II. Causes: Viral (most cases)
- Causative organism identified in only half of cases
- Common
- Enterovirus Meningitis (50.9% of all Meningitis cases in adults)
- Herpes Simplex Encephalitis (8.3% of all Meningitis cases in adults, Very poor prognosis)
- Adults: Herpes Simplex Virus I
- Neonates: Herpes Simplex Virus II
- Varicella Zoster Virus (15% of cases)
- Mumps (Generally benign)
- Arbovirus (1.1% of all Meningitis causes in adults)
- Eastern Equine Encephalitis (70-90% poor prognosis)
- Western equine Encephalitis (2-20% poor prognosis)
- St. Louis Encephalitis (2-20% poor prognosis)
- Powassan Encephalitis (Tick Borne Illness, 50% with Cognitive Impairment, 10-15% mortality)
- California Encephalitis (generally benign)
- Venezuelan equine Encephalitis (generally benign)
- West Nile Virus Encephalitis (severe in elderly)
- Japanese Encephalitis (severe disease is uncommon, but 30% mortality when it occurs)
- Limited to travelers to rural and periurban Southeast Asia, Western Pacific
- Uncommon
- Parvovirus B19
- Epstein-Barr Virus
- Influenza
- Rabies (rare in U.S.)
- Immunocompromised
III. Causes: Other non-viral (uncommon)
- Bacterial causes
- Fungal causes
- Cryptococcus
- Coccidioides
- Histoplasma
- Parasitic causes
- Miscellaneous causes
- NMDA Encephalitis (very common in age <30 years old)
IV. Symptoms
- Sudden high fever
- Severe Headache
- Meningismus (e.g. Stiff neck)
-
Altered Level of Consciousness
- Lethargy
- Mental confusion
- Coma
- Behavior change
- Seizure
- Dysarthria
- Dysphasia
- Nausea and Vomiting
- Photophobia
- Hemiparesis
- Cranial Nerve deficits
- Visual Field loss
V. Signs
- Variable signs depending on involvement and organism
- See HSV Encephalitis
- See West Nile Virus Encephalitis (C0043124)
-
Tremor
- Tongue
- Lips
- Hands
- Other neurologic changes
- Ataxia
- Spastic paralysis
- Deep Tendon Reflexes exaggerated
- Signs of Increased Intracranial Pressure
VI. Differential Diagnosis
VII. Labs
- See Altered Level of Consciousness for general labs
-
Complete Blood Count (CBC)
- Mild Leukocytosis
- Mild Lymphocytosis
- Serum Electrolytes and Glucose
- Specific testing
- Strep Throat swab
- Influenza nasal swab
- St Loius Encephalitis serum IgM
- West Nile Virus serum IgM
- Western Equine Encephalitis serum IgM
- Mycoplasma pneumoniae IgM
- Lyme Disease Screening
- Serum RPR for Syphilis
- CMV culture from urine or Saliva (Test Sensitivity approaches 100%)
- Varicella culture from vessicles
- Herpes culture from Vesicles, mucous membranes and urine
- Cerebrospinal Fluid (CSF)
- Initial tests
- CSF Gram Stain
- CSF Culture
- CSF Protein
- CSF Glucose
- CSF Cell Count with differential
- Typical non-specific findings
- Increased Intracranial Pressure
- Increased Protein
- Lymphocytic Pleocytosis
- CSF Antigens (indicated if CSF findings not consistent with Bacterial Meningitis)
- CSF HSV PCR (Send in all cases of suspected Encephalitis)
- CSF enterovirus PCR
- Initial tests
VIII. Imaging
-
CT Head
- Indicated prior to Lumbar Puncture if focal neurologic findings or signs of Increased Intracranial Pressure
-
MRI Brain
- See HSV Encephalitis for HSV specific findings
- CMV Encephalitis
- Periventricular intracranial calcifications
- Cerebral dysgenesis
-
Congenital Toxoplasmosis
- Multiple ring-enhancing lesions
-
Cysticercosis
- Cystic lesions with variable calcifications
- Ring enhancement suggests cyst degeneration
IX. Management
- Empiric HSV management
- Cerebral Edema
- Mannitol
- Corticosteroids
- Only for specific indications
- Avoid in Herpes Simplex Virus
- Seizure control
- Specific empiric Management if cause suspected (Keep high level of suspicion for treatable etiologies)
- HSV Encephalitis
- Acyclovir IV (see dosing above)
- CMV Encephalitis (AIDS)
- Rocky Mountain Spotted Fever
- Doxycycline for any age where this is strongly suspected (causes tooth staining in under age 8 years)
- Cat-Scratch Disease Encephalitis
- Mycoplasma pneumoniae Encephalitis
- Lyme Encephalitis
- Ceftriaxone 75-100 mg/kg up to 2 grams IV q24 hours
- Influenza Encephalitis
- HSV Encephalitis
X. Course
- Symptomatic: weeks to months
XI. Prognosis
- Mortality during acute illness: 10%
- High rate of Disability following infection
- Variable depending on specific etiology
XII. References
- (2016) Sanford Guide, accessed 4/11/2016
- Fuchs and Yamamoto (2012) APLS, Jones and Bartlett, Burlington, p. 180-3
- Mailles (2009) Clin Infect Dis 49(12):1838-47 +PMID:19929384 [PubMed]
- Singh (2015) Neurology 84(4):359-66 +PMID:25540320 [PubMed]
Images: Related links to external sites (from Bing)
Related Studies
| Definition (MEDLINEPLUS) |
Encephalitis is an inflammation of the brain. Usually the cause is a viral infection, but bacteria can also cause it. It can be mild or severe. Most cases are mild. You may have flu-like symptoms. With a mild case, you may just need rest, plenty of fluids, and a pain reliever. Severe cases need immediate treatment. Symptoms of severe cases include
In babies, additional symptoms may include constant crying, poor feeding, body stiffness, and bulging in the soft spots of the skull. Severe cases may require a stay in the hospital. Treatments include oral and intravenous medicines to reduce inflammation and treat infection. Patients with breathing difficulties may need artificial respiration. Some people may need physical, speech, and occupational therapy once the illness is under control. NIH: National Institute of Neurological Disorders and Stroke |
| Definition (NCI) | An acute inflammatory process affecting the brain parenchyma. Causes include viral infections and less frequently bacterial infections, toxins, and immune-mediated processes. |
| Definition (MSH) | Inflammation of the BRAIN due to infection, autoimmune processes, toxins, and other conditions. Viral infections (see ENCEPHALITIS, VIRAL) are a relatively frequent cause of this condition. |
| Definition (CSP) | inflammation of the brain due to infection, autoimmune processes, toxins, and other conditions; viral infections are a relatively frequent cause of this condition. |
| Concepts | Disease or Syndrome (T047) |
| MSH | D004660 |
| SnomedCT | 267682000, 192736002, 267578009, 45170000 |
| LNC | LP20690-1 |
| French | ENCEPHALITE, Encéphalite SAI, Encéphalite |
| Portuguese | ENCEFALITE, Encefalite NE, Encefalite, Inflamação do Encéfalo |
| Spanish | ENCEFALITIS, Encefalitis NEOM, Inflamación del Encéfalo, encefalitis, SAI (trastorno), encefalitis, SAI, encefalitis (trastorno), encefalitis, Encefalitis |
| German | ENZEPHALITIS, Enzephalitis NNB, Enzephalitis, Entzündung, Gehirn |
| English | Encephalitis NOS, Encephalitis, BRAIN INFLAMM, INFLAMM BRAIN, ENCEPH, encephalitis, encephalitis (diagnosis), Brain Inflammation, Brain Inflammations, Inflammation, Brain, Encephalitis [Disease/Finding], brain inflammation, inflammation of the brain, Encephalitis NOS (disorder), ENCEPHALITIS, Encephalitis (disorder), brain; inflammation, cerebral; inflammation, inflammation; brain, inflammation; cerebral, Encephalitis, NOS |
| Dutch | encefalitis NAO, cerebraal; ontsteking, hersenen; ontsteking, ontsteking; cerebraal, ontsteking; hersenen, encefalitis, Encefalitis, Hersenontsteking, Ontsteking, hersen- |
| Italian | Encefalite NAS, Infiammazione del cervello, Encefalite |
| Japanese | 脳炎ＮＯＳ, ﾉｳｴﾝ, ﾉｳｴﾝNOS, 脳炎 |
| Swedish | Hjärninflammation |
| Czech | mozek - zánět, encefalitida, zánět mozku, Encefalitida, Encefalitida NOS |
| Finnish | Aivotulehdus |
| Russian | ENTSEFALIT, ЭНЦЕФАЛИТ |
| Croatian | UPALA MOZGA, ENCEFALITIS |
| Polish | Zapalenie mózgu |
| Hungarian | Encephalitis k.m.n., Encephalitis |
| Norwegian | Encefalitt, Hjernebetennelse |
Ontology: Viral Encephalitis (C0243010)
| Definition (MSHFRE) | Inflammation du parenchyme de l'encéphale ayant pour étiologie une infection virale. L'encéphalite peut être une manifestation primaire ou secondaire des infections par les : Togaviridae, Herpesviridae, Adenoviridae, Flaviviridae, Bunyaviridae, Picornaviridae, Paramyxoviridae, Orthomyxoviridae, Retroviridae, Arenaviridae. |
| Definition (MSH) | Inflammation of brain parenchymal tissue as a result of viral infection. Encephalitis may occur as primary or secondary manifestation of TOGAVIRIDAE INFECTIONS; HERPESVIRIDAE INFECTIONS; ADENOVIRIDAE INFECTIONS; FLAVIVIRIDAE INFECTIONS; BUNYAVIRIDAE INFECTIONS; PICORNAVIRIDAE INFECTIONS; PARAMYXOVIRIDAE INFECTIONS; ORTHOMYXOVIRIDAE INFECTIONS; RETROVIRIDAE INFECTIONS; and ARENAVIRIDAE INFECTIONS. |
| Concepts | Disease or Syndrome (T047) |
| MSH | D018792 |
| ICD10 | A86 |
| SnomedCT | 187400005, 266190006, 154321007, 192694006, 186503001, 34476008 |
| English | Encephalitis, Viral, Unspecfd viral encephalitis, Unspecified viral encephalitis, [X]Unspecfd viral encephalitis, [X]Unspecified viral encephalitis, Encephalitis in viral dis NOS, Encephalitis in viral disease NOS, INFECT ENCEPH VIRAL, VIRAL ENCEPH, ENCEPH INFECT VIRAL, ENCEPH VIRAL, Viral Encephalitis, viral encephalitis, viral encephalitis (diagnosis), Encephalomyelitis, Infectious, Viral, Encephalomyelitis, Viral Infectious, Infectious Encephalomyelitis, Viral, Viral Infectious Encephalomyelitis, Encephalitis, Viral [Disease/Finding], encephalitis viral, Encephalitis viral NOS, Encephalitis - viral, Viral encephalitis NOS, [X]Unspecified viral encephalitis (disorder), Encephalitis in viral disease NOS (disorder), Encephalitis viral, Viral encephalitis, Viral encephalitis (disorder), encephalitis; viral, viral; encephalitis, Viral encephalitis, NOS |
| Dutch | encefalitis viraal NAO, virusencefalitis, encefalitis; viraal, viraal; encefalitis, Niet gespecificeerde virale encefalitis, virale encefalitis, Encefalitis, virale, Encefalomyelitis, infectieuze virale, Infectieuze encefalomyelitis, virale, Virale encefalitis |
| French | Encéphalite virale SAI, Encéphalite virale, Encéphalo-myélite virale, Encéphalomyélite virale |
| German | virale Enzephalitis, Enzephalitis durch Viren NNB, Virusenzephalitis, nicht naeher bezeichnet, Virale Enzephalitis, Enzephalitis, Virus-, Virusenzephalitis, Enzephalomyelitis, infektiöse, virale, Infektiöse Enzephalomyelitis, virale |
| Italian | Encefalite virale NAS, Encefalomielite virale infettiva, Encefalite virale |
| Portuguese | Encefalite viral NE, Encefalite vírica, Encefalite viral, Encefalite Viral, Encefalomielite Infecciosa Viral |
| Spanish | Encefalitis vírica, Encefalitis vírica NEOM, encefalitis virósica, encefalitis vírica, [X]encefalitis viral no especificada (trastorno), encefalitis en enfermedad viral, SAI (trastorno), [X]encefalitis viral no especificada, encefalitis en enfermedad viral, SAI, encefalitis viral (trastorno), encefalitis viral, Encefalitis viral, Encefalitis Viral, Encefalomielitis Infecciosa Viral, Encefalomielitis Viral Infecciosa |
| Japanese | ウイルス性脳炎ＮＯＳ, ｳｲﾙｽｾｲﾉｳｴﾝ, ｳｲﾙｽｾｲﾉｳｴﾝNOS, 脳炎-ウイルス性, ウイルス性脳炎, ウイルス脳炎 |
| Swedish | Hjärninflammation, viral |
| Czech | encefalitida virová, Virová encefalitida NOS, Virová encefalitida |
| Finnish | Aivojen virustulehdus |
| Russian | ENTSEFALIT VIRUSNYI, ENTSEFALOMIELIT INFEKTSIONNYI VIRUSNYI, VIRUSNYI ENTSEFALIT, ВИРУСНЫЙ ЭНЦЕФАЛИТ, ЭНЦЕФАЛИТ ВИРУСНЫЙ, ЭНЦЕФАЛОМИЕЛИТ ИНФЕКЦИОННЫЙ ВИРУСНЫЙ |
| Korean | 상세불명의 바이러스 뇌염 |
| Croatian | ENCEFALITIS, VIRUSNI, VIRUSNI ENCEFALITIS |
| Polish | Zapalenie mózgu wirusowe |
| Hungarian | Viralis encephalitis, virusos encephalitis, virusos encephalitis k.m.n. |
| Norwegian | Viral encefalitt, Virusencefalitt, Encefalomyelitt, infeksiøs viral, Infeksiøs viral encefalomyelitt, Encefalitt, viral |
