Understanding Epilepsy and Its Causes

What is Epilepsy?

Epilepsy is a chronic neurological disorder characterized by unpredictable and recurrent seizures. These seizures result from an overload of electrical activity in the brain. The specific experiences of a patient during a seizure are influenced by the region of the brain that the epileptic activity affects and the extent and speed of its spread.

Causes of Epilepsy

While medical professionals often struggle to pinpoint the exact causes of epilepsy, several factors have been associated with its onset. These include genetic predispositions, head injuries, strokes, and certain infectious diseases like viral encephalitis.

The Role of Genetics in Epilepsy

Genetic Testing for Epilepsy

One method to explore the genetic components of epilepsy is through genetic testing, specifically chromosomal microarray analysis. This process involves preparing a blood DNA sample on a glass slide that contains molecular probes. These probes are small DNA segments corresponding to clinically significant regions across the entire genome. Current microarrays feature over two million unique DNA probes.

Analyzing Hybridization Patterns

The hybridization patterns on the slide are analyzed using computer technology to determine the number of DNA copies at each probe location. This analysis can identify deletions and duplications of whole or partial chromosomes, known as copy number variants (CNVs).

Challenges in Identifying CNVs

It is important to note that hundreds of small chromosome deletions and duplications occur in everyone, complicating the determination of their significance or causative role. Nonetheless, microarray analysis is instrumental in locating specific areas where CNVs are linked to particular genetic disorders.

Recent Research Findings

Study on CNVs in Epilepsy

Both recurrent and non-recurrent CNVs have been identified across major epilepsy classifications. A recent study published in JAMA Neurology by researchers at Toronto Western Hospital examined CNVs in 143 adults (69 males and 74 females, with an average age of 24) diagnosed with unexplained childhood-onset epilepsy and intellectual disability.

Results of the Study

The study revealed that 23 participants (16%) exhibited pathogenic CNVs, with 70% located in established CNV hotspots related to epilepsy. Additionally, eight rare non-recurrent CNVs overlapping genes associated with intellectual disability, autism, and/or epilepsy were discovered.

Implications of the Findings

The identification of specific CNVs in patients with epilepsy and intellectual disability is expected to enhance diagnostic processes and treatment strategies. Furthermore, this information may provide valuable insights for genetic counseling for families planning to have children. The researchers emphasize that further studies are necessary to understand how these CNVs contribute to alterations in brain function.

References

Borlot, F., Regan, B. M., Bassett, A. S., Stavropoulos, D. J., & Andrade, D. M. (2017). Prevalence of Pathogenic Copy Number Variation in Adults with Pediatric-Onset Epilepsy and Intellectual Disability. JAMA Neurology. doi:10.1001/jamaneurol.2017.1775