The nurse assesses a client with damage to cranial nerve III. Which finding would be expected?
A.
Asymmetric facial movement
B.
Uvula deviation
C.
Anosmia
D.
Ptosis
The Correct Answer and Explanation is:
The correct answer is D. Ptosis.
Explanation:
Cranial nerve III, also known as the oculomotor nerve, is responsible for controlling most of the eye’s movements, including the constriction of the pupil and the elevation of the upper eyelid. Damage to this nerve can result in several distinct clinical manifestations, primarily affecting eye movement and eyelid position.
Ptosis, or drooping of the upper eyelid, is a hallmark sign of cranial nerve III dysfunction. This occurs because the oculomotor nerve controls the levator palpebrae superioris muscle, which is responsible for lifting the eyelid. When this nerve is damaged, the muscle cannot contract properly, leading to a drooping eyelid.
Other symptoms associated with cranial nerve III damage include:
- Diplopia (double vision): As the oculomotor nerve controls the majority of eye muscles responsible for eye movement, its dysfunction can lead to misalignment of the eyes, resulting in double vision.
- Pupil dilation: The oculomotor nerve also controls the parasympathetic fibers that constrict the pupil. Damage can cause the pupil to remain dilated or to react sluggishly to light.
- Loss of accommodation: The ability to focus on near objects can be impaired, as the nerve affects the ciliary muscle that controls lens shape.
The other options are related to different cranial nerves:
- A. Asymmetric facial movement: This is indicative of damage to cranial nerve VII (facial nerve), which controls facial expression.
- B. Uvula deviation: This is a sign of damage to cranial nerve IX (glossopharyngeal nerve) or X (vagus nerve). It often indicates a problem with the motor function of the pharynx and larynx.
- C. Anosmia: This is a loss of the sense of smell and is associated with damage to cranial nerve I (olfactory nerve).
In summary, ptosis is a direct and specific sign of damage to cranial nerve III, given its crucial role in eyelid movement and eye muscle control.