[Paroxysmal neurogenetic and neurometabolic disorders]

To provide an overview of those neurological disorders that are mainly characterized by a paroxysmal pattern of involvement, and in which a clear genetic or metabolic etiology has been identified.

The term 'paroxysmal' refers to the abrupt onset of clinical manifestations in a relatively stereotyped manner, usually upon exposure to specific triggering factors with an almost complete resolution of such findings between attacks. They are commonly not associated to either a relentless progression or a stepwise deterioration, and the majority of them do not lead to the development of gross neuropathological abnormalities. Although they are difficult to classify due to the heterogeneity of their clinical manifestations and underlying deficits, a neuroaxis-based approach is proposed for practical purposes, for example, from those conditions affecting predominantly cortical grey matter (manifesting mainly with seizures) to those with an almost exclusive muscular and/or neuromuscular pattern of involvement. The majority of them are caused by genetic defects in either transporters or neuronal channels, which can be either ions or neurotransmitters. In recent years, the concept of 'channelopathies' has grown in acceptance in the medical field, although not all of the described disorders are caused by defects in molecular channels.

Despite their individual rarity, as a group, they are important to the neurologist due to the advances that their understanding have provided for the development of the field of neurogenetics and neurosciences in general.