Meningitis
In meningitis, the brain and the spinal cord meninges become inflamed. Such inflammation may involve all three meningeal membranes—the dura mater, the arachnoid membrane, and the pia mater.
For most patients, meningitis follows onset of respiratory symptoms. In about 50% of patients, it develops over a period of 1 to 7 days; in just under 20% of patients, it occurs 1 to 3 weeks after respiratory symptoms appear. Unheralded by respiratory symptoms, meningitis has a sudden onset in about 25% of patients, who become seriously ill within 24 hours.
The prognosis is good, and complications are rare, especially if the disease is recognized early and the infecting organism responds to antibiotics. However, mortality in untreated meningitis is 70% to 100%. The prognosis is poorer for infants and elderly people.
Causes
Meningitis can be caused by various bacteria, viruses, protozoa, or fungi. It most commonly results from bacterial infection, usually caused by Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, and Escherichia coli. In some patients, no causative organism can be found.
In most patients, the infection that causes meningitis is secondary to another bacterial infection, such as bacteremia (especially from pneumonia, empyema, osteomyelitis, and endocarditis), sinusitis, otitis media, encephalitis, myelitis, and brain abscess. Meningitis may also follow skull fracture, a penetrating head wound, lumbar puncture, or ventricular shunting procedures. Meningitis caused by a virus is known as aseptic viral meningitis. (See What you should know about aseptic viral meningitis.)
Infants, children, and elderly people have the highest risk of developing meningitis as well as those living in close contact with large populations. In addition to age, other risk factors include malnourishment, immunosuppression (as from radiation therapy, chemotherapy, or
long-term steroid therapy), and central nervous system trauma.
long-term steroid therapy), and central nervous system trauma.
What you should know about aseptic viral meningitis
A benign syndrome, aseptic viral meningitis is characterized by headache, fever, vomiting, and meningeal symptoms. It results from viral infections, such as enteroviruses (most common), arboviruses, herpes simplex virus, mumps virus, or lymphocytic choriomeningitis virus.
Assessment
The history of a patient with aseptic viral meningitis usually reveals sudden onset with such signs and symptoms as fever up to 104° F (40° C) and alterations in level of consciousness (drowsiness, confusion, or stupor). The patient may also report initially minor neck or spinal stiffness that occurs upon bending forward. The history may also reveal a recent illness.
Other signs and symptoms may include headache, nausea, vomiting, abdominal pain, poorly defined chest pain, and sore throat.
The patient history and your knowledge of seasonal epidemics are essential in differentiating among the many forms of aseptic viral meningitis. Negative bacteriologic cultures and cerebrospinal fluid (CSF) analysis showing pleocytosis and increased protein suggest the diagnosis, which is confirmed by isolation of the virus from CSF.
Supportive treatment
Management of aseptic meningitis includes bed rest, maintenance of fluid and electrolyte balance, analgesics for pain, and exercises to combat residual weakness. Isolation isn’t necessary. Careful handling of excretions and good hand-washing technique prevent the spread of the disease.
Complications
Depending on the cause and severity of the illness, potential complications of meningitis include visual impairment, irritability, optic neuritis, cranial nerve palsies, deafness, personality change, headache, paresis or paralysis, endocarditis, coma, vasculitis, and cerebral infarction.
Pediatric pointerComplications seen primarily in children include unilateral or bilateral sensory hearing loss, epilepsy, mental retardation, hydrocephalus, and subdural effusions.
