Chronic whiplash injury is defined as neck pain persisting greater than 12 weeks following a whiplash mechanism of injury. A whiplash mechanism is a sudden forceful alternating flexion and extension. Usually, but not always, this involves an automobile collision. This entity is a common source of complaints among personal injury patients. Because of its prevalence and severity, whiplash injury cannot be overlooked by the physician or the litigating attorney. However, diagnosing the cause of whiplash pain is not as simple as it seems.
Incidence of whiplash injury
Simply because of its high incidence, chronic whiplash injury should be suspected in anyone following a whiplash like mechanism of injury with persistent pain. Whiplash injury is common. In general, the estimated likelihood of chronic neck pain is 15%-60% after a whiplash injury. The likelihood goes up with accident severity. In high speed motor vehicle accidents, chronic neck pain can be seen in 80% of victims. However, extensive vehicle damage or high speeds are not required. Chronic whiplash injury can occur with a force as low as 5 G’s. This force can be imparted on an occupant’s head at speeds of 11 MPH.
Severe injuries
Severe whiplash injuries are rare, but obvious. Fracture, dislocation or subluxation are easily diagnosed in the ER with x-rays. A CT scan and MRI usually follows. These patients are typically evaluated by spine surgery at the ER and are admitted to the hospital.
Disc herniations
The next most common injuries are disc herniations. These are seen about 20% of the time. An MRI of the cervical spine (neck) is essential to diagnose these patients. For this reason, an MRI is recommended by professional medical societies when symptoms have persisted beyond 4 weeks or are severe. Unfortunately, most MRI sequences have difficulty distinguishing degenerative changes from true disc herniations. To correctly make the diagnosis, the MRI should incorporate a Gradient Echo (GE) sequence. On Gradient Echo MRI, a disc is bright and degenerative changes are dark, easily distinguishing the two.
The cervical facet injury
The facet joint is a paired structure, one on each side of the disc. The facet injury is the most common whiplash injury, accounting for 80% of chronic pain cases. The hallmark of this patient is an MRI that is negative or shows degenerative changes. As a result, the alphabet soup of spine professional societies (SIS, AAPMR and ASIPP) have stated that MRI cannot be relied upon to make the diagnosis and, purely based on suspision, diagnostic injections are required. The diagnostic injections are called third occipital nerve blocks (for upper neck pain) and medial branch blocks (for lower neck pain). An anesthetic is injected through a small needle onto a tiny nerve alongside the injured facet joint. If pain is relieved the test is positive. If the test is positive, it is repeated. If both tests are positive, this is considered prima facie evidence of a cervical facet injury, even in a negative MRI. There is an abundance of scientific literature on these diagnostic injections. Dual positive blocks are one of the most sensitive tests in all of spinal medicine.
When testing for facet injuries, one must consider that injuries are multiple in two thirds of cases. Typically, a patient will have an upper joint injury (usually C2/3) as well as a lower joint injury. Both must be tested with diagnostic blocks.
Multiple injuries
When cervical disc herniations are diagnosed on MRI, one should look for a concomitant cervical facet joint injury. The facet joint has a lower threshold for injury compared to the disc. A facet joint can injure at 5G’s while a disc may take 10G’s. As a result, many whiplash disc herniations treated with disc replacement will face continued pain. Likewise, patients with lower cervical fusions may have residual upper neck pain due to facet injury.
Conclusion
The diagnosis of chronic whiplash injury is not obvious. Standard MRI sequences may miss a symptomatic herniation. In the remaining 80% of cases, MRI will be negative. While defense experts may dismiss these patients, treating physicians and plaintiff attorneys should not. Adhering to a careful diagnostic algorithm and professional society guidelines will result in the appropriate diagnosis and treatment in most patients.
Samuel Weizak, MD
The views expressed are the personal views of the author and do not represent the views of The Brain, Spine and Joint Group, its managers, affiliates, partners, employees or its clients. Furthermore, the information provided by the author is not intended to be expert or legal advice.
The content of this newsletter is confidential. It is strictly forbidden to copy, forward, reveal the content of or share any part of this newsletter content with any third party, without a written consent of The Brain, Spine and Joint Group. If you received this newsletter, or a link to it, by mistake, please message This email address is being protected from spambots. You need JavaScript enabled to view it. and follow with its deletion, so that we can ensure such a mistake does not occur in the future.