A nurse is performing a neurological assessment for a client who has head trauma. Which of the following assessments will give the nurse information about the function of cranial nerve III?
A.
Ask the client to shrug his shoulders against passive resistance
B.
Instruct the client to look up and down without moving his head
C.
Observe the client’s ability to smile and frown
D.
Have the client stand with his eyes closed and touch his nose
The Correct Answer and Explanation is:
The correct answer is B. Instruct the client to look up and down without moving his head.
Explanation:
Cranial nerve III, also known as the oculomotor nerve, plays a crucial role in controlling most of the eye’s movements and constriction of the pupil. It is responsible for innervating four of the six extraocular muscles: the superior rectus, inferior rectus, medial rectus, and inferior oblique. These muscles control eye movements such as looking up, down, and medially, as well as adjusting the lens for near vision and constricting the pupil.
To assess the function of cranial nerve III, a nurse can evaluate the eye movements and pupil responses. Here’s how each option relates to cranial nerve III function:
- A. Ask the client to shrug his shoulders against passive resistance: This action evaluates cranial nerve XI (accessory nerve), which controls the sternocleidomastoid and trapezius muscles responsible for shoulder shrugging and head rotation. It does not provide information about cranial nerve III.
- B. Instruct the client to look up and down without moving his head: This assessment directly evaluates the function of cranial nerve III. By asking the client to move their eyes up and down while keeping their head still, you assess the ability of the oculomotor nerve to control the extraocular muscles responsible for these movements. Any abnormalities in this function, such as difficulty or asymmetry in eye movement, can indicate issues with cranial nerve III.
- C. Observe the client’s ability to smile and frown: This assessment evaluates cranial nerve VII (facial nerve), which controls the muscles responsible for facial expressions, including smiling and frowning. It does not assess the function of cranial nerve III.
- D. Have the client stand with his eyes closed and touch his nose: This test evaluates proprioception and coordination, typically assessing the function of the cerebellum and sensory pathways rather than specifically cranial nerve III. It is related to coordination and balance, not directly to eye movements or pupillary response controlled by cranial nerve III.
In summary, assessing the client’s ability to look up and down without moving the head (Option B) evaluates the function of cranial nerve III by testing the control of vertical eye movements, which is crucial for determining the health of this nerve.