Pathophysiology and Presentation of SCI
A majority of spinal cord injuries are due to injury to the vertebral column. This can include:
- Fracture of the bony material
- Dislocated joints
- Torn ligaments
- Herniated discs.
The injuries show the force and the direction of what happened to produce the injury. Spinal injury mechanics display flexes, extension, rotation, and/or compression. Most vertebral injuries in older people involve dislocation and fractures.
The timeline of a spinal cord injury can be split into primary and secondary injury. Primary injury refers to the immediate effects of the trauma which may include compression, contusion, and a shear injury to the spinal cord. In the absence of a frank hemorrhage (which is rare in non penetrating injuries), the cord may appear to be completely normal right after the event occurred. Penetrating injuries, such as a stabbing, or a gunshot wound, usually result in partial or complete transection of spinal cord. A remarkable action is when a spinal cord injury occurs following a gunshot wound that does not penetrate the spinal canal. The injury is therefore caused by kinetic energy caused by the bullet. .
A secondary injury usually follows, starting within minutes and evolving over the course of hours after the injury occurred. The process that drives this is complex and not fully understood. The possible mechanisms are ischemia, hypoxia, edema, inflammation, ion homeostasis, and apoptosis. The occurrence of secondary injuries is sometimes manifested clinically by neurological deterioration over the course of eight to twelve hours.p>
Within hours after the injury, spinal cord edema develops due to the secondary injuries. The edema peaks between day three and day six, and then begins to fade away after day nine. This is eventually replaced by a central hemorrhagic necrosis.
A person who has an injury to the spinal cord often experiences pain at the site of the fracture, but not all do, and lack of pain does not rule out SCI. People with SCI often have related systemic and brain injuries that limit their ability to tell the doctor about any pain. Doctors find this to be an obstacle in evaluation of the patient, and the missed communication could affect the prognosis. Most SCI patients have have sleep-disordered breathing, too.
Almost half of the SCIs include the cervical cord and result in quadriparesis (weakness in all four limbs) or quadriplegia (paralysis). The seriousness of the cord syndromes is determined using the American Spinal Injury Association (ASIA) Scale or the Frankel scale:
Complete injury - (grade A) - There is some sensation in the next caudal level, and no sensation at all in all levels below. There will also be a lower muscle power in the level below the injury, followed by paralysis in the caudal myotomes. Reflexes are nonexistent in acute injury; there is no response to stimulation, and muscle tone is flimsy. Men with TSCI may experience priapism. Urinary problems will happen.
Incomplete injury - (Grade B - D) - There are varying degrees of motor function in the muscles that are controlled by the spinal cord below the injury. Sensation is partly saved in areas below the injury. Typically sensation is saved over motor function because sensory tracts are in a less vulnerable place of the spinal cord. Anal sensation and the bulbocavernosus reflex are usually present to some degree.
The ratio of complete versus incomplete injuries has increased over the years because of improved care and systems that recognize the importance of immobilization after the injury occurs. The number of incomplete injuries has declined.
Transient paralysis and spinal shock - Following a spinal cord injury, there could be loss of all activity in the spinal cord. In men, especially those who have a cervical cord injury, priapism may occur. There could also be bradycardia and hypotension. This altered state could last for several weeks, which is why it is referred to as spinal shock. It is believed that function loss is due to the lack of potassium in the injured cells in the spinal cord. As the potassium levels increase, the shock wears off. Clinical manifestations will normalize somewhat, typically replaced by a spastic paresis.
A transient paralysis accompanied with a full recovery occurs the most in young people with a sports-related injury. These people should be fully evaluated for any underlying conditions before they engage in athletic activities.