Viral Encephalitis

1. See Also
   1. Meninigitis
   2. HSV Encephalitis
   3. Progressive Multifocal Leukoencephalopathy
   4. West Nile Virus Encephalitis
2. Causes: Viral (most cases)
   1. Common
      1. Herpes Simplex Encephalitis (Very poor prognosis)
         1. Adults: Herpes Simplex Virus I
         2. Neonates: Herpes Simplex Virus II
      2. Arbovirus
         1. Eastern equine Encephalitis (70-90% poor prognosis)
         2. Western equine Encephalitis (2-20% poor prognosis)
         3. St. Louis Encephalitis (2-20% poor prognosis)
         4. California Encephalitis (generally benign)
         5. Venezuelan equine Encephalitis (generally benign)
         6. West Nile Virus Encephalitis (severe in elderly)
      3. Mumps (Generally benign)
   2. Uncommon
      1. Enterovirus
      2. Varicella Zoster Virus
      3. Epstein-Barr Virus
      4. Influenza
      5. Rabies (rare in U.S.)
   3. Immunocompromised
      1. Cytomegalovirus (AIDS)
3. Causes: Other (uncommon)
   1. Bacterial causes
      1. Borrelia Burgdorferi (Lyme Disease)
      2. Bartonella henselae (Cat Scratch Disease)
      3. Rickettsia rickettsii (Rocky Mountain Spotted Fever)
      4. Mycoplasma pneumoniae
      5. Treponema pallidum (Syphilis)
   2. Fungal causes
      1. Cryptococcus
      2. Coccidioides
      3. Histoplasma
   3. Parasitic causes
      1. Taenia solium (Cysticercosis)
      2. Plasmodium falciparum (Malaria)
      3. Toxoplasma gondii (Toxoplasmosis)
4. Symptoms
   1. Sudden high fever
   2. Severe Headache
   3. Meningismus (e.g. Stiff neck)
   4. Altered Level of Consciousness
      1. Lethargy
      2. Mental confusion
      3. Coma
   5. Behavior change
   6. Seizure
   7. Dysarthria
   8. Dysphasia
   9. Nausea and Vomiting
   10. Photophobia
   11. Hemiparesis
   12. Cranial Nerve deficits
   13. Visual field loss
5. Signs
   1. Variable signs depending on involvement and organism
      1. See HSV Encephalitis
      2. See West Nile Virus Encephalitis (C0043124)
   2. Tremor
      1. Tongue
      2. Lips
      3. Hands
   3. Other neurologic changes
      1. Ataxia
      2. Spastic paralysis
      3. Deep Tendon Reflexes exaggerated
      4. Signs of Increased Intracranial Pressure
6. Differential Diagnosis
   1. See Altered Level of Consciousness Causes
   2. See Drug Induced Altered Level of Consciousness Causes
7. Labs
   1. See Altered Level of Consciousness for general labs
   2. Complete Blood Count (CBC)
      1. Mild Leukocytosis
      2. Mild Lymphocytosis
   3. Serum electrolytes and Glucose
   4. Specific testing
      1. Strep Throat swab
      2. Influenza nasal swab
      3. St Loius Encephalitis serum IgM
      4. West Nile Virus serum IgM
      5. Western Equine Encephalitis serum IgM
      6. Mycoplasma pneumoniae IgM
      7. Lyme Disease Screening
      8. Serum RPR for Syphilis
      9. CMV culture from urine or Saliva (Test Sensitivity approaches 100%)
      10. Varicella culture from vessicles
      11. Herpes culture from Vesicles, mucous membranes and urine
   5. Cerebrospinal Fluid (CSF)
      1. Initial tests
         1. CSF Gram Stain
         2. CSF Culture
         3. CSF Protein
         4. CSF Glucose
         5. CSF Cell Count with differential
      2. Typical non-specific findings
         1. Increased Intracranial Pressure
         2. Increased Protein
         3. Lymphocytic Pleocytosis
      3. CSF Antigens (indicated if CSF findings not consistent with Bacterial Meningitis)
         1. CSF HSV PCR (Send in all cases of suspected Encephalitis)
         2. CSF enterovirus PCR
8. Imaging
   1. CT Head
      1. Indicated prior to Lumbar Puncture if focal neurologic findings or signs of Increased Intracranial Pressure
   2. MRI Brain
      1. See HSV Encephalitis for HSV specific findings
      2. CMV Encephalitis
         1. Periventricular intracranial calcifications
         2. Cerebral dysgenesis
      3. Congenital Toxoplasmosis
         1. Multiple ring-enhancing lesions
      4. Cysticercosis
         1. Cystic lesions with variable calcifications
         2. Ring enhancement suggests cyst degeneration
9. Management
   1. Cerebral Edema
      1. Mannitol
      2. Corticosteroids
         1. Only for specific indications
         2. Avoid in Herpes Simplex Virus
   2. Seizure control
   3. Specific empiric Management if cause suspected (Keep high level of suspicion for treatable etiologies)
      1. HSV Encephalitis: Acyclovir IV
         1. Start Acyclovir empirically for Encephalitis case and continue until diagnosis is excluded
      2. CMV Encephalitis (AIDS): Ganciclovir or Foscarnet
      3. Rocky Mountain Spotted Fever
         1. Doxycycline for any age where this is strongly suspected (causes tooth staining in under age 8 years)
      4. Cat-Scratch Disease Encephalitis
         1. Azithromycin or
         2. Doxycycline
      5. Mycoplasma pneumoniae Encephalitis
         1. Azithromycin or
         2. Doxycycline
      6. Lyme Encephalitis
         1. Ceftriaxone 75-100 mg/kg up to 2 grams IV q24 hours
      7. Influenza Encephalitis
         1. Oseltamivir (Tamiflu)
10. Course
    1. Symptomatic: weeks to months
11. Prognosis
    1. Mortality during acute illness: 10%
    2. High rate of Disability following infection
       1. Variable depending on specific etiology
12. Resources: Patients
    1. Encephalitis Global Support Website
       1. http://communities.msn.com/encephalitisglobal
13. References
    1. Fuchs and Yamamoto (2012) APLS, Jones and Bartlett, Burlington, p. 180-3