A 35-year-old patient after a severe head injury develops anosmia (complete loss of smell). The mechanism is most likely disruption of which anatomical structure?

• A Olfactory tract at the anterior perforated substance
• B Olfactory bulb only, with intact olfactory nerves
• C Piriform cortex at the uncus
• D Olfactory nerves (CN I fila) traversing the cribriform plate of ethmoid ✓

Explanation

In head injury, the delicate unmyelinated olfactory fila (CN I) that traverse the cribriform plate of the ethmoid bone are sheared by the sudden brain movement relative to the skull base. These thin nerve bundles are most vulnerable at their foraminal passage through the cribriform plate. The olfactory bulbs may also be contused against the cribriform plate. Disruption of these fila causes permanent anosmia (no regeneration capacity). CSF rhinorrhoea may also occur through cribriform plate fractures in the same mechanism.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.