Facial Nerve and Cranial Nerve Disorders
Core concepts
Know the facial nerve's course through the temporal bone and its branches, the House-Brackmann grading scale, and the difference between upper and lower motor neuron lesions. Understand Bell palsy management, Ramsay Hunt syndrome, and traumatic facial nerve injury timing.
Traps in questions
- Confusing UMN versus LMN patterns; UMN spares the forehead because of bilateral cortical innervation.
- Missing that Bell palsy is a diagnosis of exclusion and that corticosteroids within 72 hours improve outcomes.
- Forgetting antiviral therapy in Ramsay Hunt syndrome with vesicles.
- Assuming immediate nerve repair for all trauma; timing depends on whether the nerve is transected and whether the wound is clean.
Rule of thumb
Forehead sparing means an upper motor neuron lesion; forehead involvement means a lower motor neuron (peripheral) lesion.
Worked example
A patient has unilateral facial weakness including the forehead after parotid surgery. The question asks the likely lesion. The rule: forehead involvement indicates a peripheral facial nerve injury, consistent with parotid surgery. A central lesion would spare the forehead.