Dolor Neuropático En Perros Y Gatos

N europathic Pain
in Dogs a nd C ats :
I f Only They Could
Tell Us I f They Hur t
Karol A. Mathews, DVM, DVSc
KEYWORDS
 Neuropathic pain  Dogs  Cats  Gabapentin
 Ketamine  Lidocaine

During the past 10 years, the physiology of nociceptive and inflammatory pain and its
management have been taught to student veterinarians and animal health technicians.
This topic has also beenpresented at many annual veterinary continuing education
programs, wherein the focus of pain management has been predominantly associated
with surgery and osteoarthritis in dogs and cats and, to a lesser degree, with traumatic
and medical pain, but there has been little discussion on neuropathic pain as a primary
focus. In the veterinary literature, textbooks and a few clinical reports presentspecific
causes of neuropathic pain that is obvious and is presented under the specific aspects
discussed in this article. Often, the clinical signs have been insidious and present for
weeks to several months, with an obvious lesion difficult to find. Because pain in general can be difficult to recognize and isolate in many veterinary patients, neuropathic
pain can be extremely difficult toidentify unless we appreciate the occult nature of
many of the predisposing causes.
The management of chronic pain, of which neuropathic pain is included, represents
a major human public health issue. Because of the near-epidemic proportions of painful
conditions in human beings, especially as the population ages, the need to improve pain
outcomes is reflected by the congressional declaration ofthe present decade as the
‘‘Decade of Pain Control and Research,’’ and the acknowledgment in January 2001
of pain as the ‘‘fifth vital sign’’ by the Joint Commission of Healthcare Organizations.1
Harden states that ‘‘Increases in our understanding of the function of the neurologic
system over the last few years have led to new insights into the mechanisms underlying
pain symptoms, especiallychronic and neuropathic pain. The rapidly evolving symptom- and mechanism-based approach to the treatment of neuropathic pain holds
promise for improving the quality of life of our patients with neuropathic pain.’’1

Emergency and Critical Care Medicine, Department of Clinical Studies, Ontario Veterinary
College, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
E-mail address:kmathews@uoguelph.ca
Vet Clin Small Anim 38 (2008) 1365–1414
doi:10.1016/j.cvsm.2008.09.001
vetsmall.theclinics.com
0195-5616/08/$ – see front matter ª 2008 Elsevier Inc. All rights reserved.

1366

Mathews

The quest for relief from pain is pursued in human medicine because the existence
of pain is known; the patient can verbalize his or her pain, what it feels like, where it is,
and therelief he or she feels when treatment is appropriate. Because we all have
experienced pain of various degrees and durations, it is an excellent topic for comparison and understanding with our veterinary patients. Because veterinary patients
cannot tell us how painful they are, we, as veterinarians, have to understand what
can cause pain, how pain manifests,2,3 and how best to treat it. The purposeof this
article is to raise awareness of the existence of neuropathic pain in our patients, in
which pain may be a cause for behavioral changes (1) in the acute pain setting (at home
or in the hospital); (2) at a later period after a traumatic or surgical experience; or (3) as
the result of a chronic primary lesion affecting the (i) somatosensory and visceral
peripheral nerve(s), (ii) themeninges, spine, spinal cord, and its nerve roots, or
(iii) a lesion in the brain. Several alterations in sensory processing occur peripherally
and centrally in the development of chronic neuropathic pain; however, two major
events occur: (1) abnormal peripheral input and (2) abnormal central processing.
The human clinical literature and the research literature are used as potential comparisons...