Hidden HSV Encephalitis behind the Mask of Chronic Suppurative Otitis Media and Brain Abscess

Introduction: HSV encephalitis remains a severe illness with a significant risk of morbidity and death. Although HSVE exhibits characteristic imaging findings it can also mimic other life-threatening conditions. Mastoiditis is a bacterial infection of mastoid air cells. The complications of chronic mastoiditis mainly include facial paralysis, vertigo, hearing loss or brain abscess and meningitis. Presentation: To present an unusual case of a 23-year-old patient with clinical features and CT findings of chronic mastoiditis, complicated by a brain abscess and virological confirmation of HSV type 1 encephalitis, who was hospitalized at the Clinic of Infectious Diseases, UMBAL “St. George,” Plovdiv. The disease began with earache, headache, persistent fever above 39？C, and purulent otorrhea. Two days later, she presented with lethargy, dysphasia, right hemiparesis, facial paralysis, and nuchal rigidity. Although the most common and life-threatening complication of chronic mastoiditis is otogenic meningitis, a lumbar puncture confirmed an active HSV-1 infection through CSF PCR examination. Conclusion: HSV encephalitis can be masked by various diseases and should, therefore, be considered in the differential diagnosis of all neurological manifestations. This is particularly crucial in acute neurological events accompanied by fever, even in patients with conclusive brain imaging findings. Early recognition facilitates timely initiation of antiviral therapy, improving the likelihood of a favorable outcome.