Research roundup
The aim of the research roundup is to provide vet professionals with an easy-to-read digest on three items of research in pain management which focus on one common subject area.
These research roundups provide a single point of reference for the reader and are also incorporated into our accredited courses.
Subject
Neuropathic pain in cats
Link to publication here
Detailed review of the paper
The review starts with some great anatomical clarification. Figure 1 provides a clear view of the anatomy of the ascending and descending pathways involves in pain & nociception. Table 1 complements this and details the separate components involved in pain processing. Some may find new information within the detail here. Useful aspects to note that are relevant to neuropathic pain (NeuP) are;
· The dorsal root ganglion is the location of the cell body of primary afferent neuron. Changes such as gene expression and upregulation of pain processing here contribute to neuropathic pain. Glial cells surround the DRG and contribute to NeuP
· Dorsal horn NMDA receptors play a key role in excitation and increased central processing, which feature in NeuP
· The concept of the ‘pain matrix’ is introduced here – describing the extensive cortical network involved in the processing of pain at higher centres
· A description of descending control is provided, highlighting the ability of endogenous neurotransmitters to regulate input at the dorsal horn
· Inhibitory interneurons in the dorsal horn play a key role in NeuP and are activated by descending pathways involving the neurotransmitters serotonin and noradrenaline
· The role of A beta fibres in NeuP is considered whereby touch becomes a noxious input
Nocifensive behaviour is delineated in a box in the paper – this is a useful concept for when we are explaining pain to caregivers. Nocifensive describes modified behaviours associated with pain. A great example is given whereby those behaviours can be over-ridden by need ie: a cat that will continue to eat despite significant periodontal disease.
In table 2 a number of definitions are considered which are features of NeuP. These help us to understand the hallmarks of NeuP.
The figure that follows lists all of the chronic pain syndromes in cats – some of which are related to NeuP. It’s an extensive list and really useful for raising our awareness and asking if NeuP could be present in cases we are managing.
A standout part of this review is the consideration between pain and emotional health of the cat. In many of the cases presenting to us, alterations in emotional health (ie behaviour of the cat) will be what the caregiver has noticed. Definitely a section of this review to focus on!
The case sections give some examples of the approach taken to managing NeuP in cats and lead nicely into the pharmacological treatment. The pharmaceuticals are well described here and make a great reference for your NeuP toolkit. I will certainly recheck this section the next time I manage a cat with NeuP.
If you’ve listened to our podcast with Clare on syringomyelia, you will know we love a treatment algorithm and Clare has also created one for NeuP. Interestingly there is no mention of NSAIDs as first line – of course we typically see NeuP as pain that responds less well to traditional analgesics. In the next section we list a paper that demonstrates in dogs with NeuP, that the inclusion of NSAIDs alongside gabapentin actually decreased treatment efficacy.
Everyone should read this
Ruel HLM, Watanabe R, Evangelista MC, Beauchamp G, Auger JP, Segura M, Steagall PV. Pain burden, sensory profile and inflammatory cytokines of dogs with naturally-occurring neuropathic pain treated with gabapentin alone or with meloxicam. PLoS One. 2020 Nov 30;15(11):e0237121. doi: 10.1371/journal.pone.0237121.
Recommended review article
This paper by Moore (2016) on NeuP in dogs complements the review on NeuP in cats
· The review of neuroanatomy will further enhance your understanding
· Laboratory assessment of NeuP is considered, which explains how effects of analgesics can be assessed
· Pharmacological treatments in dogs are considered
Further resources to link to
Dental disease is listed as a potential cause for NeuP in cats. This study provides a useful resource for us and will aid in encouraging caregivers to seek dental treatment for their cats.
Watanabe R, Doodnaught G, Proulx C, Auger JP, Monteiro B, Dumais Y, Beauchamp G, Segura M, Steagall P. A multidisciplinary study of pain in cats undergoing dental extractions: A prospective, blinded, clinical trial. PLoS One. 2019 Mar 1;14(3):e0213195. doi: 10.1371/journal.pone.0213195.
All papers referenced are open access – follow the links to read the full papers
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