What method is used to test cranial nerve VI (abducens nerve)?

The abducens nerve, or cranial nerve VI, is primarily responsible for controlling the lateral rectus muscle, which allows for the abduction or lateral movement of the eye. Testing this nerve involves evaluating the range of motion and coordination of eye movements to ensure the lateral rectus muscle is functioning properly.

The cardinal positions of gaze test the patient’s ability to follow a target in all directions of eye movement, specifically assessing the ability to look laterally. This directly evaluates the function of the abducens nerve, as it controls the movement of the eye outward. By asking the patient to follow an object as it moves through the six cardinal positions, the examiner can determine whether the abducens nerve is intact and effectively enabling the lateral movement of the eyeball, which could indicate any potential dysfunction if the eye cannot move fully in that direction.

In contrast, other methods listed, such as sweet taste recognition, symmetry of facial movements, and hearing acuity, assess different cranial nerves and do not evaluate the function of the abducens nerve. Each of those tests is associated with other specific cranial nerves responsible for taste, facial expression, and hearing, respectively.