[Superior semicircular canal dehiscence syndrome: report of three cases].

Superior semicircular canal dehiscence syndrome is a newly defined and rare disease. The disease shows itself with vertigo and nystagmus induced by loud noise and pressure. Vertigo and nystagmus induced by loud noise is named as Tullio's phenomenon and nystagmus induced by pressure is named as Hennebert's sign. The definitive diagnosis is made by the demonstration of bone defect in superior semicircular channel with high-resolution computed tomography.