STARTLING SYNCOPES: ELECTROCLINICAL FEATURES OF A NEW TYPE OF HYPEREKPLEXIA

Objectives: To describe and demonstrate the clinical and electrographic features of a new type of hyperekplexia.

Methods: 15 year clinical follow-up from neonatal period until now, with review of ictal polygraphy and ictal and inter-ictal videorecordings; mutation analysis of a novel gene involved in glycinergic transmission.

Results: Neonatal non-epileptic convulsions were induced by startle and particularly by bathing, nose-tap was positive. During these life-threatening episodes, high voltage EMG “spikes” appeared on EEG channels overlying muscle and on the ECG channel either as repetitive giant potentials in the “clonic” phase or as closely spaced giant muscle potentials in the “tonic” phase. Meanwhile the EEG became slow and then isoelectric, whilst the ECG showed escape rhythm with junctional bradycardia. Excessive startle abated during infancy and now the nose-tap test is negative, and he plays physical contact sports with impunity. He does not have mutations in previously described genes involved in the glycinergic pathway, but does have a mutation in a novel glycine-related gene.

Conclusion: Severe hyperekplexia, remitting in infancy, is associated with a new gene affecting the glycinergic pathway.