Hyperekplexia /ˌhaɪ.pɚ.ɛkˈplɛk.si.ə/ ("exaggerated surprise") is a very rare neurologic disorder classically characterised by pronounced startle responses to tactile or acoustic stimuli and hypertonia. The hypertonia may be predominantly truncal, attenuated during sleep and less prominent after a year of age. [Source: Wikipedia 
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