Objective:

To present 3 cases of Powassan Encephalitis with varying clinical symptoms and radiographic findings.

Background:

Since it was originally discovered in 1958, Powassan virus (POWV) is an uncommon cause of encephalitis seen in Eastern Canada and Russia as well as north central, upper midwestern and northeastern United States. POWV is a tick-borne Flavivirus and transmitted by Ixodes cookie (woodchuck tick) and Ixodes Scapularis (deer tick). Neuroinvasive disease usually begins with a prodromal phase of fever, chills, malaise with progression to CNS symptoms including AMS, seizures, hemiplegia, facial palsies as well as pyramidal tract signs. It is however unclear what proportion of those exposed to ticks who are infected go on to develop neurological symptoms, and this may be due to lack of knowledge of or access to testing. 

Design/Methods:

We present 3 patients with POWV encephalitis presenting with clinical symptoms of, shortness of breath and AMS (Pt 1), Headache and aphasia with progressive AMS (Pt 2), and Headache and dysarthria progressing to tetra-paresis (Pt 3). MRI Brain wwo showed Rhombencephalitis (Pt 1), Diffuse white mater T2 FLAIR hyperintensities without contrast enhancement (Patient 2), and Putaminal T2 FLAIR hyperintensity with multifocal as well as cranial nerve enhancements (Patient 3). LP showed lymphocytic predominant pleocytosis in all three patients and resulted positive for POWV-specific IgM and neutralizing antibodies. Clinical course following discharge ranged from complete recovery to severe disability.  

Results:

NA

Conclusions:

POWV is an uncommon cause of encephalitis with increasing incidence. The clinical presentation and imaging findings associated with POWV appear to be quite varied. Neurologists should consider POWV in those presenting with clinical symptoms and imaging findings concerning for encephalitis, especially in regions known to have higher incidence of tick exposure.