Beyond a Single Etiology: Tachy-Brady Syndrome and Possible Coexisting Focal Epilepsy Presenting as Transient Loss of Consciousness

Transient loss of consciousness has overlapping cardiac and neurologic causes, and distinguishing syncope from seizure can be difficult. The co-occurrence of a primary cardiac rhythm disorder with a possible coexisting epileptic process is infrequently reported, as most cases instead describe one condition mimicking or triggering the other. We present a case of a 77-year-old woman with hypertension, hyperlipidemia, and paroxysmal atrial fibrillation who awoke with an abnormal chest sensation, a dream-like experience, and urinary incontinence and was admitted for evaluation of a possible seizure. Continuous telemetry captured a 50-second sinus arrest (initially reported as an eight-second pause), followed by an episode of atrial fibrillation with rapid ventricular response, establishing tachy-brady syndrome secondary to severe sinus node dysfunction. The patient underwent dual-chamber pacemaker implantation. Routine electroencephalography performed the following day showed occasional left temporal focal slowing and sharp waves without captured seizures, raising concern for possible focal epilepsy; incidentally identified right-sided meningiomas were discordant with the left temporal focus. The prolonged sinus arrest occurred during sleep without accompanying clinical seizures and showed a tachy-brady pattern typical of intrinsic sinus node disease, arguing against ictal asystole. Although the telemetry findings strongly supported intrinsic sinus node dysfunction, the interictal EEG abnormalities raised the possibility of an additional epileptogenic tendency. The patient was started on levetiracetam for a provisional diagnosis of epilepsy, pending reassessment. This case illustrates that a cardiac rhythm disorder and a possible coexisting epileptic process can occur together and that identifying one etiology should not preclude investigation of the other. Clinicians should maintain a low threshold for both continuous cardiac monitoring and EEG in patients with atypical transient loss of consciousness, as findings favoring one diagnosis do not preclude the other.