Clinical meaning
Spinal cord injury involves primary mechanical damage (compression, laceration, distraction, or transection) followed by secondary injury cascades that extend damage over hours to weeks. Primary injury disrupts axons, blood vessels, and cell membranes. Secondary injury begins within minutes: hemorrhage in the central gray matter (hemorrhagic necrosis), ischemia from vasospasm and thrombosis of spinal cord microvasculature, excitotoxicity (glutamate release), calcium influx causing protease activation and mitochondrial failure, free radical lipid peroxidation, and inflammatory cell infiltration. Wallerian degeneration of disrupted axons proceeds over days to weeks. Neurogenic shock (distinct from spinal shock) occurs with injuries above T6: loss of sympathetic outflow causes vasodilation, hypotension, and bradycardia with preserved or warm extremities. Spinal shock is the transient loss of all neurological function below the injury level — return of the bulbocavernosus reflex signals its resolution and allows accurate prognosis of injury completeness (ASIA classification).
Diagnosis & workup
Diagnostics & workup: - ASIA (American Spinal Injury Association) Impairment Scale: sensory and motor exam of key dermatomes/myotomes to classify as complete (A) or incomplete (B-D) - CT spine: first-line imaging for bony injury — identifies fractures, dislocations, fragments in canal - MRI spine: assess spinal cord compression, edema, hemorrhage, disc herniation, ligamentous injury — critical for surgical planning - CTA if vascular injury suspected (vertebral artery injury with cervical fractures — up to 20% with facet fractures) - Neurogenic shock assessment: hypotension (MAP < 85) with bradycardia and warm extremities (contrasts with hypovolemic shock: tachycardia, cool extremities) - Respiratory function: FVC (serial q4-6h for cervical injuries — declining FVC indicates ascending edema or diaphragm fatigue), negative inspiratory force (NIF) - Autonomic dysreflexia screening (injuries above T6): baseline BP and triggers - Bladder assessment: post-void residual, urodynamics once stable