pl. meningitides [meningo- + -itis]
Inflammation of the membranes of the spinal cord or brain, usually but not always caused by an infectious illness. Bacterial meningitis is a medical emergency that must be diagnosed and treated quickly to obtain the best outcome.
Bacterial meningitis is fatal in 10% to 40% of cases, even with optimal therapy, and may result in persistent neurological injury in about 10% of patients who survive the initial infection. In the U.S., bacterial meningitis formerly affected infants and children more than adults; the demographics of the disease changed in the 1990s after vaccines against Haemophilus influenzae were introduced into pediatric care. Infectious meningitis now is largely a disease of adults and usually is caused by Streptococcus pneumoniae or Neisseria meningitidis, although other microbes may be responsible. Intravenous steroids (such as dexamethasone) given at the beginning of therapy decreases the risk of death and disability.
Meningitis may result from infection with bacteria, viruses, mycobacteria, fungi, amebas, or noninfectious sources, such as chemical irritation. Occasionally, infectious meningitis follows head trauma or sinus or ear infection. It also may result from the spread of blood-borne infection.
SYMPTOMS AND SIGNS
The symptoms of meningitis include fever, chills, headache, stiff neck, altered mental status, vomiting, and photophobia. Many patients with meningitis present with only two or three of these clinical indicators. Acute bacterial meningitis and meningitis caused by some fungi and amebas may also cause rapid deterioration in mental status, seizures, shock, and death.
Cerebrospinal fluid (CSF) must be examined. A cell count to assess the level of inflammation, a Gram stain to look for infectious organisms, measurement of spinal fluid pressure, and levels of bacterial antigens, glucose, lactate, and protein are typically obtained. CSF may appear milky white due to the large numbers of white blood cells present.
All children in the U.S. are now vaccinated against H. influenzae type b (Hib) and pneumococcus (Prevnar) as primary prevention against the disease. Meningococcal polysaccharide vaccines are highly effective in preventing the disease during epidemic outbreaks with this organism. Close family contacts of patients with meningococcal meningitis, day care center contacts of infected children, or any persons (including health care workers) with direct contact with the saliva of infected patients are to be treated with antibiotics to prevent disease transmission.
Definitive treatment depends on identification of the underlying causes, but empirical therapies for infectious meningitis must be given immediately, hours before the causative agent is identified. Dexamethasone is administered intravenously before starting antibiotic therapy for best response to reduce the incidence of deafness in children (a common complication) and to help prevent death in adults with pneumococcal meningitis. The evolution of penicillin-resistant strains of pneumococci has altered traditional empirical treatments. Third-generation cephalosporins, ampicillin and gentamicin, chloramphenicol, or vancomycin plus rifampin have been given, depending on the patient's age, level of immune function, or clinical presentation. Antibiotic therapy is usually administered intravenously for 2 weeks, then orally for a prescribed period for bacterial infections. Viral meningitis treatment is supportive; recovery usually is complete (within 7 to 10 days). Antipyretic analgesics relieve headache and fever.
Specific measures for coexisting conditions and for shock and other complications (disseminated intravascular coagulation, metabolic acidosis, or seizures) should be initiated when indicated. Supportive therapies include bed rest, a dimly lit room, and reduced sensory stimulation. Standard precautions apply, and airborne/droplet precautions are initiated if nasal cultures are positive. Neurologic function is closely monitored for changes in level of consciousness, signs of increasing intracranial pressure (ICP), and indications of cranial nerve involvement. Fluid and electrolyte balance is monitored, and fluids are provided in quantities to prevent or treat dehydration while avoiding fluid overload and resultant cerebral edema. The patient is assessed for adverse effects of antibiotic therapy with peak and trough blood levels assessed to ensure therapeutic levels and avoid toxic overdose. The patient is repositioned carefully and assisted with range-of-motion exercises to prevent skin, muscle, and joint complications. Frequent mouth care is provided and adequate nutrition and elimination are maintained. Small frequent meals, nasogastric or parenteral feedings are provided as required. Constipation is prevented by stool softeners or mild laxatives to prevent straining, which could increase ICP. Basic explanations, realistic reassurance, and support are provided, with reorientation if delirium or confusion is present. Questions from the patient and family should be answered honestly, with reassurance that behavioral changes usually resolve.
The patient with infectious meningitis may need monitoring in an ICU. Patients with neurologic deficits that appear to be continuing should be referred to a rehabilitation program once the acute phase of illness has ended. To help prevent meningitis, patients with chronic sinusitis or other chronic infectious or inflammatory illnesses should be taught the importance of proper hand hygiene and of following through with prescribed treatments. Sterile techniques should be strictly enforced when treating patients with head wounds, skull fractures, or lumbar puncture, ventricular shunting, or other invasive therapies.
MENINGITIS Streptococcus pneumoniae in cerebrospinal fluid (Orig. mag. ×400)
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