MCQ – 86751

Damage to the structure producing the elevation marked leads to paralysis of which of the muscle?

A.	Risorius
B.	Levator palpebrae superioris
C.	Lateral rectus
D.	Superior oblique muscle

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Correct Answer � C Explanation

Ans.C. Lateral Rectus

The elevation is facial colliculus produced by Abducens nerve.

The abducens nerve supplies Lateral rectus muscle.

Facial colliculus:

• The facial colliculus is an elevation on the floor of the fourth ventricle and is not formed by the facial nerve nucleus, but by the fibers of the facial nerve arching backward around the abducens nerve (CN VI) nucleus before turning forwards once more in caudal pons.

Applied anatomy: 

Facial colliculus syndrome refers to a constellation of neurological signs due to a lesion at the facial colliculus, involving:

1. Abducens nerve (CN VI) nucleus
2. Facial nerve (CN VII) fibers at the genu
3. Medial longitudinal fasciculus

Clinical presentation:

• Lower motor neuron facial nerve palsy proximal to geniculate ganglion hence including loss of sensation of the taste in anterior two-thirds of the tongue and hyperacusis.
• Diplopia
• Horizontal conjugate gaze palsy.