[Western equine encephalitis: Brainstem involvement and clinical manifestations]

Western equine encephalitis is a zoonotic viral disease transmitted by the bite of an infected mosquito. Humans are terminal hosts and since they develop a very low and short lasting viremia, they are incapable of transmitting the disease. Most cases are asymptomatic, but it can present with high fever, myalgia and encephalitis or meningitis. There is no specific treatment and the symptoms resolve within 7 to 10 days. However, about 30% of patients present neurological sequelae, such as cognitive disorders, attention deficit, seizures and alteration in alveolar ventilation due to direct injury to the respiratory center. Magnetic resonance imaging allows the evaluation of brain involvement, with increased signal on FLAIR and T2-weighted sequences. We present the case of a 66-year-old male from Juan Bautista Alberdi (Buenos Aires) with a history of high blood pressure and obsessive compulsive disorder. He was admitted to the clinic due to 4 days of high fever and malaise, and developed signs of encephalopathy during hospitalization. Lumbar puncture showed a crystalline, although predominantly mononuclear, inflammatory cerebrospinal fluid. Brain MRI reported hyperintensity on FLAIR and T2 sequences in the dorsum of the brainstem. He was admitted to the intensive care unit due to neurological deterioration and severe respiratory acidosis, requiring mechanical ventilation. After 10 days he presented neurological improvement, without motor deficit but with alveolar hypoventilation that made it difficult to wean the patient from the ventilator. We present this case due to the infrequency of the disease, clinical evolution and MRI findings.