Snapshot A 46-year-old male is brought to the emergency department by his wife due to a seizure event. She reports that prior to the event, he complained of headache, fever, and nausea. She also reports her husband appeared confused. On exam, the patient cannot clearly answer questions. A CT of the head shows no evidence of a hemorrhage, or a space-occupying lesion. MRI of the brain is shown. A lumbar puncture is performed, and cerebral spinal fluid analysis shows a normal opening pressure, a lymphocytic pleocytosis, normal glucose, and elevated protein. PCR is positive for herpes simplex virus-1. Introduction Brain parenchymal infection abnormalities in brain functioning are expected e.g., altered mental status, changes in personality, problems with speech and movement this distinguishes encephalitis from meningitis Typically caused by infection viral (most cases) herpes simplex virus (HSV) most common cause varicella virus (VZV) epstein-barr virus (EBV) measles, mumps, rubella HIV Japanese encephalitis virus St. Louis encephalitis virus West nile virus bacterial toxoplasmosis noninfectious acute disseminated encephalitis There can be both an infection of the brain parenchyma and meninges leading to a meningoencephalitis Presentation Symptoms seizures fever headache nausea vomiting Physical exam altered mental status personality changes focal neurological deficits cranial nerve palsies hemiparesis. meningsmus only in pure encephalitis Evaluation CT scan of the head performed first rules-out space occupying lesions normal CT does not rule-out encephalitis MRI is the preferred imaging modality for HSV encephalitis Lumbar puncture perform after head imaging cerebral spinal fluid analysis to determine etiology HSV ↑ white blood cells predominantly lymphocytes ↑ red blood cells grossly bloody tap ↑ protein elevated normal glucose PCR most accurate for herpes encephalitis culture Gram stain Brain biopsy last resort only if etiology is unknown Differential Intracranial malignancy primary or metastatic Medication side-effects Paraneoplastic or autoimmune disease anti-NMDA receptor encephalitis Amoebic meningoencephalitis caused by Naegleria fowleri amoeba are seen on CSF analysis Treatment Supportive assess airway, breathing, and circulation (ABCs) initiate seizure precautions manage fever and pain Treatment is then dependent on etiology HSV encephalitis initiate acyclovir immediately if renal impairment must give IV fluids to prevent crystalline nephropathy can be considered with VZV encephalitis associated with a reduction in morbidity and mortality foscarnet in acyclovir-resistant herpes Serial monitoring of intracranial pressure Prevention, Prognosis, and Complications 50 - 75% mortality in untreated HSV encephalitis < 1 or > 55 years old, immunocompromised is associated with poorer outcome