Epilepsy is a common neurological disorder whose main symptoms are recurrent seizures. The World Health Organization estimates fifty million people have epilepsy. About sixty percent of the time seizures are classified as idiopathic, meaning their cause is not known. Cryptogenic seizures are a subgroup of idiopathic seizures thought to be the related to an infection.
Toxoplasmosis is one of the most common parasitic infections in the world. It is caused by the parasite Toxoplasma gondii, which infects as many as one third to one half of the world’s population. In the United States, the Centers for Disease Control estimates sixty million people have toxoplasmosis.
During the active stage of toxoplasmosis, the parasite forms tachyzoites which migrate through the body via the blood and lymph system. In its dormant stage, sturdy protective cysts develop around immature parasites called bradyzoites. These lodge in the brain, muscles, eyes and elsewhere in the body.
Toxoplasmosis and Epilepsy
Toxoplasmosis usually infects the brain and often causes no noticeable symptoms. When it does, these are generally mild, such as flu, fatigue, or swollen lymph glands. Toxoplasmosis is well recognized as a cause of brain damage leading to seizures in newborns or young children who were infected by their mothers before birth. With no active immune system, the fetus cannot fight off the infection.
Chronic Toxoplasmosis and the Development of Epilepsy in Adults
Research on epilepsy related to adults and toxoplasmosis is sparse. More study is needed to determine what role chronic toxoplasmosis may play in seizure disorders. Scientists and physicians have assumed toxoplasmosis causes no damage in its inactive phase, which may last years.
However, a few studies suggest toxoplasmosis may be a factor in the development of epilepsy. Several studies focused on toxoplasmosis as a possible cause of cryptogenic epilepsy. Others looked into a relationship between toxoplasmosis and seizures of all types.
Research in the United States
Elijah W. Stommel and colleagues explored the possible role of toxoplasmosis as an infectious cause of cryptogenic epilepsy. More than 20% of the US population has toxoplasmosis.
In their research Stommel observed that many infections linked to seizures can be identified by MRI, blood tests, and examining the cerebral spinal fluid (CSF). The damage from toxoplasmosis may be microscopic. Stommel wrote, “Toxoplasma gondii can form dormant cysts in the brain which are undetectable with MRI or routine CSF analysis.”
Bradyzoites in the brain are not as harmless as they may seem. They can rupture, especially if the immune system is compromised with some other infection and possibly lead to brain damage and seizures.
Stommel and his colleagues matched 22 adults who met the criteria for cryptogenic epilepsy with 29 healthy adults as controls for their study.
The subjects with cryptogenic epilepsy had 75% higher levels of toxoplasma gondii antibodies indicating chronic dormant infection than the controls. The study also found that both cryptogenic epilepsy and the rate of Toxoplasma gondii infection seem to increase with age.
This study was too small to draw conclusions but the data suggests toxoplasmosis may be a factor contributing to seizure development. Stommel noted that studies in other regions of the world could confirm what his study indicates.
Studies in Turkey
In 2006 Akyol and colleagues looked at the rates of infection from Toxoplasma gondii and Toxocara canis in patients with cryptogenic epilepsy. This study did not find a major difference in rates of infection between the subjects and controls. The researchers did note limitations in their study which may have affected the results.
In 2003, also in Turkey, Yazar and fellow researchers studied 150 subjects, 50 with a known cause for seizures, 50 with cryptogenic epilepsy, and 50 healthy subjects. They compared the rate of antibodies to Toxoplasma gondii among the different groups.
In those with cryptogenic epilepsy, 54% had anti-toxoplasma antibodies, an indication of chronic infection. The rate among those with a known cause for epilepsy was 22% and 18% among the healthy controls.
The researchers concluded, “These results are similar and confirm the results of Stommel, et al. If these results are verified with greater number of epileptic patients by other researchers, there may be new approaches to the treatment of cryptogenic epilepsy.”
Where There is Toxoplasmosis There is Epilepsy
In the United Kingdom, BS Palmer explored a possible link between cryptogenic epilepsy and chronic toxoplasmosis infection. He also looked at the rates of toxoplasmosis and all types of epilepsy in varying geographical regions. He compared the rates of T. gondii infection and epilepsy in 17 countries.
The analysis showed higher rates of toxoplasmosis among those with cryptogenic epilepsy. The data indicated chronic toxoplasmosis infection may be one of the factors leading to seizure development. Palmer suspects that kindling, the slow formation of a seizure focus from scaring due to toxoplasmosis might be the way toxoplasmosis is linked to epilepsy.
To determine whether the toxoplasmosis can be related to epilepsy, Palmer reasoned, “It should be possible to find a country, area or city where the toxoplasmosis rate is low while the rate of epilepsy is very high or vice versa.”
Among the countries included in the analysis, there were none in which there was a high level of epilepsy and a low level of toxoplasmosis. The study indicates there is a link between chronic toxoplasmosis and epilepsy.
Palmer’s study supports those of Stommel and Yazar, yet he also believes in the need for further research. His analysis showed that in areas where living conditions and hygiene improve, the rates of toxoplasmosis and epilepsy might also decline.
For those who have idopathic seizures, testing for toxoplasmosis will determine if this very common parasitic infection is a possible hidden cause.
Sources
Akyol A et al; Epilepsy and Seropositivity Rates of Toxocara Canis and Toxoplasma Gondii; Seizure(2007) 16, 233-237
Palmer BS; Meta-analysis of Three Case Controlled Studies and an Ecological Study Into the Link Between Cryptogenic Epilepsy and Chronic Toxoplasmosis infection; Seizure 2007 Dec;16(8):657-63 Epub 2007 Jun 28
Stommell E, et al; Cryptogenic Epilepsy: An Infectious Etiology?; Epilepsia, 42(3):436–438, 2001
Yazar S, et al; Investigation of Probable Relationship Between Toxoplasma Gondii and Cryptogenic Epilepsy; Seizure vol 2, is 2, March 2003, pp 107-109
Resources
Toxoplasmosis Research Institute
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
Zoe Langley - Zoe Langley is a writer living in Kentucky. She is a past winner of the Seattle Writers in Performance Award. She has a passionate ...
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