Meningoencephalitis
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# Overview
Meningoencephalitis is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain.  There are many causative organisms, including both viral and bacterial pathogens and parasitic microbes, which can give rise to meningoencephalitis along with other causative agents (such as certain antibodies).  The disease is associated with high rates of mortality and severe morbidity.

# Pathophysiology

## Microscopic Pathology
Mucormycosis meningoencephalitis

# Causes
Causative organisms include protozoans, viral and bacterial pathogens.

## Common Causes

## Causes by Organ System

## Causes in Alphabetical Order
- Acanthamoeba
- Actinomycosis
- Amyloid beta peptide protein antibodies
- Angiostrongyliasis
- Arboviral encephalitis
- Aseptic meningitis
- Bacteroides
- Balamuthia mandrillaris
- Bartonella infections
- Bartonellosis
- Behcet disease
- Biotinidase deficiency
- Campylobacter fetus
- Capnocytophaga canimorsus
- Cercopithecine herpesvirus 1
- Chagas disease
- Chandipura virus
- Cholesteatoma
- Colorado tick fever
- Cryptococcosis
- Eastern equine encephalitis
- Ehrlichiosis
- Elizabethkingia meningoseptica
- Enterobacter sakazakii
- Enterovirus
- Enterovirus 71
- Enterovirus antenatal infection
- Epstein-barr virus
- Escherichia coli
- Familial histiocytic reticulosis
- Granulomatous meningoencephalitis
- Haemophilus influenzae
- Hemophagocytic reticulosis
- Herpes simplex virus
- Hiv
- Human monocytotropic ehrlichiosis
- Japanese encephalitis
- Jc virus
- Kawasaki disease
- Klebsiella sp
- Kumlinge virus encephalitis
- Kunjin virus
- Leptospirosis
- Listeria monocytogenes
- Louping ill
- Lyme disease
- Lymphocytic choriomeningitis
- Measles
- Mumps
- Murray valley encephalitis virus
- Mycobacterium avium-intracellulare
- Mycoplasma pneumoniae
- Naegleria fowleri
- Neisseria meningitidis
- Nipah virus
- Pneumococcus
- Pontiac fever
- Powassan encephalitis virus
- Pseudomonas aeruginosa
- Queensland tick typhus
- Rabies
- Rickettsia prowazekii
- Rift valley fever
- Rubella congenital syndrome
- Salmonella typhi
- Sappinia diploidea
- Schistosoma japonicum
- Secondary syphilis
- Skull fracture
- Smith disease
- St louis encephalitis
- Staphylococcus aureus
- Streptococcus group b
- Streptococcus pneumoniae
- Streptococcus suis
- Syphilis
- Systemic lupus erythematosus
- Tick-borne encephalitis
- Tick-borne meningoencephalitis
- Toxoplasma gondii
- Toxoplasmosis
- Trypanosoma brucei
- Trypanosomiasis
- Tuberculosis
- Varicella-zoster virus
- Venezuelan equine encephalitis
- West african trypanosomiasis
- West nile virus
- Western equine encephalitis
- Yersinia pestis

## Bacterial
- Listeria monocytogenes
- Neisseria meningitidis
- Rickettsia prowazekii

## Viral
- Tick-borne meningoencephalitis
- West Nile virus
- Herpes Simplex Virus Type I. Being the primary infection than when recurrent, goes to encephalitis.
- Mumps, a relatively common cause of meningoencephalitis.  However, most cases are mild, and mumps meningoencephalitis generally does not result in death or neurologic sequalae.
- HIV, a very small number of individuals exhibit meningoencephalitis at the primary stage of infection.

## Other/multiple
- Granulomatous meningoencephalitis
- Other causes include antibodies targeting amyloid beta peptide proteins which have been used during research on Alzheimer's disease.
- The fungus, Cryptococcus neoformans, can be symptomatically manifested within the CNS as meningoencephalitis with hydrocephalus being a very characteristic finding due to the unique thick polysaccharide capsule of the organism.

## Protozoal
- Primary amoebic meningoencephalitis e.g., Naegleria fowleri, Balamuthia mandrillaris, Sappinia diploidea.
- Trypanosoma brucei
- Toxoplasma gondii (sporozoa) (immunocompromised patients)
Ameobic pathogens exist as free-living protozoans. Nevertheless, these pathogens cause rare and uncommon CNS infections. N. fowleri produces primary amebic meningoencephalitis (PAM). The symptoms of PAM are indistinguishable from acute bacterial meningitis. Other amebae cause granulomatous amebic encephalitis (GAE), which is a more subacute and can even a non-symptomatic chronic infection. Ameobic meningoencephalitis can mimic a brain abscess, aseptic or chronic meningitis, or CNS malignancy.

# Prognosis
The disease is associated with high rates of mortality and severe morbidity.

# Related Chapters
- Granulomatous meningoencephalitis
- Primary amoebic meningoencephalitis
- Tick-borne meningoencephalitis
- West Nile virus
- Meningitis
- Meningism
- Primary amoebic meningoencephalitis
- Encephalitis