Bell's palsy is associated with the lesion in?

TMC Staff Nurse - 2019

Medical & Surgical Nursing

Easy

Appeared in: TMC Staff Nurse - 2019

Explanation

Bell's palsy is defined as an idiopathic, acute paralysis of the muscles on one side of the face.
This condition is caused by a lesion affecting the 7th cranial nerve, also known as the facial nerve.
The facial nerve controls the muscles of facial expression, as well as functions like taste for the front of the tongue, salivation, and tearing.
The image clearly demonstrates the signs of a 7th nerve palsy, such as drooping of the mouth and inability to fully close the eye on one side.

Option A: The 11th cranial nerve (Spinal Accessory) innervates the sternocleidomastoid and trapezius muscles, which are responsible for head turning and shoulder shrugging, not facial expression.
Option B: The 9th cranial nerve (Glossopharyngeal) is primarily involved with sensation and taste from the posterior third of the tongue, the gag reflex, and swallowing. It does not control the main muscles of facial expression.
Option D: The 3rd cranial nerve (Oculomotor) controls most of the extraocular muscles responsible for eye movement, as well as pupil constriction and lifting the upper eyelid. It is not involved in the muscles of facial expression.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The concept tested is the identification of the specific cranial nerve involved in Bell's palsy as background academic context rather than a clinical decision trigger.
A key nursing priority for a patient with Bell's palsy is protecting the affected eye from injury. Since the eyelid cannot close completely, the cornea is at risk for drying, ulceration, and infection. Nursing interventions include applying artificial tears, using an eye patch, and taping the eyelid shut during sleep.
It is crucial for nurses to differentiate between Bell's palsy (a lower motor neuron lesion) and a stroke (an upper motor neuron lesion). A simple test is to ask the patient to raise their eyebrows. A patient with Bell's palsy will not be able to wrinkle their forehead on the affected side, whereas a stroke patient often can.
What if? If a patient presents with unilateral facial weakness AND has a vesicular rash in their ear canal, the diagnosis is more likely Ramsay Hunt syndrome (herpes zoster oticus) rather than idiopathic Bell's palsy. This requires antiviral treatment in addition to steroids.

How to Approach the Question

First, identify the core subject of the question, which is 'Bell's palsy'.
Recall the definition of Bell's palsy from your medical-surgical nursing knowledge. It is fundamentally a disorder of a specific cranial nerve.
Mentally link 'Bell's palsy' to the '7th cranial nerve' or 'facial nerve'. This is a direct recall item.
Analyze the provided image. Observe the signs of unilateral facial paralysis (drooping mouth, flattened skin folds). This visual information confirms the diagnosis of facial nerve palsy.
Evaluate the options provided. Systematically rule out the incorrect cranial nerves by recalling their primary functions (11th: shoulder/neck; 9th: throat/taste; 3rd: eye movement).
Select the option that correctly identifies the facial nerve (7th cranial nerve) as the cause of Bell's palsy.

Concept Tested & Keywords

Concept Tested: The concept tested is the identification of the specific cranial nerve involved in Bell's palsy.
Stem keywords: Bell's palsy, lesion, cranial nerve
Lead-in keywords: associated with
Clinical cues: The image showing unilateral facial paralysis is a key clinical cue for Bell's palsy.

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E6 Medicine Harrison 22e Part 2 pp. 1459-1461, 1458-1460

E6 Medicine Macleod Clinical Examination 15e p. 153-155