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Fourth Nerve Palsy
Fourth cranial nerve palsy or trochlear nerve palsy, is a condition affecting cranial nerve 4 (IV), 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 the eyes from moving in the same direction together. Because the trochlear nerve is the thinnest and has the longest intracranial course of the cranial nerves, it is particularly vulnerable to traumatic injury. To compensate for the double-vision resulting from the weakness of the superior oblique, patients characteristically tilt their head down and to the side opposite the affected muscle. When present at birth, it is known as congenital fourth nerve palsy. See also * Harada–Ito procedure The Harada–Ito procedure is an eye muscle operation designed to improve the excyclotorsion experienced by some patients with cranial nerve IV ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trochlear Nerve
The trochlear nerve (), ( lit. ''pulley-like'' nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates just one muscle: the superior oblique muscle of the eye, which operates through the pulley-like trochlea. CN IV is a motor nerve only (a somatic efferent nerve), unlike most other CNs. The trochlear nerve is unique among the cranial nerves in several respects: * It is the ''smallest'' nerve in terms of the number of axons it contains. * It has the greatest intracranial length. * It is the only cranial nerve that exits from the dorsal (rear) aspect of the brainstem. * It innervates a muscle, the superior oblique muscle, on the opposite side (contralateral) from its nucleus. The trochlear nerve decussates within the brainstem before emerging on the contralateral side of the brainstem (at the level of the inferior colliculus). An injury to the trochlear nucleus in the brainstem will result in an contralateral superior o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |