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Meningitis - Causes, Symptoms and Treatment
Definition:
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.
Special considerations
- Several vaccines are available to protect against certain types of meningitis.
- There are vaccines against Haemophilus influenzae, type B; some strains of N. meningitidis; and many types of Streptococcus pneumoniae.
- Supportive measures include bed rest, fever reduction, and mcasures to prevent dehydration. Isolation is necessary if nasal cultures are positive.
- Of course, treatment includes appropriatce therapy for any coexisting conditions, such as endocarditis or pneumonia.
- To prevent meningitis, prophylactic antibiotics are sometimes used after ventricular shunting procedures, skull fracture, or penetrating head wounds, but this use is controversial.
- Assess neurologic function often. Observe the patient's level of consciousness, and check for signs of increased ICP (plucking at the bedcovers, vomiting, seizures, change in motor functions and vital signs). Also watch for signs of cranial nerve involvement (ptosis, strabismus, diplopia).
- Watch for deterioration in the patient's condition, which may signal an impending crisis.
- Monitor fluid balance. Maintain adequate fluid intake to avoid dehydration, but avoid fluid overload because of the danger of cerebral edema. Measure central venous pressure and intake and output accurately.
- Watch for adverse reactions to I.V. antibiotics and other drugs. To avoid infiltration and phlebitis, check the I.V. site often, and change the site according to facility policy.
- Position the patient carefully to prevent joint stiffness and neck pain. Turn him often, according to a planned positioning schedule. Assist with range-of-motion exercise.
- Maintain adequate nutrition and elimination. It may be necessary to provide small, frequent meals or supplement these meals with nasogastric tube or parenteral feedings.
- To prevent constipation and minimize the risk of increased ICP resulting from straining during defecation, give the patient a mild laxative or stool softener.
- Ensure the patient's comfort. Provide mouth care regularly. Maintain a quiet environment. Darkening the room may decrease photophobia.
- Relieve the patient's headache with a nonnarcotic analgesic, such as aspirin or acetaminophen, as needed. (Narcotics interfere with neurologic assessment.)
- Provide reassurance and support. The patient may be frightened by his illness and procedures, such as frequent lumbar punctures. If he is delirious or confused, attempt to reorient him often. Reassure the family that the delirium and behavior changes caused by meningitis usually disappear.
- If a severe neurologic deficit appears permanent, refer the patient to a rehabilitation program as soon as the acute phase of this illness has passed.
- Follow strict aseptic technique when treating patients with head wounds or skull fractures.
- To help prevent development of meningitis, teach patients with chronic sinusitis or other chronic infections the importance of proper medical treatment.
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