A patient Rasmu presents with eye deviated laterally and slightly downward. The upward gaze is impaired and medial rotation is not possible. Which nerve is involved.
**Core Concept:** The oculomotor nerve (III) is responsible for controlling eye movements, including elevation, adduction, and medial rotation. It arises from the brainstem motor nuclei and branches into three parts: superior, inferior, and lateral.
**Why the Correct Answer is Right:** In the described clinical scenario, the patient's eye deviates laterally and downward due to the involvement of the lateral branch of the oculomotor nerve (III) which controls the lateral rectus muscle. The impaired upward gaze and inability to medially rotate the eye indicate that the lateral branch is affected.
**Why Each Wrong Option is Incorrect:**
A. **Superior and inferior rectus nerves (VI and IV)** are involved in eye elevation and abduction, respectively. In the given scenario, these nerves are not responsible for the patient's lateral and downward eye deviation.
B. **Medial rectus nerve (II)** controls eye adduction, not the lateral deviation seen in the patient.
C. **Photophobia and tearing** are symptoms associated with various eye disorders, not necessarily related to the oculomotor nerve.
**Clinical Pearl / High-Yield Fact:** The oculomotor nerve (III) is a crucial structure to understand for understanding eye movements and diagnosing neurological disorders affecting eye function. In this scenario, the lateral branch of the oculomotor nerve (III) is involved, leading to the observed eye deviation.
**Correct Answer:** .