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Home , Management of strabismus, Nystagmus, Sixth nerve palsy

COMPREHENSIVE UPDATE VOLUME 7, NUMBER 5 SEPTEMBER-OCTOBER 2006 CLINICAL PRACTICE

Sixth Nerve Palsy

THOMAS J. O’DONNELL, MD, AND EDWARD G. BUCKLEY, MD

Abstract. The diagnosis and etiologies of sixth cranial nerve palsies are reviewed along with non- surgical and surgical treatment approaches. Surgical options depend on the function of the paretic muscle, the field of greatest symptoms, and the likelihood of inducing in additional fields by a given procedure. (Comp Ophthalmol Update 7: xx-xx, 2006) Key words. (Botox®) • etiology • (paresis)

Introduction of the cases, the patients had and/or, less frequently, Sixth cranial nerve (abducens) palsy ; 26% were undetermined, is a common cause of acquired 5% had a , and 2% had an horizontal diplopia. Signs pointing . It was noted that patients toward the diagnosis are an who had an aneurysm or neoplasm abduction deficit and an had additional neurologic signs or increasing with gaze toward the side symptoms or were known to have a of the deficit (Figure 1). The diplopia cancer.2 is typically worse at distance. Measurements are made with the Anatomical Considerations uninvolved eye fixing (primary deviation), and will be larger with the The sixth cranial nerve nuclei are involved eye fixing (secondary located in the lower pons beneath the deviation). A small vertical deficit may fourth ventricle. The nerve on each accompany a sixth nerve palsy, but a side exits from the ventral surface of deviation over 4 prism diopters the pons. It passes from the posterior Dr. O’Donnell is affiliated with the should raise the question of cranial fossa to the middle cranial University of Tennessee Health Sci- additional , such as a fourth fossa, ascends the clivus, and passes ence Center, Memphis, TN. Dr. cranial nerve palsy or skew under the petro-clinoid ligament in Buckley is affiliated with the Duke deviation.1 Dorello’s canal. It then enters the University Eye Center, Durham, NC. In a recent population-based study cavernous sinus where, unlike its that reviewed 137 patients spanning fellow , it is Reprint address: Edward G. Buckley, a 15-year period, the sex incidence unsupported by the dural wall of the MD, Duke University Eye Center, was equal, the annual incidence was sinus. It passes through the superior Box 3802, Durham, NC 27710 11.3/100,000, and the peak incidence orbital fissure and into the email: [email protected] was in the seventh decade. In 35% through the annular ligament of the

© 2006 by Comprehensive Ophthalmology Update, LLC. All rights reserved. 1 2 Comp Ophthalmol Update 7 (5) September-October 2006 O’DONNELL

Fig. 1. Patient with a microvascular right sixth nerve palsy. Note the lack of abduction of the right eye.

Fig. 2. Patient with a right carotid artery aneurysm in the cavernous sinus causing a right sixth nerve palsy with a right Horner syndrome. Note the lack of abduction of the right eye, , and . rectus muscles, and then to the lateral additional neurologic or ocular signs) found a strong association with both rectus. is a common presentation (Table 2). diabetes and coexistent diabetes and Although shorter in length than the Traditionally, adults over 50 years of hypertension, but not with fourth cranial nerve, the course of age presenting with isolated sixth hypertension alone.8 Scott reviewed the sixth nerve leaves it vulnerable to nerve palsy and with vasculopathic the long-term outcome of 59 a variety of insults.3 Lesions in the risk factors (diabetes, hypertension) patients with vasculopathic sixth pons may be associated with may be observed without imaging nerve palsy and reported that 86% internuclear ophthalmoplegia, for 3 months, as a microvascular had complete resolution of the palsy, ipsilateral horizontal gaze palsy, and etiology is common. Warwar recently and that five of eight patients with contralateral long tract signs presented a case of a 68-year-old incomplete resolution were (weakness), as well as the possible man with vasculopathic risks who asymptomatic. He cautioned, involvement of cranial nerves V, VII, presented with an isolated sixth nerve however, that almost one-third of and VIII (Table 1). After exiting the palsy secondary to pituitary apoplexy.6 these patients had at least one pons, the nerve is susceptible to The patient developed a third cranial recurrent episode.9 An MRI should increases in from nerve palsy a few days after be performed in younger adults with a variety of causes. Petrous bone presentation, went into cardiac arrest, isolated sixth nerve palsy, and in all trauma or inflammation may be and died. The author recommended patients with sixth nerve palsy associated with decreased hearing, that neuroimaging be considered in accompanied by additional cranial facial , numbness, or patients with isolated sixth nerve nerve or other neurologic findings. hemotympanum. Cavernous sinus palsy, even in the presence of a strong The studies by Warwar and Bendszus lesions or superior orbital fissure vasculopathic history. raise controversy about whether to lesions are highlighted by fellow A prospective study of 43 patients image all patients with acute sixth cranial nerve palsies or Horner (ages 2–82, mean age = 48) with nerve palsy. syndrome (Figure 2). A sixth nerve isolated sixth nerve palsies by Patients with bilateral or nonisolated palsy with proptosis and conjunctival Bendszus identified 63% with lesions sixth nerve palsy should have an inflammation points toward an considered relevant to the palsy on MRI, medical work-up, and lumbar orbital process.4,5 MRI.7 Of these patients, 49% had puncture. Accompanying neurologic tumor or tumor-like lesions. Repeat deficits may point toward areas of Clinical Considerations MRI at 3–6 months was normal in the to focus on as discussed all patients with initial normal MRIs. above. Infectious etiologies, such as An isolated sixth nerve palsy (no The authors recommended MRI in botulism or cytomegalovirus (CMV), all patients presenting with acute sixth neoplasm (nasopharyngeal cancer), or nerve palsy, even with a inflammatory causes, such as Focus Point #1 vasculopathic history. Guillain-Barre syndrome, should be Patel, in a study of 76 patients with kept in mind.10 An esotropia increasing to one side may indicate a subtle sixth isolated nontraumatic sixth nerve Pain with a sixth nerve palsy is nerve palsy. palsy without a suspected systemic nonspecific. A microvascular sixth etiology other than microvascular, nerve palsy may or may not be SIXTH NERVE PALSY 3 Table 1 Table 2 Location and Signs of Cranial Nerve Six Lesions Etiology of Cranial Six Nerve Lesions

Site of Lesion Affecting Cranial Nerve VI Possible Associated Signs/Symptoms Adult

Pons/brainstem Horizontal gaze palsy Microvascular: age 50, vasculopathic risks Internuclear ophthalmoplegia Trauma Involvement of cranial nerves V, VII, Neoplasm VIII Infection (meningitis) Contralateral weakness Inflammation Increased intracranial pressure Aneurysm Cerebello-pontine angle Involvement of cranial nerves VII, VIII Pituitary apoplexy Cerebellar signs, nystagmus Idiopathic

Subarachnoid course Signs of increased intracranial Child pressure Postviral illness Petrous bone Involvement of cranial nerves V, VII, Trauma VIII Neoplasm Ear infections, Infection (meningitis) Inflammation Cavernous sinus/superior orbital fissure Involvement of cranial nerves III, IV, Increased intracranial pressure V(1) or sympathetics to pupi (i.e., Congenital (Duane, Mobius) Horner syndrome) Aneurysm Idiopathic Orbit Proptosis Conjunctival inflammation, chemosis

accompanied by pain. An etiology of sixth nerve palsy in 75 frequent cause of sixth nerve palsies inflammatory etiology, such as children.11 In contrast, Holmes, in a in children (Tables 2 and 3). Tolosa-Hunt syndrome, is painful population-based study of cranial and typically responds quickly to nerve palsies in children, found no Differential Diagnosis steroids. Other etiologic cases of neoplasia with isolated considerations would include palsies.12 An abduction deficit may be aneurysm, bone , and A sixth nerve palsy secondary to secondary to poor function due to ophthalmoplegic migraine. chronic infections and cranial nerve palsy, mechanical A child may develop a sixth nerve mastoiditis is less commonly seen restriction, a disease process affecting palsy following a viral illness, and the with current antibiotics and muscular function, or a congenital role of MRI in children with isolated immunizations. Pseudotumor cerebri disorder (Table 4). Restriction of the sixth nerve palsy is controversial. can be seen in children, and may be medial rectus may be the direct result Neuroimaging is recommended in a accompanied by a sixth nerve palsy. of medial orbital wall trauma, and a child with persistent, bilateral, or sixth Duane and Mobius syndromes have “tight” medial rectus may occur with nerve palsy accompanied by other abduction defects, but the deficits are time with any palsy of the lateral neurologic signs or symptoms. At a associated with other signs (palpebral rectus. Thyroid and tertiary referral center, Lee found fissure narrowing in the former, orbital inflammatory disease may neoplasm or neoplasm-related facial paresis in the latter). Trauma, result in restriction of extraocular to be the most common unfortunately, continues to be a muscles, but are typically

Fig. 3. Top: Patient with left sixth nerve palsy. Bottom: 2 weeks after botulinum toxin was injected into the left medial rectus. Note the decreased adduction and the increased abduction of the left eye from the botulinum toxin. 4 Comp Ophthalmol Update 7 (5) September-October 2006 O’DONNELL

Focus Point #2

One-third of patients with vasculopathic sixth nerve palsies may have recurrences.

Nonsurgical Treatment

Nonsurgical approaches include patching to avoid diplopia, prisms, botulinum toxin (Botox® [Allergan, Inc., Irvine, CA]) injection of the ipsilateral medial rectus, and steroids Fig. 4. Top: Patient with a mild right sixth nerve palsy. Bottom: Postoperative if the etiology is inflammatory. The photograph after a left medial rectus Faden operation. patient should be followed regularly to observe for improvement or worsening of the deviation. A accompanied by characteristic signs clinical suspicion is high. Single muscle worsening deviation may indicate and symptoms, such as proptosis, fiber electromyography (EMG) may ipsilateral medial rectus contraction, injection over the rectus muscle be the best test for a definitive and would be an indication for a insertions, lid retraction, and lid lag. diagnosis of myasthenia. It is very work-up to rule out a progressive Forced duction testing may be sensitive; however, it is not specific lesion. helpful to rule out a restrictive for myasthenia.13 Patching is an effective way to etiology for an abduction deficit. Spasm of the near reflex can temporarily relieve symptoms of is always an simulate an abduction deficit. The diplopia, and can be accomplished etiologic consideration with the acute convergence is associated with miotic with a standard eye patch or with the onset of . A history of , and ductions are full with one use of opaque tape on the patient’s variability is a red flag for this eye occluded. spectacles. Patching the palsied eye is diagnosis. The ice test and rest test Divergence paresis or divergence generally more comfortable for the are useful office procedures to look insufficiency with a comitant patient to decrease past-pointing and for functional improvement in esodeviation greater at distance than disorientation. patients with myasthenia. The near (or none at near), and with Prisms are often not effective due acetylcholine receptor antibody test decreased divergence fusional to the incomitance of the deviation, is negative in nearly half of patients amplitudes can also simulate a sixth but can be tried for small deviations with solely . nerve weakness. Divergence paresis or postoperatively if needed. A trial Tensilon testing may give a false- has little localizing value. There is with a Fresnel Press On Prism (The negative result, and repeat testing may controversy about whether these Fresnel Prism and Co., LLC, be needed if the test is negative and patients should have an MRI.14 Eden Prairie, MN) is an inexpensive

Fig. 5. Top: Patient with a complete right sixth nerve palsy. Bottom: Postoperative photograph after a transposition of the right superior and inferior rectus to the lateral rectus insertion. SIXTH NERVE PALSY 5 Table 3 Table 4 Evaluation Differential Diagnosis of an Abduction Deficit Age Isolated 6th Nerve Palsy Bilateral/Nonisolated Cranial six nerve palsy Pediatric Follow vs. MRI* MRI Myasthenia gravis Restrictive: trauma (orbital fracture), Adult < 50 MRI/med eval/lumber Same thyroid eye disease, inflammation puncture Congenital: Duane, Mobius, congenital Adult > 50 Med eval, +/- MRI* MRI/med eval/ esotropia Spasm of near reflex *Controversy about following vs. obtaining early neuroimaging; imaging should at least Divergence paresis (divergence be obtained if palsy is persistent. insufficiency) Med eval = medical evaluation; MRI = magnetic resonance imaging

way to see if a prism is effective and patients.16 Biglan reported that 7 of the function of the paretic muscle, tolerated, and allows simple power 16 patients with sixth nerve palsy the field(s) of diplopic symptoms, adjustments. were controlled by Botox®, and that and the likely secondary effects of a The role of Botox® for acute sixth patients with long-standing or severe procedure. Surgical procedures are nerve palsy remains unsettled (Figure palsy did not get as positive a result generally considered at the 6-month 3). It has been used to attempt to as patients with more acute palsies time frame, since most sixth nerve prevent or reduce the contracture of or with better lateral rectus palsies that improve will have the antagonist medial rectus, and also function.17 In a study of nine children recovered by that time. If the palsy to treat small postoperative with brain accompanied continues to improve, it may be deviations. The known occurrence by sixth nerve palsies, treatment with observed. Surgical choices depend on of spontaneous recovery of some Botox® was not felt to hasten the degree of residual lateral rectus sixth nerve palsies clouds the recovery.18 Eight patients with function as well as the direction of interpretation of case-report studies. nontraumatic sixth nerve palsies were deviation (Table 5). Function is most Reports sometimes include various reported to have excellent results frequently graded by observation. etiologies, both traumatic and from Botox®, with seven having no The forced duction test is helpful to nontraumatic, lumped together. diplopia in the long term.19 judge the degree of mechanical Hung reported a higher functional Complications of Botox® included restriction. The force generation test recovery rate in a retrospective study ptosis, induced , can help judge the strength of muscle in 14 of 33 patients with acute subconjunctival hemorrhage, action in cooperative patients. It is complete traumatic sixth nerve palsies possible perforation, and accomplished by fixating the eye with who were treated with Botox®.15 failure to maintain an effect. forceps or a cotton swab and asking Holmes reviewed the course of 84 the patient to look in a given direction patients with traumatic sixth nerve Surgical Treatment in order to judge the strength of the palsies, 22 of whom were treated muscle’s movement. Saccadic velocity with Botox® and the remainder Surgical approaches are based on may be formally tested with electro- treated conservatively. He found no difference in the outcome of the Table 5 Approach to Surgery for Cranial Sixth Nerve Lesions

Lateral Rectus Function Surgical Approach Focus Point #3 Mild LR* paresis Recess ipsilateral antagonist MR** When planning surgery, or Recess contralateral yoke MR consider the possible effects of the procedure on other fields of gaze (avoid unintended Moderate LR paresis Resect paretic LR consequences). and Recess either ipsilateral MR or contralateral MR

Severe LR paresis Transposition Focus Point #4 plus Recess contralateral MR Counsel patients on possible need for more surgery or *LR = lateral rectus postoperative prisms. **MR = medial rectus 6 Comp Ophthalmol Update 7 (5) September-October 2006 O’DONNELL oculography if available, but this is texts for details of surgical an isolated sixth cranial nerve palsy. rarely done clinically. Mild functional procedures. J Neuroophthalmol 26: 95-7, 2006 impairment is marked by only slightly In a multicenter prospective study, 7. Bendszus M, Beck A, Koltzenburg decreased motion in the field of Holmes reviewed 33 patients with M, et al: MRI in isolated sixth nerve greatest action of the muscle; acute traumatic sixth nerve palsy and palsies. Neuroradiology 43: 742-5, 2001 moderate functional impairment has found an overall spontaneous 8. Patel SV, Holmes JM, Hodge DO, et a 50% to 75% decrease in action; and recovery rate of 73%. Recovery was al: Diabetes and hypertension in severe impairment has no function higher with unilateral deficits and isolated sixth nerve palsy: a of the muscle. Scott graded lateral with better initial muscle function.21 population-based study. rectus function as poor, fair, or good In a similar study of 31 patients with Ophthalmology 112: 760-3, 2005 based on force generation testing; chronic sixth nerve palsy of multiple 9. Sanders SK, Kawasaki A, Purvin VA: medial rectus contraction based on causes (approximately one-third Long-term prognosis in patients a 0 to +3 scale of forced duction traumatic), 75% were reported to with vasculopathic sixth nerve palsy. testing; and active ductions on a 0 have an eventual surgical success Am J Ophthalmol 134: 81-4, 2002 (normal) to –5 (not able to rotate the rate.22 Of the patients, 10 required 10. Burde RM, Savino PJ, Trobe JD: Clinical Decisions in Neuro- eye from the opposite field to the second , and only two of Ophthalmology. St. Louis, C.V. 20 midline) scale. these were considered failures. The Mosby, 2002, ed 3, pp 175-6 Mild lateral rectus paresis may be success rate for patients with either 11. Lee MS, Galetta SL, Volpe NJ, et al: addressed by a recession of the traumatic or nontraumatic sixth Sixth nerve palsies in children. ipsilateral medial rectus, or by a nerve palsy is favorable, particularly Pediatr Neurol 20: 49-52, 1999 recession of the yoke contralateral for those with residual lateral rectus 12. Holmes JM, Mutyala S, Maus TL, et medial rectus (creating a matching function. If surgery is indicated, the al: Pediatric third, fourth, and sixth weakness in the contralateral eye patient should be aware that more nerve palsies: a population-based (Figure 4), which would be less likely than one procedure may be needed, study. Am J Ophthalmol 127: 388- to induce an in and prisms may be required 92, 1999 13. Scherer K, Bedlack RS, Simel DL: contralateral gaze. A contralateral postoperatively. Does this patient have myasthenia medial rectus posterior fixation suture gravis?. JAMA 293: 1906-14, 2005 (Faden operation) may also References 14. Burde RM, Savino PJ, Trobe JD: effectively serve this purpose. In a Clinical Decisions in Neuro- moderate paresis, it is usually 1. Buckley EG: Paralytic strabismus, in Ophthalmology. St. Louis, C.V. necessary to resect the paretic lateral Plager DA (ed): : Mosby, 2002, ed 3, p 182 rectus and recess either the antagonist Basic and Advanced Strategies. New 15. Hung HL, Kao LY, Sun MH: or yoke medial rectus. The same York, Oxford University Press, 2004, Botulinum toxin treatment for acute considerations apply about trying to pp 83-97 traumatic complete sixth nerve palsy. avoid creating an exotropia in 2. Patel SV, Mutyala S, Leske DA, et al: Eye 19: 337-41, 2005 Incidence, associations, and 16. Holmes JM, Beck RW, Kip KE, et contralateral gaze. A contralateral evaluation of sixth nerve palsy using al: Botulinum toxin treatment medial rectus posterior fixation suture a population-based method. versus conservative management in may be helpful in more severe palsies Ophthalmology 111: 369-75, 2004 acute traumatic sixth nerve palsy or to expand the field of single 3. Hanson RA, Ghosh S, Gonzalez- paresis. J AAPOS 4: 145-9, 2000 . In severe sixth nerve Gomez I, et al: Abducens length and 17. Biglan AW, Burnstine RA, Rogers palsy with no lateral rectus function, vulnerability?. 62: 33-6, GL, et al: a transposition procedure plus a 2004 with botulinum A toxin. weakening of the contralateral 4. Glaser JS: Neuro-Ophthalmolgy. Ophthalmology 96: 935-43, 1989 medial rectus is indicated (Figure 5). Philadelphia, Lippincott Williams & 18. Kerr NC, Hoehn MB: Botulinum If forced ductions reveal a Wilkins, 1999, ed 3, pp 409-13 toxin for sixth nerve palsies in 5. Kline LB, Bajandas FJ: Neuro- children with brain tumors. J contracted ipsilateral medial rectus, AAPOS 5: 21-5, 2001 ® Ophthalmology Review Manual, either Botox at the time of surgery Revised Edition. Thorofare, New 19. Wagner RS, Frohman LP: Long-term or a recession of the tight medial Jersey, Slack, Incorporated, 2003, ed results: botulinum for sixth nerve rectus as a second procedure to 5, pp 86-95 palsy. J Pediatr Ophthalmol decrease the chance of anterior 6. Warwar RE, Bhullar SS, Pelstring RJ, Strabismus 26: 106-8, 1989 segment ischemia may be considered. et al: Sudden death from pituitary 20. Scott AB, Kraft SP: Botulinum toxin The reader is referred to standard apoplexy in a patient presenting with injection in the management of SIXTH NERVE PALSY 7 lateral rectus paresis. Ophthalmology 22. Holmes JM, Leske DA: Long-term grant from the Research to Prevent Blind- 92: 676-83, 1985 outcomes after surgical management ness Foundation, New York, NY. 21. Holmes JM, Droste PJ, Beck RW: The of chronic sixth nerve palsy. J The authors reported no proprietary or natural history of acute traumatic AAPOS 6: 283-8, 2002 commercial interest in any product men- sixth nerve palsy or paresis. J AAPOS tioned or concept discussed in this 2: 265-8, 1998 This article was supported in part by a update.