Level of Injury-ASIA Impairment Scale

The most common method of classifying impairment from SCI is the American Spinal Injury Association (ASIA) impairment scale. The classification is based upon assessment of strength and sensation to light touch and pinprick in defined myotomes and der­matomes.

The motor examination scores strength on a six- point scale: 0-5. For each strength grade, the joint being assessed must be moved through full available range of motion. A strength grade of 0 is given for total paraly­sis. A 1 is given for a visible or palpable contraction that cannot move the joint through its available range of motion with gravity removed. A grade 2 is given if the muscle group can move the joint through its range of motion with gravity removed. The joint is positioned parallel to the ground to limit the effect of gravity. A grade 3 is given when the patient can move the joint through full available range of motion against gravity but cannot bear any additional resistance. If a patient can bear additional resistance, they are given a grade 4, and a grade 5 is given for normal strength. Motor scores are documented on the ASIA form and summed for a total motor score. A rectal exam must be performed to assess for voluntary contraction, and is scored as yes/ no. As individual muscles are almost always innervated by multiple spinal cord levels, a strength grade of 3 is considered normal for a muscle group if the level above has grade 5 strength. This implies that the grade 3 mus­cle group is only partially innervated and the more proximal innervation level is intact.

STANDARD NEUROLOGICAL CLASSIFICATION OF SPINAL CORD INJURY

Figure 11.1 American Spinal Injury Association guide.

Sensory examination is performed using pin­prick and light touch at key points, and grades as 0 for absent, 1 for impaired, and 2 for normal.

The ASIA neurologic level is the most caudal seg­ment with intact motor and sensory exam. In addition to the level is whether the injury is complete or incom­plete. With a complete injury, there is no motor or sen­sory function in the lowest sacral segment (ie, no anal sensation or voluntary anal contraction). A complete injury is classified as ASIA-A. Incomplete injuries are classified as B-E, as listed in Figure 11.1. While an “E” is described as normal sensory and motor func­tion, this is in the context of a previously abnormal examination.

Paraplegia affects the lower extremities and, to varying degrees, the trunk. It does not affect the upper extremities; thus, T2 must be normal and any deficits are below that sensory and motor level. The preferred term from ASIA for involvement of all four extremi­ties is tetraplegia, though quadriplegia is much more commonly used. Any injury that affects motor and/ or sensation at or above the T2 level is tetraplegia. In addition, a number of syndromes have been described based upon the patterns seen after specific areas of the spinal cord have been injured.