Definition
Epilepsy is a disorder of the brain defined by any of the following conditions:
Furthermore, epilepsy is considered to be resolved for individuals who had an age-dependent epilepsy syndrome but are now past that age or those who have remained seizure-free for the last 10 years, with no seizure medicines for the last 5 years.This 2014 definition of the International League Against Epilepsy is a clarification of the ILAE 2005 conceptual definition, according to which epilepsy is "a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychological, and social consequences of this condition. The definition of epilepsy requires the occurrence of at least one epileptic seizure. "It is, therefore, possible to outgrow epilepsy or to undergo treatment that causes epilepsy to be resolved, but with no guarantee that it will not return. In the definition, epilepsy is now called a disease, rather than a disorder. This was a decision of the executive committee of the ILAE, taken because the word "disorder," while perhaps having less stigma than does "disease," also does not express the degree of seriousness that epilepsy deserves.The definition is practical in nature and is designed for clinical use. In particular, it aims to clarify when an "enduring predisposition" according to the 2005 conceptual definition is present. Researchers, statistically minded epidemiologists, and other specialized groups may choose to use the older definition or a definition of their own devising.
The neurofibromas caused by NF consist of Schwann cells, fibroblasts, perineuronal cells, mast cells and axons embedded in an extracellular matrix. Another function of neurofibromin is to bind to microtubules that play a role in the release of adenylyl cyclase and its activity. Adenylyl cyclase plays an essential role in cognition. Neurofibromins role in the activity of adenylyl cyclase explains why patients with NF experience cognitive impairment.Neurofibromatosis type II is caused by a mutation on chromosome 22. The mutation falls on the NF2 tumor suppressor gene. The gene normally encodes a cytoplasmic protein known as merlin. The normal function of merlin is to regulate the activity of multiple growth factors, the mutated copy of the gene leads to merlins loss of function. The loss of function leads to increased activity of growth factors normally regulated by merlin, leading to the formation of the tumors associated with NF2.Schwannomatosis is caused by a mutation on the SMARCB1 gene. This gene is located near the NF2 tumor suppressor gene leading to the thought that schwannomatosis and NF2 were the same condition. The two conditions show different mutations on two different genes. The normal function of the SMARCB1 gene is to encode a protein called SMARCB1 that is part of a larger protein complex whose function is not completely understood. The complex including SMARCB1 plays a role in tumor suppression. The mutation of the SMARCB1 gene causes a loss of function in the complex leading to the formation of tumors indicative of schwannomatosis.