Meningoencephalitis

Meningoencephalitis, also known as herpes 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 tissue.

Signs and symptoms

Signs of meningoencephalitis include unusual behavior, personality changes, nausea, and thinking problems.
Symptoms may include headache, fever, pain in neck movement, light sensitivity, and seizure.

Causes

The organisms which cause meningoencephalitis include bacterial pathogens, protozoans, and viruses.

Bacterial

Veterinarians have observed meningoencephalitis in animals infected with listeriosis, caused by the pathogenic bacteria L. monocytogenes. Meningitis and encephalitis already present in the brain or spinal cord of an animal may simultaneously form into meningeoencephalitis. The bacteria commonly targets the sensitive structures of the brain stem. L. monocytogenes meningoencephalitis has been documented to significantly increase the number of cytokines, such as interleukin-1beta, IL-12, and IL-15, leading to toxic effects on the brain.
Meningoencephalitis may be one of the severe complications of diseases originating from several Rickettsia species, such as Rickettsia rickettsii, Rickettsia conorii, Rickettsia prowazekii, and Rickettsia africae. It can impair the cranial nerves, cause paralysis to the eyes, and sudden hearing loss. Meningoencephalitis is a rare, late-stage manifestation of tick-borne ricksettial diseases, such as RMSF and human monocytotropic ehrlichiosis, caused by Ehrlichia chaffeensis.
Other bacteria that can cause meningoencephalitis are Mycoplasma pneumoniae, Tuberculosis, Borrelia, and Leptospirosis.

Viral

The viral organisms that cause meningoencephalitis include:

Tick-borne encephalitis
West Nile virus
Measles
Epstein–Barr virus
Varicella-zoster virus
Enterovirus
Herpes simplex virus type 1
Herpes simplex virus type 2
Rabies virus
Adenovirus
* Meningoencephalitis is almost solely seen in heavily immunocompromised patients.
Mumps
* A relatively common cause of meningoencephalitis. However, most cases are mild, and mumps meningoencephalitis generally does not result in death or neurologic sequelae.
HIV
* A very small number of individuals exhibit meningoencephalitis at the Acute [HIV infection|primary stage] of infection.

Autoimmune

Antibodies targeting amyloid beta peptide proteins have been used during research on Alzheimer's disease.
Anti-N-methyl-D-aspartate receptor antibodies, which are also associated with seizures and a movement disorder, are related to anti-NMDA receptor encephalitis.
Nonvasculitic autoimmune inflammatory meningoencephalitis can be divided into glial fibrillary acidic protein negative and GFAP positive cases. The second is related to the autoimmune GFAP astrocytopathy.

Protozoal

The protozoal organisms that cause meningoencephalitis include:

Animal

The nematode Halicephalobus gingivalis is an exceptionally rare cause of meningoencephalitis.

Other/multiple

Other causes of meningoencephalitis include granulomatous meningoencephalitis and vasculitis. The fungus, Cryptococcus neoformans, can symptomatically manifest within the central nervous system as meningoencephalitis, with hydrocephalus being a very characteristic finding due to the unique thick polysaccharide capsule of the organism.

Diagnosis

Clinical diagnosis includes evaluation for the presence of recurrent or recent herpes infection, fever, headache, altered mental status, convulsions, disturbance of consciousness, and focal signs. Testing of cerebrospinal fluid is usually performed.

Treatment

Meningoencephalitis caused by bacteria can be treated with antibiotic drugs. Antiviral therapy, such as acyclovir and ganciclovir, works best when given to the individual as early as possible. Individuals may also be treated with interferon as immune therapy. Symptomatic therapy can be applied as needed. A high fever can be treated by physical regulation of body temperature. Seizures can be treated with antiepileptic drugs. High intracranial pressure can be treated with drugs such as mannitol.