MCQs on Cranial Nerves

Written by Dr. James Whitfield (MBBS, FRACGP) – General Practitioner

Question 1

A 55-year-old man presents with right-sided facial droop that developed overnight. He is unable to close his right eye, has drooling from the right side of his mouth, and cannot raise his right eyebrow. There is no limb weakness or slurred speech. Which one of the following is the most likely diagnosis?

A) Stroke
B) Bell’s palsy
C) Myasthenia gravis
D) Guillain-Barré syndrome
E) Temporal arteritis

Correct Answer: B) Bell’s palsy

Explanation:
This patient presents with unilateral lower and upper facial weakness, which is classic for Bell’s palsy, a peripheral lower motor neuron lesion of the facial nerve (cranial nerve VII). In contrast, a stroke (central UMN lesion) typically spares the forehead due to bilateral cortical representation of the upper face.

Option A (Stroke): Incorrect – In a central stroke, forehead movement is usually preserved because of dual cortical innervation. The presence of forehead weakness suggests a peripheral lesion.
Option C (Myasthenia gravis): Incorrect – Causes fluctuating muscle weakness including ptosis and diplopia, but not an isolated facial nerve palsy.
Option D (Guillain-Barré syndrome): Incorrect – Can cause facial diplegia, but usually in the context of generalized areflexia and ascending paralysis.
Option E (Temporal arteritis): Incorrect – Typically presents with headache, jaw claudication, and visual symptoms in elderly patients. It does not cause facial nerve palsy.

Question 2

A 40-year-old woman complains of difficulty swallowing, hoarseness, and episodes of aspiration. On examination, she has decreased gag reflex and uvula deviation to the left. Which cranial nerve is most likely affected?

A) Facial nerve (CN VII)
B) Glossopharyngeal nerve (CN IX)
C) Vagus nerve (CN X)
D) Accessory nerve (CN XI)
E) Hypoglossal nerve (CN XII)

Correct Answer: C) Vagus nerve (CN X)

Explanation:
The vagus nerve (CN X) innervates the palate, pharynx, and larynx, and its dysfunction leads to hoarseness, dysphagia, aspiration, and uvula deviation away from the lesion.

Option A (Facial nerve): Incorrect – Involved in facial expression, not swallowing or phonation.
Option B (Glossopharyngeal nerve): Incorrect – Involved in gag reflex and some swallowing, but would not explain hoarseness or uvula deviation.
Option D (Accessory nerve): Incorrect – Affects shoulder shrug and head turning, not swallowing or vocal cord function.
Option E (Hypoglossal nerve): Incorrect – Causes tongue deviation, not uvula deviation or hoarseness.

Question 3

A 35-year-old man reports double vision when looking to the left. On examination, his left eye fails to abduct. Which cranial nerve is affected?

A) Oculomotor nerve (CN III)
B) Trochlear nerve (CN IV)
C) Trigeminal nerve (CN V)
D) Abducens nerve (CN VI)
E) Optic nerve (CN II)

Correct Answer: D) Abducens nerve (CN VI)

Explanation:
The abducens nerve (CN VI) innervates the lateral rectus muscle, responsible for abduction of the eye. Failure of abduction indicates a lesion of this nerve.

Option A (Oculomotor nerve): Incorrect – Controls most other eye movements, not abduction.
Option B (Trochlear nerve): Incorrect – Innervates the superior oblique, involved in downward and inward gaze, not abduction.
Option C (Trigeminal nerve): Incorrect – Controls facial sensation and mastication, not extraocular movements.
Option E (Optic nerve): Incorrect – Responsible for vision, not eye movement.

Previous Next

1. Neurology Module

1.1 Cerebrovascular Disorders

1.2 Cranial Nerves

1.3 Spinal Cord

1.4 Peripheral Nerves

1.5 Headaches

1.6 Seizure Disorders

1.7 Movement Disorders

1.8 Neuroimaging

Back to MCQ Bank