Meningitis is an inflammation of the meninges (the membranes surrounding the brain and spinal cord). It is most often caused by a viral or bacterial infection. Distinguishing between a viral and a bacterial cause is difficult; however, in the case of meningitis it is extremely important. Viral meningitis usually clears up on its own and does not cause any permanent harm. However, bacterial meningitis may lead to brain damage, learning disabilities, hearing loss, or death without treatment for the specific type of bacteria. There are approximately 12,500 cases of viral meningitis and 25,000 cases of bacterial meningitis reported annually in the United States, resulting in 2,200 deaths. Meningitis can also be caused by fungal infections (cryptococcus), tuberculosis, or chemicals.
Signs and symptoms of meningitis may differ by age and may differ somewhat by the cause or type of organism that causes it.
In newborns, signs and symptoms include the following:
- High-pitched cry
- Poor feeding
- Bulging fontanelle ("soft spot" in the skull) and/or stiff neck (less common)
In children and young adults, signs and symptoms include the following:
- Stiff neck
- Upper respiratory tract infection
- Sensitivity to light
- Tiny red or purple spots on the skin (petechiae) or other bleeding in the skin
- Clouding or loss of consciousness
The elderly may have no signs or symptoms other than altered mental state and lethargy. Often they have no fever, and the signs of meningitis are less predictable.
Several types of bacteria can cause meningitis:
- Neisseria meningitidis causes meningococcal meningitis, currently the most common form of meningitis in children and young adults, and the only type that occurs in outbreaks.
- Haemophilus influenzae was the most common cause in infants and children under 6 years old prior to 1986 when an H. influenza vaccine (HiB) was introduced. The vaccine has virtually eradicated this form of meningitis in countries where the vaccine is administered.
- Streptococcus pneumonia may occur following an ear or sinus infection, pneumonia, or injury to the head.
- Listeria monocytogenes tends to affect extremes of ages (newborns and the elderly).
- Group B streptococcus occurs in newborns.
- Gram-negative bacilli (such as Escherichia coli, Proteus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella spp., Enterococcus spp.) can cause meningitis following a head injury or brain surgery.
- Staphylococcus aureus may be seen following a head injury or brain surgery.
Viral meningitis can be caused by several types of viruses
- Enteroviruses (which multiply in the intestinal tract)—common in infants and small children
- Arboviruses—carried by arthropods, such as ticks; seen in children
- Mumps virus—seen in children between the ages of 5 and 9 who have not had the MMR vaccine
- Lymphocytic choriomeningitis virus—seen in workers who have contact with hamsters, rats, or mice
- Human immunodeficiency virus (HIV)—meningitis may be the first sign a person is infected with HIV
Meningitis, especially bacterial, is considered a medical emergency. The length of treatment varies with the organism being treated, ranging from 1 to 3 weeks. If bacterial meningitis is suspected, antibiotics must be started immediately, even before results from the lumbar puncture, blood tests, and imaging studies have been completed or returned.
The following categories of medications will be used or considered in the case of bacterial meningitis:
- Antibiotics, often in combination, including ampicillin, cephalosporins, gentamicin, vancomycin, and/or trimethoprim-sulfamethoxazole
- Corticosteriods to reduce neurologic complications
- Diazepam and/or phenytoin if seizures occur
- Rifampin is given to household contacts of those with meningococcal meningitis to reduce their risk of contracting the disease.
- There is no specific antiviral therapy for infection with enteroviruses, arboviruses, mumps virus, or lymphocytic choriomeningitis virus.
- Herpes simplex virus type 2 may be treated with acyclovir, but it is not clear that this changes the course of the illness.
- HIV meningitis may be treated with antiretroviral drugs.
- Intravenous gamma globulin to boost immunity may be used for those with meningitis caused by an enterovirus.