Corpus: Superior oblique muscle

The superior oblique muscle is a skeletal muscle that is part of the external eye musculature.

The superior oblique muscle originates from the body of the sphenoid bone, as well as from the periorbita and the dural sheath of the optic nerve. It runs forward (rostrally) over the medial rectus muscle. At the edge of the orbit, the tendon of the superior oblique muscle passes through a connective tissue structure known as the trochlea, which acts as a pulley, changing the direction of the muscle's pull.

After passing through the trochlea, the muscle continues backward (dorsally) and attaches to the upper temporal quadrant of the eyeball, just behind the equatorial line on the sclera.

The superior oblique muscle is innervated by the trochlear nerve (cranial nerve IV).

The primary function of the superior oblique muscle is to rotate the eye downward (depression) and inward (intorsion), and it also assists in the abduction of the eyeball. When the eye is in an adducted position, the muscle acts primarily to depress the eye.

In cases of trochlear nerve palsy, there is a loss of function of the superior oblique muscle, leading to double vision (diplopia). Patients often compensate by tilting their head to reduce the double vision, a condition known as ocular torticollis.

The function of the superior oblique muscle is assessed by having the patient look downward and inward while the eye is in an adducted position.