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The superior oblique muscle is one of six extraocular muscles that control eye movements. It is the only extraocular muscle innervated by the trochlear nerve (the fourth cranial nerve). The trochlear nerve is the only cranial nerve that emerges from the posterior aspect of the brainstem, taking a long path through the endocranium and entering the orbit via the superior orbital fissure to innervate the superior oblique muscle. The primary action of the superior oblique muscle is intorsion (internal rotation), while its secondary action is depression (most evident in adduction).
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What You'll Learn
- The superior oblique muscle is the only extraocular muscle innervated by the trochlear nerve
- The muscle originates from the body of the sphenoid bone
- It is the longest muscle in the group of six extraocular muscles
- Its primary action is intorsion (internal rotation) of the eye
- The muscle is tested by having the patient look inwards and downwards
The superior oblique muscle is the only extraocular muscle innervated by the trochlear nerve
The superior oblique muscle is one of six extraocular muscles that control eye movements. It is responsible for abduction, depression, and internal rotation of the eyeball. It is the longest and thinnest of the extraocular muscles, spanning from the body of the sphenoid bone to the superolateral aspect of the eyeball.
The superior oblique muscle is unique among the extraocular muscles in that it is the only one innervated by the trochlear nerve. The trochlear nerve is the fourth cranial nerve, and it 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 originates externally, superomedially to the common tendinous ring, and runs anteriorly, parallel to the medial wall of the orbit. It then hooks around a cartilaginous pulley, called the trochlea of the superior oblique, which is attached to the nasal part of the frontal bone. This unique path allows the superior oblique muscle to move the eye down and out (inferolaterally).
The innervation of the superior oblique muscle by the trochlear nerve is clinically important. During neurological examinations, the superior oblique muscle is tested by asking the patient to look inwards and downwards, specifically testing the muscle's depressing action. This is in contrast to the anatomical function of the muscle, which is both depression and abduction of the eye.
In summary, the superior oblique muscle is the only extraocular muscle innervated by the trochlear nerve. This unique innervation and the muscle's path give the superior oblique muscle its distinct functions and roles in eye movements.
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The muscle originates from the body of the sphenoid bone
The superior oblique muscle is one of six extraocular muscles that control eye movements. It is the longest and thinnest of these muscles, which originate from the body of the sphenoid bone. The sphenoid bone is located in the centre of the skull, behind the eye sockets. The superior oblique muscle arises from the lesser wing of the sphenoid bone, medial to the origin of the levator palpebrae superioris muscle and superomedial to the optic canal.
The superior oblique muscle is unique in that it does not originate from the common tendinous ring. Instead, it originates externally, superomedially to the tendinous ring. From its sphenoid attachment, the muscle 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 trochlea of the superior oblique is a fibrocartilaginous structure, located just inside the superomedial orbital rim. As the superior oblique tendon passes through the trochlea, it changes direction, moving deep to the superior rectus muscle. The tendon then inserts into the sclera on the posterior surface of the eyeball, behind the midpoint of the eye. The insertion point of the tendon is about 6 to 7 mm from the optic nerve.
The superior oblique muscle is innervated by 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 trochlear nerve is also involved in supplying the lateral rectus muscle.
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It is the longest muscle in the group of six extraocular muscles
The superior oblique muscle is the longest muscle in the group of six extraocular muscles. It is also the thinnest. This muscle is responsible for abduction, depression, and internal rotation of the eyeball. It originates on the lesser wing of the sphenoid bone and passes through the trochlea, a U-shaped piece of cartilage attached to the frontal bone. The muscle inserts in the superoposterior lateral aspect of the globe.
The superior oblique muscle is unique among the extraocular muscles in that it is supplied by the trochlear nerve (CN IV). The trochlear 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 trochlear nerve originates at the level of the inferior colliculus from the dorsal surface of the medial midbrain.
The superior oblique muscle is one of the two oblique extraocular muscles. These muscles are unique in that they do not originate from the common tendinous ring, have an angular attachment to the eyeball, and attach to the posterior aspect of the eyeball. The superior oblique muscle attaches to the trochlea, a fibrous, cartilaginous pulley attached to the trochlear fovea of the frontal bone. The muscle originates from the periosteal covering of the sphenoid and reaches the trochlea by passing along the medial border of the roof of the orbit.
The primary action of the superior oblique muscle is intorsion of the eye, while its secondary action is depression of the eye, which is most evident in adduction. The depressing action of the superior oblique is most effective when the eye is in an adducted position. This is because, as the eye is abducted, the contribution of the superior oblique to depression decreases, as the inferior rectus muscle causes this movement more directly and powerfully. The superior oblique muscle is also involved in abduction, or lateral rotation, of the eyeball.
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Its primary action is intorsion (internal rotation) of the eye
The superior oblique muscle is one of six extraocular muscles that control eye movements. It is innervated by the trochlear nerve (CN IV), the only cranial nerve emerging from the posterior aspect of the brainstem. This nerve takes a long path through the endocranium and enters the orbit via the superior orbital fissure to innervate the superior oblique muscle.
The primary action of the superior oblique muscle is intorsion, or internal rotation of the eye. This movement is crucial for maintaining level vision, irrespective of the eye's position in the orbit. When the eye is in the adducted position, the superior oblique muscle is responsible for depressing the eye, causing it to look down towards the mouth. This depressing action is most effective when the eye is adducted because, as the eye abducts, the contribution of the superior oblique muscle to depression decreases, as the inferior rectus muscle takes over this movement more directly and powerfully.
The secondary action of the superior oblique muscle is depression, and the tertiary action is abduction (lateral rotation). The muscle originates from the body of the sphenoid bone and is the longest muscle in the group of extraocular muscles. It runs anteriorly, parallel to the medial wall of the orbit and inserts into the sclera on the superolateral aspect of the eyeball.
The superior oblique muscle is unique among the extraocular muscles in that it does not originate from the common tendinous ring. Instead, it originates externally, superomedially to the ring. Its tendon travels through a pulley-like structure, the trochlea of the superior oblique, which is attached to the frontal bone. This pulley system allows the superior oblique muscle to internally rotate the eye and move it "down and in" upon contraction.
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The muscle is tested by having the patient look inwards and downwards
The superior oblique muscle is one of the six extraocular muscles that control eye movements. It is the only extraocular muscle that is supplied by the trochlear nerve (CN IV), a cranial nerve that emerges from the posterior aspect of the brainstem. The muscle originates from the body of the sphenoid bone and is responsible for abduction, depression, and internal rotation of the eyeball.
During neurological examinations, the superior oblique muscle is tested by having the patient look inwards and downwards. This tests only the depressing action of the muscle, which is most effective when the eye is in an adducted position. As the eye looks laterally, the contribution of the superior oblique to depression decreases, as the inferior rectus muscle causes this movement more directly and powerfully. Therefore, testing the patient's downwards and lateral eye movement would not be specific enough, as the inferior and lateral recti muscles would also be tested.
The confusion arises as, anatomically, the muscle depresses and abducts the eye. The superior oblique muscle loops through a pulley-like structure (the trochlea of the superior oblique) and inserts into the sclera on the posterotemporal surface of the eyeball. It is the pulley system that gives the superior oblique its actions, causing depression of the eyeball despite being inserted on the superior surface.
The primary action of the superior oblique muscle is intorsion (internal rotation), the secondary action is depression (in the adducted position), and the tertiary action is abduction (lateral rotation). The muscle works in conjunction with the two rectus muscles to prevent the eye from rotating about its long axis when looking up and down. When the eye looks down, the superior oblique contracts to prevent extorsion of the eye, keeping our vision horizontally level.
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Frequently asked questions
The superior oblique muscle is one of the six extraocular muscles that control eye movements. It is the longest and thinnest of these muscles.
The primary action of the superior oblique muscle is intorsion (internal rotation) of the eye, while its secondary action is depression (making the eye look down towards the mouth).
The superior oblique muscle originates on the lesser wing of the sphenoid bone and passes through the trochlea, a U-shaped piece of cartilage attached to the frontal bone. It then inserts into the sclera on the superoposterior lateral aspect of the eyeball.
The superior oblique muscle is innervated by the trochlear nerve (CN IV). It is the only extraocular muscle that receives its innervation in this way.
The superior oblique muscle abducts, depresses and internally rotates the eye, allowing it to move down and out (inferolaterally).
