Damage of the motor branch of the 7th nerve leads to:

Appeared in: DSSSB 6 September 2024

Explanation

The 7th cranial nerve is the facial nerve, which has a major motor branch controlling the muscles of facial expression.
Bell's palsy is the specific medical term for idiopathic, unilateral facial paralysis resulting from inflammation or damage to the 7th cranial nerve.
This damage disrupts the nerve signals to facial muscles, causing them to weaken or become paralyzed, leading to facial drooping, inability to close the eye, and difficulty with expressions like smiling.

Option A: Trigeminal neuralgia is a disorder of the 5th cranial nerve (trigeminal nerve), not the 7th. It primarily causes severe, stabbing facial pain (a sensory issue) rather than motor paralysis.
Option C: Erb's palsy is an injury to the brachial plexus, specifically the upper nerve roots (C5-C6). It affects the muscles of the shoulder and arm, not the face.
Option D: Klumpke's palsy is also an injury to the brachial plexus, but it involves the lower nerve roots (C8-T1). This results in paralysis of the muscles in the forearm and hand, causing a 'claw hand' deformity.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Disorders of the Cranial Nerves as background academic context rather than a clinical decision trigger.
A priority nursing intervention for a patient with Bell's palsy is protecting the affected eye. Since the patient cannot blink or close the eyelid completely, the cornea is at high risk for drying, abrasion, and ulceration.
Nurses must provide psychological support, as the sudden and dramatic change in facial appearance can be very distressing for the patient.
What if? If the patient presented with facial weakness that spared the forehead muscles, a central (supranuclear) lesion like a stroke should be suspected, rather than a peripheral lesion like Bell's palsy. This is because the forehead receives motor input from both cerebral hemispheres.

How to Approach the Question

First, identify the core of the question, which is the consequence of damaging the '7th nerve'.
Recall that the 7th cranial nerve is the facial nerve, primarily responsible for controlling the muscles of facial expression.
Scan the options to find the condition that matches facial muscle paralysis.
Bell's palsy is the specific term for paralysis of the facial nerve.
Rule out the other options by identifying the structures they affect: Trigeminal neuralgia (5th cranial nerve - sensory), Erb's palsy (upper brachial plexus - arm), and Klumpke's palsy (lower brachial plexus - hand).

Concept Tested & Keywords

QJkVZiLp8kYP72UirPGomP

E6 Medicine Harrison 22e Part 2 p. 1457-1459

E6 Nursing Brunner Adult Health 3SA Vol 2 Part 2 p. 143-145

Practise the full DSSSB 6 September 2024

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