Meningitis

Meningitis is a medical emergency involving the inflammation of the meninges. The meninges are the protective membranes that surround the brain and spinal cord.

Because these layers sit so close to the central nervous system, swelling can be life-threatening. The term itself comes from the Greek word for membrane and the medical suffix -itis, which means inflammation. This condition can be acute, meaning it happens suddenly, or chronic, meaning it develops over time.

Most cases of meningitis are caused by infections. These infections may come from viruses, bacteria, fungi, or parasites. For example, some cases are caused by parasitic worms or amoebae. There are also non-infectious causes for this inflammation. These include malignancy, which is cancer, or a subarachnoid hemorrhage, which is bleeding in the space around the brain. Certain drugs or chronic inflammatory diseases like sarcoidosis can also trigger the condition.

In adults, the symptoms of bacterial meningitis follow a common pattern. A severe headache occurs in almost 90% of these cases. Neck stiffness is also very common, affecting about 70% of adults. This stiffness makes it difficult to flex the neck forward. Doctors often look for a "classic triad" of signs: sudden high fever, neck stiffness, and an altered mental status. However, all three signs are only present in about 44% to 46% of bacterial meningitis cases.

Doctors use specific physical tests to screen for the disease. One test is Kernig's sign, where a patient lies on their back with their hip and knee bent at 90 degrees. If pain limits the passive extension of the knee, the test is positive. Another is Brudziński's sign, where flexing the neck causes the patient's knee and hip to flex involuntarily. There is also the "jolt test," where a person rotates their head horizontally. If this movement does not make a headache worse, meningitis is considered unlikely.

Different bacteria cause meningitis depending on a person's age. In newborns, group B streptococci and Escherichia coli are common causes. Older children are more likely to be affected by Neisseria meningitidis or Streptococcus pneumoniae. In adults, these two bacteria together cause 80% of bacterial meningitis cases.

Some types, like meningococcal meningitis, can cause a specific petechial rash. This rash consists of small purple or red spots that are non-blanching. This means the spots do not fade when you press a glass against them.

To confirm a diagnosis, doctors often perform a lumbar puncture. During this procedure, a needle is inserted into the spinal canal to collect cerebrospinal fluid, or CSF. They examine this fluid to find evidence of infection. If meningitis is detected, treatment often involves antibiotics or antiviral drugs. Corticosteroids may also be used to reduce excessive inflammation. Rapid treatment is vital to prevent serious complications like deafness, epilepsy, or hydrocephalus.

The global impact of meningitis is significant. In 2019, about 7.7 million people were diagnosed with the condition worldwide. Of those, 236,000 people died. This is a decrease from 1990, when 433,000 people died. In some regions, like the "meningitis belt" in sub-Saharan Africa, outbreaks occur every year between December and June. However, with appropriate medical care, the risk of death from bacterial meningitis is less than 15%.