Anaesthetic implications of hyperekplexia--'startle disease'

This report describes anaesthesia for consanguineous siblings with the rare genetic condition hyperekplexia. This condition is also known as 'stiff baby syndrome' or 'startle disease'. Hyperekplexia can present in major and minor forms and is caused by a mutation in chromosome 5 which results in a defect in the alpha-1 subunit of the inhibitory glycine receptors in the caudal pontine reticular formation leading to neuronal hyperexcitability. The patients present with a potentially life-threatening exaggerated startle reflex. Life-threatening spasms may be terminated by forced flexion of the head and legs towards the trunk. Anaesthesia management should avoid stimuli which trigger the reflex. Clonazepam and diazepam are used to prevent and control the spasms. Propofol and other agents with the ability to potentiate both GABA-ergic and glycinergic transmission may be appropriate choices for anaesthesia. Reaction to neuromuscular blockers may be unpredictable. Both our patients had relatively prolonged but otherwise uneventful recovery.