Involvement of Spinal Cord in Disease
1. The spinal cord can be injured by fractures of the spine. These are most common in the thoracic region. Complete damage at this level leads to paraplegia. Sensations are also lost below the level of lesion.
2. Brown Sequard syndrome. This is produced by a lesion cutting through one half (right or left) of the spinal cord. The effects are as follows.
Effects on the side of lesion
a. Cutting of pyramidal tracts produces spastic paralysis below the level of lesion.
b. Cutting of posterior column tracts (fasciculus gracilis and cuneatus) causes loss of propioceptive sensations and of fine touch.
Effects on side opposite to that of lesion
Cutting of spinothalamic tracts causes loss of pain and temperature sensation. Touch is spared as the pathways for it are bilateral.
A tumour in the vertebral canal can press upon the spinal cord at any level. The effects will depend upon the tracts and nerve roots pressed upon.
The spinal cord may be pressed upon by a central prolapse of the nucleus pulposus of an intervertebral disc (Note that a lateral prolapse causes pressure on nerve roots).
In this condition, caused by syphilis, the posterior column tracts are affected. There is numbness, paraesthesias and severe pains in some parts of the body, while there is hypersensitivity in others. Maintenence of posture is affected. Romberg’s sign is positive.
Thrombosis in the anterior spinal artery, or in one of the arteries supplying the medulla can interrupt tracts with serious consequences. See anterior spinal artery syndrome, and medial and lateral medullary syndromes.
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