ ‘Peripheral Neuropathic,’ and ‘Central Sensitization’ as Mechanisms-Based Classifications of Musculoskeletal Pain.” The Clinical Journal of Pain, Oct. 2011, doi:10.1097/AJP.0b013e318215f16a.


7. Harrisson, Sarah A. PhD*,†; Ogollah, Reuben PhD‡; Dunn, Kate M. PhD*; Foster, Nadine E. DPhil*; Konstantinou, Kika PhD*,† Prevalence, Characteristics, and Clinical Course of Neuropathic Pain in Primary Care Patients Consulting With Low Back-related Leg Pain, The Clinical Journal of Pain: November 2020 - Volume 36 - Issue 11 - p 813-824 doi: 10.1097/AJP.0000000000000879


8. Kolski, Melissa C., and Annie O’Connor. A World of Hurt: A Guide to Classifying Pain. Thomas Land Publishers Incorporated, 2015.


9. Li MJ, Liu LY, Chen L, Cai J, Wan Y, Xing GG. Chronic stress exacerbates neuropathic pain via the integration of stress-affect-related information with nociceptive information in the central nucleus of the amygdala. Pain. 2017 Apr;158(4):717-739. doi: 10.1097/j.pain.0000000000000827. PMID: 28225710.


10. Lin I, Wiles L, Waller R, et al . What does best practice care for musculoskeletal pain look like? Eleven consistent recommendations from high-quality clinical practice guidelines: systematic review.British Journal of Sports Medicine 2020;54:79-86.


11. McKenzie, Robin, and Stephen May. The Lumbar Spine, Volume One: Mechanical Diagnosis and Therapy. Spinal Publications, 2003.


12. Walton, David M., and James M. Elliott. “A New Clinical Model for Facilitating the Development of Pattern Recognition Skills in Clinical Pain Assessment.” Musculoskeletal Science & Practice, vol. 36, Aug. 2018, pp. 17–24. www.mskscienceandpractice.com, doi:10.1016/j.msksp.2018.03.006.


13. Downs, M, Laporte C. “Conflicting Dermatome Maps: Educational and Clinical Implications.” Journal of Orthopaedic & Sports Physical Therapy, vol. 41, no. 6, June 2011, pp. 427–34. jospt.org (Atypon), doi:10.2519/jospt.2011.3506.