2012 Oct [ em date cited /em ]. breathing developed. Her temperature reached 102F (38.9C), and the following laboratory values were outside the reference range: leukocyte count (11.3 103/mm3), sodium level (131 mmol/L), erythrocyte sedimentation rate (49 mm/h), and protein level (2.3 mg/dL). Neurology and infectious disease specialists suspected viral encephalitis. Magnetic resonance imaging (MRI) was deferred because of the unknown composition of the aneurysm clip, and the patient underwent a computed tomography angiogram of the head and neck. Infarction, vasculitis, meningeal enhancement, and structural abnormalities were not found. Twenty-fourChour electroencephalogram monitoring and administration of ceftriaxone (2 g intravenously [IV] every 24 h), acyclovir (500 mg IV every 8 h), and doxycycline (100 mg IV every 12 h) were initiated. Overnight, the patient became apneic and required intubation. Examination D-Luciferin potassium salt revealed absent deep tendon reflexes, ocular deviation, positive Babinski response, and bilateral flaccid paralysis of the extremities. D-Luciferin potassium salt Pupillary light and corneal reflexes remained intact. No independent respirations were initiated. Complement levels were within reference range. No evidence of seizure was shown on electroencephalogram, although epileptiform discharges were D-Luciferin potassium salt seen. Given the severity of encephalopathy, prophylactic levetiracetam was initiated. Results of repeat screen for antibodies, smear for spp., and blood and urine cultures were unremarkable. Brain MRI revealed nonspecific inflammatory changes within the thalamus, midbrain, and cerebellum, with no evidence of meningeal irritation, temporal lobe abnormality, mass effect, acute infarct, or hydrocephalus (Figure 1, panel A). Acyclovir was discontinued. Routine bacterial culture of CSF was negative. Ceftriaxone and doxycycline were continued because acute Lyme disease, which rarely manifests in this manner, could not be ruled out by serologic testing alone. Open in a separate window Figure 1 A) Noncontrast, sagittal T1-weighted magnetic resonance image of the brain of a 67-year-old woman with suspected Powassan virus encephalitis, D-Luciferin potassium salt obtained 4 days after admission. Image is notable for nonspecific signal changes within the thalami, midbrain, cerebellar vermis, and both cerebellar hemispheres. B) Noncontrast, sagittal T1-weighted magnetic resonance image of the brain obtained 8 days after patients admission. Changes include marked interval progression of signal abnormality involving the cerebellum, thalamus, and midbrain. Mass effect within the posterior fossa and crowding of structures at the foramen magnum are also evident. Marked dilatation of the lateral and third ventricles with acute hydrocephalus is apparent. The patient remained unresponsive with flaccid paralysis and areflexia. Four days after the initial examination, repeat MRI showed substantial progression of signal abnormality in cerebral hemispheres, thalamus, and midbrain. Mass effect was evident with crowding of structures at the foramen magnum. Lateral and third ventricle dilation, consistent with acute hydrocephalus, was noted (Figure 1, panel B). A repeat lumbar puncture was not performed, given clinical interpretation of illness, known imaging findings, key pending results, and lack of indications for additional testing. Thirteen days after illness onset, a serology panel was negative for the following viruses: West Nile, La Crosse, Eastern equine encephalitis, St. Louis encephalitis, and Western equine encephalitis. PCR of CSF was negative for enteroviruses and herpesviruses. The Minnesota Department of Health (MDH) reported positive IgM serologic results against D-Luciferin potassium salt Powassan virus (POWV). Ceftriaxone and doxycycline were discontinued. Given the patients clinical deterioration and poor prognosis, she was electively extubated and then died. The Centers for Disease Control and Prevention confirmed POWV infection by IgM serology and reverse transcription PCR of CSF. POWV is a Rabbit polyclonal to PPP1R10 tick-borne member of the family first reported in 1958 (with human pathogenicity in North America (sppspp.) act as vectors (ticks are the typical vectors for POWV. In Minnesota and Wisconsin, ticks are the typical vectors for DTV. Although ticks are present in these states, they rarely attach to humans, and according to MDH data, all sequenced strains in Minnesota are of the DTV genotype. Transmission time from tick to host has been documented in mice.