4th Cranial nerve – Tests for the Trochlear nerve

Definition:

The use and interpretation of medical examinations to determine the integrity and adequate function the Trochlear nerve (fourth cranial nerve).

Test procedure:

The visual pursuit test is performed by asking the patient to follow the practitioner’s finger or the tip of a pen with their eyes whilst the patient’s head remains still. The examiner moves the object in a vertical, horizontal and diagonal direction, asking the patient to follow the movement with their eyes. This test is done under the assumption that the examiner’s visual fields are intact. The trochlear nerve supplies the superior oblique ocular muscle, there for particular attention should be paid as to whether the patient is capable of looking medially, towards their nose.

Test findings (inc Positive & Negative results):

An inability for the patient to look medially may be indicative of a lesion of the trochlear nerve.

Considerations:

Congenital, benign diplopia is a differential.

Commonly the third, fourth and six cranial nerves are tested together.