Spinal cord injury reduces or eliminates skin sensation in dermatomes below the injury site. Because people cannot feel or move, they may sit or lie for long times on certain parts of their body. Pressure impedes blood flow in the skin. Due to muscle atrophy, the normal tissue padding that cushions the butt may be reduced. Absence of sensation, loss of muscle padding, and long periods of pressure can lead to skin breakdown and development of pressure sores or decubiti. Decubiti are potentially life threatening but preventable.
Spinal cord injury impairs skin blood flow responses. Normally, skin responds to pressure, mechanical stimulation, or inflammation with increased blood flow. Loss of this response not only adds to the vulnerability of the skin to pressure sores but reduces the ability of the skin to repair decubiti. Thus, great care must be taken to prevent decubiti by shifting sitting positions and frequent turning. Special seats that distribute the pressure are used in wheelchairs to prevent sacral decubiti. Vulnerable areas such as the heels must be padded. If a decubitus develops, all pressure must be removed or the decubitus can progress to loss of skin and tissues to the point of exposing bone. The sores must be kept clean or they can become infected. Plastic surgery may be necessary to repair the decubitus.
Spinal cord injury also paralyzes sweating in dermatomes below the injury level. People with spinal cord injury must be very careful to maintain their body temperatures. In contrast to loss of sweating below the injury site, many people with spinal cord injury may have abnormal increases of sweating above the injury site, often in their upper torso and face. This is a form of autonomic hyperexcitability or spasticity. It is not unusual for people to sweat profusely on one side of the face and not the other. Such abnormal sweating responses may develop early or late after injury.
Spinal cord injury disables vascular responses that maintain blood pressure when a person sits or stands up. Blood vessels in the guts and legs normally constrict when a person stands up, to keep blood from pooling. When people with spinal cord injury sit up for the first time after injury, their blood pressure may drop sharply. Such postural hypotension may prevent a person from sitting or standing during the first weeks after spinal cord injury. The vascular responses recover over time but people must be be tilted gradually into the vertical position over the several weeks after spinal cord injury. Loss of vascular responses in the legs leads to a tendency for fluid to accumulate in the legs when people sit for long times. Such dependent edema can be prevented to some extent with stockings.
