Solving the mystery of chronic whiplash symptoms

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Solving the mystery of chronic whiplash symptoms

New scans reveal that whiplash changes the pain processing areas of the brain

• By David Vállez García, PhD 
• December 7, 2016

Illustration of neck contortion associated with whiplash. © istock.com/raycat

Jane has had a car crash: a truck ran into the back of her car when she was stopped at a red light, causing her head to whip violently forwards and backwards. Luckily, she had no visible injuries, so she exchanged insurance details with the other driver and headed home.

But that evening she began to feel an ache in her neck, which spread to her head and jaw in the following days. She visited a doctor, who carried out tests but could find no physical cause of her pain. Weeks, months and years passed, but the pain remained. Her friends and family began to wonder if she was making it up – a string of specialists had found nothing wrong with her.

When I was a physiotherapist, I had a lot of patients like Jane – people with chronic whiplash associated disorders (cWAD). Patients often report these symptoms for years, but if they do see a doctor, nothing shows up on the tests. It’s complicated to work with them because the condition is a black box. With other conditions, you can explain to the patient what’s going on, but with cWAD, you don’t know for sure what approach is best – and often the patient is not convinced there’s really anything physically wrong.

An estimated 3 in 1,000 people suffer from whiplash, and one in four of them report chronic symptoms. We need to understand what’s happening to cause this pain, so when I had a chance to investigate this disorder during and after my PhD, it was the perfect opportunity to work with colleagues at the University of Groningen in the Netherlands and Offenburg University in Germany to help unravel the mystery.

In EBioMedicine, we share the results of some state-of-the-art imaging experiments, showing that there are real, functional changes in the brain that affect the way cWAD patients process pain.

Analyzing blood flow

Eight healthy women and 12 women with chronic whiplash-associated disorders were scanned during electrical neck stimulation to reveal changes in blood flow in the brain. (Credit: David Vállez García)

This isn’t the first time researchers have studied what’s happening in cWAD patients; previous studies have shown changes in the blood flow in the brain. Previous research has also shown that people with cWAD can be more sensitive to pain through a phenomenon called central hyperexcitability – the nerves become super excited, signaling pain where there shouldn’t be any.

But until now, no studies have addressed these two things together and focused on what’s happening in the brain. We did that to see if the connection between the neck and deeper parts of the brain is what’s causing whiplash pain. Our hypothesis – one we’re still exploring – is that the connections between the neck and the deeper parts of the brain could be involved in the chronic pain experienced in cWAD.

To look at blood flow in the brain, we performed a special type of scanning technique; we used positron emission tomography (PET) to scan the brains of 20 women (8 healthy, pain-free women and 12 with cWAD). We used an electrical current to induce non-painful feeling in the neck so we could scan under different conditions. We then observed the whole brain to see if there were any changes.

Our results revealed changes in the blood flow in areas of the brain involved in pain perception and processing sensory information from within the body, which is called interoceptive stimuli. We think these changes could be down to a mismatch in the way interoceptive stimuli are integrated in pain processing regions.

Whiplash symptoms originate in the brain

The scans revealed changes in blood flow in brain regions linked to the processing of pain and of stimuli from within the body. (Credit: Vállez García, David et al, EBioMedicine, August 2016)

Adding our findings to previous research, we can now say there is something happening in the brain in cWAD patients. After years of failed diagnoses, many people start thinking they may be making the symptoms up or trying to make a claim for compensation. It’s a tricky situation in which the patient is in pain, the doctors can’t explain it and people think they’re making it up.

I think our study will improve awareness about the disease among the public as well as medical professionals, and help people with chronic whiplash-associated disorders get the treatment they need.

Although our research goes a long way to explaining why cWAD patients can experience chronic pain, this is really the start of understanding what’s happening in the brain. We need more research to see what’s going on in detail. With our scanning technology, we can use different compounds to explore different functions of the brain, such as the blood flow in this study, for example. We are also considering looking more closely at other factors, such as inflammation in the brain, to see if anything else is involved.

We hope our ongoing research will help patients who have suffered without recognition of their pain for too long.

 

Read the study

Elsevier has published this article open access:

Vállez García, David et al: “Altered Regional Cerebral Blood Flow in Chronic Whiplash Associated Disorders,” EBioMedicine (August 2016)

With the leadership of Cell and The Lancet, EBioMedicine covers the entire breadth of translational and clinical research within all disciplines of life and health sciences, ranging from basic science to clinical and public/global health science. Placing a high priority on rapid publication, the journal covers a broad range of research study types, from experimental findings, critical analyses, methodological and technical innovations and hypotheses to observational epidemiological studies, clinical trials, meta-analyses and study protocols. In addition, EBioMedicine publishes commentaries, reviews, and viewpoints that enhance the accessibility and applicability of basic research findings for health professionals, and promote a better understanding of clinical challenges for biomedical researchers. This journal is published by Elsevier.