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| Segmental Spinal Cord Level and Function | |
|---|---|
| Level | Function |
| Cl-C6 | Neck flexors |
| Cl-T1 | Neck extensors |
| C3, C4, C5 | Supply diaphragm (mostly C4) |
| C5, C6 | Shoulder movement, raise arm (deltoid); flexion of elbow (biceps); C6 externally rotates the arm (supinates) |
| C6, C7, C8 | Extends elbow and wrist (triceps and wrist extensors); pronates wrist |
| C7, C8, T1 | Flexes wrist |
| C8, T1 | Supply small muscles of the hand |
| Tl -T6 | Intercostals and trunk above the waist |
| T7-L1 | Abdominal muscles |
| L1, L2, L3, L4 | Thigh flexion |
| L2, L3, L4 | Thigh adduction |
| L4, L5, S1 | Thigh abduction |
| L5, S1 S2 | Extension of leg at the hip (gluteus maximus) |
| L2, L3, L4 | Extension of leg at the knee (quadriceps femoris) |
| L4, L5, S1, S2 | Flexion of leg at the knee (hamstrings) |
| L4, L5, S1 | Dorsiflexion of foot (tibialis anterior) |
| L4, L5, S1 | Extension of toes |
| L5, S1, S2 | Plantar flexion of foot |
| L5, S1, S2 | Flexion of toes |
- Trauma : automobile accidents, falls, gunshots, diving accidents, etc.
- Disease : polio, spina bifida, tumors, Friedreich's ataxia, etc.
Spinal cord injuries are not the same as back injuries such as ruptured disks, spinal stenosis or pinched nerves. It is possible to "break one's neck or back" and not sustain a spinal cord injury if only the vertebrae are damaged, but the spinal cord remains intact.
About 450,000 people in the United States live with spinal cord injury, and there are about 11,000 new spinal cord injuries every year. The majority of them (78%) involve males between the ages of 16-30 and result from motor vehicle accidents (42%), violence (24%), or falls (22%).
The Effects of Spinal Cord Injury
The exact effects of a spinal cord injury vary according to the type and level injury, and can be organized into two types:
- In a complete injury, there is no function below the level of the injury. Voluntary movement is impossible and physical sensation is impossible. Complete injuries are always bilateral, that is, both sides of the body are affected equally.
- A person with an incomplete injury retains some sensation below the level of the injury. Incomplete injuries are variable, and a person with such an injury may be able to move one limb more than another, may be able to feel parts of the body that cannot be moved, or may have more functioning on one side of the body than the other.
In addition to a loss of sensation and motor function below the point of injury, individuals with spinal cord injuries will often experience other changes.
Bowel and bladder function is associated with the sacral region of the spine, so it is very common to experience dysfunction of the bowel and bladder. Sexual function is also associated with the sacral region, and is also affected very often. Injuries very high on the spinal cord (C-1, C-2) will often result in a loss of many involuntary functions, such as breathing, necessitating mechanical ventilators or diaphragmatic pacemakers. Other effects of spinal cord injury can include an inability to regulate heart rate (and therefore blood pressure), reduced control of body temperature, inability to sweat below the level of injury, and chronic pain. Physical therapy and orthopedic instruments (e.g., wheelchairs, standing frames) are often necessary, depending on the location of the injury.
Between about three weeks and twelve years after lesions above T10 autonomic dysreflexia may occur.
The Location of the Injury
Knowing the exact level of the injury on the spinal cord is important when predicting what parts of the body might be affected by paralysis and loss of function.Below is list of typical effects of spinal cord injury by location (refer to the spinal cord map to the right). Please keep in mind that the prognosis of complete injuries are predictable, incomplete injuries are very variable and may differ form the descriptions below.
Cervical injuries
Cervical (neck) injuries usually result in full or partial tetraplegia. Depending on the exact location of the injury, one with a spinal cord injury at the cervical may retain some amount of function as detailed below, but are otherwise completely paralyzed.- C-3 vertebrae and above : Typically lose diaphragm function and require a ventilator to breathe.
- C-4 : Have some use of biceps and shoulders, but weaker than C-5 and lower'''
- C-5 : May retain the use of shoulders and biceps, but not of the wrists or hands.'''
- C-6 : Generally retain some wrist control, but no hand function.
- C-7 and T-1 : Can usually straighten their arms but still may have dexterity problems with the hand and fingers. C-7 is the level for functional independence.
Thoracic injuries
Injuries at the thoracic level and below result in paraplegia. The hands, arms, head, and breathing are usually not affected.- T-1 to T-8 : Most often have control of the hands, but lack control of the abdominal muscles so control of the trunk is difficult or impossible. Effects are less severe the lower the injury.
- T-9 to T-12 : Allows good trunk and abdominal muscle control, and sitting balance is very good.
Lumbar and Sacral injuries
The effect of injuries to the lumbar or sacral region of the spinal canal are decreased control of the legs and hips, and anus.Central Cord Syndrome
Central cord syndrome is a form of incomplete spinal cord injury characterized by impairment in the arms and hands and, to a lesser extent, in the legs. This is also referred to as inverse paraplegia, because the hands and arms are paralyzed while the legs and lower extremities work correctly.Most often the damage is to the cervical or upper thoracic regions of the spinal cord, and characterized by weakness in the arms with relative sparing of the legs with variable sensory loss.
This condition is associated with ischemia, hemorrhage, or necrosis involving the central portions of the spinal cord (the large nerve fibers that carry information directly from the cerebral cortex). Corticospinal fibers destined for the legs are spared due to their more external location in the spinal cord.
This clinical pattern may emerge during recovery from spinal shock due to prolonged swelling around or near the vertebrae, causing pressures on the cord. The symptoms may be transient or permanent.
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