Excyclotorsion
Encyclopedia
Excyclotorsion is a term applied to the outward, torsional (rotational) movement of the eye, mediated by the inferior oblique
muscle of the eye. The inferior oblique muscle is innervated by cranial nerve III (oculomotor nerve
).
) palsy
. The trochlear nerve supplies the superior oblique
muscle, and when this muscle is non-functional (as in trochlear palsy) the eye excyclotorts; i.e. twists/rotates outward.
This excyclotorsion may be corrected through surgery using the Harada-Ito procedure
.
Inferior oblique muscle
The Obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit.-Action:Its actions are lateral rotation, elevation and abduction of the eye....
muscle of the eye. The inferior oblique muscle is innervated by cranial nerve III (oculomotor nerve
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
).
Pathophysiology
Excyclotorsion may also be used to describe the condition or state of the eye when a patient has a cranial nerve IV (trochlear nerveTrochlear nerve
The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....
) palsy
Palsy
In medicine, palsy is the paralysis of a body part, often accompanied by loss of sensation and by uncontrolled body movements, such as shaking. Medical conditions involving palsy include cerebral palsy , brachial palsy , and Bell's palsy ....
. The trochlear nerve supplies the superior oblique
Superior oblique muscle
For the abdominal muscle see: Abdominal external oblique muscleThe superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit which abducts, depresses and internally rotates the eye...
muscle, and when this muscle is non-functional (as in trochlear palsy) the eye excyclotorts; i.e. twists/rotates outward.
This excyclotorsion may be corrected through surgery using the Harada-Ito procedure
Harada-Ito procedure
The Harada-Ito procedure is an eye muscle operation designed to improve the excyclotorsion experienced by some patients with cranial nerve IV palsy. In this procedure, the superior oblique tendon is split, and the anterior fibers -- the fibers most responsible for incyclotorsion -- are moved...
.