WHAT: A new study by National Institute of Allergy and Infectious Diseases (NIAID) scientist Theodore E. Nash, M.D., and colleagues provides strong evidence associating seizures with areas of brain tissue swelling in people infected by a parasitic tapeworm. The swellings, called perilesional edemas, form around dead, calcified cysts that result when larvae of Taenia solium tapeworms lodge in the brain. The illness caused by T. solium infection--neurocysticercosis--is the most common cause of adult-onset seizures and epilepsy in developing countries where the tapeworm is endemic. Brain scans of individuals with this parasitic infection frequently show calcified cysts, but the clinical significance of perilesional edema around these calcifications and whether such edema is associated with seizures was not known.
The research was conducted in collaboration with Hector H. Garcia, M.D., in Lima, Peru. Dr. Nash, Dr. Garcia and their co-investigators studied 110 people with calcified cysts and a history of seizures. Between 1999 and 2006, 29 study participants had a seizure; of these, 24 were assessed by magnetic resonance imaging (MRI) within 5 days of the seizure. Perilesional edema was seen on MRI in 50 percent of cases (12 out of 24 patients)--a strong association between edema and seizure relapse. In a control group of patients with infection but without an incident seizure while enrolled in the study, only 9 percent (2 of 23 cases) had perilesional edema.
The scientists conclude that perilesional edema is common and is associated with episodic seizure activity in people who have calcified T. solium cysts. Since perilesional edema is not found in most common diseases causing seizures, its presence here suggests a different mechanism as a cause. Therefore, seizures due to T. solium infection may be preventable and treatable in novel ways including with agents that control this type of inflammation.
ARTICLE: TE Nash et al. Perilesional brain oedema and seizure activity in patients with calcified neurocysticercosis: a prospective cohort and nested case-control study. The Lancet Neurology. (Published online Nov. 4, 2008) DOI: 10.1016/S1474-4422(08)70244-8.
WHO: Theodore Nash, M.D., chief, Gastrointestinal Parasites Section, Laboratory of Parasitic Diseases, NIAID, is available to discuss this study.
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News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at <http://www.