The superior oblique muscle is a muscle of the outer eye muscles, which belongs to the skeletal muscles and is motor-innervated by the fourth cranial nerve. The muscle is crucial for the downward vision of the eyes and is in harmony with the other muscles of the outer eye muscles. A paralysis of the muscle leads to strabismus with double images.

What is the superior oblique muscle?

From an evolutionary biological point of view, humans are referred to as eye-controlled living beings. Accordingly, evolutionary biologists argue that in the past people have relied primarily on their visual perception to get an idea of ‚Äč‚Äčtheir surroundings and to respond to the environment.

Eye movements have contributed to the survival of the human species. Eye movements are a complex interaction of contractions of different muscles. The eye muscles are composed of several skeletal muscles. One of these is the superior oblique muscle, also known as the upper oblique muscle. In animals, this muscle is sometimes referred to as the oblique dorsalis or the musculus patheticus.

The muscle is a skeletal muscle of the outer eye muscles, which also includes the rectus superior, lateral rectus, inferior rectus, rectus medialis and inferior muscles. All eye movements of the person are caused by the outer eye muscles.

Anatomy & Construction

The superior oblique muscle originates from the sphenoid bone, the periorbita, and the dura mater on the optic nerve. The motor muscle pulls over the medial rectus muscle in the rostral direction. At the edge of the orbita, the tendon of the muscle pierces the connective tissue of the trochlea, which in the form of the hypomochlion serves to deflect the muscular traction.

In its further course in the dorsal direction, the superior oblique muscle has an attachment to the temporal upper quadrant of the eyeball, where it sits dorsally on the equator line over the sclera. The motor innervation of the muscle is given to the trochlear nerve, the fourth cranial nerve. Like all other motor nerves, this nerve does not carry only motor fibers, but is also endowed with sensitive parts.

Positional and tonus information from the muscle spindles and the Golgi tendon apparatus of the muscle are permanently sent to the central nervous system via the afferent sensitive parts. As a skeletal muscle, the superior oblique muscle consists of the actual muscle fibers that cause the contraction and some auxiliary tissues, such as a tough connective tissue outer layer in the form of the fascia.

Function & Tasks

The main function of the superior oblique muscle is the lowering or depression of the eye, which is accompanied by an inward rolling of the eyes and a slight abduction. The inside roll is also called inzykloduktion. In terms of adduction, the muscle is a pure sinker. The inward rolling of the eye increases with increasing view to the outside.

Together with the other muscles of the outer eye muscles, the superior oblique muscle is responsible for all movements of the eye. Man has four straight and two oblique eye muscles, which are in a complex interaction with each other. By harmonizing contraction, the outer eye muscles jointly execute all the rotational movements of the eye in all directions. In addition, all external eye muscles together ensure that the eye positions are in a stable relationship to each other.

The trochlear nerve causes only the superior oblique muscle to contract. The other eye muscles of the outer eye muscles receive their commands from the central nervous system via the oculomotor nerve and the nervus abducens, ie the third and sixth cranial nerves. At rest, ie without active nerve-initiated muscle contraction, the underlying tone of the outer eye muscles ensures that the eye does not twist.

Diseases

Failure of the trochlear nerve causes the superior oblique muscle to fail, affecting the eye position in the resting position. If all other muscles of the outer eye muscles are still functional, the affected eye is turned medially upward after the failure of the superior oblique muscle by the tone of the still functioning eye muscles.

The paralysis of the motor innervating trochlear nerve is also known as trochlear nerve palsy and is clinically associated with strabismus and corresponding double vision in the sense of a diplopia. The deviation of the affected eye upwards is also called hypertrophy. The simultaneous introversion of the gaze is called esotropia. The paralysis-related roll around the sagittal axis outwards again corresponds to an ex-cyclotomy. In the case of paralysis of the superior oblique muscle, there are double images, especially on the vertical, which are triggered especially by the downward view of the healthy opposite side.

Often patients with such eye muscle palsy tend their head to the healthy side to compensate for the double vision and functional impairments. This symptom is also known as ocular torticollis. Paralysis of the motor-supplying nerve and the resulting paralysis of the superior oblique muscle are caused by traumatic, defect-induced, tumor-induced, compression-related or bacterial or autoimmunological inflammatory damage to the nerve tissue.

In an isolated unilateral damage to the supplying nerve it comes because of its anatomical peculiarities on exactly the opposite side of the actually affected side to paralysis. Beyond paralysis, the proximity of its broad attachment site to the external vortex vein should be considered during therapeutic procedures on the superior oblique muscle. The immediate proximity of the muscle to this vein makes it particularly easy for vascular injuries to occur during surgical procedures within this area.

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