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//THE EFFECTS OF INJURY

THE EFFECTS OF INJURY

SPINAL CORD INJURY AND VERTEBRAL COLUMN INJURY

In the assessment of a patient with spinal injury and neurological damage, it is important to remember that the level of cord and root injury will not coincide with that of the skeletal damage to the vertebral column.

In estimating the vertebral levels of cord segments in the adult, a useful approximation is that in the cervical region the tip of a vertebral spinous process corresponds to the succeeding cord segment (i.e. the sixth cervical spine is opposite the seventh spinal segment); at upper thoracic levels the tip of a vertebral spine corresponds to the cord two segments lower (i.e. the fourth spine is level with the sixth segment), and in the lower thoracic region there is a difference of three segments (i.e. the tenth thoracic spine is level with the first lumbar segment). The eleventh thoracic spine overlies the third lumbar segment and the twelfth is opposite the first sacral segment. In making this estimate by palpation of the vertebral spines, the relationship of the individual spines to their vertebral bodies should be remembered (p. 745).

  

Fig. 43.10  Arterial disposition within the spinal cord.
(Reprinted from Netter Anatomy Illustration Collection, © Elsevier Inc. All Rights Reserved.)

Complete division above the fourth cervical segment causes respiratory failure because of the loss of activity in the phrenic and intercostal nerves. Lesions between C5 and T1 paralyse all four limbs (quadriplegia), the effects in the upper limbs varying with the site of injury: at the fifth cervical segment paralysis is complete; at the sixth, each arm is positioned in abduction and lateral rotation, with the elbow flexed and the forearm supinated, due to unopposed activity in the deltoid, supraspinatus, rhomboid and brachial flexors (all supplied by the fifth cervical spinal nerves). In lower cervical lesions upper limb paralysis is less marked. Lesions of the first thoracic segment paralyse small muscles in the hand and damage the sympathetic outflow to the head and neck, resulting in contraction of the pupil, recession of the eyeball, narrowing of the palpebral fissure and loss of sweating in the face and neck (Horner’s syndrome). However, sensation is retained in areas innervated by segments above the lesion, thus cutaneous sensation is retained in the neck and chest down to the second intercostal space, because this area is innervated by the supraclavicular nerves (C3 and C4). At thoracic levels, division of the cord paralyses the trunk below the segmental level of the lesion, and both lower limbs (paraplegia). The first sacral neural segment is approximately level with the thoracolumbar vertebral junction: injury, which commonly occurs here, paralyses the urinary bladder, the rectum and muscles supplied by the sacral segments, and cutaneous sensibility is lost in the perineum, buttocks, the back of the thighs and the legs and soles of the feet. The roots of lumbar nerves descending to join the cauda equina may be damaged at this level, causing complete paralysis of both lower limbs. Lesions below the first lumbar vertebra may divide or damage the cauda equina, but severe nerve damage is uncommon and is usually confined to the spinal roots at the level of the trauma. Neurological symptoms may also occur as a result of interference with the spinal blood supply, particularly in the lower thoracic and upper lumbar segments.

Spinal cord injury without radiological abnormality: ‘SCIWORA’

The spinal cord may be damaged without radiological evidence of skeletal injury in some injuries to the vertebral column. This is particularly liable to occur if the vertebral canal is abnormally narrowed, usually by osteoarthritic changes. In the elderly patient there may in addition be occlusive arterial disease, directly compromising an already precarious blood supply to the cord. This type of injury not uncommonly occurs in hyperextension injuries of the cervical spine in this age group. The cause of the damage may be direct injury to neural tissue by osteophytes or by an infolded ligamentum flavum, or direct or indirect injury to the vasculature of the cord. For cervical spinal injury, several cord syndromes have been described, relating the clinical picture to the anatomy of the neurological lesion within the cord. The commonest of these is central cord syndrome, which usually results from hyperextension injury to an osteoarthritic neck, in which the major injury is to the central grey matter. This gives a greater motor loss in the upper than in the lower limbs, with variable sensory loss. In anterior cord syndrome, which may occur in flexion–compression injuries of the neck, the damage occurs in the area of supply of the anterior spinal artery, sparing the posterior columns: the motor loss is usually proportionately greater in the lower than in the upper limbs, while sensory loss is less of a problem.

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