Spinal cord injury (SCI) refers to an injury to the spinal cord. It can cause myelopathy or damage to nerve roots or myelinated fiber tracts that carry signals to and from the brain. Depending on its classification and severity, this type of traumatic injury could also damage the grey matter in the central part of the cord, causing segmental losses of interneurons and motor neurons.
The American Spinal Injury Association (ASIA) defined an international classification based on neurological responses, touch and pinprick sensations tested in each dermatome, and strength of ten key muscles on each side of the body, e.g. shoulder shrug (C4), elbow flexion (C5), wrist extension (C6), elbow extension (C7), hip flexion (L2). Traumatic spinal cord injury is classified into five categories by the American Spinal Injury Association and the International Spinal Cord Injury Classification System:
- A indicates a "complete" spinal cord injury where no motor or sensory function is preserved in the sacral segments S4-S5.
- B indicates an "incomplete" spinal cord injury where sensory but not motor function is preserved below the neurological level and includes the sacral segments S4-S5. This is typically a transient phase and if the person recovers any motor function below the neurological level, that person essentially becomes a motor incomplete, i.e. ASIA C or D.
- C indicates an "incomplete" spinal cord injury where motor function is preserved below the neurological level and more than half of key muscles below the neurological level have a muscle grade of less than 3, which indicates active movement with full range of motion against gravity.
- Dindicates an "incomplete" spinal cord injury where motor function is preserved below the neurological level and at least half of the key muscles below the neurological level have a muscle grade of 3 or more.
- E indicates "normal" where motor and sensory scores are normal. Note that it is possible to have spinal cord injury and neurological deficits with completely normal motor and sensory scores.
Signs and symptoms
The effects of a spinal cord injury may vary depending on the type, level, and severity of injury, but can be classified into two general categories: In a complete injury, function below the "neurological" level is lost. Absence of motor and sensory function below a specific spinal level is considered a "complete injury". Recent evidence suggests that less than 5% of people with "complete" spinal cord injuries recover locomotion. In an incomplete injury, some sensation and/or movement below the level of the injury is retained. The lowest spinal segment in humans is located at vertebral levels S4-5, corresponding to the anal sphincter and peri-anal sensation. The ability to contract the anal sphincter voluntarily or to feel peri-anal pinprick or touch, the injury is considered to be "incomplete". Recent evidence suggests that over 95% of people with "incomplete" spinal cord injuries recover some locomotor function. In addition to loss of sensation and motor function below the level of injury, individuals with spinal cord injuries will also often experience other complications: Bowel and bladder function is regulated by the sacral region of the spine. In that regard, it is very common to experience dysfunction of the bowel and bladder, including infections of the bladder and anal incontinence, after traumatic injury. Sexual function is also associated with the sacral spinal segments, and is often affected after injury. During a psychogenic sexual experience, signals from the brain are sent to spinal levels T10-L2 and in case of men, are then relayed to the penis where they trigger an erection. A reflex erection, on the other hand, occurs as a result of direct physical contact to the penis or other erotic areas such as the ears, nipples or neck. A reflex erection is involuntary and can occur without sexually stimulating thoughts. The nerves that control a man’s ability to have a reflex erection are located in the sacral nerves (S2-S4) of the spinal cord and could be affected after a spinal cord injury.
Injuries at the C-1/C-2 levels will often result in loss of breathing, necessitating mechanical ventilators or phrenic nerve pacing.
Inability or reduced ability to regulate heart rate, blood pressure, sweating and hence body temperature.
Spasticity (increased reflexes and stiffness of the limbs).
Autonomic dysreflexia or abnormal increases in blood pressure, sweating, and other autonomic responses to pain or sensory disturbances.
Atrophy of muscle.
Superior Mesenteric Artery Syndrome.
Osteoporosis (loss of calcium) and bone degeneration.
Gallbladder and renal stones.