The superior oblique is a fusiform (spindle-shaped) muscle belonging to the extraocular group of muscles. It originates near the nose. Along with the other extraocular muscles, it performs the role of controlling eye movements.

These muscles are unique in that they do not originate from the common tendinous ring, have an angular attachment to the eyeball, and they attach to the posterior aspect of the eyeball. The superior oblique functions explicitly to move the eye in the down-and-out position and intort the eye.

The superior oblique muscle’s primary action is eye intorsion, with secondary and tertiary actions being eye depression and abduction, respectively. Because the superior oblique helps depress the eye, trochlear nerve palsy results in upward deviation of the eye (hypertropia).

There are two oblique muscles – the superior and inferior obliques. Unlike the recti group of muscles, they do not originate from the common tendinous ring.

[2] The inferior oblique is responsible for extorsion, elevation, and abduction. Because of their course, the superior and inferior oblique muscles are the only muscles that can depress or elevate the eye, respectively when the eye moves in adduction.

Due to its oblique course and attachment on the posterolateral side of the eyeball, contraction of the inferior oblique muscle pulls the eyeball in a direction posterior to its vertical axis, and therefore rotates the eye laterally around this axis.

The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye. It is the only extraocular muscle innervated by the trochlear nerve (the fourth cranial nerve).

The Parks–Bielschowsky three-step test, also known as Park’s three-step test or Bielschowsky head tilt test, is a method used to isolate the paretic extraocular muscle, particularly superior oblique muscle and trochlear nerve (IVth cranial nerve), in acquired vertical double vision.

1. In a fourth nerve palsy, ocular torsion and hypertropia should be unaffected by positional changes.
2. Skew deviation may demonstrate decreasing vertical strabismus with position change from upright to supine. Greater than 50% change in vertical strabismus with position change from upright to supine is a positive test.

The trochlear nerve is purely a motor nerve and is the only cranial nerve to exit the brain dorsally. The trochlear nucleus gives rise to nerves that cross (decussate) to the other side of the brainstem just prior to exiting the brainstem.

Vagus nerve

the vagus nerve

Cranial Nerves

Vagus nerves

The trigeminal nerve is the largest of your cranial nerves and has both sensory and motor functions. The trigeminal nerve has three divisions, which are: Ophthalmic. The ophthalmic division sends sensory information from the upper part of your face, including your forehead, scalp, and upper eyelids.

Cranial nerve 3, also called the oculomotor nerve, has the biggest job of the nerves that control eye movement.

The main difference between neurilemma and myelin sheath is that neurilemma is the plasma membrane layer of the Schwann cells whereas myelin sheath is the fatty acid layer that encloses the nerve fiber. The myelin sheath is enclosed by the neurilemma in the peripheral nervous system.

noun. the thin membrane that forms a sheath around nerve fibresAlso: neurilemma.

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. In this disorder, your immune system attacks the myelin sheath or the cells that produce and maintain it.

Nodes of Ranvier. These are the gaps formed between the myelin sheath where the axons are left uncovered. Because the myelin sheath is largely composed of an insulating fatty substance, the nodes of Ranvier allow the generation of a fast electrical impulse along the axon.