A 30-year-old man dives into shallow water and sustains a C5 burst fracture with complete motor and sensory loss below C5. On examination at 48 hours, bulbocavernosus reflex is absent. This finding indicates:
- A Cauda equina injury — surgical decompression must be performed within 6 hours
- B Complete spinal cord injury — no motor or sensory recovery is expected
- C Spinal shock is still present — neurological assessment is unreliable at this stage ✓
- D Incomplete spinal cord injury — some recovery may occur
Explanation
The bulbocavernosus reflex (BCR) is a sacral reflex arc (S3–S4) that is suppressed during spinal shock — the transient period following acute spinal cord injury during which all segmental reflexes below the injury are absent. Spinal shock typically lasts 24–72 hours. Absence of BCR within the first 48 hours does NOT allow classification of the injury as complete (ASIA-A). Completeness can only be reliably determined AFTER return of the BCR (confirming exit from spinal shock), which serves as the sentinel reflex. Only then can persistent absence of perianal sensation and voluntary anal sphincter contraction be used to classify the injury.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.