Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.
The
introduction of Hib vaccine as part of routine pediatric immunization has significantly reduced the occurrence of serious Hib disease. Newborns are usually infected with coliform (bacteria in the gut, contracted at birth) such as Escherichia coli or
Listeria.
How organisms are transmitted: Unlike the flu or the common
cold, which can be transmitted by casual contact or by simply breathing the air in the same room with an infected person, most of the bacteria causing meningitis are not very contagious. It would take the exchange of respiratory and throat secretions, from coughing, sneezing, or kissing, to spread the bacteria. The only exception is meningococcal meningitis. Anyone in the same household, or who had a prolonged contact, or was in direct contact with a person's oral secretions would be considered at increased risk of contracting the infection. People who have been exposed in this manner should receive preventive antibiotics.
Those most at risk: Anyone can get bacterial meningitis. It most commonly affects infants and small children. Anyone who had close or prolonged contact with a person affected by certain powerful bacteria (such as N. meningitidis or Hib) are also at increased risk. This includes day care workers, military recruits, jail cellmates, and anyone directly exposed to discharges from the mouth or nose of an infected person. The other groups at risk include people with weakened immune systems, diabetics, chronic alcoholics, IV drug abusers, and anyone older than 60 years
of age.
The following are other common brain infections:
Toxoplasmosis (also known as toxo) is caused by
the parasite Toxoplasma gondii. Infection is acquired, for example, from an infected mother to an unborn baby, by eating unwashed vegetables or undercooked meat, or by direct contact with cat feces (the cat is a host for this organism). The symptoms are similar to a mild form of bacterial meningitis. People at risk are pregnant women and those with weakened immune systems, such as people who are HIV positive. Prognosis is poor for infections transmitted from mother to newborn. More than 50% of affected infants die within a few weeks after birth. The disease also is severe in someone with a weakened immune system, and aggressive treatment with medications is used. Frequently, death results.
Cerebral cysticercosis is caused by the pork tapeworm. The infestation is acquired when people eat food contaminated by feces or eat the larvae. This disease has recently become relatively common in the
southwestern U.S. Depending on the stage of the disease, it could present as a mild form of meningitis, or more severe form, or even cause sudden death. The most common symptoms are seizures. Few medications can stop the progression of the disease. However, once the cerebral form is acquired, the treatment is usually given to relieve the symptoms.
Trichinosis is caused by the roundwormTrichinella spiralis. It is acquired by eating larvae in raw or undercooked pork. An infected person may have symptoms similar to encephalitis with confusion and delirium. Coma, seizures, paralysis, and other signs of neurologic loss are found in more severe forms. Most people recover within a few days or weeks without any long-term problems. The treatment is usually for the symptoms.
Cerebral abscess is often a complication of chronic sinus or middle-ear infections or the distant spread of the infection from somewhere else (such as a lung abscess or pneumonia). It can also be a consequence of head trauma or a neurosurgical procedure. The symptoms depend on the location of the abscess, but almost all people with this condition have a severe headache, fever, or generalized malaise. Treatment includes IV antibiotics and frequently surgical drainage.
Spinal abscess is caused by various bacteria. Most commonly, infection spreads to the spinal canal directly from any inflammation near the spine, such as certain ulcers or large and deep skin abscesses, or from a source of infection elsewhere in the body. Groups at risk include IV drug users, people with diabetes, or anyone on therapy with a weakened immune system. The spinal abscess usually develops suddenly, with fever, back pain, redness, and swelling of the affected area. Without treatment, muscular weakness and paralysis of the extremities may develop. Treatment includes surgical drainage and extensive use of IV antibiotics in the hospital.
Poliomyelitis (polio) is caused by a small poliovirus. The spread to the nervous system occurs when orally ingested virus multiplies in the digestive system, then gets into the bloodstream, and eventually enters the central nervous system. The disease progressively worsens and eventually leads to paralysis, coma, and arrest of the respiratory and cardiac muscle. Since the advent of the polio vaccine, the incidence of this disease has decreased dramatically in most of the developed countries. In the U.S., it is limited to
a few isolated cases and small epidemics in unvaccinated groups. The vaccination includes
three doses of vaccine within the first year of life, which would give a lifelong immunity. Infants with weak immune systems are at risk for contracting polio through immunization, but the risk is extremely small.
Rubella (German measles) is caused by the rubella virus. The consequences of this disease, affecting the unborn fetus infected during the first trimester of the pregnancy, could be devastating. The baby may be born with a variety of defects including deafness, mental retardation, and heart problems. At birth, the infant has a meningitis-like illness and usually is lethargic and inactive. The proper immunization of the mother, with a series of the vaccinations given throughout adolescence and early adulthood, would prevent a woman from getting rubella, which is especially important during pregnancy.
Mumps and measles are both caused by viruses. Young children are most commonly affected. Transmission occurs through the respiratory routes. Complications may include viral meningitis or encephalitis in varying degrees of severity. The most common complications of mumps
and measles are deafness and seizures, respectively. Prevention is attained through adequate childhood immunization.
Rabies is another viral infection. It is transmitted to humans by the bite of an infected animal or, in rare instances, by an inhalation of airborne viral particles in bat-infested caves or by laboratory workers. Worldwide, the disease is commonly caused by the bite of the rabid dog but also might be transmitted by cats, raccoons, skunks, foxes, wolves, and many other domestic and wild animals. Despite popular beliefs, no transmission has occurred from the bite of the mouse, rat, or rabbit. The disease is rare in the U.S., where we have tight control of rabid animals. The virus causes a severe form of encephalitis and myelitis. It may cause initial flu-like symptoms, very high (up to 107 F) fever, extreme restlessness, hypersensitivity to touch, general convulsions, total body paralysis, bizarre hallucinations, excessive flow of saliva, absolute refusal to drink any fluids, with gradual paralysis, coma, and almost invariably death. There is no specific antiviral therapy available, but preventive immunization is very effective and widely available.
AIDS and HIV encephalitis (also known as AIDS dementia) is caused by the human immunodeficiency virus (HIV). The HIV could directly infect the central nervous system, causing a range of neurologic conditions. The most common is so-called AIDS dementia. It is characterized by
the slow onset of
behavioral, intellectual, and motor impairment. Early symptoms include confusion, loss of libido, social withdrawal, decreased concentration, poor balance, and weaknesses. Psychiatric problems are common. In the late stage, severe dementia, inability to control urine flow,
and an inability to speak and walk are found. The treatment includes standard antiviral drugs, with variable results.
