How Is the Level of Spinal Cord Injury Determined?

When defining spinal cord injury or spinal cord paralysis, the level and severity of the injury are specified. The spinal cord is our nervous system organ located in the vertebrae from our neck to our waist. Our spine consists of neck (cervical = C), back (thoracic = T), lumbar (lumbar = L), rump (sacrum = S) and tailbone (coccyx). The spinal cord is examined at 8 levels in the neck, 12 in the back, 5 in the waist, and 5 in the sacrum, according to the level of the spine where the nerve roots come out. The level of spinal cord paralysis is expressed with a combination of letters and numbers in the form of “C6”, “T4” or “L2”. So how exactly is this level determined?

Spinal bones and spinal cord levels are expressed with similar symbols, but they are not exactly equal concepts. For example, the spinal cord usually ends at the level of the L1 or L2 vertebrae in the lower back, and continues to lower levels as nerve fibers (cauda equina). A trauma that injures the L2 vertebral bone can injure lower levels of nerve tissue, such as the S level. Trauma at the bone level can be detected by X-ray, tomography, or MRI. The level of damage to the nerve tissue is determined by physical examination. For this, sensation and muscle strength are evaluated.

The muscle movements stimulated by the nerve roots coming out of each spinal cord level and the skin areas where they receive sensation are determined. By examining the strength of these muscles and the sensation of the skin, the doctor determines to what level the functions are normal and after which level it deteriorates.

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Movement and Muscles Examined to Determine the Level of Spinal Cord Paralysis

  • C5: Bending elbow, biceps brachialis
  • C6: Bending the wrist back, extensor carpi radialis
  • C7: Opening the elbow, triceps
  • C8: Bending fingers, flexor digitorum profundus
  • T1: Little finger outward, abductor digiti minimi
  • L2: Bending the hip, iliopsoas
  • L3: Open knee, quadriceps
  • L4: Ankle lift, tibialis anterior
  • L5: Big toe pull up, extensor hallucis longus
  • S1: Pressing down on the ankle, gastrocnemius

This movement and muscles are examined left and right. Muscle strength is scored as “0”, “1”, “2”, “3”, “4”, “5”. “0” means no movement, “5” means normal force. The level of movement (motor level) of spinal cord paralysis is determined according to the level of deterioration of the force.

There are no specific muscles that can be used in the examination for all levels of the spinal cord. At levels that cannot be evaluated with specific muscles, the level of sensation determined by sensory examination gains importance. This is how the level is determined for high-level neck injuries (C2, C3, C4), back injuries (T2 to T12), and low-level sacral injuries (S2, S3, S4/5). A piece of cotton and safety pin are used in the sensory examination. The sense of light touch is evaluated with cotton, and the sense of sharp-blunt separation (pin-prick) is evaluated with safety pins.

Injury Stage

The second feature expressed along with the level is the stage or severity of the injury. For this, criteria developed by the American Spinal Cord Injury Association (ASIA) are used. Accordingly, if spinal cord injuries are ordered from the most severe to the mildest, there are 5 stages: A, B, C, D and E. The stage of injury of the patient is stated in medical language with expressions such as ASIA A or ABS (ASIA Disorder Scale) A. The meaning of these phases is as follows:

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Stage A: Complete loss of movement and sensory function below the level of injury. Whether there is a complete loss is understood by evaluating the anus, which is controlled by the lowest level of the spinal cord. For this, the patient is examined from the rectum. A patient with stage A injury cannot receive rectal sensation and cannot tighten their muscles.

Stage B: Some sensory function is preserved below the level of injury. In the rectal examination, the patient feels sensation but cannot tighten his muscles.

Stage C: Some range of motion function is preserved below the injury level, but half of the muscles below the injury level are not strong enough to overcome gravity.

Stage D: More than half of the muscles below the injury level are strong enough to overcome gravity.

Stage E : If all functions have returned to normal in the follow-up of a patient with a known spinal cord injury, it is classified as stage E.

It gives an idea about the stage of spinal cord injury, the course of the disease and the treatment goals. Stage A is also called complete injury. Other stages are incomplete (partial) injury.

Coming back to the level of injury, injuries to the neck, or cervical level, often result in tetraplegia, that is, both arms and legs are affected. Spinal cord injuries at the level of the back and waist result in paraplegia; The arms are intact, but the strength and sensation of the legs are impaired.

In summary, the level of spinal cord injury is determined by a detailed muscle strength and sensory examination. The result of this examination is noted with an expression such as “T5, ASIA B”. Injury level and stage guide the setting of rehabilitation goals.

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