Isolated bilateral abducent nerve palsy in infectious mononucleosis.

Abstract

A 7-year-old boy presented with fever for 10 days, along with sore throat, cough, headache and occasional vomiting. A maculopapular rash developed all over the body on day-4 of illness, and on on day-8 of illness, child developed diplopia. There was no history of convulsions, altered sensorium, head trauma, or any joint pain or swelling. Examination revealed, generalized tender lymphadenopathy, hepatosplenomegaly and swelling of both upper eyelids. Neurological examination revealed bilateral lateral rectus palsy without any other cranial nerve involvement, no meningial sign, and normal size and reaction of both pupils. Investigations were: hemoglobin 9.9 g/dL, total leucocyte count 13200/mm 3 (N37, L59, few atypical lymphocytes), and platelet count 152000/mm 3 . Liver function tests were normal. Dengue serology, malarial antigen, malaria parasite and Widal test were negative. Fundoscopy was normal. Examination of CSF showed 6 cells/ mm 3 (all lymphocytes), protein 52 mg/dL and glucose 82 mg/dL. Anti-Viral Capsid antigen (VCA) IgM antibody in serum for Epstein Barr virus (EBV) was 84 mIU/mL (Normal <8 mIU/mL). Magnetic resonance imaging of brain, including angiography was normal. Child was prescribed oral Co-amoxyclav and antipyretics for 5 days. Child became afebrile by 15th day, and diplopia began to improve on seventeenth day. After 4 weeks, marked improvement of opthalmoplegia was noted. Single or multiple cranial nerve palsy may occur in infectious mononucleosis infectious mononucleosis but isolated bilateral 6th cranial nerve involvement is very rare. Other causes of cranial nerve palsy, including head trauma, vasculitis and multiple sclerosis were considered but no clue was found regarding any of these etiologies. Bilateral 6th cranial nerve palsy in infectious mononucleosis can be due to immunological mechanism; rapid reversal of neurodeficit can occur [3]. Short course of prednisolone may be helpful for such complications in infectious mononucleosis but no definite evidence regarding efficacy of corticosteroid therapy is available till date [4]. To conclude, bilateral 6th cranial nerve palsy may be the isolated neurological finding in children with IM, without any other features of brainstem involvement or encephalitis. It seems to have a good prognosis with only supportive measures.