Brain Infection (cont.)
More Brain Infection Causes
- 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, extension from the GI tract, 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.
- The West Nile virus and other members of the encephalitis-causing virus family (St. Louis encephalitis, western equine and eastern equine encephalitis, and La Crosse encephalitis) are usually spread by bites of ticks, mosquitoes, and flies. Specifically, the West Nile-transmitting vector is the mosquito, feeding on infected birds (which serve as a natural reservoir), and then passing the infected blood to humans. The virus itself, as well as the host's immune response, disrupt normal function of nerve cells, especially in the gray matter of the brain. This leads to various cognitive and psychiatric signs including confusion, lethargy, problems with coordination, and possible seizures. Very common symptoms of the infected person, especially with West Nile infection, are headaches, fever, nausea, vomiting, and photophobia (sensitivity to light). Most of the infections have a mild course with a favorable prognosis; however, the patients with more severe degree of infection may develop altered mental status, very high fever, neck stiffness, and seizures. Rarely, especially in very old and immunocompromised patients, the disease progresses to full-blown encephalitis, with subsequent coma, stupor, and death. Unfortunately, there is no specific treatment for this type of viral infection. All patients should get supportive therapy for symptom relief. Preventive measures include the liberal use of insect repellants when spending time outdoors in endemic areas.
- The members of herpes virus family (herpes simplex types 1 and 2, varicella zoster, Epstein-Barr, as well as cytomegalovirus) can enter the central nervous system from the peripheral nervous system (along the nerves outside of the brain and spinal cord), where they reside, and cause severe illness such as fulminant meningitis, encephalitis, or myelitis. These infections are particularly deadly in immunocompromised patients. The clinical presentation is usually typical for CNS infection, with headaches, lethargy, nausea, vomiting, and neck stiffness. The signs and symptoms of specific infection can include psychiatric features and multiple seizures in herpes simplex 1, radicular symptoms (compression of nerve roots at the spinal column; numbness and tingling of the arms or legs) with urinary retention in herpes simplex type 2; and blindness from cytomegalovirus infection in severely immunocompromised patients. The Epstein-Barr virus CNS infection is a very strong risk factor for developing multiple sclerosis in the future. Unlike most of the other viral CNS infections, there are multiple effective antiviral medications available to treat these potentially deadly infections.
- 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 imported from overseas. The last naturally occurring case of wild polio in the U.S. was in 1979. 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 pregnancy, can be devastating. The baby may be born with a variety of defects including deafness, cognitive dysfunction, 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 vaccinations given throughout adolescence and early adulthood, prevents 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 a rabid dog but also might be transmitted by cats, raccoons, skunks, foxes, wolves, and many other domestic and wild animals. Despite popular belief, no transmission has occurred from the bites of mice, rats, or rabbits. 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 fever (up to 107 F), 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 postexposure immune globulin and immunization are very effective and widely available.
- AIDS and HIV encephalitis (also known as AIDS dementia) is caused by the human immunodeficiency virus (HIV). HIV can 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 weakness. Psychiatric problems are common. In the late stage, severe dementia, inability to control urine flow, and an inability to speak and walk may occur. The treatment includes standard antiretroviral drugs for HIV with variable results.
- Infection with Zika virus has been in the recent news due to a significant increase in the birth of babies with head deformities (microcephaly) and various neurologic complications born to mothers infected with this virus. There is still an ongoing debate about the causal link between the infection of the pregnant woman and this devastating adverse pregnancy complication and outcome. Zika virus is transmitted to humans by the bite of an infected mosquito, with the majority of cases occurring in South and Central America. The illness has a very mild course in most cases, with a fine rash as the most common presenting sign, as well as some other symptoms such as low-grade fever, headache, muscle and joint aches, and pink or reddened eyes. The disease is usually self-limiting, with most patients recovering fully in a few days.
- Very few patients infected with Zika virus develop a rare late neurologic complication known as a Guillain-Barré syndrome. This potentially fatal condition is triggered by a severe autoimmune reaction to the central and peripheral nervous system. It is characterized by progressively worsening weakness and paralysis of the muscles of the entire body, painful sensations in the extremities, and involvement of the nerves that supply the head and neck. All patients diagnosed with Guillain-Barré syndrome are admitted to the hospital for observation and management of symptoms, since there is no specific medication or treatment for this condition. Most patients will have a complete recovery, with very few remaining with debilitating residual neurologic symptoms.
Medically Reviewed by a Doctor on 6/10/2016
Igor Boyarsky, DO, FACEP, FAAEM
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