Central Nervous System Infections in Children (Meningitis & Encephalitis)
Viral infections of the central nervous system cause serious illnesses, some of them potentially fatal. They include Meningitis, which affects tissue layers enveloping the brain and the spinal cord, as well as Encephalitis, which is an infection of the brain.
- The main symptoms of viral central nervous system infections are fever and irritability; the child may refuse food, and in some cases, have seizures.
- Meningitis as well as encephalitis can be caused by viruses.
- Testing of the cerebrospinal fluid help diagnose the infection.
- Some viral infections of the central nervous system are not serious, but some others are potentially fatal.
- Treatment mainly involves supportive measures to help the body overcome the infection, since antibiotics as well as antiviral therapies are not very effective in eliminating the infections.
- Increasing fluid intake, and keeping the child warm, may help in overcoming the infection.
Several different types of viruses can cause infection in the brain and the meninges which enclose the brain and the spinal cord. Some of them are coxsackieviruses, arboviruses, and herpesviruses. Enteroviruses and echoviruses also cause infections of the central nervous system. Those infections which mainly affect the meninges which enclose the brain as well as the spinal cord are termed meningitis, which is very common among infants and children. When the infection is mainly affecting the brain, it is referred to as encephalitis. Encephalitis is not as common in infants as meningitis. If both the brain and the meninges are infected, it is termed as meningoencephalitis.
There are two ways in which viral infections can cause damage to the central nervous system. Viruses can infect the cells and destroy them at the time of acute illness. After the patient recovers from a direct viral infection in any part of the body, secondary damage may occur to the tissue surrounding the nerves due to the body’s immune reaction. The symptoms of this acute disseminated encephalomyelitis or post infectious encephalomyelitis may start appearing in the child many weeks after complete recovery from the original infection.
Viral infections of the central nervous system are acquired by children in different ways. For example; if the herpes virus is present in the secretions of the mother’s birth canal, it can infect a newborn infant as it passes through the birth canal at the time of delivery. People who have viral infections can disperse the virus into the atmosphere when they sneeze, cough and exhale air. When an infant or child is exposed to this air contaminated by virus-laden droplets, they can contract the infection. Insects infected with Arbovirus can spread the infection to children when they bite.
Older children as well as adolescents have symptoms similar to the ones adults with the same illnesses display. Their treatment is also similar in nature. Infants have immature immune systems which make them highly susceptible different infections at the same time, which makes it difficult to identify specific infections. Their inability to express many of their distressing symptoms makes the diagnosis even more difficult. However, certain characteristic symptoms are commonly observed in infants who have viral infections of the central nervous system.
Symptoms
Fever is usually the first symptom of a viral infection of the central nervous system in infants. In newborns, fever may be the only symptom present, and they may not even appear particularly ill. Infants one month of age, or older, may display irritability and fussiness. Refusal to feed and vomiting are the other common symptoms. Bulging out or tightening of the fontanelle, or soft spot present at top of the head, is another indication of the pressure build-up in the brain due to the infection. Movement worsens the pain and irritation of the inflamed meninges; hence, infants who have meningitis typically cry more when they are carried or rocked. An unusually high-pitched cry is another symptom that some infants have. Encephalitis usually causes seizures and uncontrolled movements in the affected infants. In severe cases of encephalitis, the infants become listless and lethargic. Coma and death may follow as the disease progresses. Herpes simplex infection usually affects a localized area of the brain, and may lead to weakness in a particular part of the infant’s body, besides causing seizures.
Post infectious encephalomyelitis which follows an episode of encephalitis can cause several neurologic problems which may either permanent or temporary. The symptoms depend on the location and the extent of brain damage that has occurred. Weakness of a particular limb, loss of hearing, blindness, mental retardation, and recurrent seizures, are some of the neurological disorders precipitated by this illness. They are usually recognized only much later when the child undergoes testing. Some of the symptoms eventually disappear, but some may be permanent.
Diagnosis
When a newly born infant has fever, doctors are alerted to the possibility of a central nervous system infection such as meningitis or encephalitis. If older infants have irritability or unusual behavior along with fever, they are also tested for these illnesses. The testing involves a lumbar puncture or spinal tap to retrieve a sample of the cerebrospinal fluid which is then analyzed in the laboratory to detect the cause of the infection. The absence of a bacterial infection, and the presence of abnormally high number of lymphocytes in the cerebrospinal fluid, is considered to be an indication of viral infections. Tests to detect specific antibodies against particular viruses are also done, but they are time-consuming. Enteroviruses and herpesviruses can be identified by a technique called polymerase chain reaction.
Electroencephalography which tests the electrical activity of the brain can help detect encephalitis due to a herpes virus infection. An MRI scan or a CT scan can confirm it. Occasionally, a biopsy of the brain may have to be done to detect the exact cause of the infection.
Prognosis and Treatment
Prognosis is greatly dependent on the type of virus causing the illness, and the severity of the infection. Children recover rapidly and completely from milder forms of viral meningitis as well as encephalitis with nothing more than rest and supportive care. However, certain types of infections are extremely serious, especially those caused by the virus called herpes simplex. The mortality among infants who have an infection of herpes simplex in the brain is around 15% with the best medical care. If some other parts of the body besides the brain are affected, it is often fatal in about 50% cases. Even among those who survive, 30% have permanent neurologic damage.
Supportive care is the main treatment for viral infections of the central nervous system. The child should be provided warmth and sufficient amounts of fluids, which may help the body to fight the disease. Antiviral therapy is not very effective in most cases of meningitis and encephalitis. However, if the infective organism is herpes simplex virus, the antiviral drug acyclovir is administered intravenously.
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Yasser Elnahas
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