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The trochlear nerve (/ ˈ t r ɒ k l ɪər /), [1] (lit. pulley-like nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates a single muscle - the superior oblique muscle of the eye (which operates through the pulley-like trochlea).
Fourth cranial nerve palsy or trochlear nerve palsy, is a condition affecting cranial nerve 4 (IV), [1] the trochlear nerve, which is one of the cranial nerves. It causes weakness or paralysis of the superior oblique muscle that it innervates. This condition often causes vertical or near vertical double vision as the weakened muscle prevents ...
Trochlear: Motor Dorsal aspect of Midbrain: Located in the superior orbital fissure. Innervates the superior oblique muscle, which depresses, abducts, and intorts the eyeball. V Trigeminal: Both sensory and motor Pons: Three Parts: V 1 (ophthalmic nerve) is located in the superior orbital fissure V 2 (maxillary nerve) is located in the foramen ...
The cranial nerves are considered components of the peripheral nervous system (PNS), [3] although on a structural level the olfactory (I), optic (II), and trigeminal (V) nerves are more accurately considered part of the central nervous system (CNS). [4] The cranial nerves are in contrast to spinal nerves, which emerge from segments of the ...
Congenital fourth nerve palsy is a condition present at birth characterized by a vertical misalignment of the eyes due to a weakness or paralysis of the superior oblique muscle. Other names for fourth nerve palsy include superior oblique palsy and trochlear nerve palsy. [1]
The trochlear nucleus is located in the midbrain, at an intercollicular level between the superior colliculus and inferior colliculus. [3] As with all motor nuclei of cranial nerves, it is located near the midline (i.e. in the medial midbrain). [2] It is embedded within the medial longitudinal fasciculus.
The trochlear nerve controls the superior oblique muscle to rotate the eye along its axis in the orbit medially, which is called intorsion, and is a component of focusing the eyes on an object close to the face. The oculomotor nerve controls all the other extraocular muscles, as well as a muscle of the upper eyelid.
Involvement of the cranial nerves that pass through the superior orbital fissure may lead to diplopia, paralysis of extraocular muscles, exophthalmos, and ptosis. Blindness or loss of vision indicates involvement of the orbital apex, which is more serious, requiring urgent surgical intervention.