Herpes Simplex Encephalitis (HSE) is a rare but serious condition caused by the Herpes Simplex Virus (HSV), primarily affecting the brain. It typically occurs when the virus spreads to the central nervous system, leading to inflammation of the brain tissue. Symptoms may include fever, headache, confusion, seizures, and changes in behavior. Diagnosis is often made through imaging tests like MRI and analysis of cerebrospinal fluid. Early treatment with antiviral medications, such as acyclovir, is crucial for improving outcomes. If left untreated, HSE can lead to severe complications, including long-term neurological damage or death.