The Gazette 1989

GAZETTE

DECEMBER 1 9 89

Whiplash Whiplash injury of the spine and supporting structures is arguably the most common injury experienced by victims of motor accidents in the Republic today. Public perception of whiplash is of a minor injury, often exaggerated by the patient. Unfortunately, lawyers can be of a similiar opinion, and this article should improve their understanding of this debilitating injury. The force of impact on the spine the sensory nerves causes pain or

At the upper end of the spine, the skull and brain suffer approximately three times as much force as the lumbar area. Injury to the frontal cortex, temporal lobes and tissues around the limbic system of the brain results. These areas govern mood, feelings and behaviour in the normal subject, and their injury is followed by poor memory, de- creased concentration and irrita- bility. The pain and discomfort interfere wi th sleep, and this com- pounds tiredness and irritability. The muscles of the throat and the temporomandibular joint can also be strained by whiplash, and pain on swallowing and chewing is then seen. Headache is a prominent part of this syndrome, and may arise in two ways. Firstly, sudden decelera- tion/acceleration of the brain within its fixed compartment of the skull causes a contra coup effect, with cortical oedema and micro haem orrhages of the brain stem. Secondly, reflex spasm of the muscles in the back of the skull and upper neck produces a tension headache at the back of the skull. "The patient . . . is unable to sit comfortably or adopt a normal posture on standing."

and skull varies in proportion to the speed of collision. Studies show a rear end impact at 10 mph pro- duces a force of nine times gravity (9g) in the area of the lower spine, and causes a whiplash effect of acceleration and deceleration or hyperextension (backward) and hyperflexion (forward) movement of the spine. By leverage the impact force at the lower spine is amplified almost threefold at the upper spine and skull, and thus the skull con- tents suffer a force of twenty three times gravity (23g) even at this low speed of 10 mph. Thus, speeds of 30 mph can bring forces up to seventy times gravity (70g) to bear • on the skull contents. " . . . speeds of 30 mph can bring forces up to seventy times gravity (70g) to bear on the skull contents." Although the range of movement between any t wo adjacent verte- brae is very restricted (probably blocked by the intervertebral discs), the spine has a relatively wide range of movement due to the sum of all the vertebral movements. Hyperextension and hyperflexion greatly exceed the normal move- ment range of the spinal joints, and they react as any other joint, e.g. ankle, subjected to sprain. Trau- matic arthrosis w i t h oedema (swelling) of their synovial lining and supporting ligaments is pro- duced. This swelling may cause pressure on the nerves which exit from the spinal cord through the intervertebral foramina. The three main nerve types which emanate from the spinal cord through the intervertebral foramina are: (i) sensory, (ii) motor and (iii) sympathetic. Pressure on

paraesthesiae (numbness) over the dermatome (the portion of skin subserved by the particular nerve). Motor nerve impingement may pro- duce power loss, as when one's knee suddenly gives way. Injury to the sympathetic nervous system is

By Cahal J, Mu l d o o n,

F.R.C.S.Ed., F.D.S.R.C.S

suspected when blurring of vision and hearing upsets occur. " . . . the syndrome of pain and muscle spasm is self-perpetuating." The paraspinal muscles are arranged in mirror images of each other on either side of the spine, and work together by propriocept- ion to maintain a normal posture throughout all movements. Some of these muscles are torn and injured by the whiplash mechan- ism, and are painful in use. This pain and the pressure on the sens- ory nerves due to joint swelling will produce a reflex arc involving the motor nerves, and cause muscle spasm. Pain and spasm prompt inappropriate movements of com- plementary muscles e.g. spasm of one trapezius muscle activates the contralateral trapezius muscle of the neck and upper back, and so the syndrome of pain and muscle spasm is self-perpetuating. " . . . pain and discomfort interfere with sleep, and this compounds tiredness and irritability."

Cahal J. Muldoon.

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