Whiplash is a descriptive term for the type of motion experienced by a person’s head and neck following a rear-end collision. The head and neck are at rest when the impact occurs. The vehicle and seat are pushed forward with the head and neck moving backward into hyperextension initially and then recoiling forward into hyperflexion as illustrated in the image below.

Whiplash injuries are the most common condition sustained in motor vehicle accidents and are the most costly to the medical system and insurance companies. There have been millions of medical publications on the topic and yet the exact cause for the symptoms that people experience is still poorly understood. In most cases there is no specific injury that can be identified on imaging studies such as x-rays, CT scans or MRI scans. It has been suspected that the forces caused by the accident result in injuries to the muscles, ligaments or facet joints in the cervical spine. However, it has been difficult to prove this.

Whiplash injuries have been categorized by the Quebec Task Force as Whiplash Associated Disorders (WAD) grade 1 – 4 with grade 1 having neck pain, stiffness or tenderness but a normal examination, grade 2 having neck pain with decreased range of motion of the neck and tenderness on examination, grade three having neck pain and neurological symptoms such as weakness or sensory abnormalities, and grade 4 with damage to the spine demonstrated on an x-ray or CT in the form of a fracture or subluxation with associated damage to the spinal cord or nerves in the cervical spine. The most common type of injury is Whiplash associated disorder type 2 (WAD2). Most people who suffer a whiplash injury experience a gradual improvement in their neck pain and stiffness over a few weeks or months with complete recovery by 3 months. However, there are large numbers of people who develop pain that can last for months or years and some people have permanent pain after whiplash injuries. It has been difficult to determine who will get better, who won’t, and why they don’t get better.

Head restraints can limit the motion of the head and neck at the time of impact and can reduce the injuries. Having the head turned to the side at the time of impact can be associated with worse symptoms. Placing people in a neck collar after the injury can make the symptoms worse and more prolonged. Active treatment with range of motion exercises can hasten recovery and decrease the chance of long-term disability.

Studies have identified the facet joints in the back of the neck as common sources of pain following whiplash injuries. Autopsy studies on people who have died in car accidents have identified damage to the facet joints in the neck. Some people with neck pain from whiplash injuries also experience headaches, which are felt to be associated with damage to the facet joints in the upper part of the neck. These are called cervicogenic headaches and are probably due to the tension in the muscles that attach to skull at the back of the head. People who experience pain in the lower neck and shoulders or upper back probably have damage to one or more of the facet joints in the lower part of the neck. Injection of local anesthetic onto the medial branch nerves that supply the facet joints can determine if the neck pain is arising from the facet joints and which joints are involved. These injections are called medial branch or facet joint blocks. There are also publications that suggest that chronic whiplash symptoms are due to damage to the shoulder joint or ligaments.

Animal experiments have shown that damage to the discs can result in changes in the muscles in the neck with an increase in the fat content. This is due to the release of inflammatory chemicals in the region of the injury. These changes can be reversed by the injection of stem cells into the damaged disc. This has not been done in human whiplash patients. Fatty changes in the neck muscles are often seen on the MRI scan of patients with chronic neck pain following whiplash injuries. Whether it is due to reduced movement because of pain or due to damage of the disc or other structures is unclear. Exercises to strengthen the neck muscles can result in a progressive decrease in the fatty infiltrates in the muscles.

Most MRI scans are performed months or years after the whiplash injury and usually do not show any signs of damage. MRIs that are performed within days of the injury sometimes show damage to the muscles or ligaments, but this is a small percentage of patients. Performing upright flexion and extension MRI scans in the early days after injury has greater potential to identify an injury to a muscle, ligament or facet joint than delayed images that are not weight bearing.

In most people who develop chronic neck pain and headaches after a whiplash injury, the exact source of pain cannot be identified. Treatment such as physiotherapy, massage therapy, chiropractic treatment and medication can help improve the pain. Studies have shown that stress, anxiety and depression can worsen the symptoms and prolong disability after whiplash injuries. Therefore, these symptoms also need to be identified and treated if the patient is to make a full recovery.

The Welcome Back Centre has the only MRI machine in Canada that can perform scans with the person sitting and bending their head and neck forward (flexion) and backward (extension), mimicking the mechanism of injury. The clinic also performs diagnostic medial branch blocks to determine if the facet joints in the neck are the source of pain following whiplash injuries. The clinic also performs a minor surgical procedure called facet joint rhizotomies that cauterizes the nerves that transmit pain signals from the painful joints to the brain. This can relieve the neck pain for a year or more and can be repeated if and when the pain recurs. PRP and stem cell injections can result in the healing of damaged facet joints with more permanent relief of neck pain.

Understanding Whiplash Through MRI