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MBBS QUESTION #10173
Question 1
A patient develops sudden unilateral facial weakness affecting both the upper and lower face (including inability to close the eye and wrinkle the forehead) after facial nerve injury near the stylomastoid foramen. This presentation is best explained by:
  • A lesion affecting only the buccal branch
  • A lower motor neuron lesion affecting all ipsilateral facial muscles, since the nerve trunk carries fibers to both upper and lower facial muscles✔️
  • A central (upper motor neuron) lesion sparing the forehead
  • Damage limited to chorda tympani only, sparing motor fibers
Correct Answer Explanation
Facial muscles receive bilateral upper motor neuron input to the upper face but only contralateral input to the lower face. A peripheral (LMN) lesion of the facial nerve trunk, as in Bell's palsy, affects all ipsilateral facial muscles (upper and lower), unlike a central stroke lesion which spares forehead movement.