(Infection)

Overview

• Inflammation of the brain parenchyma
• Bimodal age distribution → highest incidence in those <1 yr and >65 yrs
• Most commonly due to viral infection → Herpes Simplex Virus Type 1 most common in the UK
• Can also be due to bacterial, fungal and parasitic infections. Also in immunocompromised patients or patients with autoimmune/paraneoplastic syndromes.
• Risk Factors → age under 1 or over 65 years, immunosuppression, viral infections, body fluid exposure, organ transplantation, animal or insect bites, travel, and season

Making Diagnosis

Clinical Features:

• Self-limiting & mild in most cases
• Altered mental state (differs from meningitis) → ie. sudden change in behaviour (KEY DISTINGUISHING FACTOR FROM MENINGITIS)
• Fever + Malaise
• Flu like prodromal illness
• Rash
• Focal neurological deficit → aphasia, hemianopia, hemiparesis
• History of seizures