However, mutations of KCNA1, encoding the K(+) channel subunit hKv1.1, have been reported in rare families with neuromyotonia, and mutations in KCNQ2, encoding voltage-gated potassium M channel subunit, in families with benign neonatal seizures and myokymia.
The diminished activity of mutant KCNQ2 channels accounts for neonatal epilepsy and myokymia; the cellular locus of these effects may be axonal initial segments and nodes.
We propose that a difference in firing patterns between motoneurons and central neurons, combined with the drastically slowed voltage activation of the R207W mutant, explains why this particular KCNQ2 mutant causes myokymia in addition to BFNC.