Cauda equina

Abstract: This article represents the content of the booklet, International Standards for Neurological Classification of Spinal Cord Injury, revised 2011, published by the American Spinal Injury Association (ASIA). For further explanation of the clarifications and changes in this revision, see the accompanying article (Kirshblum S., et al. J Spinal Cord Med. 2011:doi 10.1179/107902611X13186000420242 The spinal cord is the major conduit through which motor and sensory information travels between the brain and body. The spinal cord contains longitudinally oriented spinal tracts (white matter) surrounding central areas (gray matter) where most spinal neuronal cell bodies are located. The gray matter is organized into segments comprising sensory and motor neurons. Axons from spinal sensory neurons enter and axons from motor neurons leave the spinal cord via segmental nerves or roots. In the cervical spine, there are 8 nerve roots. Cervical roots of C1-C7 are named according to the vertebra above which they exit (i.e. C1 exits above the C1 vertebra, just below the skull and C6 nerve roots pass between the C5 and C6 vertebrae) whereas C8 exists between the C7 and T1 vertebra; as there is no C8 vertebra. The C1 nerve root does not have a sensory component that is tested on the International Standards Examination. The thoracic spine has 12 distinct nerve roots and the lumbar spine consists of 5 distinct nerve roots that are each named accordingly as they exit below the level of the respective vertebrae. The sacrum consists of 5 embryonic sections that have fused into one bony structure with 5 distinct nerve roots that exit via the sacral foramina. The spinal cord itself ends at approximately the L1-2 vertebral level. The distal most part of the spinal cord is called the conus medullaris. The cauda equina is a cluster of paired (right and left) lumbosacral nerve roots that originate in the region of the conus medullaris and travel down through the thecal sac and exit via the intervertebral foramen below their respective vertebral levels. There may be 0, 1, or 2 coccygeal nerves but they do not have a role with the International Standards examination in accordance with the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI). Each root receives sensory information from skin areas called dermatomes. Similarly each root innervates a group of muscles called a myotome. While a dermatome usually represents a discrete and contiguous skin area, most roots innervate more than one muscle, and most muscles are innervated by more than one root. Spinal cord injury (SCI) affects conduction of sensory and motor signals across the site(s) of lesion(s), as well as the autonomic nervous system. By systematically examining the dermatomes and myotomes, as described within this booklet, one can determine the cord segments affected by the SCI. From the International Standards examination several measures of neurological damage are generated, e.g., Sensory and Motor Levels (on right and left sides), NLI, Sensory Scores (Pin Prick and Light Touch), Motor Scores (upper and lower limb), and ZPP. This booklet also describes the ASIA (American Spinal Injury Association) Impairment Scale (AIS) to classify the severity (i.e. completeness) of injury. This booklet begins with basic definitions of common terms used herein. The section that follows describes the recommended International Standards examination, including both sensory and motor components. Subsequent sections cover sensory and motor scores, the AIS classification, and clinical syndromes associated with SCI. For ease of reference, a worksheet (Appendix 1) of the recommended examination is included, with a summary of steps used to classify the injury (Appendix 2). A full-size version for photocopying and use in patient records has been included as an enclosure and may also be downloaded from the ASIA website (www.asia-spinalinjury.org). Additional details regarding the examination and e-Learning training materials can also be obtained from the website15.