How are the American Spinal Injury Association (ASIA) Impairment Scale categories defined?

Updated: Nov 01, 2018
  • Author: Lawrence S Chin, MD, FACS; Chief Editor: Brian H Kopell, MD  more...
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Answer

The extent of injury is defined by the ASIA Impairment Scale (modified from the Frankel classification), using the following categories [1, 2] :

  • A = Complete: No sensory or motor function is preserved in sacral segments S4-S5 [3]

  • B = Incomplete: Sensory, but not motor, function is preserved below the neurologic level and extends through sacral segments S4-S5

  • C = Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade less than 3

  • D = Incomplete: Motor function is preserved below the neurologic level, and most key muscles below the neurologic level have muscle grade greater than or equal to 3

  • E = Normal: Sensory and motor functions are normal

Thus, definitions of complete and incomplete spinal cord injury, as based on the above ASIA definition, with sacral-sparing, are as follows [1, 2, 3] :

  • Complete: Absence of sensory and motor functions in the lowest sacral segments

  • Incomplete: Preservation of sensory or motor function below the level of injury, including the lowest sacral segments

With the ASIA classification system, the terms paraparesis and quadriparesis have become obsolete. Instead, the ASIA classification uses the description of the neurologic level of injury in defining the type of spinal cord injury (eg, "C8 ASIA A with zone of partial preservation of pinprick to T2").


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