Spinal Cord InjuriesArticle Last Updated: Aug 8, 2006
BackgroundPatients with spinal cord injury (SCI) usually have permanent and often devastating neurologic deficits and disability. According to the National Institutes of Health, "among neurological disorders, the cost to society of automotive SCI is exceeded only by the cost of mental retardation."The goals for the emergency physician are to establish the diagnosis and initiate treatment to prevent further neurologic injury from either pathologic motion of the injured vertebrae or secondary injury from the deleterious effects of cardiovascular instability or respiratory insufficiency.PathophysiologyThe spinal cord is divided into 31 segments, each with a pair of anterior (motor) and dorsal (sensory) spinal nerve roots. On each side, the anterior and dorsal nerve roots combine to form the spinal nerve as it exits from the vertebral column through the neuroforamina. The spinal cord extends from the base of the skull and terminates near the lower margin of the L1 vertebral body. Thereafter, the spinal canal contains the lumbar, sacral, and coccygeal spinal nerves that comprise the cauda equina. Therefore, injuries below L1 are not considered SCIs because they involve the segmental spinal nerves and/or cauda equina. Spinal injuries proximal to L1, above the termination of the spinal cord, often involve a combination of spinal cord lesions and segmental root or spinal nerve injuries.The spinal cord itself is organized into a series of tracts or neuropathways that carry motor (descending) and sensory (ascending) information. These tracts are organized anatomically within the spinal cord. The corticospinal tracts are descending motor pathways located anteriorly within the spinal cord. Axons extend from the cerebral cortex in the brain as far as the corresponding segment, where they form synapses with motor neurons in the anterior (ventral) horn. They decussate (cross over) in the medulla prior to entering the spinal cord.The dorsal columns are ascending sensory tracts that transmit light touch, proprioception, and vibration information to the sensory cortex. They do not decussate until they reach the medulla. The lateral spinothalamic tracts transmit pain and temperature sensation. These tracts usually decussate within 3 segments of their origin as they ascend. The anterior spinothalamic tract transmits light touch. Autonomic function traverses within the anterior interomedial tract. Sympathetic nervous system fibers exit the spinal cord between C7 and L1, while parasympathetic system pathways exit between S2 and S4.Injury to the corticospinal tract or dorsal columns, respectively, results in ipsilateral paralysis or loss of sensation of light touch, proprioception, and vibration. Unlike injuries of the other tracts, injury to the lateral spinothalamic tract causes contralateral loss of pain and temperature sensation. Because the anterior spinothalamic tract also transmits light touch information, injury to the dorsal columns may result in complete loss of vibration sensation and proprioception but only partial loss of light touch sensation. Anterior cord injury causes paralysis and incomplete loss of light touch sensation.Autonomic function is transmitted in the anterior interomedial tract. The sympathetic nervous system fibers exit from the spinal cord between C7 and L1. The parasympathetic system nerves exit between S2 and S4. Therefore progressively higher spinal cord lesions or injury causes increasing degrees of autonomic dysfunction.Neurogenic shock is characterized by severe autonomic dysfunction, resulting in hypotension, relative bradycardia, peripheral vasodilation, and hypothermia. It does not usually occur with SCI below the level of T6. Shock associated with an SCI involving the lower thoracic cord must be considered hemorrhagic until proven otherwise. In this article, spinal shock is defined as the complete loss of all neurologic function, including reflexes...
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