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The superior oblique muscle is one of six extraocular muscles that completely surround the eyeball, facilitating its movement in various directions. It is the longest and thinnest of these muscles, and the only one that is innervated by the trochlear nerve (the fourth cranial nerve). The primary action of the superior oblique muscle is intorsion (internal rotation), the secondary action is depression (primarily in the adducted position) and the tertiary action is abduction (lateral rotation).
| Characteristics | Values |
|---|---|
| Type | Extraocular muscle |
| Group | Oblique muscles |
| Location | Upper medial portion of the orbit, adjacent to its medial wall |
| Origin | Sphenoid bone |
| Insertion | Posterotemporal surface of the eyeball |
| Innervation | Trochlear nerve (CN IV) |
| Blood Supply | Anterior ciliary arteries, branches of the ophthalmic artery |
| Main Action | Intorsion (internal rotation) |
| Secondary Action | Depression (primarily in the adducted position) |
| Tertiary Action | Abduction (lateral rotation) |
| Function | Directs gaze inferolaterally by abducting, depressing and internally rotating the eye |
| Palsy | Superior oblique palsy, a common complication of closed head trauma |
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What You'll Learn
Superior oblique muscle is the longest of the extraocular muscles
The superior oblique muscle is the longest of the extraocular muscles, which are a group of six extrinsic muscles of the eye. These muscles are located within the orbit and surround the eyeball, facilitating its movement in various directions. The superior oblique muscle is also the thinnest of the extraocular muscles. It originates on the lesser wing of the sphenoid bone, which is located medial to the origin of the levator palpebrae superioris muscle and superomedial to the optic canal.
The superior oblique muscle runs anteriorly, parallel to the medial wall of the orbit. It loops through a pulley-like structure called the trochlea of the superior oblique, which is made of cartilage and attached to the nasal part of the frontal bone. This unique pulley system gives the superior oblique muscle its distinct actions, allowing it to depress the eyeball despite attaching to its superior surface.
The tendon of the superior oblique muscle takes a sharp turn before inserting onto the posterior-superolateral scleral surface of the eye, behind the equator of the eyeball. This insertion is located between the attachments of the superior rectus and lateral rectus muscles. The belly of the muscle is positioned posterior to the eye, while the tendon approaches the eyeball from the front, allowing for a wide range of eye movements.
The primary function of the superior oblique muscle is to produce eye movements that direct the gaze inferolaterally. It achieves this by abducting, depressing, and internally rotating the eye. This muscle is the only extraocular muscle innervated by the trochlear nerve (CN IV), which is the fourth cranial nerve. The trochlear nerve is unique among cranial nerves as it emerges from the posterior aspect of the brainstem.
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It originates from the sphenoid bone and passes through the trochlea
The superior oblique muscle is the longest and thinnest of the six extraocular muscles in the eye. These muscles are located within the orbit and completely surround the eyeball, facilitating its movement in various directions. The superior oblique muscle originates from the sphenoid bone, specifically from the medial, upper side of the orbit, and passes through the trochlea, a U-shaped piece of cartilage attached to the frontal bone. The muscle tendon hooks around this cartilaginous pulley, called the trochlea of the superior oblique.
The trochlea of the superior oblique is a fibrocartilaginous ring or pulley attached to the trochlear fossa of the frontal bone. It is located between the tendon and the nasal part of the frontal bone, with a thin separating synovial sheet. From the trochlea, the tendon takes a sharp turn before inserting onto the scleral surface of the eye. This insertion is located behind the equator of the eyeball, between the attachments of the superior rectus and lateral rectus muscles.
The superior oblique muscle is the only extraocular muscle that receives its innervation through the trochlear nerve (CN IV). The trochlear nerve is the only cranial nerve that emerges from the posterior aspect of the brainstem. It enters the orbit via the superior orbital fissure to innervate the superior oblique muscle. The other extraocular muscles, except for the lateral rectus, are supplied by the oculomotor nerve (CN III).
The primary action of the superior oblique muscle is intorsion or internal rotation, which directs the gaze inferolaterally. It also has secondary actions of depression, primarily when the eye is in an adducted position, and tertiary action of abduction or lateral rotation. The depressing action of the superior oblique makes the eye look down towards the mouth. This movement is most effective when the eye is adducted, as in this position, the contribution of the superior oblique to depression is greater than when the eye is abducted, where the inferior rectus muscle has a more direct and powerful effect on this movement.
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It is innervated by the trochlear nerve (CN IV)
The superior oblique muscle is the longest muscle in the group of six extrinsic muscles of the eye, also known as the extraocular muscles. It originates from the body of the sphenoid bone and is located in the upper medial portion of the orbit, adjacent to its medial wall.
The superior oblique muscle is innervated by the trochlear nerve (CN IV). This is the only cranial nerve that emerges from the posterior aspect of the brainstem. It takes a long path through the endocranium and enters the orbit via the superior orbital fissure to innervate the superior oblique muscle.
The trochlear nerve is responsible for supplying the superior oblique muscle with nerve fibres, allowing it to receive signals from the brain and coordinate eye movements. It is important to note that the superior oblique muscle is the only extraocular muscle that receives its innervation through the trochlear nerve.
A lesion of the trochlear nerve (CN IV) will result in paralysis of the superior oblique muscle. This condition is known as superior oblique palsy and can lead to diplopia (double vision) and a head tilt away from the side of the lesion.
The superior oblique muscle plays a crucial role in eye movements and gaze direction. Its primary action is intorsion or internal rotation, while it also contributes to depression (making the eye look down) and abduction (lateral rotation). The muscle's unique position and function help stabilise the eyeball and counteract head movements, ensuring clear and coordinated vision.
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Its primary action is intorsion (internal rotation)
The primary action of the superior oblique muscle is intorsion, or internal rotation of the eye. This is a crucial function, as it works in conjunction with the other muscles of the eye to ensure that our vision remains horizontally level, irrespective of the position of the eye in its orbit.
The superior oblique muscle is the longest and thinnest of the six extraocular muscles of the eye. These muscles are located within the orbit and completely surround the eyeball, facilitating its movement in various directions. The superior oblique muscle originates from the body of the sphenoid bone and runs anteriorly, parallel to the medial wall of the orbit.
The muscle tendon hooks around a cartilaginous pulley, called the trochlea of the superior oblique. This loop is attached to the nasal part of the frontal bone. The tendon then takes a sharp posterolateral turn before inserting onto the posterolateral scleral surface of the eye, behind its equator.
The superior oblique is the only extraocular muscle that receives its innervation through the trochlear nerve (CN IV). This nerve is the only cranial nerve that emerges from the posterior aspect of the brainstem. It takes a long path through the endocranium and enters the orbit via the superior orbital fissure to innervate the superior oblique muscle.
The superior oblique muscle's primary action of intorsion is essential for maintaining the stability and coordination of the eye during movement. This internal rotation of the eye helps to counteract head movements and ensures that our vision remains level, even when the eye moves up or down.
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Superior oblique palsy is a complication of closed head trauma
The superior oblique muscle is one of six extraocular muscles located within the orbit that completely surround the eyeball, facilitating its movement in various directions. It is the longest muscle in this group, originating from the body of the sphenoid bone and spanning to the superolateral aspect of the eyeball. The primary action of the superior oblique muscle is intorsion (internal rotation), the secondary action is depression (primarily in the adducted position), and the tertiary action is abduction (lateral rotation).
Superior oblique palsy is a condition that can manifest as congenital or acquired. Congenital SOP is present at birth due to anomalies such as a misshapen skull or developmental abnormalities. Acquired SOP, on the other hand, usually occurs following closed head trauma, such as a concussion or traffic accident, but can also be caused by respiratory viral infections, central nervous system lesions, vascular abnormalities, or microvascular ischemia. In rare cases, it can result from a stroke, tumour, or aneurysm.
Closed-head trauma can cause direct damage to the trochlea and SO tendon, leading to combined SO palsy and ipsilateral Brown's syndrome, also known as "canine tooth syndrome." This rare condition results in ocular motility disorders, with patients experiencing double vision (diplopia), abnormal head posture, and restricted eye movement.
The treatment for superior oblique palsy may involve surgery, prism lenses, or prismatic correction. However, the specific treatment approach depends on the individual case, and it is recommended to consult with an ophthalmologist for a thorough evaluation and specialized care.
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Frequently asked questions
The superior oblique muscle is a fusiform muscle that originates in the upper, medial side of the orbit (from beside the nose) and inserts into the sclera on the posterotemporal surface of the eyeball. It is the longest muscle in the group of extraocular muscles.
The primary function of the superior oblique muscle is intorsion (internal rotation), the secondary function is depression (making the eye look down towards the mouth), and the tertiary function is abduction (lateral rotation).
The superior oblique muscle loops through a pulley-like structure (the trochlea of superior oblique) and inserts into the sclera of the eyeball. The pulley system gives the superior oblique its actions, allowing it to depress the eyeball despite being inserted on the superior surface.
During neurological examinations, the superior oblique is tested by asking the patient to look inward and downward, specifically testing the depressing action of the muscle.
A lesion of the trochlear nerve (CN IV) will paralyse the superior oblique muscle, resulting in double vision (diplopia) and a head tilt away from the site of the lesion.
