Which cranial nerve is also known as pathetic nerve?

DSSSB 12 August 2024

Applied Anatomy

Easy

Appeared in: DSSSB 12 August 2024

Explanation

The Trochlear nerve is also known as the pathetic nerve or Cranial Nerve IV (CN IV).
This historical name is derived from the 'pathetic' or sorrowful expression seen in patients with trochlear nerve palsy.
The nerve supplies the superior oblique muscle, which is responsible for moving the eye downward and inward (intorsion).
Paralysis of this nerve leads to vertical diplopia (double vision), especially when looking down, and a characteristic compensatory head tilt away from the affected side.

Option B: The Oculomotor nerve (CN III) is the chief motor nerve to the extraocular muscles, but it is not known as the pathetic nerve. Its palsy results in a 'down and out' gaze, drooping eyelid (ptosis), and a dilated pupil.
Option C: The Accessory nerve (CN XI) is a motor nerve that innervates the sternocleidomastoid and trapezius muscles, controlling head and shoulder movements. It has no function related to the eye.
Option D: The Optic nerve (CN II) is a purely sensory nerve that transmits visual information from the retina to the brain. It does not control any muscles.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cranial nerve nomenclature and function as background academic context rather than a clinical decision trigger.
Nurses performing neurological assessments must be able to identify signs of cranial nerve palsy. A patient complaining of new-onset vertical double vision, especially when reading or walking downstairs, should be assessed for trochlear nerve dysfunction.
The Bielschowsky head tilt test, where the patient tilts their head towards each shoulder, can help diagnose superior oblique palsy. The vertical misalignment of the eyes worsens when the head is tilted toward the side of the paralyzed muscle.
What if? If a patient presented with a drooping eyelid (ptosis) and an eye that is deviated 'down and out', the suspicion should shift to an Oculomotor nerve (CN III) palsy, which is often a more urgent neurological sign, especially if the pupil is also dilated.

How to Approach the Question

First, identify the core of the question, which is to match a historical name ('pathetic nerve') to a specific cranial nerve.
Recognize this as a factual recall question based on anatomical nomenclature.
Systematically review the functions of the given options. The Optic (vision) and Accessory (shoulder/neck movement) nerves can be quickly eliminated as they are not involved in eye movement control in the way described.
Differentiate between the Oculomotor and Trochlear nerves. The Oculomotor nerve controls most eye muscles, while the Trochlear nerve controls only the superior oblique.
Recall or deduce that the term 'pathetic' relates to the specific clinical appearance of a palsy. The head tilt and vertical diplopia from trochlear nerve palsy create a 'sorrowful' look, linking it to the name.
Select the Trochlear nerve as the correct answer based on this association.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 276-278

E6 Anatomy Applied Ashalatha 4e p. 425-427