Case Presentation

A 17-year-old healthy male presented with a two-week history of progressively worsening occipital headache radiating to the temples. Initially mild, the headache escalated to 10/10 severity on arrival. Associated symptoms included nausea, more than seven to eight episodes of vomiting, dizziness, diplopia, blurry vision, vertigo, and neck stiffness. He denied fever, photophobia, phonophobia, rash, trauma, or recent travel.

Past medical history was unremarkable. The patient was a student athlete, and denied current or former tobacco use, alcohol consumption, or illicit substance use. Of note, he frequently took runs through wooded areas; however, he denied any known insect bites. Family history was notable only for maternal migraines. The patient’s only known international travel was to Mexico, roughly 10 years earlier.

On arrival, the patient was febrile and hemodynamically stable. The neurologic exam was notable for a preferential right gaze, diplopia, ataxic gait, vertigo with leftward gaze, and neck stiffness. Strength, sensation, coordination, and speech were intact. No nystagmus or altered mental status was appreciated.

Investigations

Laboratory studies revealed neutrophilia, elevated erythrocyte sedimentation rate (ESR) (18 mm/hr), and lactate of 3.1 mmol/L; electrolytes and liver/kidney function were within normal limits. Lumbar puncture demonstrated an opening pressure of 52 cm H₂O, CSF pleocytosis (149 WBC/µL), elevated protein (155 mg/dL), normal glucose, and sterile cultures.

Cerebrospinal fluid analysis demonstrated the presence of Lyme IgG bands; however, no other significant abnormalities were identified. Given concurrent serum Lyme antibody testing was negative, Lyme disease was determined to be an unlikely cause.

Electroencephalography was obtained as part of the diagnostic evaluation and demonstrated no evidence of seizure or other epileptiform activity.

A broad infectious and autoimmune evaluation, including viral and parasitic testing, was conducted and yielded no abnormal results.

An initial noncontrast CT scan of the head was performed to rule out possible hemorrhage. The result did not suggest any hemorrhage but did suggest loss of cerebellar folia and increased density of the cerebellum. However, this was considered nonspecific and MRI was recommended.

Axial brain MRI demonstrating diffuse T2/FLAIR hyperintensity and swelling of the cerebellar hemispheres, consistent with acute cerebellar inflammation. Findings are compatible with acute cerebellitis in the appropriate clinical context, without evidence of focal mass lesion or hemorrhage. (Click to enlarge.)

MRI of the brain with contrast showed asymmetric T2/FLAIR hyperintensity within the left greater than right cerebellar hemisphere and vermis, with mild folial enhancement, mass effect on the fourth ventricle. There was no hydrocephalus, midline shift, or diffusion restriction. Initial interpretation from radiology was cerebellitis or rhomboencephalitis. This was compared to an external MRI performed the previous day.