All are motor nerves, except?

Appeared in: DSSSB Public Health Nurse - 2015

Explanation

The question requires identifying the cranial nerve from the options that is not exclusively a motor nerve.
The Trigeminal nerve (cranial nerve V) is classified as a mixed nerve because it contains both sensory and motor fibers.
Its sensory component supplies the face, scalp, and mucous membranes of the nose and mouth.
Its motor component innervates the muscles of mastication (chewing).

Option A: The Accessory nerve (cranial nerve XI) is a motor nerve that innervates the sternocleidomastoid and trapezius muscles, controlling head and shoulder movements.
Option B: The Abducent nerve (cranial nerve VI) is a motor nerve that controls the lateral rectus muscle, responsible for abducting the eye (moving it outward).
Option C: The Trochlear nerve (cranial nerve IV) is a motor nerve that innervates the superior oblique muscle of the eye, which is involved in downward and inward eye movement.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of Cranial Nerves as background academic context rather than a clinical decision trigger.
Assessing the function of all 12 cranial nerves is a fundamental part of a neurological examination. It helps nurses and doctors localize lesions within the brainstem and other parts of the nervous system.
Damage to the Trigeminal nerve can lead to trigeminal neuralgia (intense facial pain), loss of sensation in the face, or weakness/paralysis of the chewing muscles, impacting nutrition and quality of life.
What if? If a patient presents with sudden difficulty chewing and facial numbness after a head injury, the nurse should suspect potential damage to the Trigeminal nerve (CN V) and perform a focused cranial nerve assessment, reporting the findings promptly.

How to Approach the Question

First, identify the keyword "except" in the question. This indicates you need to find the option that does not fit the category described in the stem.
The stem specifies the category as "motor nerves". Your task is to find the nerve that is NOT purely motor.
Recall the classification of cranial nerves into three types: sensory, motor, and mixed (both).
Evaluate each option: Accessory (XI), Abducent (VI), and Trochlear (IV) are all primarily motor nerves.
Evaluate the final option: Trigeminal (V) is a well-known mixed nerve, with major sensory and motor functions.
Conclude that the Trigeminal nerve is the correct exception.

Concept Tested & Keywords

Concept Tested: Classification of Cranial Nerves
Stem keywords: motor nerves, cranial nerves
Lead-in keywords: except
Negative lead-in flag: The question asks for the exception among the given options.

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E6 Medicine Harrison 22e Part 2 p. 1455-1457

E6 Anatomy Grays 43e Vol 1 Part 3 p. 34-36

Practise the full DSSSB Public Health Nurse - 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.