Meningitis is an inflammation of the arachnoid, the pia mater, and the intervening cerebrospinal fluid (CSF). The inflammatory process extends throughout the subarachnoid space about the brain and spinal cord and regularly involves the ventricles.
Causes of meningitis:
Meningitis is caused by different bacteria, viruses, mycobacterium tuberculosis, inflammatory diseases like SLE (systemic lupus erythematosis), behcet disease. Because bacterial infections are the most serious and can be life-threatening, 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, young children and adults in the United States. It more commonly causes pneumonia or ear or sinus infections.
- 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. It affects mainly teenagers and young adults, and may cause local epidemics in college dormitories, boarding schools and military bases.
- Haemophilus influenzae (haemophilus). Before the 1990s, Haemophilus influenzae type b (Hib) bacterium was the leading cause of bacterial meningitis in children. 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. 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. People with weakened immune systems, due to disease or medication effect, are most vulnerable.
Each year, viruses cause a greater number of cases of meningitis than do bacteria. Viral meningitis is usually mild and often cures on its own within two weeks. A group of viruses known as enteroviruses are responsible for about 30 percent of viral meningitis cases in the United States. As many viral meningitis episodes never have a specific virus identified as the cause.
The most common signs and symptoms of enteroviral infections are rash, sore throat, diarrhea, joint aches and headache. These viruses tend to circulate in late summer and early fall. Viruses such as herpes simplex virus, La Crosse virus, West Nile virus and others also can cause viral meningitis.
Chronic forms of meningitis is rare and occur when slow-growing organisms invade the membranes and fluid surrounding your brain. Although acute meningitis strikes suddenly, chronic meningitis develops over two weeks or more. Nevertheless, the signs and symptoms of chronic meningitis (headaches, fever, vomiting and drowsiness) are similar to those of acute meningitis.
Fungal meningitis is relatively uncommon and causes chronic meningitis. Occasionally it can mimic acute bacterial meningitis. Cryptococcal meningitis is a common 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,behcet’s disease.
SYMPTOMS OF MENINGITIS:
The classic signs and symptoms of meningitis are headache, fever, and stiff neck (in adults and older children). Symptoms of meningitis usually appear suddenly and can also cause nausea and vomiting. Behavioral changes, such as confusion, sleepiness, and difficulty waking up, are important symptoms. In infants, symptoms of meningitis are often much less specific and may include irritability or tiredness, poor feeding, and fever. Some types of meningitis like bacterial meningitis can be deadly if not treated promptly. Anyone experiencing symptoms of meningitis should see a doctor immediately.
Signs Of Meningitis:
Evidence of meningeal irritation (drowsiness), stiff neck, Kernig’s and Brudzinski’s signs is usually present. Although the classic triad of fever, stiff neck, and change in mental status is present in only 44% of episodes, a combination of two of four symptoms (headache, fever, stiff neck, and altered mental status) is found in 95% of patients. The findings of meningitis may be easily overlooked in infants or elderly patients with heart failure or pneumonia, who may have meningitis without prominent meningeal signs; their lethargy should be investigated carefully.
The presence of a petechial, purpuric, or ecchymotic rash in a patient with meningeal findings almost always indicates meningococcal infection and requires prompt treatment because of the rapidity with which this infection can progress. Cranial nerve abnormalities, involving principally the third, fourth, sixth, or seventh nerve, occur in 5 to 10% of adults with community-acquired meningitis and usually disappear shortly after recovery. Seizures focal or generalized occur in 20 to 30% of patients.
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