Which of the following cranial nerve commonly affected in peripheral diabetes neuropathy?

NORCET 5 Prelims - Sept 2023 (Shift-2)

Medical & Surgical Nursing

Easy

Appeared in: NORCET 5 Prelims - Sept 2023 (Shift-2)

Explanation

The oculomotor nerve (CN III) is the most frequently affected cranial nerve in diabetic mononeuropathy.
This condition is caused by microvascular ischemia, where damage to small blood vessels from high blood sugar interrupts the nerve's blood supply.
The classic presentation is a sudden onset of double vision (diplopia) and a drooping eyelid (ptosis).
A key diagnostic feature is 'pupil sparing,' where pupillary function remains intact because the ischemic damage is central to the nerve, sparing the peripheral fibers that control the pupil.

Option B: While the incidence of facial nerve palsy (Bell's Palsy) is higher in individuals with diabetes, it is not the most common or characteristic cranial mononeuropathy associated with the disease compared to oculomotor nerve palsy.
Option C: The optic nerve is primarily affected by diabetic retinopathy, a complication of the blood vessels in the retina, not a direct neuropathy of the cranial nerve itself in the way that CN III is affected. While ischemic optic neuropathy exists, it's less common than diabetic oculomotor palsy.
Option D: The vagus nerve is involved in diabetic autonomic neuropathy, a systemic condition affecting involuntary functions like digestion and heart rate. It does not typically present as an isolated, acute cranial nerve palsy.

Visual 1: Diagram - Illustration of a patient with left oculomotor nerve palsy, showing ptosis (drooping eyelid) and the eye deviated 'down and out'.
Visual 2: Flowchart - A diagnostic flowchart starting with 'Sudden Onset Diplopia' and branching to differentiate between pupil-sparing (suggesting ischemia/diabetes) and pupil-involving (suggesting compression/aneurysm) oculomotor palsy.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diabetic cranial mononeuropathy as background academic context rather than a clinical decision trigger.
A sudden, isolated third nerve palsy is a neurologic red flag. As a nurse, your prompt assessment and reporting can lead to a timely diagnosis of new-onset diabetes or adjustment of therapy for a known diabetic.
Patient education is crucial. Reassure the patient that while distressing, diabetic oculomotor palsy typically has a good prognosis for spontaneous recovery within 2-3 months, and focus on managing the underlying diabetes.
What if? If the patient's oculomotor palsy also involved a dilated, non-reactive pupil, the situation becomes a medical emergency. This suggests a compressive lesion, such as a posterior communicating artery aneurysm, which requires immediate neurosurgical evaluation, rather than an ischemic cause.

How to Approach the Question

First, identify the key concepts in the question: 'cranial nerve,' 'diabetes neuropathy,' and 'commonly affected.'
This is a factual recall question requiring knowledge of the neurological complications of diabetes.
Recall that diabetes can cause several types of neuropathy: peripheral polyneuropathy, autonomic neuropathy, and mononeuropathies.
The question specifies cranial nerves, pointing towards a mononeuropathy.
Differentiate between the options. Consider how diabetes affects each nerve. The oculomotor nerve is classically associated with an ischemic mononeuropathy. The vagus nerve is associated with autonomic neuropathy. The optic nerve is affected by retinopathy. The facial nerve link is less specific.
Select the option that represents the most common and characteristic cranial mononeuropathy in diabetes.

Concept Tested & Keywords

qiYIr_-Fyijw00ugoLn8Y