The right eye abducens nerve palsy as a cranial neuropathy of dengue fever: The benefit of corticosteroids in an unusual dengue sequela

Dengue fever is very common in tropical climate countries and the number of reported cases in Malaysia shows an increasing trend recently, according to the Malaysian Clinical Practice Guidelines. Although dengue fever is common, cranial nerve mononeuropathy is a very rare manifestation in relation to other neurological-associated syndromes. We report a rare case of cranial mononeuropathy of dengue fever in Malaysia and highlight the option of steroid usage as an alternative treatment to hasten the neurological recovery. The patient, a 25-year-old healthy policeman, presented with symptomatic viral fever, which was serologically confirmed as dengue fever. He developed acute-onset binocular diplopia, which was secondary to right eye isolated abducens nerve palsy during the critical phase of dengue fever. His visual acuity was 6/6 in both eyes with slightly restricted abduction of the right eye, consistent with right abducens nerve palsy, which was confirmed with a Hess test. There was corresponding diplopia over the right paracentral visual field. Urgent contrasted brain imaging was done, which ruled out the life-threatening intracranial pathology; therefore, a diagnosis of possible subclinical inflammatory changes causing sixth nerve palsy was made. Subsequently, he was treated with intravenous methylprednisolone 500 mg daily for 3 days and regained full extraocular muscle movement after 1 week. Oral steroid was not initiated. In conclusion, although the isolated unilateral cranial mononeuropathy may improve spontaneously within a certain period of time, a short course of systemic corticosteroids may be considered to hasten the recovery, as it has a favourable outcome.