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Epilepsy is a common chronic neurological disorder characterized by recurrent unprovoked seizures.[1][2] These seizures are transient signs and/or symptoms of abnormal, excessive or synchronous neuronal activity in the brain.[3] About 50 million people worldwide have epilepsy at any one time.[4] Epilepsy is usually controlled, but not cured, with medication, although surgery may be considered in difficult cases. However, over 30% of people with epilepsy do not have seizure control even with the best available medications [5][6]. Not all epilepsy syndromes are lifelong – some forms are confined to particular stages of childhood. Epilepsy should not be understood as a single disorder, but rather as a group of syndromes with vastly divergent symptoms but all involving episodic abnormal electrical activity in the brain.
Epilepsies are classified in five ways:
In 1981, the International League Against Epilepsy (ILAE) proposed a classification scheme for individual seizures that remains in common use.[7] This classification is based on observation (clinical and EEG) rather than the underlying pathophysiology or anatomy and is outlined later on in this article. In 1989, the ILAE proposed a classification scheme for epilepsies and epileptic syndromes.[8] This can be broadly described as a two-axis scheme having the cause on one axis and the extent of localisation within the brain on the other. Since 1997, the ILAE have been working on a new scheme that has five axes: ictal phenomenon, seizure type, syndrome, etiology and impairment.[9]
The diagnosis of epilepsy usually requires that the seizures occur spontaneously. Nevertheless, certain epilepsy syndromes require particular precipitants or triggers for seizures to occur. These are termed reflex epilepsy. For example, patients with primary reading epilepsy have seizures triggered by reading. Photosensitive epilepsy can be limited to seizures triggered by flashing lights. Other precipitants can trigger an epileptic seizure in patients who otherwise would be susceptible to spontaneous seizures. For example, children with childhood absence epilepsy may be susceptible to hyperventilation. In fact, flashing lights and hyperventilation are activating procedures used in clinical EEG to help trigger seizures to aid diagnosis. Finally, other precipitants can facilitate, rather than obligately trigger, seizures in susceptible individuals. Emotional stress, sleep deprivation, sleep itself, and febrile illness are examples of precipitants cited by patients with epilepsy. Notably, the influence of various precipitants varies with the epilepsy syndrome. [10]. Likewise, the menstrual cycle in women with epilepsy can influence patterns of seizure recurrence. Catamenial epilepsy is the term denoting seizures linked to the menstrual cycle.[11]
Epilepsy is one of the most common of the serious neurological disorders.[12] Genetic, congenital, and developmental conditions are mostly associated with it among younger patients; tumors are more likely over age 40; head trauma and central nervous system infections may occur at any age. The prevalence of active epilepsy is roughly in the range 5–10 per 1000 people. Up to 5% of people experience non febrile seizures at some point in life; epilepsy’s lifetime prevalence is relatively high because most patients either stop having seizures or (less commonly) die of it. Epilepsy’s approximate annual incidence rate is 40–70 per 100,000 in industrialized countries and 100–190 per 100,000 in resource-poor countries; socioeconomically deprived people are at higher risk. In industrialized countries the incidence rate decreased in children but increased among the elderly during the three decades prior to 2003, for reasons not fully understood.[13]
Beyond symptoms of the underlying diseases that can cause certain epilepsies, people with epilepsy are at risk for death from four main problems: status epilepticus (most often associated with anticonvulsant noncompliance), suicide associated with depression, trauma from seizures, and sudden unexpected death in epilepsy (SUDEP) [14][15][16] Those at highest risk for epilepsy-related deaths usually have underlying neurological impairment or poorly controlled seizures; those with more benign epilepsy syndromes have little risk for epilepsy-related death.
Certain diseases also seem to occur in higher than expected rates in people with epilepsy, and the risk of these “comorbities” often varies with the epilepsy syndrome. These diseases include depression and anxiety disorders, migraine and other headaches, infertility and low sexual libido. Attention-deficit/hyperactivity disorder (ADHD) affects three to five times more children with epilepsy than children in the general population. [17] Epilepsy is prevalent in autism. [18]
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