Periodic electroclinical seizures following an ischemic stroke revealed by continuous-EEG

Periodic EEG patterns are mostly associated with critical illnesses and acute disruptions of the central nervous system. Periodic or cyclic seizures are extremely rare phenomena, most of which are nonconvulsive, only reported in critically ill patients. Here we report a patient with periodic focal impaired awareness seizures following a minor stroke and address possible pathophysiological mechanisms.

A 49 years old male patient presented with periodic seizures, associated with an acute stroke in the left occipital and parietal regions. These focal seizures, recorded during long-term video-EEG monitoring in the scalp EEG, appeared every 9-11 min, and responded to iv valproic acid treatment but not to iv treatments of diazepam, phenytoin, and levetiracetam.

We believe that the blood-brain barrier disruption due to stroke, in conjunction with hyperglycemia and antiphospholipid antibodies have led to an imbalance of the surrounding tissue and sustained hyperexcitability to a point of pacemaker potentials. It is tempting to speculate that repetitive cycles of cortical spreading depression due to tissue injury have aided the periodicity of the seizures.

Continuous EEG monitoring is crucial, not only to diagnose and appropriately treat accompanying subtle seizures but also to further understand the underlying intriguing pathophysiological processes like periodicity.