Spinal Cord Injury — Levels & Classification
A C4 injury and a T10 injury both damage the spinal cord — but one patient needs a ventilator and the other walks into rehab. The level changes everything.
Core Concept
Spinal cord injury (SCI) level determines what the client can and cannot do. The key landmark is C4 — the phrenic nerve originates at C3-C5, so complete injuries at C3 or above eliminate diaphragmatic breathing; C4 injuries may have partial or absent diaphragm function and often require ventilatory support. C5 injuries spare the diaphragm but lose hand and trunk function; the client can flex the elbow (biceps) but cannot extend the wrist. C6 adds wrist extension, C7 adds elbow extension (triceps), and C8-T1 restores hand grip. Thoracic-level injuries preserve upper extremity function entirely; the client is paraplegic rather than quadriplegic. T1-T6 injuries lose intercostal muscle control and have impaired cough; T6-T12 injuries retain more trunk stability. Lumbar injuries affect the lower extremities with variable motor and sensory loss. Complete versus incomplete injury matters: complete SCI means no motor or sensory function below the level; incomplete injuries (e.g., Brown-Séquard, anterior cord, central cord syndromes) preserve partial function in predictable patterns. Sensory dermatome landmarks help localize the level: C6 = thumb, T4 = nipple line, T10 = umbilicus, L1 = groin.
Watch Out For
Don't confuse paraplegia (thoracic/lumbar — lower extremities only) with quadriplegia/tetraplegia (cervical — all four extremities). Students mix up neurogenic shock (a sibling atom covering hemodynamic collapse from lost sympathetic tone) with the functional motor-sensory deficits taught here. Central cord syndrome spares lower extremities more than upper — the opposite of what students expect.
Clinical Pearl
C3-4-5 keeps the diaphragm alive. If the injury is at or above C4, plan for a ventilator — breathing depends on that phrenic nerve.
Test Your Knowledge
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