Atlas of pathophysiology, 2 Edition
Part II - Disorders
Spinal cord injury
Spinal injuries include fractures, contusions, and compressions of the vertebral column, usually as the result of trauma to the head or neck. The real danger lies in spinal cord damage—cutting, pulling, twisting, or compression. Damage may involve the entire spinal cord or be restricted to one-half, and it can occur at any level. Fractures of the C5, C6, C7, T12, and L1 vertebrae are most common.
· Motor vehicle accidents
· Sports injuries or diving into shallow water
· Gunshot or stab wounds
· Lifting heavy objects
· Neoplastic lesions
Like head trauma, spinal cord trauma results from acceleration, deceleration, or other deforming forces usually applied from a distance.
Mechanisms triggered by spinal cord trauma include:
· hyperextension—acceleration-deceleration forces and sudden reduction in the anteroposterior diameter of the spinal cord
· hyperflexion—sudden and excessive force, propelling the neck forward or causing an exaggerated movement to one side
· vertical compression—upward or downward force along the vertical axis
· rotation and shearing—twisting.
Injury causes microscopic hemorrhages in the gray matter and pia-arachnoid. The hemorrhages gradually increase in size until all of the gray matter is filled with blood, which causes necrosis. From the gray matter, the blood enters the white matter, where it impedes the circulation within the spinal cord. Ensuing edema causes compression and decreases the blood supply. The edema and hemorrhage are greatest at the injury site and approximately two segments above and below it. The edema temporarily adds to the patient's dysfunction by increasing pressure and compressing the nerves. Edema near the C3 to C5 vertebrae may interfere with phrenic nerve-impulse transmission to the diaphragm and inhibit respiratory function.
In the white matter, circulation usually returns to normal in about 24 hours. However, in the gray matter, an inflammatory reaction prevents restoration of circulation. Phagocytes appear at the site within 36 to 48 hours after the injury, macrophages engulf degenerating axons, and collagen replaces the normal tissue. Scarring and meningeal thickening leave the nerves in the area blocked or tangled.
Signs and symptoms
· Muscle spasm and back pain that worsens with movement:
§ In cervical fractures, pain may cause point tenderness.
§ In dorsal and lumbar fractures, pain may radiate to other body areas such as the legs.
· Mild paresthesia to quadriplegia and shock, if the injury damages the spinal cord (in milder injury, such symptoms may be delayed several days or weeks)
Specific to injury type or degree
· Loss of motor function; muscle flaccidity
· Loss of reflexes and sensory function below the level of injury
· Bladder and bowel atony
· Loss of perspiration below the level of injury
· Respiratory impairment
Diagnostic test results
· Spinal X-rays, the most important diagnostic measure, detect the fracture.
· Thorough neurologic evaluation locates the level of injury and detects cord damage.
· Lumbar puncture shows increased cerebrospinal fluid pressure from a lesion or trauma in spinal compression.
· Computed tomography scan or magnetic resonance imaging reveals spinal cord edema and compression and may reveal a spinal mass.
· Immediate immobilization to stabilize the spine and prevent cord damage (primary treatment), including the use of sandbags on both sides of the patient's head, a hard cervical collar, or skeletal traction with skull tongs or a halo device for cervical spine injuries
· High doses of methylprednisolone
· Bed rest on firm support (such as a bed board), analgesics, and muscle relaxants
· Plaster cast or a turning frame
· Laminectomy and spinal fusion
· Medications, including analgesics, anticoagulants, antiulcer agents, antidepressants, anticholinergics, antispasmodics, and laxatives
EFFECTS OF SPINAL CORD INJURY