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Encephalitis 

Study guide:

Definition:
 Generalized inflammation of brain parenchyma often seen with/or after meningitis.

Risk Factors:

  1. AIDS CD4+<200 & immunity suppression

  2. Traveling to undeveloped countries

  3. Exposure to insects (mosquitoes) bites in endemic areas

  4. Exposure to bats in endemic areas  


Causes:

  • Viral origin:

    • HSV-1➔    Cowdry bodies on microscope (most common cause of encephalitis).

    • Rabies (Arbovirus)➔    Negri bodies on microscope (Eastern equine encephalitis).

    • Measles➔Subacute sclerosing panencephalitis (SSPE).

    • Others: CMV, mumps, EBV, CJD.

  • Non-viral:

    • Toxoplasmosis

    • Aspergillosis

  • Non-infectious:

    • T-cell lymphoma

    • Metabolic encephalopathies

 

Clinical Presentation:

  • Prodrome of headache, malaise, and myalgias.

  • S&S of meningitis.

  • 2 important features:

    1. Change in the mental status.

    2. Focal neurological deficit (hemiparesis, Cranial nerve lesions, aphasias, seizures etc.)

 

Diagnosis:

  • CBC

  • CT brain to exclude any space-occupying lesion (initially).

  • MRI is the imaging modality of choice to rule out abscesses or focal neurological deficits. 

  • CSF analysis:

    1. ↑↑Lymphocytes.

    2. Normal/↓ glucose.

  • CSF PCR is the most sensitive test for identifying viral causes. 

  • Brain biopsy is the last reservoir used for critically ill patients with no clear Dx and in CJD.
    (refer to the dementia overview document for more information on CJD)

 

Management:

  • Supportive management (mechanical ventilation if needed).

  • Antiviral for:  

    1. HSV-1: Acyclovir

    2. CMV: Gancyclovir or Foscarnet

  • Steroids are not effective (according to the current evidence).


References: 

  • Kumar, Parveen J, and Michael L Clark. Kumar & Clark's Clinical Medicine. Print.

  • Hauser, Stephen, and Scott Josephson. Harrison's Neurology In Clinical Medicine. 3rd ed. McGraw Hill. Print.

  • Yogarajah, Mahinda. Neurology. Edinburgh: Mosby/Elsevier, 2014. Print.

  • Agabegi, Steven S, Elizabeth D Agabegi, and Adam C Ring. Step-Up To Medicine. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins, 2013. Print.

  • Walker, Brian R et al. Davidson's Principles And Practice Of Medicine. Print.

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First author:        Roaa Amer

Second author :  Abdullah AlAsaad  

Reviewers:          Bayan AlZomaili

Format Editor:   Adel Yasky 

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