Loss of consciousness, “dysrhythmic EEG“, epilepsy in the familial history – but no epilepsy!

Objective: Differential diagnostic evaluation of a 12 year old boy with two unclear events with sudden loss of consciousness and consecutive commotio cerebri. Previous findings: An EEG was performed which showed “dysrhythmia, there were no clear epileptiform potentials“. MRI has been carried out without pathological findings. In the family history, the father and an uncle on the mother's side both had epilepsy.

Methods: Complete physical and neurological examination as well as standard-EEG and ECG were without pathological findings. For further clarification a polygraphic EEG during the night and a mobile long-term-EEG with simultaneous ECG-recording were performed.

Results: The EEG was normal for age. The ECG in wakeness was inconspicuous. During sleep repeated bradycardias with RR-intervals of up to 3 seconds, partly associated with apnoeas/hypopnoeas were seen. These findings led to extensive cardiological examination. The Holter-ECG showed frequent sinus arrests during the night, the longest interval was 3,1 seconds and episodes of bradycardia (25 bpm). The cardiological diagnosis was dysfunction of the sinus node (sick sinus). The cardiologists considered this to be life threatening and progredient. A DDD-pacemaker was therefore implanted.

Conclusion: This case illustrates that in unclear seizures or losses of consciousness apart from epileptic seizures alternative reasons have to be considered especially cardiac causes. In addition to the so called standard-EEG examinations the polygraphic long-term monitoring with simultaneous ECG leads, in most cases, to the correct diagnosis.

In the case presented it was, using these techniques, possible to detect a dysfunction of the sinus node. This is a rare but potentially life-threatening dysrhythmia which is often difficult to diagnose with routine examinations as the characteristic disturbances are often only detectable using long-term ECG monitoring. The advantage of EEG polygraphic recordings over long-term ECG recording alone in such cases is that both epileptic or cardial disturbances can be detected.