Anatomy of a Spinal Cord Injury

The lasting impact of a spinal cord injury (SCI) is generally determined by two factors: the location of the injury and the severity of the injury.

Injury severities, says the Mayo Clinic, vary according to “how much of the cord width is damaged.” SCI are typically described as complete (total or nearly total loss of motor function below the point of injury) or incomplete (partial sensation and motor function below the point of injury) because, the Mayo Clinic explains, the spinal cord is still able to send and receive some input from the brain.

SCI are also identified according to which part of the spinal cord is injured and its location — cervical, thoracic, lumbar or sacral — within the column of bony vertebrae.

Cervical Injuries

C1: Located below the base of the skull are the seven cervical vertebrae (and eight cervical nerves). C1, the topmost vertebra, is referred to as the atlas because it holds the globe of the skull. The cervical nerves supply movement to the arms, neck and upper trunk.

C2: Enables the head to turn and tilt; it’s referred to as the axis. When an injury occurs at C1 or C2, the patient may experience a loss of involuntary functions, including the ability to breathe, to regulate blood pressure effectively or to maintain sufficient blood pressure, to regulate body temperature and to sweat below the level of injury. Patients with SCI at this level might also suffer chronic pain.

C3: Patients with C1–C3 injuries have limited head and neck movement; complete paralysis of the arms, body and legs; and the inability to breathe using their chest muscles or diaphragms. Patients will need complete assistance transferring from a bed to a wheelchair or a wheelchair to a car, and will need complete assistance with meals. The sympathetic nervous system — the body’s “fight-orflight” system that increases heart rate, raises blood pressure and slows digestion — will also be compromised, and assistance will be required to clear secretions from the trachea. Injuries above C4 may require a ventilator for the patient to breathe properly.

C4: The fourth neck vertebra controls the area just below the clavicle. Patients with C4 injuries experience limited shoulder movement while potentially retaining full head and neck movement, depending on muscle strength. The body and legs are completely paralyzed with no finger, wrist or elbow flexion or extension. The sympathetic nervous system is compromised, and total assistance will be needed when transferring. A C4 SCI patient needs complete assistance during meals and complete domestic and personal assistance.

C5: Patients have no control at the wrist and hand, but often maintain shoulder and biceps control. C5 injuries often result in paralysis of the body and legs with full head and neck movement, if there is good muscle strength. The patient will not have finger or wrist movement or elbow extension. However, he will have good elbow flexion. The sympathetic nervous system will be compromised. Total assistance will be required when transferring, clearing secretions and coughing. Complete personal and domestic assistance will be needed.

C6: Covers the forearm and the thumb side of the hand. Patients experience paralysis of the body and legs. No finger movement, elbow extension or wrist flexion will be present. These injuries generally allow wrist control, but not hand function. The patient will, however, have full head and neck movement with good muscle strength and shoulder movement. Assistance is needed when transferring from floor to chair; assistance will vary for transfers among beds, wheelchairs and cars. Personal assistance is required, but the patient will be able to partially dress his upper body, shave, and brush his hair and teeth with palm straps.

C7: Represents the middle finger and elbow extensors, while C8 represents the lateral part of the hand and finger flexors.When C7 and C8 injuries occur, they cause paralysis of body and legs with partial finger movement and full elbow extension and flexion along with full wrist extension and flexion. Patients with these injuries also experience full head and neck movement with good muscle strength and good shoulder movement. A C7-injured patient will have movement in the thumb. He may need assistance making car transfers, depending on upper-body strength. The sympathetic nervous system will be compromised. Food may need to be cut, but the person will be able to independently feed himself. Assistance will be required to clear secretions, and assistance in coughing may be required. The person may need assistance in lower-body dressing and showering, but can independently dress and shower his upper body. Partial domestic assistance is required, but the person is usually independent in grooming.

Thoracic Injuries

T1–T4: Injuries here result in paralysis of the lower body and legs. Patients with injuries in this area have varying levels of upper-body strength and balance, depending on injury level. Patients have good chest-muscle strength, but strength weakens the higher up the injury is. Patients also experience full head and neck movement with normal muscle strength, normal shoulder movement and full use of arms, wrists and fingers. The sympathetic nervous system may be compromised. The patient should be independent in personal care, as long as no other factors are involved, such as additional injuries or severe spasticity. Partial domestic assistance may be required, along with assistance during car transfers, depending on upper-body strength.

T5–T9: Patients will have full head and neck movement with normal muscle strength, and normal shoulder movement along with full use of arms, wrists and fingers. Injuries in this region result in paralysis of lower body and legs with varying upper-body strength, depending on the level of injury. The lower the level of the injury, the stronger the upper-body strength and balance will be. The person may need assistance with car transfers, depending on upper-body strength. Partial domestic assistance is required for heavy household cleaning and home maintenance. As long as other injuries don’t exist, patients should also be independent in personal care.

T10: Located at the umbilicus; T12 ends just above the hip girdle. T10–L1 injuries affect certain parts of the abdominal and leg muscles. This type of injury results in partial paralysis of the lower body and legs. People with these injuries will experience full head and neck movement with normal muscle strength, and normal shoulder movement along with full use of arms, wrists and fingers. The strength of the upper body will vary depending on the level of injury. The person has the ability to prepare complex meals and perform general household duties independently. The person should also be independent in personal care as long as no other medical conditions are involved. Partial domestic assistance is required for heavy household cleaning and home maintenance.

Lumbar & Sacral Injuries

Injuries here cause decreasing control of the hip flexors and legs. The sacrum is located behind the pelvis and fits below the lumbar vertebrae. Back pain or leg pain can typically arise due to injury where the lumbar spine and sacral region connect (at L5-S1), because this section of the spine is subjected to a large amount of stress and twisting. L1 to L5 represent the hip girdle and groin area. L2 and L3 control the front part of the thighs, while L4 and L5 control the medial and lateral aspects of the lower leg.

L2–S5 injuries affect leg muscle, bowel, bladder and sexual functions. A patient with these injuries will have full upper-body control and balance along with some knee, hip and foot movement, depending on the level of injury. The patient may be able to walk with assistance or walking aids, depending on the level of injury; however, a manual wheelchair may be useful for daily living activities. The person should be independent in personal care as long as no other factors are involved.

This article originally appeared in the SCI Handbook: September 2009 issue of Mobility Management.

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