Fourth cranial nerve (trochlear nerve) palsy in children
- Andrew G Lee, MD
Andrew G Lee, MD
- Professor of Ophthalmology, Neurology, and Neurological Surgery
- Weill Cornell College of Medicine
- Paul W Brazis, MD
Paul W Brazis, MD
- Section Editor — Neuroophthalmology
- Professor of Neurology, Department of Ophthalmology
- Mayo Clinic College of Medicine
- Section Editors
- Evelyn A Paysse, MD
Evelyn A Paysse, MD
- Section Editor — Pediatric Ophthalmology
- Professor of Ophthalmology and Pediatrics
- Baylor College of Medicine
- Douglas R Nordli, Jr, MD
Douglas R Nordli, Jr, MD
- Section Editor — Pediatric Neurology
- Professor of Neurology and Pediatrics
- Northwestern University Feinberg School of Medicine
Paralytic strabismus or squint is caused by weakness or paralysis of one or more of the extraocular muscles. Dysfunction of the fourth cranial nerve (trochlear nerve) can result from lesions anywhere along its path between the fourth nerve nucleus in the midbrain and the superior oblique muscle within the orbit. These lesions can be congenital or acquired.
The manifestations and diagnosis of fourth nerve palsy, also known as superior oblique paralysis and trochlear nerve palsy, are reviewed here. Palsies of the third and sixth cranial nerves are discussed separately. (See "Third cranial nerve (oculomotor nerve) palsy in children" and "Sixth cranial nerve (abducens nerve) palsy in children".)
The fourth cranial nerve (trochlear nerve) has the longest intracranial course and is the only cranial nerve that has a dorsal exit from the brainstem (figure 1). It begins in the midbrain at the level of the inferior colliculus as fascicles extending from the fourth nerve nuclei. The trochlear nerves cross as they exit dorsally in the anterior medullary velum. The fourth nerve passes between the superior cerebellar artery and the posterior cerebral artery and runs in the subarachnoid space. It travels within the lateral wall of the cavernous sinus and enters the orbit via the superior orbital fissure to innervate the superior oblique muscle [1-10]. The primary action of the superior oblique muscle is intorsion of the eye, but it has additional eye movements of abduction and depression (table 1).
The long course of the fourth cranial nerve renders it particularly prone to injury from blunt head trauma or compression from changes in intracranial pressure, brain tumors, or swelling anywhere along its course. (See "Elevated intracranial pressure (ICP) in children".)
Children with fourth nerve palsies may complain of binocular (ie, present with both eyes open) vertical diplopia and/or subjective tilting of objects (torsional diplopia). This subjective torsion can be measured objectively with a double Maddox rod. The affected eye usually is extorted because the superior oblique muscle is an intorter of the eye. Objects viewed in primary position or especially in down-gaze may appear double (eg, when going down a flight of stairs so that the child does not know which step to select).
- Berlit P. Isolated and combined pareses of cranial nerves III, IV and VI. A retrospective study of 412 patients. J Neurol Sci 1991; 103:10.
- Burger LJ, Kalvin NH, Smith JL. Acquired lesions of the fourth cranial nerve. Brain 1970; 93:567.
- Coppeto JM, Lessell S. Cryptogenic unilateral paralysis of the superior oblique muscle. Arch Ophthalmol 1978; 96:275.
- Harley RD. Paralytic strabismus in children. Etiologic incidence and management of the third, fourth, and sixth nerve palsies. Ophthalmology 1980; 87:24.
- Keane JR. Fourth nerve palsy: historical review and study of 215 inpatients. Neurology 1993; 43:2439.
- Khawam E, Scott AB, Jampolsky A. Acquired superior oblique palsy. Diagnosis and management. Arch Ophthalmol 1967; 77:761.
- Richards BW, Jones FR Jr, Younge BR. Causes and prognosis in 4,278 cases of paralysis of the oculomotor, trochlear, and abducens cranial nerves. Am J Ophthalmol 1992; 113:489.
- RUCKER CW. Paralysis of the third, fourth and sixth cranial nerves. Am J Ophthalmol 1958; 46:787.
- Rucker CW. The causes of paralysis of the third, fourth and sixth cranial nerves. Am J Ophthalmol 1966; 61:1293.
- Rush JA, Younge BR. Paralysis of cranial nerves III, IV, and VI. Cause and prognosis in 1,000 cases. Arch Ophthalmol 1981; 99:76.
- von Noorden GK, Murray E, Wong SY. Superior oblique paralysis. A review of 270 cases. Arch Ophthalmol 1986; 104:1771.
- Holmes JM, Mutyala S, Maus TL, et al. Pediatric third, fourth, and sixth nerve palsies: a population-based study. Am J Ophthalmol 1999; 127:388.
- Helveston EM, Mora JS, Lipsky SN, et al. Surgical treatment of superior oblique palsy. Trans Am Ophthalmol Soc 1996; 94:315.
- Brazis PW. Palsies of the trochlear nerve: diagnosis and localization--recent concepts. Mayo Clin Proc 1993; 68:501.
- Astle WF, Rosenbaum AL. Familial congenital fourth cranial nerve palsy. Arch Ophthalmol 1985; 103:532.
- Botelho PJ, Giangiacomo JG. Autosomal-dominant inheritance of congenital superior oblique palsy. Ophthalmology 1996; 103:1508.
- Sydnor CF, Seaber JH, Buckley EG. Traumatic superior oblique palsies. Ophthalmology 1982; 89:134.
- Kushner BJ. The diagnosis and treatment of bilateral masked superior oblique palsy. Am J Ophthalmol 1988; 105:186.
- Younge BR, Sutula F. Analysis of trochlear nerve palsies. Diagnosis, etiology, and treatment. Mayo Clin Proc 1977; 52:11.
- Halpern JI, Gordon WH Jr. Trochlear nerve palsy as a false localizing sign. Ann Ophthalmol 1981; 13:53.
- Müller D, Neubauer BA, Waltz S, Stephani U. Neuroborreliosis and isolated trochlear palsy. Eur J Paediatr Neurol 1998; 2:275.
- Carter N, Miller NR. Fourth nerve palsy caused by Ehrlichia chaffeensis. J Neuroophthalmol 1997; 17:47.
- Rush JA, Shafrin F. Ocular myasthenia presenting as superior oblique weakness. J Clin Neuroophthalmol 1982; 2:125.
- Kim JH, Hwang JM, Hwang YS, et al. Childhood ocular myasthenia gravis. Ophthalmology 2003; 110:1458.
- Donahue SP, Lavin PJ, Hamed LM. Tonic ocular tilt reaction simulating a superior oblique palsy: diagnostic confusion with the 3-step test. Arch Ophthalmol 1999; 117:347.
- Ohashi T, Fukushima K, Chin S, et al. Ocular tilt reaction with vertical eye movement palsy caused by localized unilateral midbrain lesion. J Neuroophthalmol 1998; 18:40.
- Parulekar MV, Dai S, Buncic JR, Wong AM. Head position-dependent changes in ocular torsion and vertical misalignment in skew deviation. Arch Ophthalmol 2008; 126:899.
- Wong AM, Colpa L, Chandrakumar M. Ability of an upright-supine test to differentiate skew deviation from other vertical strabismus causes. Arch Ophthalmol 2011; 129:1570.
- Bixenman WW. Diagnosis of superior oblique palsy. J Clin Neuroophthalmol 1981; 1:199.
- Muthusamy B, Irsch K, Peggy Chang HY, Guyton DL. The sensitivity of the bielschowsky head-tilt test in diagnosing acquired bilateral superior oblique paresis. Am J Ophthalmol 2014; 157:901.
- CLINICAL MANIFESTATIONS
- DIFFERENTIAL DIAGNOSIS
- Restrictive vertical strabismus
- Other paretic vertical strabismus
- Myasthenia gravis
- Ocular tilt reaction and skew deviation
- Thyroid ophthalmopathy
- CLINICAL EVALUATION
- Unilateral fourth nerve palsy
- Bilateral fourth nerve palsies
- Measurement of torsion
- RADIOLOGIC EVALUATION
- ADDITIONAL EVALUATION
- SUMMARY AND RECOMMENDATIONS