Meningitis - Causes, Symptoms and Treatment
In meningitis, the brain and the spinal cord meninges become inflamed, usually as a result of viral or bacterial infection. Viral meningitis is more prevalent than a bacterial cause. Such inflammation may involve all three meningeal membranesthe dura mater, arachnoid, and pia mater. The prognosis is good and complications are rare, especially if the disease is recognized early and the infecting organism responds to antibiotics. The prognosis is poorer for infants and older adults. In the case of children, the prognosis is poor for some types of bacterial meningitis, unless antibiotic therapy is started within hours of onset of symptoms.
Causes of Meningitis
Meningitis is almost always a complication of another bacterial infection-bacteremia (especially from pneumonia, empyema, osteomyelitis, and endocarditis), sinusitis, otitis media, encephalitis, myelitis, or brain abscess - usually caused by Neisseria meningitidis, Haemophilus intluenzae, Streptococcus pneumoniae, and Escherichia coli.
Meningitis may also follow skull fracture, a penetrating head wound, lumbar puncture, or ventricular shunting procedures. Aseptic meningitis may result from a virus or other organism. Sometimes no causative organism can be found. Meningitis often begins as an inflammation of the pia-arachnoid, which may progress to congestion of adjacent tissues and destroy some nerve cells.
Signs and Symptoms of Meningitis
Typical signs include the following features:
Cardinal Signs: Cardinal signs of meningitis include infection (fever, chills, malaise) and increased intracranial pressure (headache, vomiting and, rarely, papilledema).
Meningeal Irritation: Signs of meningeal irritation include nuchal rigidity, positive Brudzinski's and Kernig's signs, exaggerated and symmetrical deep tendon reflexes, and opisthotonos (a spasm in which the back and extremities arch backward so that the body rests on the head and heels).
Other Manifestations: Other features of meningitis are sinus arrhythmias; irritability; photophobia, diplopia, and other visual problems; delirium, deep stupor, and coma. An infant may show signs of infection but often is simply fretful and refuses to eat. Such an infant may vomit a great deal, leading to dehydration, which prevents a bulging fontanel and thus masks his important sign of increased intracranial pressure (ICP). As the illness progresses, twitching, seizures (in 30% of infants) or coma may develop. Most older children have the same symptoms as adults. In subacute meningitis, onset may be insidious.
Diagnosis for Meningitis
A lumbar puncture showing typical findings in cerebrospinal fluid (CSF) and positive Brudzinski's and Kernig's signs usually establish this diagnosis.The lumbar puncture usually indicates elevated CSF pressure from obstructed CSF outflow at the arachnoid villi. The fluid may appear cloudy or milky white, depending on the number of white blood cells present. CSF protein levels tend to be high; glucose levels may be low. (In subacute meningitis, CSF findings may vary.) CSF culture and sensitivity tests usually identify the infecting organism, unless it's a virus. Other useful tests include the following:
1. Cultures of blood, urine, and nose and throat secretions; a chest X-ray; electrocardiography; and a physical examination, with special attention to skin, ears, and sinuses, can uncover the primary infection site.
2. Blood tests commonly reveal leukocytosis and serum abnormalities.
3. Computed tomography scan can rule out cerebral hematoma, hemorrhage, or tumor.
Differential diagnoses include many diseases that can cause acute meningeal syndrome, such as brain abscess, subdural empyema, epidural abscess, encephalitis, CNS syphilis, bacterial endocarditis, rickettsial infections, sarcoidosis, CNS neoplasms, and neuroleptic malignant syndrome.
Treatment for Meningitis
In bacterial meningitis, treatment includes appropriate antibiotic therapy and vigorous supportive care. Usually, I.V. antibiotics are given for at least 2 weeks and are followed by oral antibiotics. Such antibiotics include ampicillin and a third-generation cephalosporin, such as ceftriaxone, or ampicillin and an aminoglycoside. Other drugs include a digitalis glycoside, such as digoxin, to control arrhythmias, mannitol to decrease cerebral edema, an anticonvulsant (usually given I. V.) or a sedative to reduce restlessness, and aspirin or acetaminophen to relieve headache and fever.
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