07.12.2015
Although cases of epilepsy in which cause remains unknown can often be managed effectively, determining a cause can sometimes point to a particular course of treatment.
Epilepsy is a neurological disorder in which events called seizures disrupt normal brain function. Accurate diagnosis of seizure type often provides clues about the underlying cause of an individual's seizures. One of the most difficult aspects of epilepsy diagnosis is that seizures are symptoms that can result from many different causes. However, cause is not always easy to identify and remains unknown in 65 to 70 percent of epilepsy cases.
In this video, epileptologist Elizabeth Thiele, MD, PhD, discusses why it is difficult to pinpoint the specific cause in most children with epilepsy. Physicians use the term idiopathic to describe medical conditions for which there is no known cause. Although determining the cause of seizures can serve an important role in diagnosis, prognosis, and treatment, it is not essential to finding effective treatments.
Even so, determining the cause of an individual's seizures can be helpful in identifying an appropriate course of treatment. Of the many known causes of epilepsy all fit into two broad categories: inherited and acquired.
To date, researchers have linked more than 70 genes to disorders that can lead to epilepsy.
Scientists have identified some epilepsy types that are caused by the mutation of a single gene. To learn more about these and other epilepsy syndromes and disorders, see the Seizure Types and Syndromes section.
In addition to these epilepsy syndromes, a number of other genetic disorders with wide-ranging manifestations can also give rise to epilepsy. Although some of the disorders described above are uncommon, the identification of gene or chromosome abnormalities associated with many of them has enabled physicians to use relatively simple genetic tests and diagnostic criteria to diagnose patients and family members suspected of having a given disorder. In addition to the role gene mutations play in causing epilepsy, it is also thought that genes may influence the effectiveness of treatment options for some people. Some of the most common non-idiopathic causes of seizures in children are acquired, as opposed to being present at birth or developing as the result of genetic abnormalities.


In this video, epileptologist Elizabeth Thiele, MD, PhD, discusses the term seizure threshold and conditions that can affect the occurrence of seizures. Key elements in understanding seizure threshold, and therefore finding good treatments, are the neurons themselves—in particular, the membranes of these neurons. Some environmental and metabolic conditions can trigger seizures by effectively lowering seizure threshold. Scientists think that many of the genes linked to epilepsy are involved in mechanisms that regulate the flow of electrical charges into and out of nerve cells, thereby affecting their electrical excitability and overall seizure threshold. An understanding of these regulatory mechanisms in the brain and how they malfunction in people with epilepsy has led to the development of medications that can help restore electrochemical balance and greatly reduce or eliminate seizures.
To determine the cause, or causes, of a child's epilepsy, physicians rely, in part, on information from parents and other family members. This information may be helpful in determining the risk of seizures recurring and worsening over time, and may also reveal an appropriate course of treatment. In fact, idiopathic epilepsies can be successfully treated, and it is common for children with this diagnosis to grow out of their seizures entirely. As described in the Diagnosis section, neurologists rely on eyewitness accounts of the seizures and electroencephalogram (EEG) analysis to determine seizure type, and neuroimaging technologies such as computed tomography (CT) and magnetic resonance imaging (MRI) to identify structural abnormalities in the brain.
These relatively rare epilepsy syndromes are caused by mutations that result in abnormal protein function, leading to seizures.
Acquired causes include, for example, lack of oxygen (hypoxia), head injuries, and infections of the central nervous system. In some cases, infections cause injury to the brain significant enough to cause recurrent seizures.
A likely place for a gene mutation to affect neuron function in such a way as to cause epilepsy is at the level of the neurotransmitters, chemicals that act as messengers between nerve cells, as well as the ion channels that maintain the neuron's firing threshold.
Depending upon which brain regions are involved, seizures may influence behavior, sensory perception, motor function, or all of the above. This does not mean that such cases have no underlying cause, but rather that a cause cannot be determined. Also, physicians increasingly rely on genetic tests to determine the role that gene mutations might play in an individual's seizures.
Studies have found that the risk of epilepsy in siblings and children of individuals with the disorder ranges from 4 to 8 percent, compared to 1 to 2 percent in the general population.


Researchers believe that the most common types of epilepsy are almost certainly caused or influenced by more than one gene, as well as by a number of environmental factors. Brain tumors and degenerative disorders are not as common in children as they are in older adults, but in rare cases they can also cause childhood epilepsy. Drowning, choking, suffocation, cardiac arrest, head trauma, and complications during birth can all lead to hypoxia and seizures. Studies suggest that head injuries resulting in hematomas, wherein blood collects in a mass on the surface of the brain, are more likely to result in seizures and epilepsy. It may be that they are made up of abnormal cells that affect the neuronal network and cause abnormal neuronal firing.
For example, a fever of 104 degrees Fahrenheit that leads to seizures in one child may not have that effect on another child. The lower an individual's seizure threshold, the fewer the stimuli required to cause neurons in the brain to misfire. In fact, physicians can often determine the location and extent of abnormal brain activity based solely upon the seizure type and its observed clinical effects. Often this is because a diagnostic test sensitive or specific enough to determine the cause does not yet exist. Researchers hope that identifying the genetic causes of epilepsy may one day lead to better treatments and potentially a cure for some types of the disorder.
Whatever the cause, it is important, especially with regard to treatment and follow-up, to distinguish between factors and conditions that cause isolated seizures and those that cause the recurrent seizures characteristic of epilepsy. Treatment depends on the underlying cause of the hypoxia but typically involves basic life-support procedures, including ventilation, medications to support blood pressure and heart rate, and medications to suppress seizures. This is because of variability from one person to another in what doctors call seizure threshold, defined as the minimal conditions required to produce a seizure.



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