Laminitis Pain Might Originate from Different Source

Scottish researchers have discovered that neuropathic pain--damage to the sensory neurons innervating the foot--might play an import role in the chronic pain experienced by laminitic horses.

This finding could explain why horses with laminitis often do not respond to conventional analgesics, including non-steroidal anti-inflammatory drugs such as phenylbutazone.

Laminitis is a debilitating disease caused by a disruption between the dermal and epidermal laminae in the foot. Horses diagnosed with this disease are frequently euthanatized due to uncontrollable pain.

"It was hypothesized that the pain associated with laminitis is at least partly due to damage to sensory neurons innervating the foot (i.e., neuropathic pain)," said Susan Fleetwood-Walker, BSc, PhD, chair of Sensory Neuroscience from the Centre for Neuroscience Research, The Royal (Dick) School of Veterinary Studies at the University of Edinburgh,

Fleetwood-Walker explained that the mechanisms of neuropathic pain could involve:

  • The sensation of unpainful stimuli perceived as painful;
  • A heightened response to painful stimuli;
  • Perception of spontaneous pain, and;
  • A lack of an adequate response to anti-inflammatory pain medications.

This study observed the behavior of seven laminitic horses via video surveillance for 72 hours and analyzed the microscopic structure of the nerves innervating the hoof in five horses with laminitis and four normal horses.

Both the behavior and analyzed nerves of the laminitic horses were abnormal.

"These results suggest that neuropathic pain may play a key part in equine laminitis, in addition to the 'traditional' pain caused by inflammation or nociception," said Fleetwood-Walker. "As such, drugs that have significant secondary effects as anti-neuropathic analgesics (e.g., tricyclic antidepressant or anticonvulsant drugs) might have a role in the successful management of laminitis in addition to the current mainstays."

The multidisciplinary study "Neuropathic changes in equine laminitis pain" was published in Volume 132 (2007) of Pain by Fleetwood-Walker and colleagues.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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