Compression of nerves after trauma is a proposition frequently encountered by personal injury lawyers. Controversial aspects of mechanism of injury and diagnostic criteria have been addressed in previous digests on Thoracic Outlet Syndrome and Long Thoracic Nerve Palsy .
The contribution of nerve entrapment to Cervical Whiplash and chronic Low Back Pain and their relation to degeneration of Intervertebral Discs are sources of continuing vigorous debate in the medical research literature.
Among the mechanisms which are proposed to account for Traumatic Headache, the basis of cervicogenic headache is trapped nervous tissue.
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POINT In cervical whiplash the 2 millimetre clearance may be insufficient to prevent crushing of the second cervical nerve root |
Recent studies4 of cadavers suggest that the second cervical nerve root ganglion is particularly susceptible to post-traumatic trapping because of its anatomical location between the first two vertebrae of the neck. The ganglion takes up three-quarters of the height available in the intervertebral foramen, the space between the atlas and the axis. The researchers suggest that this tight fit gives little reserve when there is soft tissue swelling, and/or bony outgrowths (osteophytes) as a result of wearing changes to the vertebrae (cervical spondylosis).
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POINT Medically-briefed counsel can and should always challenge unsupported Authoritarian diagnosis with a specific checklist |
Establishing diagnosis and causation of nerve entrapment is more demanding than in the heyday of Authoritarian Medicine. Evidence-based Medicine is more rigorous than "it is my considered opinion..." Plaintiff and defence personal injury lawyers should by carefully crafted, forced choice questions require, from both medical witnesses to fact and medical experts, empirical support for those views, in addition to theoretical plausibility.
Whiplash-induced cervicogenic headache jumps the first theoretical hurdle, for the combination of rotation and extension of the upper neck may obliterate the reserve space in the intervertebral foramen, causing crushing of the ganglion of the second cervical nerve root 5. Does the contemporaneous (not revisionist or coached) patient history support such an injury?
| PRACTICE
POINT Medical experts and witnesses to fact should be required to address
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Does the location of the headache correspond to the anatomical distribution of the nerve? Just as pain is entirely subjective, tenderness, numbness and paresthesia (abnormal sensation like tingling) are only quasi-objective, even though they may be established during physical examination. Thus, sophisticated clients can be coached to report and demonstrate anatomically correct symptoms, so clinical assessment is necesssary but not sufficient.
Provocation or exacerbation of symptoms by pressure over the nerve or nerve root is more difficult to simulate to a discerning clinician, because anatomical localisation of the sensory nervous tissue itself is much more precise than the boundaries of the skin served by it.
In other locations, such as median nerve at the wrist (carpal tunnel syndrome) or ulnar nerve injury at the elbow, nerve conduction studies can provide objective evidence of impaired transmission of nerve impulses. Because the nerve or nerve root involved in cervicogenic headache is purely sensory, and the nerve trunk too short, this source of evidence is not available. Theoretically it would be possible to show an asymmetry of Sensory Evoked Potentials (SEP)6, in which the brain-waves produced by electrical stimulation of a sensory nerve are monitored by ElectroEncephaloGraphy (EEG).
Of more practical value in diagnosis of cervicogenic headache is temporary interruption of nerve conduction by a precisely localised injection of local anesthetic in the area of the nerve root 7 8 Abolition of pain only for known duration of action of the particular medication is the strongest objective support for the diagnosis.
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