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Adult Encephalitis Cases Need Improvements in Diagnosis

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Encephalitis related image Photo: Getty Images

Adult encephalitis can be a serious illness that is difficult to diagnose. It is characterized by inflammation of the brain, and may be caused by a variety of infections. Clare Huppatz and colleagues in Australia studied a case series of adult encephalitis patients and provided recommendations for improved diagnostic workup.

Headache, fever, and altered consciousness are the “classic clinical encephalitis triad”, Huppatz reported. However, in the Australian study of 74 adult patients, only 35 percent had all three symptoms. The frequency of symptoms was found as follows:

1. Fever, 77 percent
2. Altered consciousness state, including irritability and/or coma, 70 percent
3. Headache, 62 percent
4. Lethargy, 32 percent
5. Focal neurological signs, 31 percent
6. Seizures, 26 percent
7. Light sensitivity, 18 percent
8. Neck stiffness, 15 percent
9. Abnormal behavior, 12 percent
10. Rash, 9.5 percent
11. Muscle and/or joint pain, 3 percent

Diagnostic factors include the following:

1. Signs and symptoms present when the patient first sees a doctor, or in the previous 24 hours, plus those that develop within 48 hours of admission to a hospital.

2. History of relevant exposures and risk factors. These include occupational exposures to pathogens, travel, contact with animals, exposure to insects, water sports, and other exposures relevant to the local area.

3. Laboratory results from blood tests, lumbar puncture, and brain biopsy.

4. Neuroimaging studies.

5. Electroencephalogram (EEG) results.

“An important next line of research would be to formulate and trial an algorithm for diagnostic work-up”, Huppatz concluded. Some of the pathogens that cause encephalitis have public health implications.

Brain infections caused by viruses that are transmitted by mosquitoes are a signal that better insect control is needed. Encephalitis can also be caused by vaccine-preventable viruses including influenza, mumps, measles, and rubella.

Magnetic resonance imaging (MRI) of the brain can be a valuable aid to diagnosis of adult encephalitis, according to Shinji Ito and colleagues in Japan. These authors provided a case report on a 26-year-old man with influenza complicated by encephalitis. The patient recovered fully after treatment with the steroid methylprednisolone.

Correct diagnosis of the pathogen can be life-saving for some patients, Huppatz explained. Specific antimicrobial or antiviral drugs are available for some infections. The herpes simplex virus is one of the most common causes of encephalitis, and is susceptible to the drug acyclovir.

Mortality can be reduced from 70 percent to less than 30 percent by use of acyclovir in these patients. Antibiotics are effective against the less common bacterial cases of encephalitis.


1. Huppatz C et al, “Should there be a standardised approach to the diagnostic workup of suspected adult encephalitis? a case series from Australia”, BMC Infectious Diseases 2010; 10: 353. http://www.ncbi.nlm.nih.gov/pubmed/21159185

2. Ito S et al, “Transient splenial lesion of the corpus callosum in H1N1 influenza virus-associated encephalitis/encephalopathy”, Internal Medicine 2011; 50: 915-18. http://www.ncbi.nlm.nih.gov/pubmed/21498942

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Reviewed November 8, 2011
by Michele Blacksberg RN
Edited by Jody Smith

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