A patient develops inability to wrinkle the forehead AND inability to close the eye on the left side, with left facial drooping. Upper motor neuron (UMN) or lower motor neuron (LMN) lesion, and at which level?

• A UMN lesion of right cortex sparing forehead
• B LMN lesion of CN VII at or distal to the geniculate ganglion ✓
• C LMN lesion of CN VII at the stylomastoid foramen only
• D UMN lesion involving the facial nucleus in the pons

Explanation

Involvement of both the upper and lower face (forehead wrinkling AND lower face) indicates a LMN lesion because the upper facial nucleus (forehead) receives bilateral UMN input and is thus spared in UMN lesions. In LMN (peripheral) CN VII palsy, all ipsilateral facial muscles are involved. The geniculate ganglion or distal lesion will produce complete ipsilateral facial palsy. If the lesion is proximal to the geniculate ganglion (e.g., at internal acoustic meatus), additional features like loss of taste (chorda tympani), hyperacusis (nerve to stapedius), and decreased lacrimation (greater petrosal nerve) help localize the exact level.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.