Aims: Syncope, epilepsy, and psychogenic pseudo-syncope are the most common causes of transient loss of consciousness (T-LOC or blackout). All can present with similar features, including abnormal limb movements. It is reported that somewhere between 13 and 42% of patients with 'epilepsy' may be misdiagnosed. A UK Parliamentary working group found that at least 74 000 English patients are misdiagnosed with epilepsy, and taking antiepileptic drugs. The likely alternative diagnosis is 'convulsive' syncope, mimicking an epileptic seizure. We hypothesized that many patients misdiagnosed with epilepsy have convulsive reflex syncope, and that prolonged electrocardiographic (ECG) monitoring with an implantable ECG recorder (ILR) would show reflex cardioinhibition during T-LOC. This would respond to permanent pacing and allow antiepileptic drugs to be withdrawn. We also aimed to evaluate tilt testing and other tests done in these patients.
Methods and results: We included patients previously diagnosed with epilepsy, but considered to have a definite or likely misdiagnosis of epilepsy after specialist neurological review. All received an ILR (Reveal Plus(®)/Reveal DX(®), Medtronic Inc.), and tilt-table testing. One hundred and three patients were included, mean age of 46 ± 17 years, with 58 of 103 (56%) female patients. A diagnosis of epilepsy was previously made by a neurologist in 69%, but definite tonic-clonic seizures were only noted in the history in 4%. In 22 patients (21%), the ILR recorded profound bradyarrhythmia or asystole with convulsive features, and they were offered pacemaker implantation. After pacing and withdrawal of antiepileptic drugs, 60% of these patients were asymptomatic. Only 14% of patients had a positive tilt-table test. In these, there was no correlation with the ECG findings of a spontaneous blackout during ILR recording.
Conclusion: This study shows a high incidence of the cardioinhibition of reflex syncope in patients with convulsive T-LOC previously diagnosed as epilepsy and treated with antiepileptic drugs. We believe that reflex syncope with convulsive features mimics generalized epilepsy, leading to a misdiagnosis. This may be a widespread problem accounting for many wrong diagnoses of epilepsy. There was also poor correlation in ECG findings between tilt testing and ILR recording.