Ryanodine calcium channel: a novel channelopathy for seizures

Catecholamine-induced polymorphic ventricular tachycardia (CPVT) is one of the most severe inherited arrhythmogenic disorders, where patients clinically present with syncope or seizures.

An 18-year-old white male with a history of mild developmental delay and CPVT, was brought to the ED after an episode of unresponsiveness for several minutes. The EMS documented a rhythm strip showing sinus tachycardia. The patient was awake and alert with no clinical evidence of any focal neurologic deficits, but unable to recall the event. Initial blood works including cardiac enzymes were normal. EKG showed sinus rhythm at 86 bpm, along with bigeminy and couplets of bidirectional QRS morphology with a QT interval of 0.3 seconds. Imaging studies including computed tomography scans of head, magnetic resonance imaging of brain, and 2D cardiac echo were normal. A routine EEG revealed abnormal bursts of spike and aftergoing slow wave complexes, highly suggestive of a potential for seizure activity. A 24-hour video EEG-EKG confirmed abnormal brain activity in the presence of normal sinus rhythm. A recent experimental study showed that knock in models of mice mutated with leaky calcium channels in the heart and brain exhibited seizures independent of arrhythmias.

Our patient is probably the clinical paradigm of this study. This episode of unresponsiveness, most probably a complex partial seizure, may have been caused by the same mutations known to precipitate CPVT.