What is it?
Meningitis is an inflammation of the membranes (meninges) and cerebrospinal fluid surrounding your brain and spinal cord, usually due to the spread of an infection. The swelling associated with meningitis often triggers the "hallmark" symptoms of this condition, including headache, fever and a stiff neck.
Most cases of meningitis are caused by a viral infection, but bacterial and fungal infections also can lead to meningitis. Depending on the cause of the infection, meningitis can resolve on its own in a couple of weeks — or it can be a life-threatening emergency.
If you suspect that you or someone in your family has signs or symptoms of meningitis, seek medical care right away. Early treatment can prevent serious complications.
It's easy to mistake the early signs and symptoms of meningitis for the flu (influenza). Meningitis symptoms may develop over a period of one or two days and typically include:
- A high fever
- Severe headache
- Vomiting or nausea with headache
- Confusion, or difficulty concentrating — in the very young, this may appear as inability to maintain eye contact
- Sleepiness or difficulty waking up
- Stiff neck
- Sensitivity to light
- Lack of interest in drinking and eating
- Skin rash in some cases, such as in viral or meningococcal meningitis
Earlier signs and symptoms that may suggest a serious infection, although not necessarily meningitis, include:
- Leg pain
- Ice-cold hands and feet
- Abnormally pale skin tone
Signs in newborns
Newborns and young infants may not have the classic signs and symptoms of headache and stiff neck. Instead, signs and symptoms of meningitis in this age group may include:
- Constant crying
- Excessive sleepiness or irritability
- Poor feeding
- A bulge in the soft spot on top of a baby's head (fontanel)
- Stiffness in the baby's body and neck
Infants with meningitis may be difficult to comfort, and may even cry harder when picked up.
If you or your child has bacterial meningitis, delaying treatment increases the risk of permanent brain damage. In addition, bacterial meningitis can prove fatal in a matter of days. Seek medical care right away if you or anyone in your family has any signs or symptoms.
Meningitis usually results from a viral infection, but the cause may also be a bacterial infection. Less commonly, a fungal infection may cause meningitis. Because bacterial infections are the most damaging, identifying the source of the infection is an important part of developing a treatment plan.
Acute bacterial meningitis usually occurs when bacteria enter the bloodstream and migrate to the brain and spinal cord. But it can also occur when bacteria directly invade the meninges, as a result of an ear or sinus infection or a skull fracture.
A number of strains of bacteria can cause acute bacterial meningitis. The most common include:
- Streptococcus pneumoniae (pneumococcus). This bacterium is the most common cause of bacterial meningitis in infants and young children in the United States. It can also cause pneumonia and ear and sinus infections. When pneumococcal meningitis is associated with an ear infection, it's not always clear which came first — the meningitis or the ear infection — because they usually occur together.
- Neisseria meningitidis (meningococcus). This bacterium is another leading cause of bacterial meningitis. Meningococcal meningitis commonly occurs when bacteria from an upper respiratory infection enter your bloodstream. This infection is highly contagious and may cause local epidemics in college dormitories and boarding schools and on military bases.
- Haemophilus influenzae (haemophilus). Before the 1990s, Haemophilus influenzae type b (Hib) bacterium was the leading cause of bacterial meningitis. But new Hib vaccines — available as part of the routine childhood immunization schedule in the United States — have greatly reduced the number of cases of this type of meningitis. When it occurs, it tends to follow an upper respiratory infection, ear infection (otitis media) or sinusitis.
- Listeria monocytogenes (listeria). These bacteria can be found almost anywhere — in soil, in dust and in foods that have become contaminated. Contaminated foods have included soft cheeses, hot dogs and luncheon meats. Many wild and domestic animals also carry the bacteria. Fortunately, most healthy people exposed to listeria don't become ill, although pregnant women, newborns and older adults tend to be more susceptible. Listeria can cross the placental barrier, and infections in late pregnancy may cause a baby to be stillborn or die shortly after birth.
Viruses cause a greater number of cases of meningitis each year than do bacteria. Viral meningitis is usually mild and often clears on its own within two weeks. A group of common viruses known as enteroviruses are responsible for about 90 percent of viral meningitis.
The most common signs and symptoms of enteroviral infections are rash, sore throat, joint aches and headache. Many older children and adults with enteroviral meningitis describe the "worst headache I've ever had." These viruses tend to circulate in late summer and early fall. Viruses associated with mumps, herpes infection, West Nile virus or other diseases also can cause viral meningitis.
Ongoing (chronic) forms of meningitis occur when slow-growing organisms invade the membranes and fluid surrounding your brain. Although acute meningitis strikes suddenly, chronic meningitis develops over four weeks or more. Nevertheless, the signs and symptoms of chronic meningitis — headaches, fever, vomiting and mental cloudiness — are similar to those of acute meningitis. This type of meningitis is rare.
Fungal meningitis is relatively uncommon. Cryptococcal meningitis is a fungal form of the disease that affects people with immune deficiencies, such as AIDS. It's life-threatening if not treated with an antifungal medication.
Other meningitis causes
Meningitis can also result from noninfectious causes, such as drug allergies, some types of cancer and inflammatory diseases such as lupus.
Not completing the childhood vaccine schedule increases your risk of meningitis. So do a few other risk factors:
- Age. Most cases of viral meningitis occur in children younger than age 5. In the past, bacterial meningitis also usually affected young children. But since the mid-1980s, as a result of the protection offered by current childhood vaccines, the median age at which bacterial meningitis is diagnosed has shifted from 15 months to 25 years.
- Living in a community setting. College students living in dormitories, personnel on military bases, and children in boarding schools and child care facilities are at increased risk of meningococcal meningitis, probably because infectious diseases tend to spread quickly wherever large groups of people congregate.
- Pregnancy. If you're pregnant, you're at increased of contracting listeriosis — an infection caused by listeria bacteria, which may also cause meningitis. If you have listeriosis, your unborn baby is at risk, too.
- Working with animals. People who work with domestic animals, including dairy farmers and ranchers, have a higher risk of contracting listeria, which can lead to meningitis.
- Compromised immune system. Factors that may compromise your immune system — including AIDS, diabetes and use of immunosuppressant drugs — also make you more susceptible to meningitis. Removal of your spleen, an important part of your immune system, also may increase your risk.
The complications of meningitis can be severe. The longer you or your child has the disease without treatment, the greater the risk of seizures and of permanent neurological damage, including hearing loss, blindness, loss of speech, learning disabilities, behavior problems and brain damage, even paralysis.
Non-neurological complications may include kidney failure and adrenal gland failure. Your adrenal glands produce a number of important hormones including cortisol, which helps your body deal with stress.
Bacterial infections of your central nervous system progress quickly. Within a matter of days, the disease can lead to shock and death.
Your family doctor or pediatrician can diagnose meningitis based on a medical history, a physical exam and certain diagnostic tests. During the exam, your doctor may check for signs of infection around the head, ears, throat and the skin along the spine. You or your child may undergo the following diagnostic tests:
- Throat culture. A throat culture can find and identify the bacteria causing throat pain, neck pain and headache, but can't determine what pathogens may be in your spinal fluid.
- Imaging. X-rays and computerized tomography (CT) scans of the chest, skull or sinuses may reveal swelling or inflammation. These tests can also help your doctor look for infection in other areas of the body that may be associated with meningitis.
- Spinal tap (lumbar puncture). The definitive diagnosis of meningitis is often made by analyzing a sample of your cerebrospinal fluid (CSF), which is collected during a procedure known as a spinal tap. In people with meningitis, the CSF fluid often shows a low sugar (glucose) level along with an increased white blood cell count and increased protein. CSF analysis may also help your doctor identify the exact bacterium that's causing the illness.
- Polymerase chain reaction analysis. If your doctor suspects meningitis, he or she may order a DNA-based test known as a polymerase chain reaction (PCR) amplification to check for the presence of certain causes of meningitis.
If you have chronic meningitis caused by cancer or an inflammatory illness, you may need additional tests.