Fourth Nerve Palsy

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Identifier 929-2
Title Fourth Nerve Palsy
Ocular Movements Hypertropia; Superior Oblique Paresis; Inferior Oblique Overaction; Fourth Nerve Palsy; Trochlear Nerve; Bielchowsky Test; Head Tilt
Creator Shirley H. Wray, M.D., Ph.D., FRCP, Professor of Neurology Harvard Medical School, Director, Unit for Neurovisual Disorders, Massachusetts General Hospital
Contributor Primary Shirley H. Wray, MD, PhD, FRCP, Professor of Neurology, Harvard Medical School; Director, Unit for Neurovisual Disorders, Massachusetts General Hospital
Subject Hypertropia; Superior Oblique Paresis; Inferior Oblique Overaction; Fourth Nerve Palsy; Trochlear Nerve; Bielchowsky Test; Head Tilt
Presenting Symptom Double vision
History The patient is a 64 year old engineer who noted whilst driving around Thanksgiving time double vision with one image on top of the other. Vertical double vision persisted and he was referred to the Massachusetts General Hospital for evaluation. Past History: 1991 Hyperthyroidism with Graves' Disease treated with radio active iodine. 1989-1990 Writer's cramp treated with botulinium toxin injection 1989 Cancer of the colon, status colonectomy. No previous episodes of diplopia No strabismus as a child or need to wear prism glasses No history of head or eye trauma Medications: Synthroid 600 mg Calcium daily Aspirin daily Family History: Positive for diabetes Mother died cancer of the ovary Neuro-ophthalmological examination: Visual acuity 20/20 OU corrected Visual fields, color vision, pupils and fundus examination normal. Tests for diplopia showed: Left (contralateral) head tilt Good stereopsis in primary gaze 6/9 circles. Cover/uncover test: Hypertropia OD primary gaze Hypertropia most marked with right head tilt Hypertropia diminished, almost absent, left head tilt Hypertropia almost fully corrected with prism glasses at distance. Exophthalmometry 23 OU base 97 normal orbital resilience. Ocular Motility OD: Hypertropia and excyclotorsion Superior oblique (SO) paretic Inferior oblique (IO) overaction with elevation of the globe looking left. Cranial nerves 3 and 6 normal Ocular Motility OS: Full eye movements Hypotropia on cover/uncover test CT of the Orbits 1/17/92: Study showed enlargement of the inferior rectus muscle bilaterally and the right medial rectus muscle attributed to earlier Graves' disease in the past associated with hyperthyroidism. Brain MRI showed: Calcification of the wall of the carotid siphon and changes consistent with small vessel microangiopathy. Strabismus Consultation: The patient was tested with two Maddox rods and found to have an 8 diopter right hyper with the right eye extorted approximately 5 diopters in primary position. Diagnosis fourth nerve palsy, presenting in a somewhat unusual manner, possibly modified by his early Graves' disease and persistent enlargement of the inferior recti OU and the medial rectus muscle OD. Diagnosis: Right fourth nerve palsy Mild thyroid associated orbitopathy Strabismus surgery was not recommended. He returned in June 1992 and annually until July 1996 with no change in ocular motility.
Clinical This tape records the "diplopia" history. The patient answers a list of specific questions with regard to his vertical double vision from a right fourth (trochlear) nerve palsy. He had no diplopia with one eye covered confirming binocular diplopia. With a history of vertical diplopia, attention is paid to the ocular muscles controlling vertical gaze. • SO: Paresis SO resulted in impaired downgaze in the adducted position with absent incyclotorsion of the eye • IO: Overaction of IO with elevation of the eyeball on gaze left, in the adducted position Alternate cover test: OD moved down to take up fixation (hypertropia) OS moved up to take up fixation (hypotropia) Review of old photographs showed that he had a longstanding left head tilt which helped establish the chronicity of the fourth nerve palsy. The Three-Step Test aids in establishing the diagnosis. Step 1 - Identify which eye is hypertropic e.g. hypertropia OD. Step 2 - Determine whether the hypertropia increases on right or left gaze Step 3 - Bielchowsky's head tilt test: Tilt the head to the right and to the left. Hypertropia is maximized as the head is tilted toward the side of the lesion and minimized on contralateral head tilt, as in this case. The most reliable clinical test to diagnose fourth nerve palsy is the Bielchowsky's head tilt test. During right head tilt, the right eye incyclotorts (SO and SR), and the left eye excyclotorts (IO and IR) During left head tilt, the right eye excyclotorts (IO and IR) and the left eye incyclotorts (SO and SR). The question always asked is why does the hypertropia increase on right head tilt in right fourth nerve palsy. The explanation is as follows: During right head tilt, the otolith-ocular reflex (ocular counter roll) is activated, such that the right eye incyclotorts (SO and SR) and the left eye excyclotorts (IO and IR). The primary action of SO is incyclotorsion, and its secondary action depression, whereas the primary action of SR is elevation and its secondary action is incyclotorsion. Thus, normally, during the right head tilt, the net movement of the right eye is incyclotorsion with minimal vertical movement because the vertical action of the SO and SR cancels each other out. In right fourth nerve palsy, the elevating action of SR is unopposed by the palsied SO; thus, the hypertropia increases during right head tilt. Differential Diagnosis: 1. Skew deviation 2. Thyroid-related ophthalmopathy 3. Brown's Syndrome 4. Primary inferior oblique overaction
Neuroimaging No imaging studies are available in this patient. In patients who lack a history of head trauma, Brain MRI may show relevant brainstem lesions and gadolinium enhancement usually demonstrates infiltrative or inflammatory processes involving the long course of the fourth nerve. Often the cause of the fourth nerve cannot be ascertained and these patients require long term follow-up.
Anatomy The nucleus of the fourth (trochlear) nerve lies at the ventral border of the periaqueductal gray matter at the level of the inferior colliculus in the brainstem. It lies at the dorsal margin of the medial longitudinal fasciculus. The fascicle of the fourth nerve crosses the midline at the anterior medullary vellum (anterior floor of the fourth ventricle, before exiting the brainstem) thus, the right fourth nerve fascicle becomes the left fourth nerve which innervates the left superior oblique muscle. The fourth nerve is the only cranial nerve that exits the brainstem on the dorsal surface and it has the longest intracranial course (approximately 75mm). In the subarachnoid space the nerve curves around the lateral surface of the upper pons, passing between the superior cerebellar and posterior cerebral arteries to reach the prepontine cistern. It then runs forward on the free edge of the tentorium for 1 to 2 cm before penetrating the dura of the tentorial attachment and entering the cavernous sinus. Within the lateral wall of the cavernous sinus, the nerve lies below the third cranial nerve and above the ophthalmic division (V1) of the fifth (trigeminal) nerve. It then crosses over the third nerve and receives filaments from the carotid sympathetic plexus. To reach the orbit the nerve enters through the superior orbital fissure above the annulus of Zinn. In company with the frontal and lacrimal branches of the ophthalmic division of the trigeminal nerve. It divides into several small fascicles that innervate the superior oblique muscle.
Pathology Graves'
Etiology Trauma is the commonest cause of a fourth nerve palsy. Head trauma can result in a contusion or hemorrhage of the tegmentum at the junction of the midbrain and pons. Because of the short course of the fourth nerve fascicle in the brainstem, distinguishing a nuclear from a fascicular fourth nerve palsy is virtually impossible. Damage to the descending sympathetic fibers from the hyperthalamus in the dorsal brainstem, causes a Horner's syndrome, and lesions of the trochlear nucleus or fascicle may be accompanied by a Horner's syndrome. For example, a right sided midbrain lesion causes damage to the right trochlear nucleus (resulting in a left fourth nerve palsy) and damage to descending sympathetic fibers results in a right Horner's syndrome. If the lesion affects the fascicle of the fourth nerve as it crosses the midline, then the Horner's syndrome is on the same side as the fourth nerve palsy.
Disease/Diagnosis Fourth Nerve Palsy; Graves Orbitopathy
Treatment 1. Occlusion 2. Prism glasses 3. Strabismus surgery only after the palsy has been stable for at least six months using one or a combination of the following procedures: a) Weakening of the ipsilateral inferior oblique (the antagonist of the affected superior oblique) b) Weakening of the contralateral inferior rectus (the yoke muscle of the affected superior oblique) c) Strengthening the affected superior oblique
References 1. Arruga J, DeRivas P, Espinet HL, Conesa G. Chronic isolated trochlear nerve palsy produced by intracavernous internal carotid artery aneurysm. J Clin Neuro-Ophthalmol 1991;11:104-108. 2. Brazis PW, Lee AG. Binocular vertical diplopia. Mayo Clin Proc 1998;73:55-66. 3. Cackett P, Fleck B, Mulhivill A. Bilateral fourth nerve palsy occurring after shaking injury in infancy. J AAPOS 2004;8:280-281. 4. Gentry LR, Mehta RC, Appen RE, Weinstein JM. MR imaging of primary trochlear nerve neoplasms. Am J Neuroradiol 1991;12:707-713. 5. Jacobson DM, Warner JJ, Choucair AK, Ptacek LJ. Trochlear nerve palsy following minor head trauma. A sign of structural disorder. J Clin Neuro-ophthalmol 1988;8:263-268. 6. Keane JR. Fourth nerve palsy: historical review and study of 215 inpatients. Neurology 1993; 43:2439-2443. 7. Leigh JR, Zee DS. Diagnosis of Peripheral Ocular Motor Palsies and Strabismus. Chp 9;385-474. In: The Neurology of Eye Movements, 4th Edition. Oxford University Press 2006. 8. Lepore FE. Disorders of ocular motility following head trauma. Arch Neurol 1995;52:924-926. 9. Richards BW, Jones FR, Younge BR. Causes and prognosis in 4,278 cases of paralysis of the oculomotor trochlear and abducens nerves. Am J Ophthalmol 1992;113:489-496. 10. Schievink WI, Mokri B, Garrity JA, Nichols DA, Piegras DG. Ocular motor nerve palsies in spontaneous dissection of the cervical internal carotid artery. Neurology 1993;43:1938-1941.
Relation is Part of 940-1
Contributor Secondary Ray Balhorn, Video Compressionist; Steve Smith, Videographer
Publisher Spencer S. Eccles Health Sciences Library, University of Utah
Date 1992
Type Image/MovingImage
Format video/mp4
Source 3/4" Umatic master videotape
Rights Management Copyright 2002. For further information regarding the rights to this collection, please visit:
Holding Institution Spencer S. Eccles Health Sciences Library, University of Utah, 10 N 1900 E SLC, UT 84112-5890
Collection Neuro-ophthalmology Virtual Education Library: NOVEL
Language eng
ARK ark:/87278/s6q26wrm
Setname ehsl_novel_shw
ID 188602
Reference URL