Action of Superior Oblique Muscle

The anatomical basis of how to clinically test the superior oblique muscle and the trochlear nerve ... Trochlear nerve lesions are often missed in routine cranial nerve examinations. Unlike the oculomotor nerve, there is no effect on eyelids or pupils or detectable abnormal position at rest. The only symptom is often not being able to read clearly (blurred vision/diplopia on looking down and in). The eyeball will in fact be extorted, but this will not be detectable clinically. I will produce another video shortly which shows where the diplopia is maximal using the tradional 'H' pattern by controntation.

Category:

Education

Tags:

• superior
• oblique
• trochlear
• nerve
• cranial
• extraocular
• muscles

[DoctorCallan]

So diplopia (and any nystagmus) will be ellicited and maximal when the patient's affected eye is adducted and then asked to look down ... The two images (real and false) will be orientated obliquely to one another ... Unlike the two parallel images in a lateral rectus/abducens lesion.

[DoctorCallan]

There is some confusion out there regarding testing the trochlear nerve and isolating the position where a patient with a trochlear nerve lesion will have diplopia and likely nystagmus ... This is the explanation right here. Only when the eye is adducted (turned in towards the nose) does the superior oblique act as almost a pure depressor of the eyeball ... In the neutral or straight ahead position the principle action of the superior oblique is intortion ...

[miguelj86]

A really nice explanation with a good visualisation! Well done! Thanks

[ivinsha91]

does make sense