Epilepsy

Overview

According to the International League against Epilepsy (ILAE), epilepsy is a syndrome characterized by an “enduring predisposition to generate epileptic seizures.” Epileptic seizures are clinical events that can affect sensory, motor, and autonomic functions, as well as consciousness, emotional state, cognition, and behavior (1). Epilepsy can be caused by a variety of etiologies, such as congenital brain abnormalities and traumatic brain injuries, and onset can occur at any age (depending on the type and cause of seizures) (2). Seizures are typically managed with medications. In cases where seizures are unresponsive to medications, surgery and brain stimulation techniques may be employed.

Typology

Based on the latest ILAE guidelines, epilepsy is diagnosed with either: 1) the presence of at least two unprovoked (or reflex) seizures, or 2) one unprovoked (or reflex) seizure and a probability of further seizures. Epileptic events are accompanied by epileptiform brain electrical activity detected by electroencephalography (EEG). It can be generalized, in which the entire brain is affected, or focal, in which onset can be localized to be a specific part of the brain. Generalized seizures can either be convulsive or non-convulsive. The most common convulsive seizure is a tonic-clonic (also known as grand mal) seizure. Nonconvulsive generalized seizures, on the other hand, are termed absence (also known as petit mal) seizures. Focal seizures can either be simple partial (without alteration of consciousness) or complex partial (with alteration of consciousness). A complex partial seizure can be preceded by a simple partial seizure, which is called an aura (e.g., déjà vu feeling). A focal seizure can also secondarily generalize to a tonic-clonic seizure (2).

Symptoms

The semiology (behavioral manifestation) of a seizure varies by the type of seizure. A tonic-clonic seizure involves rapid jerking and shaking of the extremities, which many people associate with seizures. However, there are other kinds of semiologies. Absence seizures appear as staring spells, which occur more commonly in children. Therefore, some parents and teachers may misinterpret these signs as inattention. Temporal lobe seizures, which are the most common type of focal seizures, are often associated with altered consciousness (person is unresponsive), motor automatisms (e.g., chewing, lip-smacking, pill rolling finger movements, picking at air or clothes, etc.), and amnesia beginning minutes before onset and lasting through the seizure event itself (3). Untreated seizures can further lead to cognitive dysfunction due to the deleterious effects of seizure activity on brain structure and function. Depending on affected brain regions, different cognitive abilities may be impacted. Temporal lobe epilepsy may be associated with memory loss, while frontal lobe epilepsy may lead to impairments in higher-order cognitive abilities, such as planning, organizing, problem-solving, and cognitive flexibility. Although most forms of epilepsy consist of unprovoked seizures, some rarer forms of epilepsy involve reflexive seizures, in which seizures occur in response to a specific stimulus, such as language processing (4), hot water (5), and music (6).

Prevalence

Epilepsy is the fourth most common neurological condition, after migraine, stroke, and Alzheimer’s disease. The Epilepsy Foundation (7) estimates the yearly incidence of epilepsy in the U.S. to be 150,000 (or 48 per 100,000) people, meaning that 150,000 people will develop epilepsy each year. The prevalence, or the total number of people who have epilepsy at a given time, ranges from 1.3 million to 2.8 million (or 5 to 8.4 per 1000) people. Children and young adults are more likely to develop epilepsy.

Course

The severity and course of epilepsy vary widely, depending on the brain origin, age of onset, number and type of antiepileptic drugs, and many other factors. Frequency ranges from multiple seizures per day to once every few months or years. With successful treatment, some people may be seizure-free for years.

Treatments

Antiepileptic drugs (AEDs) are used to control seizures. Different AEDs operate through different mechanisms in the brain and have different side effects. The most common side effects are fatigue and cognitive dysfunction (particularly slowed thinking). Physicians need to achieve the optimal balance between ridding of the deleterious effects of seizures and minimizing the negative side effects of AEDs. For focal epilepsy, resection surgery to remove the part of the brain that is producing the seizures may be considered. Alternatively, responsive neurostimualtion (RNS) and vagus nerve stimulation (VNS), as well as neurofeedback (EEG operant conditioning), can be used to treat medically refractory epilepsy (when seizures are unresponsive to traditional treatments) (8).

By Michelle Chen

References

1. Fisher, R, Boas, W, Blume, W, Elger, C, Genton, P, Lee, P, & Engel, J (2005). Epileptic seizures and epilepsy: definitions proposed by the International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy (IBE). Epilepsia, 46(4), 470-472.
2. Ropper, H, Samuels, A, & Klein, P (2014). Epilepsy and other seizure disorders. In A Ropper & R Brown, Adams and Victor’s principles of neurology (pp. 319-356). NY: McGraw-Hill.
3. Blair, R (2012). Temporal lobe epilepsy semiology. Epilepsy research and treatment, 2012. Fisher, R. S., Acevedo, C., Arzimanoglou, A., Bogacz, A., Cross, J. H., Elger, C. E., & Hesdorffer, D. C. (2014). A practical clinical definition of epilepsy. Epilepsia, 55(4), 475-482.
4. Zifkin, B, & Trenité, D (2000). Reflex epilepsy and reflex seizures of the visual system: a clinical review. Epileptic disorders, 2(3).
5. Satishchandra, P, Shivaramakrishana, A, Kaliaperumal, V, & Schoenberg, B (1988). Hot‐Water Epilepsy: A Variant of Reflex Epilepsy in Southern India. Epilepsia, 29(1), 52-56.
6. Critchley, M (1937). Musicogenic epilepsy. Brain, 60(1), 13-27.
7. Shafer, P & Sirven, J (2013, October). Epilepsy Statistics. Retrieved from https://www.epilepsy.com/learn/about-epilepsy-basics/epilepsy-statistics.
8. Sterman, M & Egner, T (2006). Foundation and practice of neurofeedback for the treatment of epilepsy. Applied psychophysiology and biofeedback, 31(1), 21.