Small fibre pathology in chronic whiplash neck pain

22 April 2021

What is the research about?

In people with long-term whiplash neck pain, we often see changes in sensory perception of warm, cold and painful stimulation in the neck as well as in the limbs. It is not clear why this happens, but one reason could be changes in the nerves in the skin that send sensory information (as has been observed in other pain conditions).

So, we aimed to investigate the structure of the nerves in the skin in people with long-term whiplash neck pain as a possible explanation for changes in sensory function.

What did the researchers do?

We recruited two groups of people: 1) Whiplash Group – people with long-term neck pain after a whiplash injury, and 2) Control Group – people without neck pain, but matched to the age and sex of people in the whiplash group.

Each person completed questionnaires, had a skin biopsy at the finger and ankle, and did sensory testing at the finger.

What did the researchers find?

At the finger, people in the Whiplash Group (labelled (b) in the figure below) had lower density of nerves in the skin than people in the Control Group (labelled (a)). They were also less sensitive to warm, cold and light touch stimulations.

Figure 1 Nerve fibre density (solid white arrows) in the skin is reduced in people with long term whiplash neck pain (b) compared with people without pain (a)

What you need to know:

There are a few ways that these differences could be interpreted. As we only studied people at one time point, we do not know if these differences existed before the whiplash injury, or if they developed after the injury. So, perhaps this is pre-existing. If the changes developed after the whiplash injury, perhaps it is a ‘downstream’ effect of the neck strain on the nervous system.

How can you use this research?

These results provide basis for a new avenue of research in whiplash neck pain. From a clinical perspective on individual patient management, we do not yet know the significance of these findings. So there is no need for people with whiplash neck pain to be alarmed or rush to their GPs for skin biopsy. Further research is needed to determine what exactly nerve fibre density in the skin means for clinical decision-making in people with whiplash neck pain.

About the researchers

Dr Scott Farrell is a physiotherapist researcher at RECOVER Injury Research Centre. Professor Michele Sterling leads the ‘Improving health outcomes after musculoskeletal injury’ program at RECOVER. A/Prof Annina Schmid is a neuroscientist at Oxford University and Dr Helen Irving-Rodgers is a medical scientist at Griffith University.

Citation

Farrell, Sterling, Irving-Rodgers & Schmid. (2020). Small Fibre Pathology in Chronic Whiplash‐Associated Disorder: A Cross‐Sectional Study. Eur J Pain, 24 (6), pp1045-1057 https://doi.org/10.1002/ejp.1549