Dr. Mark Epstein looks at what can result in this maladaptive pain state in veterinary patients.
When the normal protective mechanisms of nociception and pain signaling go awry, neuropathic pain results. In Part 1 of this series, I discussed what neuropathic pain is, its effects on the body—manifesting as either hyperalgesia or allodynia—and how to identify it in veterinary patients. Now let's look at specific syndromes and components associated with this form of pain in patients.
Mark-Epstein DVM, Dipl. ABVP, CVPP
Human medicine has identified a number of quintessentially neuropathic pain syndromes. In animals, it's axiomatic that any trauma or surgery can result in the creation of neuropathic pain, with the possibility increasing proportionate to the degree of tissue and, especially, nerve damage. Examination of the literature supports neuropathic pain in the following conditions in animals:
Other conditions encountered in veterinary medicine that are likely to have neuropathic components, based either on established analogous conditions in humans known to be associated with neuropathic pain15 or on empirical observation and suspicion, include feline hyperesthesia syndrome, along with its probable cousin, feline self-mutilation syndrome; aortic thromboembolism; lymphocytic-plasmacytic gingivostomatitis in cats; possibly, chronic periodontal disease of any species; and acral lick granulomas.
In addition to pancreatitis, inguinal hernia repair, delayed union fractures, chronic otitis, keratitis and dermatitis, other conditions that could have neuropathic components include:
The question of whether animals experience neuropathic pain from these conditions or suffer from common human neuropathic pain phenomena such as postherpetic neuralgia (e.g., cats with chronic feline herpesvirus, horses with EHV-1 myelopathy), headache syndromes, fibromyalgia and so on remains unanswered at this time. But based on the emerging literature and the commonality of biologic systems where the literature does not yet exist, we should be attentive to the possibility of neuropathic pain in a much wider population of veterinary patients than previously considered.
This should not be taken as bad news, however. Once a condition or patient is suspected to have a neuropathic pain component, a world of therapeutic targets opens up to the clinician, and the prospect of creating vast improvement in patient comfort is very real.
Dr. Epstein is president of the International Veterinary Academy of Pain Management and medical director at the Total Bond Ainmal Hospital in Gastonia, N.C.
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