Rationale:
Ictal asystole is a rare form of central autonomic dysregulation predominantly in patients with temporal lobe epilepsy. Seizure-induced bradycardia and asystole is a rare cause of unexplained syncope that can occur in patients without underlying cardiac conditions; it could additionally be a risk factor for the development of Sudden Unexpected Death in Epilepsy (SUDEP). While ictal activation of the insular cortex has long been implicated in the pathophysiology of ictal tachycardia, bradycardia, and even ictal asystole, there are few cases which have been precisely demonstrated with stereo-electroencephalography (SEEG). We discuss such a case below where inclusion of stereo-EEG electrodes with contacts in the insula confirmed this diagnosis.Methods:
Clinical CaseResults:
A 35 year old male with a previous history of drug-resistant temporal lobe epilepsy consisting of focal impaired awareness seizures (FIAS) with auras, consisting of episodes of expressive aphasia, began experiencing new, unexplained event types comprised of falls and loss of consciousness (LOC) resembling syncope. He underwent cardiac work-up for syncope, including implantable loop recorder placement, but it was unrevealing as to an etiology. The patient was then admitted after another fall with LOC, resulting in a cerebral contusion and subarachnoid hemorrhage. Video EEG during that admission captured episodes of ictal bradycardia without asystole or clinical syncope, raising suspicion for possible insular lobe involvement in his seizures as a possible mechanism to explain his episodes of syncope.
Given the drug-resistant nature of his seizures, he was admitted to the Epilepsy Monitoring Unit (EMU) for surgical evaluation during which he underwent SEEG monitoring. Electrodes with contacts in the anterior, posterior, and superior insula were included to further clarify his diagnosis.
During SEEG monitoring, three electroclinical seizures were captured, all with electrographic onset in the left amygdala. All three seizures spread to the left insular region, immediately resulting in ictal bradycardia. Two of these seizures progressed to ictal asystole and clinically led to brief syncopal episodes.
He underwent surgical resection of the left amygdala and cardiac pacemaker placement. The patient remained free of disabling seizures (Engel class 1 outcome) over the course of follow-up one year post-operatively.
Conclusions:
It is important to recognize the relationship between seizures leading to autonomic dysregulation and syncope as these types of seizures carry a greater risk of morbidity and mortality. In this case, additional electrodes with contacts in the insula during SEEG monitoring aided confirmation of the underlying diagnosis. Furthermore, this is among one of the few reported cases in which the relationship between ictal asystole and insular lobe activation has been precisely demonstrated via the use of stereo-EEG electrodes. Greater recognition of this pathology may lead to earlier intervention to reduce the risk of morbidity and mortality in this patient population and may also reduce the incidence of SUDEP.Funding: The authors received no funding on this project.