Meningitis
Meningitis is inflammation of the membranes (meninges) that surround the brain and spinal cord. Encephalitis refers to inflammation of the brain itself, which may occur alongside meningitis.
Encephalomyelitis is inflammation of both the brain and spinal cord, usually caused by viruses that infect the nervous tissues. People with encephalomyelitis may exhibit symptoms of either encephalitis or meningitis.
Types of meningitis
Meningitis may be acute or chronic. Infectious types include bacterial, viral, fungal, and parasitic meningitis.
- Bacterial meningitis
- Viral meningitis
- Fungal meningitis
- Parasitic meningitis
Most infectious meningitis is community-acquired, but hospital-acquired cases are rare. In 2015, an outbreak of fungal meningitis was linked to improperly prepared steroid medication from the New England Compounding Pharmacy.
Common causes of viral meningitis include enteroviruses, influenza, measles, mumps, and West Nile virus. Herpes simplex and varicella-zoster virus can cause viral meningoencephalitis.
Bacterial meningitis, particularly Streptococcus pneumoniae and Neisseria meningitidis, is life-threatening. Pneumococcus commonly affects young children, while meningococcus can cause gangrene and limb amputations.
Advances in medical care have decreased the incidence of meningococcal disease, and vaccination has played a significant role in prevention.
Other causes of acute bacterial meningitis include Hemophilus influenzae and Group B Streptococcus. Listeria monocytogenes is a serious cause of meningitis in pregnant women and people with weak immunity.
Fungal meningitis mostly affects individuals with compromised immune systems. Coccidioides immitis and Cryptococcus are common causative agents.
Parasitic causes of meningitis are rare and often associated with contact with animals or specific eating habits.
- Angiostrongylus cantonensis
- Bayliscaris procyonis
- Gnathostoma spinigerum
- Toxoplasma gondii
- Free-living amoebae
Primary amoebic meningitis and granulomatous meningoencephalitis are caused by amoeba found in water and soil, often leading to fatal outcomes.
Chronic meningitis, lasting four weeks or longer, is uncommon in developed countries. Tuberculosis is the most common cause worldwide, while other causes include syphilis, Lyme disease, fungi, and certain viruses.
