Influenza B is a relatively common cause of influenza worldwide. Despite this, the recognition of neurological complications is very low. We report a case of isolated third and fourth cranial nerve palsies associated with influenza B infection, and to our knowledge, this is the first such reported case.
CASE REPORTThe patient is a 42-year-old man who presented to the emergency department with a one day history of diplopia, left eyelid droopiness and headache, preceded by a two day history of cough, coryza, myalgias, and fever. He described the headache as dull in quality, moderate in severity, and localized behind his left eye. There was no alteration in level of consciousness and no other focal neurological symptoms. He was an otherwise healthy man and was on no medications. He denied any risk factors for HIV. He had recently travelled to South Africa four months previously where he spent two weeks hunting in remote areas of the country.Initial examination revealed he was febrile with a temperature of 39.3˚C, was tachycardic with a heart rate of 120 BPM and normotensive. Chest was clear on auscultation and there was no lymphadenopathy. He was not encephalopathic and had no nuchal rigidity. He had marked left eye ptosis but no evidence of conjunctival injection, edema, or discharge. His pupils were asymmetrical, the left being significantly larger than the right, although both were reactive to light. On primary gaze, he had an exotropia of his left eye. On extraocular movement testing, his left eye would abduct with left gaze but would not reach midline with right gaze. There were no discernible vertical eye movements noted in his left eye. There was no intortion noted in his left eye on attempted downgaze. Eye movements were full in his right eye. There was no sensory disturbance to his face. The remainder of his neurological exam was normal. We considered his findings to be consistent with complete left third and fourth nerve palsies.Initial laboratory investigations revealed no abnormalities other than a moderately low lymphocyte count at 0.5 x 10 9 cells/L. Magnetic resonance image of the brain with gadolinium enhancement and 3D time of flight MRA were normal. The CSF studies were normal with a WBC count of 1 x 10 6 cells/L, a RBC count of 2 x 10 6 cells/L, protein of 0.28 g/L and glucose of 3.7 mmol/L. A nasopharyngeal swab (direct fluorescent antibody) was positive for influenza B and negative for influenza A, parainfluenza and RSV. Acute and convalescent influenza serologies were not obtained. Treatment with oral oseltamivir was initiated.