Introduction

In 1991, Ptàcek et al. identified the cause of hyperkalemic periodic paralysis as a mutation of the gene of the SCN4A Na+ channel. The following years saw the publication of a series of papers by the same and other researchers, which confirmed and completed the finding by demonstrating that other conditions belonging to the same group of muscular diseases (myotonic/periodic paralyses) could be attributed to mutations of the genes coding Na+, Ca2+ or Cl- channel subunits (Ptàcek, 1998). Other ion channel gene mutations were subsequently identified as being involved in episodic ataxias (K+ and Ca2+ channels), hemiplegic migraine (Ca2+ channel), long-QT cardiac arrhythmias (K+ and Na+ channels), hyperekplexia (glycine receptor), and autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) (cholinergic receptor). All of these ‘channelopathies’ (Ptàcek, 1997), have the common characteristic of acute and transient presentation in subjects who otherwise seem to be perfectly normal, and this is also a common characteristic of idiopathic epilepsies due to alterations in neuronal excitability that cannot be attributed ‘to any underlying cause other than a possible hereditary predisposition’ (Commission, 1989). The aim of this chapter is to summarize some of the data suggesting that idiopathic epilepsies may be considered channelopathies.

Epileptogenic alterations in neuronal excitability

The excitability of neuronal cells depends on the movement of ions through specific cell membrane channels.