Acute encephalitis - diagnosis and management

Abstract

Encephalitis, inflammation of the brain, is most commonly caused by a viral infection (especially herpes simplex virus [HSV] type 1 in the UK) although autoimmune causes, such as N-methyl D-aspartate receptor (NMDAR) antibody encephalitis, are increasingly recognised. Most patients present with a change in consciousness level and may have fever, seizures, movement disorder or focal neurological deficits. Diagnosis hinges crucially on lumbar puncture and cerebrospinal fluid (CSF) examination, but imaging and electroencephalography (EEG) may also be helpful. Treatment of HSV encephalitis with aciclovir dramatically improves outcome, but the optimal management of autoimmune encephalitis is still uncertain. Many patients with encephalitis are left with residual physical or neuropsychological deficits which require long-term multidisciplinary management. Here we review assessment of patients with suspected encephalitis, general aspects of management and areas of ongoing research.

Keywords: brain infection; confusion; encephalitis; encephalopathy; lumbar puncture.

Fig 1.

Algorithm for basic management of acute encephalitis (based on UK guidelines). CSF = cerebrospinal fluid; GCS = Glasgow Coma Scale; HSV = herpes simplex virus; LP = lumbar puncture; VZV = varicella zoster virus

Fig 2.

Brain imaging in encephalitis. (a) CT scan of 69-year-old male with acute HSV-1 encephalitis showing low intensity area in right temporal lobe. (b) T2 weighted axial MRI from same patient showing bilateral asymmetrical signal abnormality in medial temporal lobes. (c) T2 weighted axial MRI of 55-year-old male with LGI-1 antibody encephalitis showing high signal in the left medial temporal lobe. (d) Coronal T2 FLAIR from same patient showing high signal in left medial temporal lobe. CT = computed tomography; FLAIR = fluid attenuation inversion recovery; HSV = herpes simplex virus; LGI-1 = leucin-rich glioma inactivated 1; MRI = magnetic resonance imaging