Some Forms of Epilepsy Could Be Autoimmune in Nature, Suggests Study Linking Parasitic Infection and Nodding Syndrome
Some forms of epilepsy such as nodding syndrome, could be autoimmune in nature according to a study published in the journal Science Translational Medicine.
“The findings … suggest that therapies targeting the immune system may be effective treatments against this disorder and possibly other forms of epilepsy,” said the senior author of the study Dr Avindra Nath who is also the clinical director of the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), in a press release.
Nodding syndrome is a form of childhood epilepsy seen in certain areas of East Africa. It is characterised by head nodding, seizures, severe impairment in thinking ability and restricted growth.
The cause of the condition remained a mystery until now. The present study suggests that the condition might be caused by an immune response triggered by a parasitic worm called Onchocerca volvulus, which then attacks the body’s own nervous system.
For the study, Dr Nath and colleagues compared blood samples from children with nodding syndrome and children without, who all lived in the same village in Uganda. They found antibodies in the blood of children with nodding syndrome, which recognised proteins from the parasitic worm as well as a protein called leiomodin-1. Leiomodin-1 antibodies were also present in the fluid covering the brain and the spinal chord of the children with nodding syndrome.
Leiomodin-1 is highly expressed in human nerve cells grown in the laboratory and is also found in certain areas of the mouse brain. These areas of the brains are the counterparts of the areas in the children’s brain that were affected by nodding syndrome.
When the researchers treated normal nerve cells grown in the laboratory with serum from nodding syndrome patients, they saw that the nerve cells died suggesting that the serum of the children contains a factor that was toxic for nerve cells. In order to test whether this factor could be leiomodin-1 antibodies, the researchers treated the nerve cells with the antibody directly and obtained the same results: the nerve cells died. And when they treated the nerve cells with serum from which the leiomodin-1 antibodies had been removed, the nerve cells survived
The researchers concluded that nodding syndrome may be an auto-immune epileptic disorders triggered by infection with a parasitic worm. The antibodies that the body produces to fight off the parasite wrongly recognise a protein found in the nerve cells and attacks them.
According to the authors, more research is needed to better understand the role of leiomodin-1 in healthy people and people with epilepsy.
Author: Dr Özge Özkaya
What is Nodding Syndrome? This information is from the WHO website
Nodding syndrome (NS) is a neurological condition with unknown etiology. It was first documented in the United Republic of Tanzania (URT) in the 1960s, then later in the Republic of South Sudan in the 1990s and in northern Uganda in 2007. Typically, NS affects children between the ages of 5 and 15 years old, causing progressive cognitive dysfunction, neurological deterioration, stunted growth and a characteristic nodding of the head. Despite numerous and extensive investigations in all three countries, very little is known about the cause of the disease.
To date, Nodding Syndrome is known to occur in the southern region of the United Republic of Tanzania (URT) (Mahenge mountains, Ulanga District), South Sudan (Western Equatoria State, Eastern Equatoria State, Central Equatoria State, and Lakes State) and northern Uganda (Pader, Kitgum and Lamwo districts, with new cases starting to present in Gulu, Amuru, Oyam and Lira districts).
Jilek et al (1962) first described several children with attacks of “head nodding” in Mahenge, a region in URT. The current burden of NS in URT is unknown but observations during case control studies in 2005 and 2009 in the Mahenge region do not suggest a notable increase in the number of cases relative to those detected in the late 1950s and early 1960s.
Samaritan Purse, a local NGO, described observations of head nodding among several children in southern Sudan in the Lui and Amadi villages of East Mundri County in the mid-1990s. A physician from Samaritan Purse reported the outbreak to WHO in 1997. The 2001-2002 investigations by WHO and partners estimated the prevalence of NS at 4.6% among a small population in Western Equatoria State, which appeared to have the highest burden of the illness. By 2003, an estimated 300 cases had been reported from this region. The Ministry of Health of South Sudan estimates the current burden of NS at between six and seven thousand cases, but no systematic large-scale prevalence study has been conducted. The Mundri region in the northeast of Western Equatoria is the presumed epicentre for the disease.
In 2008 and 2009, an illness consistent with NS was reported from Kitgum and Pader Districts in northern Uganda. As of February 2012, Uganda has reported over 3 000 cases of NS from the three districts of Kitgum, Lamwo and Pader. A community survey is underway in Uganda to determine the real burden of NS in the affected districts. Kaiser et al (2009) referred to a phenomenon of head nodding observed in the Kabarole District in Western Uganda as possibly constituting a feature of an epileptic syndrome caused by Onchocerca volvulus (O. volvulus).
The prevalence of both onchocerciasis and epilepsy in the areas affected by NS is high. The affected populations are impoverished and experience regular and prolonged periods of severe food shortages. In South Sudan and in northern Uganda, affected populations have a history of internal displacement and living in internally displaced persons (IDPs) camps.
Familial clustering has been observed in some families with NS patients, with more than one sibling with NS and/or siblings or relatives with other forms of epilepsy.
The age of onset in the vast majority of cases ranges between 5 and 15 years old, but cases have been reported in children as young as 2 years old and in adults up to 32 years old. There is no observed significant difference in the proportion of males to females among the affected, nor is there an observed seasonal variation.