Epilepsy

Epilepsy is one of the most common of the serious neurological disorders. 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 50 per 1000 people experience nonfebrile 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.
Children with epilepsy are three to nine times more likely to have mental health problems than healthy children. Although the search for risk factors has often produced inconsistent results, there is evidence that the development of mental health problems in children with epilepsy is moderated and mediated by family risk factors. Attention-deficit/hyperactivity disorder (ADHD) affects three to five times more children with epilepsy than children in the general population, and children with epilepsy also have significantly higher rates of depression and anxiety. There is a strikingly higher prevalence of epilepsy in children with autism, and evidence suggests that epilepsy is a risk factor for autism, independent of other central nervous system problems.

Classification
Epilepsies are classified in five ways:
1. By their first cause (or etiology).
2. By the observable manifestations of the seizures, known as semiology.
3. By the location in the brain where the seizures originate.
4. As a part of discrete, identifiable medical syndromes.
5. By the event that triggers the seizures, as in primary reading epilepsy.
In 1981, the International League Against Epilepsy (ILAE) proposed a classification scheme for individual seizures that remains in common use.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. 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.

Diagnosis
The diagnosis of epilepsy requires the presence of recurrent, unprovoked seizures; accordingly, it is usually made based on the medical history. EEG, brain MRI, SPECT, PET, and magnetoencephalography may be useful to discover an etiology for the epilepsy, discover the affected brain region, or classify the epileptic syndrome, but these studies are not useful in making the initial diagnosis.
Long-term video-EEG monitoring for epilepsy is the gold standard for diagnosis, but it is not routinely employed owing to its high cost, low availability and inconvenience.
Convulsive or other seizure-like activity, non-epileptic in origin, can be observed in many other medical conditions. These non-epileptic seizures can be hard to differentiate and may lead to misdiagnosis.
Epilepsy covers conditions with different aetiologies, natural histories and prognoses, each requiring different management strategies. A full medical diagnosis requires a definite categorisation of seizure and syndrome types.