FCPS part 1 Medicine solved mcqs with explanation Q20

Q20: A patient has difficulty closing his right eye and also has distorted facial appearance. He has damage to:

a) Right facial nerve

b) Right trigeminal nerve

c) Left facial nerve

d) Left trigeminal nerve

Correct Answer: a

Explanation:

UMN Lesion:

Upper face receives bilateral Upper motor neuron (UMN) innervation while lower face receives only contra lateral UMN innervation, so that if there is an UMN lesion ther e is contralateral paralysis of lower face only.

LMN Lesion of Facial Nerve:

In LMN lesion of facial nerve, whole (upper plus lower) face on the ipsilateral side is affected. So if the patient is unable to close right eye (upper face part) this definitely means that there is a LMN lesion or in other words the facial nerve on the affected side is lesioned.