A 63-year-old male, with a history of hypothyroidism presented to the emergency department with symptoms including fatigue, headache, gait ataxia, nausea, and vomiting. He reported a history of recent tick exposure. Initial neurological exam showed dysarthria, positive Romberg test, wide-based gait, and dysmetria on finger to nose bilaterally. Due to rapid clinical deterioration, the patient was intubated and sedated in the ICU within a week of his initial presentation. Lumbar puncture revealed an elevated WBC (28), normal CSF glucose (46), and elevated CSF protein (152). MRI of the brain with contrast showed acute infarcts in the bilateral cerebellum, bilateral thalami, bilateral midbrain, and right frontal lobe. RNA RT-PCR test confirmed diagnosis of Powassan Virus.  He completed a 5-day course of IV Solumedrol and IVIG, however, the patient remained non-verbal, had no spontaneous limb movements, and only responded by opening and blinking his eyes and was diagnosed with locked-in syndrome. 

Powassan virus can lead to critical neurological symptoms including encephalitis. While our patient demonstrated many of the typical neurological sequelae observed in Powassan patients, a unique outcome in his case was development of "locked-in" syndrome. This is the only reported case of Powassan virus that progressed to 'locked-in' syndrome. The purpose of this case report is to show vascular involvement as a complication of Powassan virus.