Startle disease--hyperekplexia (two sibling cases).

Two sisters aged 12 and 13 applied to our hospital with complaints of jerking tonic contraction triggered by sudden noise. Diffuse bilaterally polyspike-wave discharges appeared on waking electroencephalography and during that time a startle-induced tonic contraction was seen. Their neurological examinations and neuro-radiological imaging were normal except for hyperreflexia. We presented these cases because of being rare.