Editing Trochlear nerve (section)

===Clinical assessment===
The trochlear nerve is tested by examining the action of its muscle, the superior oblique. When acting on its own this muscle depresses and abducts the eyeball. However, movements of the eye by the extraocular muscles are [[synergy|synergistic]] (working together). Therefore, the trochlear nerve is tested by asking the patient to look 'down and in' as the contribution of the superior oblique is greatest in this motion. Common activities requiring this type of convergent gaze are reading the newspaper and walking down stairs. Diplopia associated with these activities may be the initial symptom of a fourth nerve palsy.

[[Alfred Bielschowsky]]'s [[Bielschowsky's head tilt test|head tilt test]] is a test for palsy of the superior oblique muscle caused by damage to cranial nerve IV (trochlear nerve).