Visual Diagnosis in Emergency Medicine| Volume 57, ISSUE 2, P245-246, August 2019

The Double Doughnut Sign on Brain Magnetic Resonance Imaging Caused by Japanese Encephalitis

      A 30-year-old previously healthy man presented to the emergency department with a fever and recurrent vomiting for 2 days followed by altered sensorium for 6 h, a history that was provided by his spouse. There was no history of seizures or recent travel. The physical examination revealed that he was febrile (38.3°C [101°F]) with a pulse of 112 beats/min, a blood pressure of 146/98 mm Hg, a respiratory rate of 32 breaths/min, and there were no rashes anywhere on the body. A neurologic examination revealed obtunded sensorium (Glasgow coma scale score 6/15), and the motor, sensory, and cerebellar system could not be examined because of altered mentation. There was hyperreflexia and neck rigidity. Cardiac, pulmonary, and abdominal examinations were within normal limits. A clinical possibility of meningo-encephalitis was considered, with a differential diagnosis of bacterial or viral encephalitis. Viral encephalitis was considered to be more likely because the patient lived in a location where Japanese encephalitis was endemic. Cerebrospinal fluid analysis, including polymerase chain reaction testing for viral antibodies was positive for Japanese encephalitis. A contrast-enhanced magnetic resonance imaging scan was obtained, which revealed a distinctive finding that contributed to the determining diagnosis (Figure 1).
      Figure thumbnail gr1
      Figure 1(A) T2 and (B) diffusion-weighted images show symmetrically enlarged hyperintense bilateral thalami (black arrows) with intense central diffusion restriction (white arrows).
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