Encephalitis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Common encephalidites include:

Viral encephalitis

• Herpes simplex encephalitis
• VZV encephalitis
• Nipah virus encephalitis

Vector-borne encephalitis

• Tick-borne encephalitis
• California encephalitis
• Eastern equine encephalitis
• Western equine encephalitis
• Japanese encephalitis
• Venezuelan equine encephalitis
• West Nile encephalitis
• La Crosse encephalitis
• St. Louis encephalitis

Protozoan encephalitis

• Granulomatous amebic encephalitis
• Toxoplasmic encephalitis

Differential diagnosis

Encephalitis must be differentiated from other causes of headache, seizures and loss of consciousness.

Diseases	Symptoms				Physical Examination					Past medical history	Diagnostic tests			Other Findings
	Headache	↓LOC	Motor weakness	Abnormal sensory	Motor Deficit	Sensory deficit	Speech difficulty	Gait abnormality	Cranial nerves		CT /MRI	CSF Findings	Gold standard test
Meningitis	+	-	-	-	-	+	+	-	-	History of fever and malaise	-	↑ Leukocytes, ↑ Protein ↓ Glucose	CSF analysis	Fever, neck rigidity
Encephalitis	+	+	+/-	+/-	-	-	+	+/-	+	History of fever and malaise	+	↑ Leukocytes, ↓ Glucose	CSF PCR	Fever, seizures, focal neurologic abnormalities
Brain tumor	+	-	-	-	+	+	+	-	+	Weight loss, fatigue	+	Cancer cells	MRI	Cachexia, gradual progression of symptoms
Hemorrhagic stroke	+	+	+	+	+	+	+	+	-	Hypertension	+	-	CT scan without contrast	Neck stiffness
Subdural hemorrhage	+	+	+	+	+	-	-	-	+	Trauma, fall	+	Xanthochromia	CT scan without contrast	Confusion, dizziness, nausea, vomiting
Neurosyphilis	+	-	+	+	+	+	-	+	-	STIs	+	↑ Leukocytes and protein	CSF VDRL-specifc CSF FTA-Ab -sensitive	Blindness, confusion, depression, Abnormal gait
Complex or atypical migraine	+	-	+	+	-	-	+	-	-	Family history of migraine	-	-	Clinical assesment	Presence of aura, nausea, vomiting
Hypertensive encephalopathy	+	+	-	-	-	-	+	+	-	Hypertension	+	-	Clinical assesment	Delirium, cortical blindness, cerebral edema, seizure
Wernicke’s encephalopathy	-	+	-	-	-	+	+	+	+	History of alcohal abuse	-	-	Clinical assesment and lab findings	Ophthalmoplegia, confusion
CNS abscess	+	+	-	-	+	+	+	-	-	History of drug abuse, endocarditis, immunosupression	+	↑ leukocytes, ↓ glucose and ↑ protien	MRI is more sensitive and specific	High grade fever, fatigue,nausea, vomiting
Drug toxicity	-	+	-	+	+	+	-	+	-	-	-	-	Drug screen test	Lithium, Sedatives, phenytoin, carbamazepine
Conversion disorder	+	+	+	+	+	+	+	+		History of emotional stress	-	-	Diagnosis of exclusion	Tremors, blindness, difficulty swallowing
Metabolic disturbances (electrolyte imbalance, hypoglycemia)	-	+	+	+	+	+	-	-	+	-	-	Hypoglycemia, hypo and hypernatremia, hypo and hyperkalemia	Depends on the cause	Confusion, seizure, palpitations, sweating, dizziness, hypoglycemia
Multiple sclerosis exacerbation	-	-	+	+	-	+	+	+	+	History of relapses and remissions	+	↑ CSF IgG levels (monoclonal bands)	Clinical assesment and MRI	Blurry vision, urinary incontinence, fatigue
Seizure	+	+	-	-	+	+	-	-	+	Previous history of seizures	-	Mass lesion	Clinical assesment and EEG	Confusion, apathy, irritability,

Comprehensive List of Causes of Encephalitis & Encephalopathy

Cardiovascular	Kawasaki disease
Chemical / poisoning	Arsenic, heavy metal toxicity, icaridin, organophosphate poisoning, poison hemlock, thallium
Dermatologic	Behcet disease, systemic lupus erythematosus, Vogt-Koyanagi-Harada syndrome
Drug Side Effect	Acyclovir, interferon, kynurenic acid, levodopa, methamphetamine, trimethobenzamide, zanamivir
Ear Nose Throat	Cholesteatoma, labyrinthitis, sinusitis
Endocrine	Myasthenia gravis
Environmental	No underlying causes
Gastroenterologic	Porphyria, Reye's syndrome
Genetic	Aicardi-Goutières syndrome, biotinidase deficiency, familial histiocytic reticulosis, hemophagocytic reticulosis, ornithine transcarbamylase deficiency, porphyria, Smith disease, Tourette syndrome
Hematologic	Familial histiocytic reticulosis, hemophagocytic reticulosis, lymphoproliferative syndrome, porphyria, x-linked agammaglobulinemia
Iatrogenic	No underlying causes
Infectious Disease	alkhurma virus, Borrelia burgdorferi, botulism, brome mosaic virus, California encephalitis virus, campylobacter fetus, capnocytophaga canimorsus, cardiovirus, cat scratch disease, cercopithecine herpesvirus 1, Chagas disease, chandipura virus, chicken pox, coccidioides spp, Colorado tick fever, congenital herpes simplex, congenital rubella syndrome, congenital syphilis, coxiella burnetii , coxsackievirus, Creutzfeldt-Jakob disease, cryptococcosis, cryptococcus neoformans, cysticercosis, cytomegalovirus, dengue fever, diphtheria, duvenhage virus, Eastern equine encephalitis virus, Ebstein-Barr virus, ehrlichia chaffeensis, ehrlichiosis, elizabethkingia meningoseptica, enterobacter sakazakii, enterovirus 70, enterovirus 71, enteroviruses, escherichia coli, feline viral rhinotracheitis, fetal parainfluenza virus type 3, flavivirus infections, flu, gnathostoma hispidum infection, gnathostoma spinigerum, gnathostoma spinigerum infection, gnathostomiasis, streptococcus, group B, haemophilus influenzae, hand-foot-and-mouth disease, hantavirosis , hemorrhagic fever, hendra virus, henipavirus, hepatitis E virus, herpes B virus, herpes simplex virus, histoplasma capsulatum, HIV, human granulocytotrophic ehrlichiosis, human herpesvirus 6, human monocytotrophic ehrlichiosis, immunosuppressive measles encephalitis, infectious canine hepatitis, influenza virus, Japanese encephalitis, JC virus, klebsiella, kumlinge virus encephalitis, kunjin virus, La Crosse encephalitis, labyrinthitis, lassa fever, listeria monocytogenes, listeriosis , louping ill, Lyme disease, lymphocytic choriomeningitis, lyssavirus, malaria, measles, mokola virus, mononucleosis , mumps , mumps virus, Murray Valley encephalitis virus, mycobacterium avium-intracellulare, mycobacterium tuberculosis, mycoplasma pneumoniae, naegleria fowleri, neisseria meningiditis, neonatal herpes, nipah virus, nocardia, pertussis, phlebovirus, pneumococcus, poliomyelitis, pontiac fever, Powassan virus, poxviridae disease, primary amoebic meningoencephalitis , primary encephalitis, progressive multifocal leukoencephalopathy, pseudomonas aeruginosa, psittacosis, Q fever, Queensland tick typhus, rabies, Rasmussen's encephalitis, rickettsiae, Rift Valley fever, rocio encephalitis, Rocky Mountain spotted fever, rubella, salmonella typhi, schistosoma japonicum, secondary encephalitis, shingles, Simian B virus infection, sinusitis, St. Louis encephalitis, staphylococcus aureus, streptococcus pneumoniae, streptococcus suis, subacute sclerosing panencephalitis, taenia solium, tick-borne encephalitis, togaviridae disease, TORCH syndrome, toxocariasis, toxoplasma gondii, toxoplasmosis, trench fever, treponema pallidum, trichinella, trichinosis, tropheryma whipplei, trypanosoma brucei gambiense, trypanosomiasis, typhoid fever, vaccinia, varicella zoster, varicella zoster virus, Venezuelan equine encephalitis, viral encephalitis, visna virus, West Nile fever, Western equine encephalitis, whooping cough, yersinia pestis
Musculoskeletal / Ortho	Metabolic myopathies, multiple sclerosis, skull fracture
Neurologic	Aicardi-Goutières syndrome, amyotrophic lateral sclerosis, aseptic meningitis, cauda equina syndrome, cerebral palsy, chronic inflammatory demyelinating polyneuropathy, conus medullaris, Creutzfeldt-Jakob disease, Lennox-Gastaut syndrome, multiple sclerosis, opsoclonus myoclonus syndrome, paraneoplastic neurologic disorders, poliomyelitis, progressive multifocal leukoencephalopathy, Rasmussen syndrome, Schilder's disease, St. Louis encephalitis, status epilepticus, subacute sclerosing panencephalitis, temporal lobe epilepsy, Tourette syndrome, tourettism, Vogt-Koyanagi-Harada syndrome
Nutritional / Metabolic	Biotinidase deficiency, metabolic myopathies, ornithine transcarbamylase deficiency
Obstetric/Gynecologic	TORCH syndrome
Oncologic	Paraneoplastic neurologic disorders
Opthalmologic	Vogt-Koyanagi-Harada syndrome
Overdose / Toxicity	Heavy metal toxicity, Reye's syndrome
Psychiatric	Progressive multifocal leukoencephalopathy, shaken baby syndrome, Tourette syndrome
Pulmonary	Flu, pertussis, whooping cough
Renal / Electrolyte	Systemic lupus erythematosus
Rheum / Immune / Allergy	Behcet disease, chronic inflammatory demyelinating polyneuropathy, multiple sclerosis, systemic lupus erythematosus, x-linked agammaglobulinemia
Sexual	No underlying causes
Trauma	Cauda equina syndrome, shaken baby syndrome, skull fracture
Urologic	No underlying causes
Miscellaneous	Porphyria