Unilateral trochlear nerve injury can occur after frontolateral impact whereas bilateral trochlear nerve injury can occur from midfrontal impact. The fourth cranial nerve trochlear nerve has the longest intracranial course. Brainstem stroke usually haemorrhagic is a rare cause of an isolated trochlear nerve palsy. The trochlear nerve cn iv cranial nerves anatomy geeky. Due to the long course of the 6th nerve it is easily affected, for example in patients with raised intracerebral pressure. Paralysis of the trochlear nerve results in rotation of the eyeball upward and outward and, therefore, in double vision. It is the only cranial nerve that emerges dorsally from the brain near the back, giving it the longest pathway. The trochlear nerve, also called the fourth cranial nerve or cn iv, is a motor nerve a somatic efferent nerve that innervates only a single muscle.
Vascular loop compression of the trochlear nerve by anomalous left pca 30. Trochlear nerve palsy associated with claude bernard. Damage to the trochlear nerve results in a loss of function to the superior oblique muscle and is known as palsy. Trochlear nerve palsy causes an inability to move the eye in inward rotation, downward, and laterally. First, it is the only cranial nerve to exit the dorsal side of the brainstem. Trauma is the most common cause of an acquired fourth nerve palsy. When this nerve gets damaged or diseased it can lead to diplopia, and palsy which are common trochlear nerve disorders. In addition, out of all of the cranial nerves, it is the only one that originates on the opposite site of the body. Effects of ocular electroacupuncture on trochlear nerve palsy. Second, fibres from the trochlear nucleus cross in. Often doctors cannot identify the cause, but when they can, the cause is usually a head injury, sometimes a minor one. Given the small size of the trochlear nerve, it is prone to injury from shearing forces seen in head trauma.
It is a motor nerve which stimulates and supplies the superior oblique muscle of the eye. Another way to examine the trochlear nerve is with the bielchowsky head tilt test. Diplopia is experienced as parallel images and is greatest when looking towards the affected side. The differentiation between acutely acquired palsy vs. Damage to the trochlear nerve that results in a loss of function is called palsy. Diseases or injuries to the fourth cranial nerve can cause the superior oblique muscle to be paralyzed.
The nerve that controls the superior oblique muscle of the eye, one of the muscles that move the eye extraocular muscles. Its nucleus is present in inferior colliculus of mid brain, when we see the section of mid brain at the level of inferior colliculus there is cerebral aqueduct, around this cerebral aqueduct there is central gray matter periaqueductal gray matter. The superior oblique muscle moves the eye downward when the eye is turned toward the nose. Tilt typically away from affected side 70% to overcome inward rotation of affected eye to create wider separation of images. Bilateral trochlear nerve palsies following dorsal midbrain haemorrhage 31. The more common causes of trochlear nerve palsy are. The nucleus of the trochlear nerve is located in the caudal mesencephalon beneath the cerebral aqueduct. It is a slender, fragile nerve since it supplies a single muscle and its long intracranial. Fourth nerve palsies effect the superior oblique muscle trochlea. Damage to the trochlear nerves may result in the upward or side movement of the eyes often referred as vertical and torsional diplopia.
It begins in the midbrain at the level of the inferior colliculus as fascicles extending from the fourth nerve nuclei. Presentation of sixth nerve palsy vi nerve palsy is can be a false localising sign. Other causes of trochlear nerve injury are vascular injuries, diabetes mellitus, and transient viral infections causing a pseudobells palsy phenomenon. Congenital aplasia or hypoplasia of the oculomotor or abducens nerve has been documented on mr imaging in patients with congenital oculomotor nerve palsy and duane retraction syndrome. Fourth cranial nerve trochlear nerve palsy uptodate. People see double images, but tilting the head to the side opposite the affected eye can eliminate them. The fourth cranial nerve controls the actions of one of the external eye muscles. The trochlear nerve is also called the fourth cranial nerve. Trochlear nerve palsies, or fourth nerve palsies, result in weakness of the superior oblique muscle. Bilateral trochlear nerve palsies from a brainstem hematoma. Prognosis the prognosis for trochlear nerve palsies is dependent upon the underlying cause. For claims with a date of service on or after october 1, 2015, use an. A palsy of the 4th cranial nerve affects vertical eye movements. The case highlights the need for neuroimaging in selected cases of isolated trochlear nerve palsy.
It is the smallest nerve in terms of the number of axons it contains. When a trochlear nerve palsy is suspected, the diplopia can be abolished by tilting the head toward the shoulder of the unaffected side. The fourth cranial nerve is unique for three reasons. Trochlear nerve palsy treatment answers on healthtap. Causes and prognosis in 4,278 cases of paralysis of the oculomotor, trochlear, and abducens cranial nerves. Trochlear nerve palsy is mentioned in ophthalmology texts dating to the mid nineteenth century. We report acute isolated fourth nerve palsy in an 18yearold lady due to a midbrain hemorrhage probably due to a midbrain cavernoma. This condition often causes vertical or near vertical double vision as the weakened muscle prevents the eyes from moving in the same direction together. In children, it is most often present at birth congenital. Surgery should be scheduled not earlier than 12 months after onset of the palsy. Isolated trochlear nerve palsy in patients with multiple sclerosis. The prognosis of a fourth nerve palsy depends on the underlying etiology. Trochlear nerve palsy may be clinically characterized by vertical diplopia, incomitant hypertropia that increases upon head tilt toward the paralyzed site positive bielschowskys test, excyclotropia, and head tilt.
It has several unique features in that it contains the fewest axons of any of the 12 cranial nerves and is the longest. Functional components somatic efferentconcerned with movement of eye ball through so. It causes weakness or paralysis of the superior oblique muscle that it innervates. Trochlear nerve palsy, also known as 4th nerve palsy, causes a condition called diplopia. The trochlear nerve is also known as cranial nerve iv cniv. This patient presented after closed head trauma with a complaint of predominantly vertical, binocular diplopia ever since the event. Treatment of trochlear nerve palsy is nearly exclusively surgical. The trochlear nerve, also called the fourth cranial nerve or cn iv, is a motor nerve a somatic. Isolated trochlear nerve palsy with midbrain hemorrhage. Trochlear nerve palsy also affects torsion rotation of the eyeball in the plane of the face. No, the trochlear nerve is the 4th cranial nerve and is affected by structures in the brain not the neck. The trochlear nerve, also known as the fourth nerve or the fourth cranial nerve, is located near the brain and serves the superior oblique muscle of the eye. A critical decision to make in the treatment of fourth nerve palsy is whether to perform a onemuscle or twomuscle surgery.
The purpose of the study is to testify whether ocular electroacupuncture or ocular acupuncture is effective for trochlear nerve palsy tnp, through treating tnp patient for 6 weeks, using selfinvented acupoints according to anatomy of extraocular muscles innervated by trochlear nerve, and using sham acupuncture as controlled group, and try to. In this video we quickly summarise trochlear nerve palsy. Eye adducted and intorted resulting in vertical diplopia. It might not be diagnosed until it becomes more severe because patients tend to compensate for the diplopia. Since the trochlear nerve functions to control the superior oblique eye muscle. He adopted a mild left head tilt and had a right hypertropia in.
Trochlear nerve palsy fourth nerve palsy differential. Rare, dorsal exit of cn iv, cavernous sinus thrombosis. This video shows the cranial nerve palsies that affect the eye specifically third nerve palsy, fourth nerve palsy, and sixth nerve palsy. The trochlear nerve is the fourth cranial nerve, and it is the only cranial nerve that arises from the back of the brain stem. However, it received little more than a brief mention and was no doubt an underrecognized entity.
Fourth nerve palsy may also be known as superior oblique palsy or trochlear nerve palsy. Highresolution 3d mr imaging of the trochlear nerve. It is caused by disease or injury to the fourth cranial nerve. Fourth cranial nerve palsy, is a condition affecting cranial nerve 4 iv, the trochlear nerve, which is one of the cranial nerves. The trochlear nerve the fourth cranial nerve, also called the fourth nerve, iv is a motor nerve a somatic efferent nerve that innervates a single muscle. Doctors give trusted, helpful answers on causes, diagnosis, symptoms, treatment, and more. The trochlear nucleus is in close proximity to the. Fourth nerve palsy means that a certain muscle in your eye is paralyzed. Idiopathic, traumatic and congenital abnormalities are the most common causes of fourth nerve palsy. If the eye is turned outward, it causes the eye to rotate inward. Bilateral fluctuating trochlear nerve palsy secondary to cerebellar astrocytoma. Trochlear nerve nuclie,course and palsy notes ophthnotes. Trauma accounts for roughly 44% of acquired trochlear nerve palsies with nearly 25% of cases being bilateral and, thus, it is the most common etiology of an acquired cn iv palsy 1. Some patients with microvascular or traumatic trochlear nerve palsy have some improvement 39 months after presentation.
Diplopia is more commonly known as double vision, and is caused by the eyes inability to mesh muscle movement to create a single, unified image. In 1935, bielschowsky correctly noted that trochlear nerve palsy was the most common cause of vertical diplopia and introduced his classic headtilt test. The diplopia was worse with left gaze and improved with left head tilt. Can be paradoxical, where patient tilts head toward affected side 3% vascular. The trochlear nerve is also a part of the cranial nerve which stems from. Association of superior oblique muscle volumes with the presence or absence of the trochlear nerve on highresolution mr imaging in congenital superior oblique palsy. The leading causes are congenital and trauma lepore and glaser, 1980. Other names for it are superior oblique palsy and trochlear nerve palsy. Trochlear nerve paralysis fourth trochlear nerve palsy. Fourth nerve palsy an overview sciencedirect topics. Cranial nerve disorders medicine flashcards quizlet. Palsy can be temporary, usually resulting from head trauma.
Cranial nerve examination questions oculomotor iii. Trochlear nerve palsy is the most frequent isolated cranial neuropathy that affects ocular motility. The trochlear nerve is the fourth cranial nerve having the longest intracranial course and is the only nerve that originates from the back of the brain stem. The trochlear nucleus and nerve fourth nerve fourth nerve palsy is the commonest ocular motor palsy in children 80% lepore and glaser, 1980.
The trochlear nerve is the fourth cranial nerve and is the motor nerve of the superior oblique muscle of the eye. Isolated trochlear nerve palsy with dorsal midbrain hemorrhage 32. A fourth nerve palsy is the loss or decrease in innervation to the superior oblique muscle. You may have fourth nerve palsy from birth, or you may develop it later.
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