What are the symptoms of encephalitis?

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Last updated: March 21, 2025View editorial policy

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From the Guidelines

The symptoms of encephalitis include fever, headache, confusion, altered mental status, seizures, and neck stiffness, and can progress to more severe neurological manifestations, making it a medical emergency requiring immediate attention. Patients may also experience drowsiness, nausea, vomiting, sensitivity to light, and in severe cases, coma. Early symptoms often resemble flu-like illness before progressing to more serious neurological manifestations. Movement disorders, weakness or paralysis in limbs, speech problems, hearing or vision defects, and personality changes can also occur. The severity and combination of symptoms vary depending on the cause (viral, bacterial, autoimmune) and the specific brain regions affected. Symptoms typically develop rapidly over hours to days.

Key Symptoms

  • Fever
  • Headache
  • Confusion
  • Altered mental status
  • Seizures
  • Neck stiffness
  • Drowsiness
  • Nausea
  • Vomiting
  • Sensitivity to light
  • Coma (in severe cases)
  • Movement disorders
  • Weakness or paralysis in limbs
  • Speech problems
  • Hearing or vision defects
  • Personality changes According to the study by 1, confirmed encephalitis requires one of the following: pathologic confirmation of brain inflammation consistent with encephalitis, defined pathologic, microbiologic, or serologic evidence of acute infection with a microorganism strongly associated with encephalitis, or laboratory evidence of an autoimmune condition strongly associated with encephalitis. The study also notes that fever is a common finding in patients with acute encephalitis, but is nonspecific, and that seizures associated with encephalitis may be generalized or focal.

Diagnosis and Treatment

The diagnosis of encephalitis is crucial, as prompt treatment with antivirals (like acyclovir for herpes encephalitis) or appropriate medications for other causes can significantly improve outcomes and prevent long-term neurological damage, as noted in the study by 1. The study by 1 also highlights the importance of early recognition and treatment of encephalitis in children, where symptoms can be non-specific and resemble those of other acute illnesses.

Importance of Prompt Treatment

Encephalitis is a medical emergency requiring immediate attention, and prompt treatment can significantly improve outcomes and prevent long-term neurological damage. The inflammation of brain tissue causes these symptoms by disrupting normal neurological function and increasing intracranial pressure.

From the Research

Symptoms of Encephalitis

The symptoms of encephalitis can vary depending on the brain zone affected. Some common symptoms include:

  • Mild symptoms:
    • Fever
    • Headache
    • Confusion
    • Stiff neck
  • Severe symptoms:
    • Seizures
    • Weakness
    • Hallucinations
    • Coma These symptoms can occur in individuals of all ages, but encephalitis is frequently observed in pediatric and elderly populations 2.

Clinical Presentation

Most patients with encephalitis present with a change in consciousness level and may have additional symptoms such as:

  • Fever
  • Seizures
  • Movement disorder
  • Focal neurological deficits Diagnosis of encephalitis hinges crucially on lumbar puncture and cerebrospinal fluid (CSF) examination, but imaging and electroencephalography (EEG) may also be helpful 3.

Specific Types of Encephalitis

Certain types of encephalitis, such as acute disseminated encephalomyelitis (ADEM), can present with distinct symptoms, including:

  • Acute onset of focal neurological signs
  • Encephalopathy
  • Coma
  • Seizures
  • Tetraplegia These symptoms can require intensive care unit admission and have a significant impact on the patient's quality of life 4.

Seizures and Encephalitis

Encephalitis is an important cause of acute symptomatic seizures and subsequent epilepsy. Seizures can occur in the context of various types of encephalitis, including herpes simplex virus encephalitis and Japanese encephalitis virus 5, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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