Several schemes have been devised for determining which patients may require imaging; these are comparable to “rules” for the use of imaging in head injury that are discussed in Chap. 34. The two more widely cited ones for spinal injury are those of the NEXUS group (Hoffman et al) and the “Canadian C-spine Rule” (Stiell et al). The former identifies those at low risk for spinal cord injury on the basis of the absence of posterior midline cervical-spine tenderness, no evidence of intoxication, a normal level of alertness (thereby allowing accurate reporting of the circumstances of injury and the presence of neck pain, and suggesting there has not been serious brain injury), no focal neurologic deficit, and no other painful injuries that distract the patient from reporting neck pain. The Canadian rule has been found to be slightly more sensitive and specific (this has been disputed); it is based on three high-risk criteria: age older than 65 years, a dangerous mechanism of injury, and limb paresthesias; and on any of six features that are associated with low-risk of cord injury: simple rear-end motor vehicle collision, sitting position in the emergency department, being ambulatory at any time after injury, delayed (not immediate) onset of neck pain, absence of midline cervical-spine tenderness, coupled with the ability to turn the head 45 degrees in both directions without pain.
Pathology of Traumatic Spinal Cord Injury
As a result of squeezing or shearing of the spinal cord, there is destruction of gray and white matter and a variable amount of hemorrhage, chiefly in the more vascular central parts. These changes, designated as traumatic necrosis of the cord, are maximal at the level of injury and at one or two segments above and below it. Rarely is the cord cut in two, and seldom is the pia-arachnoid lacerated. Separation of the components of traumatic necrosis, such as hematomyelia, concussion, contusion, and hematorrhachis (bleeding into the spinal canal) is not of great value either clinically or pathologically. As the lesion heals, it leaves a gliotic focus or cavitation with variable amounts of hemosiderin and iron pigment. Progressive cavitation (traumatic syringomyelia) may develop after an interval of months or years and, as the cavity enlarges beyond the main lesion, lead to a delayed central or incomplete transverse cord syndrome. In some instances, the lesion is virtually restricted to the centrally situated gray matter, giving rise to segmental weakness and sensory loss in the arms with few long tract signs. This is the central cervical cord syndrome, also called the Schneider syndrome (see further on; Schneider et al). Fragments of the central cord syndrome commonly occur as transient phenomena that reverse over several days.