Encefalit

Encefalit, or encephalitis, is inflammation of brain tissue, most often due to viral infections but also caused by autoimmune processes, paraneoplastic syndromes, or toxins. Typical presentation includes fever and altered mental status, with headache, seizures, confusion, or focal neurological deficits. If meningitis accompanies it, the condition is called meningoencephalitis.

Causes include viruses such as herpes simplex type 1, enteroviruses, West Nile, Japanese encephalitis, Zika, and varicella zoster; bacteria, fungi, and parasites can also cause encephalitis. Autoimmune encephalitis, defined by antibodies to neuronal surface antigens (eg, anti-NMDA receptor, LGI1, CASPR2), is increasingly recognized. In many cases no cause is identified.

Diagnosis relies on clinical suspicion and tests: lumbar puncture with CSF analysis, CSF PCR for viruses, and blood cultures. MRI is typically the preferred imaging modality and may show characteristic patterns; EEG can detect seizures or diffuse slowing. Autoimmune panels may be pursued when an autoimmune etiology is suspected.

Treatment starts with empiric antiviral therapy, typically acyclovir, if herpes encephalitis is not excluded. Antibiotics cover potential bacterial infection while results return. If an autoimmune cause is identified, immunotherapy such as steroids, IVIG, plasmapheresis, or rituximab is used. Supportive care includes hydration, fever control, seizure management, and monitoring in hospital.

Prognosis is variable; some recover fully, others have lasting neurologic deficits. Early diagnosis and treatment improve outcomes. Prevention focuses on vaccination against preventable viral infections where available and reducing exposure to vectors for arboviral encephalitis.