KCNMA1-Related Episodes of Behavioral Arrest and Loss of Postural Reflexes: A Critical Reappraisal

KCNMA1-linked channelopathy is characterized by neurodevelopmental disorder, epileptic seizures and non-epileptic paroxysmal episodes.

To describe the phenotype of paroxysmal non-epileptic episodes related to KCNMA1 pathogenic variants.

Videos of paroxysmal episodes were reviewed according to a standardized protocol by a group of movement disorders experts.

Fourteen videos were reviewed (6 previously published patients and a new patient). The typical pattern of an episode was (i) facial changes including dyskinetic movements of tongue and jaws (ii) behavioral arrest (iii) loss of postural reflexes that could be associated with focal body stiffness, eventually leading to fall (iv) rapid recovery without post-ictal drowsiness. Attacks were brief, with a high daily frequency, occasionally triggered by emotion, and dramatically improved by psychostimulant therapy in three patients.

KCNMA1-related attacks are clearly distinguishable from paroxysmal dyskinesia, cataplexy or episodic ataxia indicating a unique phenomenological entity whose recognition will enhance accurate diagnosis and treatment.