Fourth Nerve Palsies

282 Clinical Pathways in Neuro-Ophthalmology, second edition

3.Pseudo-overaction of the superior oblique in the uninvolved eye may occur with spread of comitance. Secondary contracture of the superior rectus muscle in the involved eye may cause hypertropia involving the entire lower field of gaze. In a patient with a superior oblique muscle paralysis who habitually fixates with the paretic eye and in whom overaction of the ipsilateral inferior oblique muscle has developed, less than the normal amount of innervation will be required when the patient looks up and to the contralateral side. Because the innervation flowing to the opposite superior rectus is ‘‘determined’’ by the overacting ipsilateral inferior oblique (Hering’s law), the opposite superior rectus muscle will seem paretic (inhibitional palsy of the contralateral antagonist). In these cases, the head tilt test will correctly determine which of the two eyes is paretic.

4.Excyclotropia due to loss of incyclotorsion function of the superior oblique muscle. This torsion may be evident on fundus exam and can be measured using double Maddox rod testing. The excyclotropia is usually symptomatic in acquired cases but is often asymptomatic in congenital cases.

5.An anomalous head tilt eliminates the hypertropia or less commonly the cyclotropia. This head tilt is present in approximately 70% of patients and is usually away from the involved side but may be paradoxical (toward the involved side) in about 3%.

It is important to differentiate patients with decompensation of a congenital fourth nerve palsy (FNP) from those with an acquired FNP. In patients with congenital FNPs:

3.Large vertical fusional amplitudes (> 8 prism diopters) in primary gaze are characteristic of congenital cases.

4.Facial asymmetry (hypoplasia on side of head turn) suggests a congenital lesion.

Bilateral FNPs are suggested by the following:

1.A right hypertropia in left gaze and left hypertropia in right gaze (a reversing hypertropia).

2.A positive Bielschowsky test on tilt to either shoulder (‘‘double Bielschowsky test’’).

3.Large excyclotropia (> 10 degrees).

4.V-pattern esotropia (15 prism diopters or more difference in esotropia between upward and downward gaze). The V pattern is caused by a decrease of the abducting effect of the superior oblique(s) in depression and secondary overaction of the abducting effect of the inferior oblique muscle(s).

5.Underaction of both superior oblique muscles and=or overaction of both inferior oblique muscles on duction testing.

6.In general, bilateral FNPs tend to have a smaller hypertropia in primary position than do unilateral FNPs.

The criteria for the diagnosis of FNPs are listed in Table 12–1. FNP may be categorized as either isolated or nonisolated. For diagnostic classification based on topographic localization, nonisolated FNP may be grouped into the following four syndromes:

1.Midbrain (nucleus=fascicle syndrome) FNP

2.Subarachnoid space FNP

3.Cavernous sinus FNP

284 Clinical Pathways in Neuro-Ophthalmology, second edition

Table 12–2. The Localization of Trochlear Nerve Lesions

A: Lesions affecting the trochlear nucleus and=or fascicles (superior oblique palsy contralateral to lesions)

B: Lesions affecting the trochlear nerve within the subarachnoid space (superior oblique palsy usually ipsilateral to lesion unless mesencephalon compressed)

Source: Modified from Brazis, 2001, with permission from Lippincott Williams & Wilkins.

Is the FNP Caused by an Orbital Lesion?

Orbital lesions usually produce signs such as proptosis, chemosis, and orbital or conjunctival edema. Neuroimaging (preferably MRI) should be directed to the orbit (class II–III, level B).

We define six types of FNP, as shown in Table 12–4.

Table 12–3. Etiologies for a Fourth Nerve Palsy Based on Clinical Topographic Localization

Midbrain (nuclear=fascicular) (Elliot, 1991; Tho¨mke, 2000) Aplasia of the nucleus

Arteriovenous malformation (Gonyea, 1990; Kim, 1992) Demyelination (Jacobson, 1999)

Hemorrhage (Galetta, 1998; Kim, 1993; Mon, 1996; Mu¨ ri, 1995; Tachibana, 1990; Tho¨mke, 1999)

Ischemia=infarction (Kim, 1993; Tho¨mke, 1999; Ulrich, 1998) Tumor (e.g., glioma) (Barr, 1997; Landolfi, 1998; Mielke, 2001) Trauma (including surgical)

Sarcoidosis (Leiba, 1996)

Arachnoid cyst of quadrigeminal cistern (Ohtsuka, 1998) Subarachnoid space

Aneurysm (e.g., superior cerebellar artery) (Agostinis, 1992; Collins, 1992) Hydrocephalus

Infections (mastoiditis, meningitis) (Carter, 1997; Ferreira, 1997; Sadun, 1999) Wegener’s granulomatosis (Newman, 1995)

Sarcoidosis (Frohman, 2001)

Superficial siderosis of central nervous system (CNS) (Hashimoto, 1996; Shinmei, 1997) Post–lumbar puncture or spinal anesthesia

Pseudotumor cerebri (Lee, 1995; Patton, 2000; Speer, 1999)

Trauma, including surgical (Baker, 1991; Hara, 2001; Hoya, 2000; Jacobson 1995; Lepore, 1995; Sabates, 1991)

Neoplasm

Carcinomatous meningitis Cerebellar hemangioblastoma Ependymoma

Meningioma

Metastasis

Neurolemmoma=schwannoma (Feinberg, 1999; Gentry, 1991; Santoreneos, 1997) Pineal tumors

Trochlear nerve sheath tumors Fisher’s syndrome (Tanaka, 1998) Churg-Strauss syndrome (Vitali, 1996)

Cavernous sinus

Neoplasm (e.g., meningioma, pituitary adenoma) (Eisenberg, 1999; Keane, 1996; Petermann, 1999)

Infectious: herpes zoster (Chang-Godinich, 1997), mucormycosis (Keane, 1996) Inflammation: Tolosa-Hunt syndrome, Wegener’s granulomatosis (Herman, 1999)

Internal carotid artery aneurysm (Arruga, 1991; FitzSimon, 1995; Hahn, 2000; Keane, 1996; Shimo-oku, 1998)

Dural carotid-cavernous sinus fistula (Tsai, 2000) Superior ophthalmic vein thrombosis (Polito, 1996) Foramen ovale electrode placement (Herrendorf, 1997)

Balloon test occlusion of cervical internal carotid artery (Lopes, 1998)

(continued)

286 Clinical Pathways in Neuro-Ophthalmology, second edition

Table 12–3. (continued)

Orbit Neoplasm Infection Infiltration

Waldenstro¨m’s macroglobulinemia Inflammation (orbital pseudotumor) Progressive systemic sclerosis Trauma (orbital floor fracture)

Other

Migraine (Wong, 1996)

Congenital (Botelho, 1996; Holmes, 1999)

Congenital unmasked by botulinum toxin therapy for cervical torticollis) (Varrato, 2000)

Cephalic tetanus (Orwitz, 1997)

Table 12–4. Definitions of the Six Types of Fourth Nerve Palsy (FNP)

Type 1: nonisolated

FNPs are considered nonisolated in the presence of the following features: Other neurologic or neuro-ophthalmologic signs

Evidence to suggest myasthenia gravis such as ptosis, or fatigability of the motility deficit Evidence for systemic inflammatory disorders such as giant cell arteritis

Type 2: traumatic

Isolated, unilateral, or bilateral FNPs that have a clearly established temporal relationship to previous head trauma and do not progress are considered traumatic in origin; patients have no other neurologic deficits other than those associated with the initial

traumatic event Type 3: congenital

Congenital FNPs may show the following:

Large vertical fusional amplitudes (greater than 8 prism diopters) Facial asymmetry or sternocleidomastoid muscle hypertrophy

Long-standing anomalous head position that may be present in old photographs Type 4: vasculopathic

Vasculopathic FNPs occur in patients older than 50 years of age with or without known hypertension or diabetes, or in younger patients with known vasculopathic risk factors

Type 5: nonvasculopathic

Patients without vasculopathic risk factors and not classified as any of the above types are classified nonvasculopathic FNP

Type 6: progressive or unresolved

FNPs that worsen after the acute stage (greater than 1 week) as defined by a significant increase in the measured ocular vertical deviation are considered to be progressive, and patients without improvement in the measured ocular vertical deviation after 6 to 8 weeks are considered unresolved

*Patient developed progression of deviation after 2 years.

disease over an extensive follow-up period. Although type 5 patients who improve may not require neuroimaging, the clinical certainty of such a recommendation is not sufficiently strong in our opinion to obviate the need for neuroimaging in these nonvasculopathic patients (class III, level U). However, neuroimaging should be considered for patients who do not improvement in 2 months (class III, level C). Some reports have described aneurysm as an extremely rare cause for isolated FNP (Agostinis, 1992; Arruga, 1991; Collins, 1992; Richards, 1992; Rucker, 1956; Rush, 1981), and cerebral angiography is not recommended unless an aneurysm is suggested by other neuroimaging studies (class III, level B). Agostinis et al and Collins et al reported isolated FNP due to superior cerebellar aneurysms, but both patients described headaches (Agostinis, 1992; Collins, 1992). In these cases, neuroimaging studies confirmed the presence of the aneurysm before angiography. There are insufficient data to make a comment on the usefulness of MR angiography in FNP (class III–IV, level U).

Although MR scans are generally felt to be a more sensitive and specific than CT in the evaluation of cranial neuropathies, no conclusive evidence demonstrates an increased yield from performing an MR scan rather than a CT scan for the specific evaluation of FNP. Richards et al reported an etiologic diagnosis in 69 of 144 (48%) FNP using MRI and in 289 of 684 (42%) cases using CT. These authors felt that ‘‘multiplanar CT may be a sufficient noninvasive study, especially when clinical suspicion is high . . .

[or] in patients with other neurologic findings’’ (Richards, 1992). Nevertheless, we believe that MRI is the study of choice for patients with FNP (class II–III, level B).

A number of cases have been reported in the literature documenting intracranial lesions in patients with FNP. Table 12–6 summarizes 86 cases of ‘‘isolated’’ FNP due to

Figure 12–1. Evaluation of fourth nerve palsy (FNP).

an intracranial lesion. Of these 86 patients, only five (5.8%) did not have other neurologic signs or symptoms and thus would be considered truly isolated by our criteria. One developed other neurologic signs after a short follow-up period, and in the remaining four patients persistence or progression of symptoms would have eventually resulted in a neuroimaging study. Of the remaining 81 patients, six had headache or

292 Clinical Pathways in Neuro-Ophthalmology, second edition

pain (7%), 31 had other neurologic signs (38%), and the clinical information was insufficient to determine if the FNP was truly isolated in 44 patients (54%). Keane reported intracranial tumor as an etiology in 12 of 95 unilateral cases, but all 12 (100%) had other neuro-ophthalmic signs, and none of 81 isolated FNP later reported by Keane had an intracranial tumor (Keane, 1993). This would suggest that the yield for evaluation of an isolated FNP is low (class III, level C).

All patients with progressive FNP (type 6) should undergo neuroimaging (preferably MRI). Lumbar puncture should be considered if neuroimaging is normal or if there are signs or symptoms of meningeal irritation (class III, level C).

An approach to FNP is outlined in Figure 12–1.

References

Agostinis C, Caverni L, Moschini L, et al. (1992). Paralysis of fourth cranial nerve due to superior cerebellar artery.

Neurology 42:457–458.

Arruga J, De Rivas P, Espinet HL, et al. (1991). Chronic isolated trochlear nerve palsy produced by intracavernous internal carotid artery aneurysm: report of a case. J Clin Neuro-ophthalmol 11:104–108.

Baker RS, Epstein AD. (1991). Ocular motor abnormalities from head trauma. Surv Ophthalmol 35:245–267. Barr DB, McFadzean RM, Hadley D, et al. (1997). Acquired bilateral superior oblique palsy: a localizing sign in the

dorsal midbrain syndrome. Eur J Ophthalmol 7:271–276.

Berlit P. (1991). Isolated and combined pareses of cranial nerves III, IV, and VI: a retrospective study of 412 patients. J Neurol Sci 103:10–15.

Boggan JE, Rosenblum ML, Wilson CB. (1979). Neurilemmoma of the fourth cranial nerve. J Neurosurg 50:519–521. Botelho PJ, Giangiacomo JG. (1996). Autosomal-dominant inheritance of congenital superior oblique palsy.

Ophthalmology 103:1508–1511.

Brazis PW. (1993). Palsies of the trochlear nerve: diagnosis and localization-recent concepts. Mayo Clin Proc 68:501. Brazis PW, Masdeu JC, Biller J. (2001). Localization in Clinical Neurology. 4th ed. Philadelphia, Lippincott Williams &

Wilkins.

Burde RM, Savino PJ, Trobe JD. (1992). Clinical Decisions in Neuro-ophthalmology. 2nd ed. St. Louis, Mosby Year Book, pp. 289–311.

Burger LJ, Kalvin NH, Smith JL. (1970). Acquired lesions of the fourth cranial nerve. Brain 93:567–574. Carter N, Miller NR. (1997). Fourth nerve palsy caused by Ehrlichia chaffeensis. J Neuro-Ophthalmol 17:47–50.

Celli P, Ferrante L, Acqui M, et al. (1992). Neurinoma of the third, fourth, and sixth cranial nerves: a survey and report of a new fourth nerve case. Surg Neurol 38:216–224.

Chang-Godinich A, Lee AG, Brazis PW, et al. (1997). Complete ophthalmoplegia after zoster ophthalmicus. J Neuro-Ophthalmol 17:262–265.

Collins TE, Mehalic TF, White TK, et al. (1992). Trochlear nerve palsy as the sole initial sign of an aneurysm of the superior cerebellar artery. Neurosurgery 30:258–261.

Coppeto JM, Lessell S. (1978). Cryptogenic unilateral paralysis of the superior oblique muscle. Arch Ophthalmol 96:275–277.

Eisenberg MB, Al-Mefty O, DeMonte F, Burson GT. (1999). Benign nonmeningeal tumors of the cavernous sinus.

Neurosurgery 44:949–955.

Elliot D, Cunningham Jr ET, Miller NR. (1991). Fourth nerve paresis and ipsilateral relative afferent pupillary defect without visual sensory disturbance: a sign of contralateral dorsal midbrain disease. J Clin Neuroophthalmol 11:169–172.

Ellis FD, Helveston EM. (1976). Superior oblique palsy: diagnosis and classification. Int Ophthalmol Clin 16:127–135.

Feinberg AS, Newman NJ. (1999). Schwannoma in patients with isolated trochlear nerve palsy. Am J Ophthalmol 127:183–188.

Ferreira R, Phan G, Bateman JB. (1997). Favorable visual outcome in cryptococcal meningitis. Am J Ophthalmol 124:558–560.

FitzSimon JS, Toland J, Philips J, et al. (1995). Giant aneurysms in the cavernous sinus. Neuro-ophthalmology 15:59–65.

Frohman LP, Grigorian R, Bielory L. (2001). Neuro-ophthalmic manifestations of sarcoidosis: clinical spectrum, evaluation, and management. J Neuro-Ophthalmol 21:132–137.

Galetta SL, Balcar LJ. (1998). Isolated fourth nerve palsy from midbrain hemorrhage. Case report. J NeuroOphthalmol 18:204–205.

Gentry LR, Mehta RC, Appen RE, et al. (1991). MR imaging of primary trochlear nerve neoplasms. AJNR 12:707– 713.

Gonyea EF. (1990). Superior oblique palsy due to a midbrain vascular malformation. Neurology 40:554–555. Green WR, Hackett ER, Schlezinger NS. (1964). Neuro-ophthalmic evaluation of oculomotor nerve paralysis.

Arch Ophthalmol 72:154–167.

Hahn CD, Nicolle DA, Lownie SP, Drake CG. (2000). Giant cavernous carotid artery aneurysms: clinical presentation in fifty-seven cases. J Neuro-Ophthalmol 20:253–258.

Hara N, Kan S, Simizu K. (2001). Localization of post-traumatic trochlear nerve palsy associated with hemorrhage at the subarachnoid space by magnetic resonance imaging. Am J Ophthalmol 132:443–445.

Harley RD. (1980). Paralytic strabismus in children: etiologic incidence and management of the third, fourth, and sixth nerve palsies. Ophthalmology 87:24–43.

Hashimoto M, Hoyt WF. (1996). Superficial siderosis and episodic fourth nerve paresis. Report of a case with clinical and magnetic resonance imaging findings. J Neuro-Ophthalmol 16:277–280.

Herman M, Bobek-Billewicz B, Bullo B, et al. (1999). Wegener’s granulomatosis with unusual cavernous sinus and sella turcica extension. Eur Radiol 9:1859–1861.

Herrendorf G, Steinhoff BJ, Vadokas V, et al. (1997). Transitory fourth cranial nerve palsy due to foramen ovale electrode placement. Acta Neurochur 139:789–790.

Ho KL. (1981). Schwannoma of the trochlear nerve. J Neurosurg 55:132–135.

Holmes JM, Mutyala S, Maus TL, et al. (1999). Pediatric third, fourth, and sixth nerve palsies: a population-based study. Am J Ophthalmol 127:388–392.

Hoya K, Kirino T. (2000). Traumatic trochlear nerve palsy following minor occipital impact—four case reports.

Neurol Med Chir 40:358–360.

Jacobson DM, Moster ML, Eggenberger ER, et al. (1999). Isolated trochlear nerve palsy in patients with multiple sclerosis. Neurology 53:877–879.

Jacobson DM, Warner JJ, Choucair AK, et al. (1988). Trochlear nerve palsy following minor head trauma: a sign of structural disorder. J Clin Neuro-ophthalmol 8:263–268.

Jacobson DM, Warner JJ, Ruggles KH. (1995). Transient trochlear nerve palsy following anterior temporal lobectomy for epilepsy. Neurology 45:1465.

Khawam E, Scott AB, Jampolsky A. (1967). Acquired superior oblique palsy. Arch Ophthalmol 77:761–768. Keane JR. (1993). Fourth nerve palsy: historical review and study of 215 patients. Neurology 43:2439–2443. Keane JR. (1996). Cavernous sinus syndrome. Analysis of 151 cases. Arch Neurol 53:967–971.

Kim JS, Kang JK. (1992). Contralateral trochlear nerve palsy and facial sensory change due to a probable brainstem vascular malformation. Neuro-ophthalmology 12:59–62.

Kim JS, Kang JK, Lee SA, et al. (1993). Isolated or predominant ocular motor nerve palsy as a manifestation of brain stem stroke. Stroke 24:581–586.

King JS. (1976). Trochlear nerve sheath tumor. J Neurosurg 44:245–247.

Krohel GB, Mansour AM, Petersen WL, et al. (1982). Isolated trochlear nerve palsy secondary to a juvenile pilocytic astrocytoma. J Clin Neuro-Ophthalmol 2:119–123.

Ksiazek S, Behar R, Savino PJ, et al. (1988). Isolated acquired fourth nerve palsies. Neurology 38(suppl 1):246. Landolfi JC, Thaler HT, De Angelis LM. (1998). Adult brainstem gliomas. Neurology 51:1136–1139.

Lee AG. (1995). Fourth nerve palsy in pseudotumor cerebri. Strabismus 3:57–59.

Leiba H, Siatkowski RM, Culbertson WW, Glaser JS. (1996). Neurosarcoidosis presenting as an intracranial mass in childhood. J Neuro-ophthalmol 16:269–273.

Lepore FE. (1995). Disorders of ocular motility following head trauma. Arch Neurol 52:924–926.

Leunda G, Vaquero J, Cabezudo J, et al. (1982). Schwannoma of the oculomotor nerves: report of four cases. J Neurosurg 57:563–565.

Lopes DK, Mericle RA, Wakhloo AK, et al. (1998). Cavernous sinus syndrome during balloon test occlusion of the cervical internal carotid artery. Report of two cases. J Neurosurg 89:667–670.

Mansour AM, Bailey BJ. (1997). Ocular findings in Ramsay Hunt syndrome. J Neuro-Ophthalmology 17:199–201.

McKinna AJ. (1983). Eye signs in 611 cases of posterior fossa aneurysms: their diagnostic and prognostic value.

Can J Ophthalmol 18:3–6.

Mielke C, Alexander MSM, Anand N. (2001). Isolated bilateral trochlear nerve palsy as the first clinical sign of a metastatic bronchial carcinoma. Am J Ophthalmol 132:593–594.

Miller NR. (1989). Walsh and Hoyt’s Clinical Neuro-ophthalmology. 4th ed. Baltimore, Williams & Wilkins, p. 686.

294 Clinical Pathways in Neuro-Ophthalmology, second edition

Mittleman D, Folk E. (1976). The evaluation and treatment of superior oblique muscle palsy. Trans Am Acad Ophthalmol Otolaryngol 81:893–898.

Mon Y. (1996). Midbrain hemorrhage presenting with trochlear nerve palsy—-a case report. Rinsho Shinkeigaki 36:71–73.

Mu¨ ri RM, Baumgartner RW. (1995). Horner’s syndrome and contralateral trochlear nerve palsy. Neuroophthalmology 15:161.

Neetens A, Van Aerde F. (1981). Extra-ocular muscle palsy from minor head trauma. Initial sign of intracranial tumor. Bull Soc Belge Ophthalmol 193:161–167.

Nemet P, Godel V, Baruch E, et al. (1980). Benign palsy of the superior oblique. J Pediatr Ophthalmol Strabismus 17:320–322.

Newman NJ, Slamovits, Friedland S, et al. (1995). Neuro-ophthalmic manifestations of meningocerebral inflammation from the limited form of Wegener’s granulomatosis. Am J Ophthalmol 120:613–621.

Orwitz JI, Galetta SL, Teener JW. (1997). Bilateral trochlear nerve palsy and downbeat nystagmus in a patient with cephalic tetanus. Neurology 9:894–895.

Ohtsuka K, Hashimoto M, Nakamura Y. (1998). Bilateral trochlear nerve palsy with arachnoid cyst of the quadrigeminal cistern. Am J Ophthalmol 125:268–270.

Patton N, Beatty S, Lloyd IC. (2000). Bilateral sixth and fourth cranial nerve palsies in idiopathic intracranial hypertension. J R Soc Med 93:80–81.

Petermann SH, Newman NJ. (1999). Pituitary macroadenoma manifesting as an isolated fourth nerve palsy. Am J Ophthalmol 127:235–236.

Polito E, Leccisotti A. (1996). Painful ophthalmoplegia caused by superior ophthalmic vein thrombosis. Neuroophthalmology 16:189–192.

Reich KA, Giansiracusa DR, Strongwater SL. (1990). Neurologic manifestations of giant cell arteritis. Am J Med 89:67–72.

Richards BW, Jones FR Jr, Younge BR. (1992). Causes and prognosis in 4,278 cases of paralysis of the oculomotor, trochlear, and abducens cranial nerves. Am J Ophthalmol 113:489–496.

Robb RM. (1990). Idiopathic superior oblique palsies in children. J Pediatr Ophthalmol Strabismus 27:66–69. Robert CM, Geigenbaum JA, Stern WE. (1973). Ocular palsy occurring with pituitary tumors. J Neurosurg

38:17–19.

Rucker CW. (1958). Paralysis of the third, fourth and sixth cranial nerves. Am J Ophthalmol 46:787–794.

Rucker CW. (1966). The causes of paralysis of the third, fourth, and sixth cranial nerves. Am J Ophthalmol 61:1293–1298.

Rucker C, Dyer J, Smith D, et al. (1956). The causes of acquired paralysis of the ocular muscles. Am J Ophthalmol 41:951–955.

Rush JA, Younge BR. (1981). Paralysis of cranial nerves III, IV, and VI. Arch Ophthalmol 99:76–79.

Sabates NR, Gonce MA, Farris BK. (1991). Neuro-ophthalmological findings in closed head trauma. J Clin Neuroophthalmol 11:273–277.

Sadun F, De Negri AM, Santopadre P, Pezzi PP. (1999). Bilateral trochlear nerve palsy associated with cryptococcal meningitis in human immunodeficiency virus infection. J Neuro-Ophthalmol 19:118–119.

Santoreneos S, Hanieh A, Jorgensen RE. (1997). Trochlear nerve schwannomas occurring in patients without neurofibromatosis: case report and review of the literature. Neurosurgery 41:282–287.

Scully RE, Galdabini JJ, McNeely BU. (1976). Case records of the Massachusetts General Hospital: weekly clinicopathological exercises. Case 36-1976. N Engl J Med 295:553–561.

Shimo-oku M, Izaki A, Shim-myo A. (1998). Fourth nerve palsy as an initial sign of internal carotid-posterior communicating artery aneurysm. Neuro-ophthalmology 19:185–190.

Shinmei Y, Harada T, Ohashi T, et al. (1997). Trochlear nerve palsy associated with superficial siderosis of the central nervous system. Japanese J Ophthalmol 41:19–22.

Shrader EC, Schlezinger NS. (1960). Neuro-ophthalmologic evaluation of abducens nerve paralysis. Arch Ophthalmol 63:84–91.

Slavin ML. (1987). Isolated trochlear nerve palsy secondary to cavernous sinus meningioma. Am J Ophthalmol 104:433–434.

Speer C, Pearlman J, Phillips PH, et al. (1999). Fourth nerve palsy in pediatric pseudotumor cerebri. Am J Ophthalmol 127:236–237.

Suzuki J, Wada T, Kowada M. (1962). Clinical observations on tumors of the pineal region. J Neurosurg 19:441–445.

Tachibana H, Mimura O, Shiomi M, et al. (1990). Bilateral trochlear nerve palsies from a brainstem hematoma. J Clin Neuro-ophthalmol 10:35–37.

Tanaka H, Yuki N, Hirata K. (1998). Trochlear nerve enhancement on three-dimensional magnetic resonance imaging in Fisher syndrome. Am J Ophthalmol 126:322–324.

Tho¨mke F, Hopf HC. (2000). Isolated superior oblique palsies with electrophysiologically documented brainstem lesions. Muscle Nerve 23:267–270.

Tho¨mke F, Ringel K. (1999). Isolated superior oblique palsies with brainstem lesions. Neurology 53:1126–1127. Tsai RK, Chen HY, Wang HZ. (2000). Painful fourth cranial nerve palsy caused by posteriorly-draining dural

carotid-cavernous sinus fistula. J Formosan Med Assoc 99:730–732.

Ulrich A, Kaiser HJ. (1998). Bilateral trochlear nerve palsy in systemic lupus erythematosus (SLE). Neuroophthalmology 20:28.

Vanooteghem P, Dehaene I, Van Zandycke M, et al. (1992). Combined trochlear nerve palsy and internuclear ophthalmoplegia. Arch Neurol 49:108–109.

Varrato J, Galetta S. (2000). Fourth nerve palsy unmasked by botulinum toxin therapy for cervical torticollis.

Neurology 55:896.

Vitali C, Genovesi-Ebert F, Romani A, et al. (1996). Ophthalmological and neuro-ophthalmological involvement in Churg-Strauss syndrome: a case report. Graefes Arch Clin Exp Ophthalmol 234:404–408.

von Noorden GK, Helveston EM. (1994). Strabismus: A Decision Making Approach. St. Louis, Mosby, pp. 162–169. von Noorden GK, Murray E, Wong SY. (1986). Superior oblique paralysis. A review of 270 cases. Arch Ophthalmol

104:1771–1776.

Wise BL, Palubinskas AJ. (1965). Persistent trigeminal artery (carotid-basilar anastomosis). J Neurosurg 21:199–206. Wong AMF, Sharpe JA. (1996). Fourth nerve palsy in migraine. Neuro-Ophthalmology 16:51–54.

Wray SH. (1977). Neuro-ophthalmologic manifestations of pituitary and parasellar lesions. Clin Neurosurg 24:86–117.

Wright HG, Hansotia P. (1977). Isolated fourth cranial nerve palsies: etiology and prognosis. Wis Med J 76:26–28. Yamamoto M, Jimbo M, Ide M, et al. (1987). Trochlear neurinoma. Surg Neurol 28:287–290.

Younge BR, Sutula F. (1977). Analysis of trochlear nerve palsies. Mayo Clin Proc 52:11–18.