Clinical Reasoning: An adolescent girl presenting with worsening vertigo, headache, and ataxia

A 16-year-old girl presents to the Emergency Department with 1 week of vertigo. Her vertiginous symptoms began acutely and were described as a sensation of the room spinning. She subsequently developed a headache, nausea, and difficulty walking. On day 2 of illness, her primary care physician prescribed a 5-day course of prednisone and meclizine twice daily. Her symptoms did not improve following the steroid course, prompting an outpatient MRI of the brain. This study identified sinus disease, but no intracranial abnormality. Her meclizine dose was increased, and she was started on cefdinir for treatment of sinusitis. However, her symptoms continued to worsen. At the time of presentation to our service, she was unable to stand due to the vertigo. She complained of headache and nausea and was found to have nystagmus, ataxia, and dysmetria on examination. The patient had experienced one episode of headache approximately a year prior to presentation but was otherwise healthy. Her family history was significant for a grandmother with multiple sclerosis (MS) and a brother with Factor V Leiden and prothrombin gene mutation.