<prompt> Perilymph communicates with subarachnoid space through:Ductus reunionsHelicotremaUtriculosaccular ductCochlear aqueduct  <response>: Ans: D Cochlear aqueduct Ref: Diseases of the Ear Nose and Throat by PL Dhingra 5th edn .2010.Page 12Explanation: PerilymphComposition is like extracellular fluidLies between the bony and membranous labyrinthRich in Na ions EndolymphFills the membranous labyrinth.It is rich in K ions.Composition is like intracellular fluid.Secreted by the stria vascularis of the crista and dark cells which are seen in the utricle and the ampullary ends of the semi circular canals. 