Eye on Ocular Disorders: Isolated Abducent Nerve Palsy

A 65-year-old woman presented withdouble vision of 2 days' duration.The diplopia mainly occurred whenshe looked toward her right. She deniednausea, vomiting, vision loss,headache, change in mental status,facial pain, weakness in the extremities,and sinus infection. She had nohistory of head trauma or systemicmalignancy.The patient had well-controlledtype 2 diabetes mellitus and hypertensionof 8 years' duration. Her medicationsincluded metformin, 500 mgbid; glipizide, 5 mg bid; rosiglitazone,4 mg/d; lisinopril, 20 mg/d; andhydrochlorothiazide, 25 mg/d.The patient was afebrile. Herblood pressure was 140/90 mm Hg;heart rate, 83 beats per minute;and respiration rate, 16 breaths perminute. She was unable to abducther right eye (A). Diplopia developedon the right lateral gaze. Other extraocularmovements and cranialnerves were intact. Funduscopic findingswere unremarkable. Results ofthe systemic examination were normal.Isolated abducent nerve (cranialnerve VI) palsy was diagnosed.About 20% of isolated abducentnerve palsies are caused by disordersthat lead to vascular microangiopathy,such as diabetes, hypertension,and hyperlipidemia. The typicalpresentation is the sudden onset ofdefective lateral gaze followed bydiplopia and/or retro-orbital pain.Usually, there are no associated neurologicdeficits.In most patients, isolated abducentnerve palsy is benign andself-limited. Complete recovery isexpected within 2 to 3 months. Insome patients, the palsy recurs.¹It is important to immediatelyrule out other causes of sixth nervepalsy, such as mass lesions and infection.In elderly persons in whomtemporal arteritis is suspected, obtainthe erythrocyte sedimentationrate and C-reactive protein level.²If symptoms persist beyond4 months, order an MRI scan of thehead. Additional indications for imagingstudies are:

• The presence of other neurologicsigns, such as altered mental status,severe headache, and other cranialnerve deficits.
• A history of cancer within the past5 years.
• A history of head trauma withinthe past 6 months.