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Brain Infection (cont.)

What Causes a Brain Infection?

Causes of bacterial meningitis: Three types of bacteria are the most common causes of meningitis in all age groups except newborns:

  • Streptococcus pneumonia (causing pneumococcal meningitis)
  • Neisseria meningitidis (causing meningococcal meningitis)
  • Haemophilus influenza type b (Hib)

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 (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 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 containing tapeworm eggs. This disease has recently become relatively common in the southwestern U.S. Depending on the stage of the disease, symptoms could be those of 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, treatment is usually given to relieve the symptoms.
    • Trichinosis is caused by the roundworm Trichinella spiralis. It is acquired by eating larvae in raw or undercooked pork and some other wild meats, including bear, moose, and wild boar. 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 directed at symptom relief.
    • One of the most common infections transmitted by insects in the U.S. is Lyme disease. It is caused by the bacterium Borrelia burgdorferi, which infects and multiplies inside of ticks of the Ixodes species. Then it is transmitted to humans by the tick bite. If remained untreated, the disease can have serious complications, which include various neurologic problems. The most common neurologic complication is facial seventh nerve palsy (Bell's palsy, presenting as a facial droop) or damage to other facial nerves, and inflammatory radiculopathy (compression of nerve roots in the spine), which appears as tingling, burning pain, or numbness in an extremity. Although rare, the most concerning neurologic complication of late Lyme disease is meningitis, with its typical symptoms and signs. A small percentage of the patients with untreated Lyme disease and neurologic complications developed short-term memory problems and other cognitive deficits. Early treatment with antibiotics is advised when Lyme disease is suspected.
    • Coccidioidal meningitis is a severe complication of coccidiomycosis (valley fever), a common fungal infection in the southwestern U.S. The primary disease is caused by the inhalation of the Coccidioides soil fungal spores, leading to predominantly respiratory symptoms. Once the infection spreads to other organs via the bloodstream, almost half of those affected develop meningitis. The meningitis, in addition to the typical signs and symptoms, is most commonly complicated by the presence of a hydrocephalus, which is the abnormal accumulation of cerebrospinal fluid (CSF, fluid that bathes the brain and spinal cord) in the ventricles of the brain. Additionally, the inflammatory changes of the brain and its great vessels could cause symptoms similar to those of a stroke. The treatment of this condition is very complex, with both intravenous antifungal therapy and occasional direct infusion of the medication in fluids bathing the brain and spinal cords. The hydrocephalus frequently requires the placement of a ventriculoperitoneal shunt (which drains the extra CSF directly from the brain ventricles into the abdominal cavity). Despite all the technological and pharmacological developments in recent years, the prognosis for this condition remains poor.
    • An uncommon causative agent of meningitis, affecting almost exclusively immunocompromised people, is a fungus from the Cryptococcus family. This ubiquitous fungus thrives in soil and in the debris around tree bases, with a particular predilection for bird droppings. The usual mode of transmission is the inhalation of the fungal spores in soil, with subsequent spread through the bloodstream to the CNS. Cryptococcal CNS infection causes the typical symptoms and signs of meningitis. If left untreated, the patient has severe complications with permanent brain damage, hearing loss, and coma. In patients with severe immunodeficiency, the untreated disease is invariably fatal. The usual treatment is in-hospital long-term infusion of intravenous antifungal drugs. All people at risk should avoid bird droppings and any outside activities, including digging and working with soil.
    • Tuberculosis, caused by Mycobacterium tuberculosis, can spread through the lymphatic system to the CNS. The resulting meningitis, has a short initial period with symptoms of upper respiratory infection, followed by the onset of various neurologic deficits, such as visual impairment, focal weakness and numbness, and unstable gait with paralysis. The treatment is the same as for tuberculosis, with a multidrug regimen and symptomatic management in a hospital. Some studies suggested that BCG vaccination offers significant protection against tuberculous meningitis and should be strongly considered in people with high risk of contracting this disease.
    • 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.
Medically Reviewed by a Doctor on 6/10/2016
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