eMedicine Specialties > Ophthalmology > Extraocular Muscles
Abducens Nerve Palsy
Updated: May 21, 2009
Introduction
Background
Cranial nerve VI, also known as the abducens nerve, innervates the ipsilateral lateral rectus (LR), which functions to abduct the ipsilateral eye. It has the longest subarachnoid course of all the cranial nerves; therefore, its syndromes are similar to those of the fourth nerve because of their long intracranial courses. The sixth nerve nucleus is located in the pons, just ventral to the floor of the fourth ventricle and just lateral to the medial longitudinal fasciculus (MLF). About 40% of its neurons project into the ipsilateral MLF only to cross over to the contralateral side and ascend to innervate that contralateral medial rectus subnucleus to participate in contralateral eye adduction.1,2,3
Patients usually present with binocular horizontal diplopia (double vision producing a side-by-side image with both eyes open) and esotropia in primary gaze. The deviation, as would be expected, is noted to be greater when the patient fixates with the paretic eye at distance. Patients also may present with a head-turn to maintain binocularity and binocular fusion and to minimize diplopia.
It is rare to find true congenital sixth nerve palsy. A typical workup of a sixth nerve palsy involves excluding paresis of other cranial nerves (including VII and VIII), checking ocular muscle motility, and evaluating pupillary responsiveness. Checking deep tendon reflexes (DTRs) and motor function to exclude corticospinal tract involvement also is important. MRI is indicated for any brainstem findings to exclude pontine glioma in children (most have papilledema and nystagmus without other cranial nerve involvement) and in adults who show no improvement.
In young adults, a lumbar puncture (LP) for cerebrospinal fluid (CSF) analysis is completed to exclude meningitis in patients who have no history of diabetes or hypertension and who have a head CT scan negative for other pathology. Elderly patients should have blood testing for an erythrocyte sedimentation rate (ESR) and/or a C-reactive protein to screen for giant cell arteritis (also known as temporal arteritis or cranial arteritis). Poor or no resolution should prompt a full neurologic evaluation and a consideration of other possible diagnoses (eg, congenital esotropia, Möbius syndrome, Duane syndrome).
Pathophysiology
Only the ipsilateral lateral rectus that is solely innervated by the involved peripheral sixth cranial nerve is affected; therefore, only deviations in the horizontal plane are produced. In isolated cases of peripheral nerve lesions, no vertical or torsional deviations are present. Central nervous system lesions of the abducens nerve tract are localized easily secondary to the typical findings associated with each kind of lesion. Damage to the sixth nerve nucleus results in an ipsilateral gaze palsy. The lack of a contralateral adduction defect makes it easy to differentiate a nuclear lesion from a fascicular or nonnuclear lesion.2
Abducens nerve palsy is frequently seen as a postviral syndrome in younger patients and as an ischemic mononeuropathy in the adult population.Frequency
United States
Sixth nerve palsies fall into the following categories: 8-30% idiopathic, 10-30% miscellaneous, 3-30% trauma, 0-6% aneurysm, and 0-36% ischemic.
The sixth cranial nerve is the most commonly affected of the ocular motor nerves. In children, it is the second most common after the fourth nerve, with an incidence of 2.5 cases per 100,000 in the population.
Mortality/Morbidity
A young patient should have an aggressive workup because of the greater likelihood of a neoplasm causing the palsy. Patients older than 40 years require a less aggressive workup because of the greater likelihood of the etiology being more benign in nature (eg, ischemic mononeuropathy, vasculopathy).
Age
Cranial nerve VI palsy can occur in all age groups; however, the etiology varies depending on the age group.
Clinical
History
Clinical history includes the following:
- Esotropia
- Head-turn
- Binocular diplopia (worse at distance)
- Vision loss
- Pain
- Hearing loss
- Symptoms of vasculitis, particularly giant cell arteritis
- Trauma
Physical
Physical findings include the following:
- An esodeviation that increases on ipsilateral gaze and is often greater at a distance
- An isolated abduction deficit
- Slowed ipsilateral saccades
- Papilledema (if increased intracranial pressure)
- Nystagmus (usually in children, ie, secondary to pontine glioma)
- Otitis media
- Orbital wall fracture
- Tender, enlarged, nonpulsatile temporal arteries in giant cell arteritis
Causes
Not all abduction deficits are cranial nerve VI palsies. Mimickers are orbital lesions, medial wall fractures, Duane syndrome, thyroid disease, and myasthenia gravis.4
- Elevated intracranial pressure can result in downward displacement of the brainstem, causing stretching of the sixth nerve secondary to its anatomic location within the Dorello canal. This is believed to be the reason that about 30% of patients with pseudotumor cerebri have an isolated abducens nerve palsy.
- Subarachnoid space lesions can be causes of abducens nerve palsy (eg, hemorrhage, infection, inflammation, space-occupying tumor, cavernous sinus mass). Inflammatory (eg, postviral, demyelinating, sarcoid, giant cell arteritis)
- Vascular
- Metabolic (eg, vitamin B, Wernicke-Korsakoff syndrome)
- Neoplasm (children) - Pontine glioma
- Infectious (eg, Lyme disease, syphilis)
- Congenital absence of the sixth nerve (eg, Duane syndrome)5
- Trauma, particularly if it results in a torsional head motion6,7,8,9
- Post–lumbar tap10
Differential Diagnoses
Giant Cell Arteritis
Orbital Fracture, Medial Wall
Other Problems to Be Considered
Isolated abducens nerve palsy
Break in the fusion of a patient with congenital esophoria
Workup
Laboratory Studies
- Complete blood cell (CBC) count
- Glucose levels
- Glycosylated hemoglobin (HbA1C)
- Erythrocyte sedimentation rate and/or C-reactive protein
- Rapid plasma reagin test
- Fluorescent treponemal antibody-absorption test
- Lyme titer
- Glucose tolerance test
- Antinuclear antibody test
Imaging Studies
- Skull series
- Stereoscopic submental-vertex basal view of the skull (to inspect the basal foramina)
- If no marked improvement after 6 weeks or if other cranial nerves become involved, then a more thorough evaluation is indicated, such as a full medical and neurologic workup, CT scan with and without contrast, MRI, LP, and cerebral angiography.
- MRI is indicated for the following:
- Patients younger than 45 years
- Associated pain or other neurologic abnormality
- History of cancer
- Bilateral sixth nerve palsy
- Papilledema
- Patients younger than 55 years with no vasculopathic history
- In the event no marked improvement is seen or other nerves become involved
- An LP should be considered if MRI results are negative.
Other Tests
- Check history for diabetes mellitus, cancer, thyroid disease, and hypertension.
- Ask about history of recent trauma, ear infections (children), and fluctuation of symptoms.
- An otoscopic examination may be performed in children to rule out a complicated otitis media (consider an LP).
- Rule out other cranial nerve involvement.
Procedures
- A temporal artery biopsy may be indicated if findings and laboratory studies suggest giant cell arteritis.
Treatment
Medical Care
Truly isolated cases often are benign. They can be followed with a serial examination, at least every 6 weeks, over a 6-month period to note decreasing symptoms (diplopia) and resolution of the paretic lateral rectus (increasing motility).11,3
Children with sixth nerve palsy who are in the amblyopic age group can be treated with an alternating patching to decrease their chances of developing any amblyopia in the paretic eye. Additionally, prescribing the full amount of hyperopic correction helps to decrease the esodeviation by relaxing the child's accommodative effort.
Adult patients and those children beyond the amblyopic age can be patched or have their lenses "fogged" with clear tape or nail polish to reduce their diplopia. Fresnel prisms also can be prescribed as an alternative.
Older patients in whom giant cell arteritis is a consideration should start the standard treatment with prednisone or intravenous methylprednisolone as soon as possible.
Surgical Care
If after 6 months of follow-up care the remaining deviation is still unacceptable and is too large to be corrected with prisms, surgical corrective options should be discussed with the patient. The procedure that is chosen depends on the remaining function of the lateral rectus and the experience of the surgeon.
If some residual function exists in the lateral rectus, a graded recession/resection is the procedure of choice.
When little or no residual function is present, a transposition procedure, such as the Hummelsheim or the Jensen, can be used, along with, in appropriate patients, weakening the antagonist ipsilateral medial rectus.
Consultations
With persistent defect, a neurology consult may be needed.
Activity
Patients who occlude an eye to alleviate diplopia should be warned that the resulting effects on depth perception may interfere with their ability to drive or perform certain occupations safely.
Follow-up
Complications
- Persistent esotropia may require a surgical procedure.
Prognosis
- This condition generally resolves within 6 months.
Miscellaneous
Medicolegal Pitfalls
- With younger people, an aggressive workup should be completed because of the concern of a neoplasm.
- Giant cell arteritis must be considered in all patients older than 50 years to avoid the devastating complication of bilateral blindness or stroke.
References
Evans NM. Ophthalmology. 2nd ed. Oxford University Press Inc; 1995.
Kline LB, Bajandas FJ. Neuro-ophthalmology Review Manual. 3rd ed. University of Alabama, Birmingham; 1988.
Yanoff M, Duker JS. Ophthalmology. Mosby International Ltd; 1999.
Ayberk G, Ozveren MF, Yildirim T, et al. Review of a series with abducens nerve palsy. Turk Neurosurg. Oct 2008;18(4):366-73. [Medline].
Denis D, Dauletbekov D, Girard N. Duane retraction syndrome: Type II with severe abducens nerve hypoplasia on magnetic resonance imaging. J AAPOS. Feb 2008;12(1):91-3. [Medline].
Calisaneller T, Ozdemir O, Altinors N. Posttraumatic acute bilateral abducens nerve palsy in a child. Childs Nerv Syst. Jul 2006;22(7):726-8. [Medline].
Dwarakanath S, Gopal S, Venkataramana NK. Post-traumatic bilateral abducens nerve palsy. Neurol India. Jun 2006;54(2):221-2. [Medline].
Kurbanyan K, Lessell S. Intracranial hypotension and abducens palsy following upper spinal manipulation. Br J Ophthalmol. Jan 2008;92(1):153-5. [Medline].
Hanu-Cernat LM, Hall T. Late onset of abducens palsy after Le Fort I maxillary osteotomy. Br J Oral Maxillofac Surg. Dec 16 2008;[Medline].
Anwar S, Nalla S, Fernando DJ. Abducens nerve palsy as a complication of lumbar puncture. Eur J Intern Med. Dec 2008;19(8):636-7. [Medline].
Rhee DJ, Pyfer MF. The Wills Eye Manual: Office and Emergency Room diagnosis and treatment of eye disease. Lippincott Williams & Wilkins; 1999.
Keywords
abducens nerve palsy, sixth nerve palsy, VI nerve palsy, 6th nerve palsy, cranial nerve VI palsy
Contributor Information and Disclosures
Author
Michael P Ehrenhaus, MD, Director, Department of Cornea, External Disease & Refractive Surgery, Assistant Professor, Department of Ophthalmology, State University of New York Downstate Medical Center
Michael P Ehrenhaus, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, American Medical Association, American Society of Cataract and Refractive Surgery, and Contact Lens Association of Ophthalmologists
Disclosure: Nothing to disclose.
Coauthor(s)
Mohammedyusuf E Hajee, MD, Clinical Instructor, Staff Physician, Department of Ophthalmology, Director, Blood Flow Laboratory, State University of New York-Downstate Medical Center
Mohammedyusuf E Hajee, MD is a member of the following medical societies: American Academy of Ophthalmology, Association for Research in Vision and Ophthalmology, and National Medical Association
Disclosure: Nothing to disclose.
Hampton Roy Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Hampton Roy Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, and Pan-American Association of Ophthalmology
Disclosure: Nothing to disclose.
Medical Editor
Andrew W Lawton, MD, Medical Director of Neuro-Ophthalmology Service, Section of Ophthalmology, Baptist Eye Center, Baptist Health Medical Center
Andrew W Lawton, MD is a member of the following medical societies: American Academy of Ophthalmology, Arkansas Medical Society, and Southern Medical Association
Disclosure: Nothing to disclose.
Pharmacy Editor
Simon K Law, MD, PharmD, Assistant Professor of Ophthalmology, Jules Stein Eye Institute; Chief of Section of Ophthalmology Surgical Services, Department of Veterans Affairs Healthcare Center, West Los Angeles
Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, American Glaucoma Society, and Association for Research in Vision and Ophthalmology
Disclosure: Nothing to disclose.
Managing Editor
Brian R Younge, MD, Professor of Ophthalmology, Mayo Clinic School of Medicine
Brian R Younge, MD is a member of the following medical societies: American Medical Association, American Ophthalmological Society, and North American Neuro-Ophthalmology Society
Disclosure: Nothing to disclose.
CME Editor
Lance L Brown, OD, MD, Ophthalmologist, Affiliated With Freeman Hospital and St John's Hospital, Regional Eye Center, Joplin, Missouri
Disclosure: Nothing to disclose.
Chief Editor
James P Gills, MD, Founder, St Luke's Cataract and Laser Institute; Professor, Department of Ophthalmology, University of South Florida College of Medicine
James P Gills, MD is a member of the following medical societies: American Academy of Ophthalmology
Disclosure: Nothing to disclose.