Affiliations: [a] Institute of General Physiology, University of Pavia, IRCCS Policlinico S. Matteo, Pavia, Italy | [b] Department of Otolaryngology, IRCCS Policlinico S. Matteo, Pavia, Italy
Note: [1] Reprint address: Prof. Paolo Valli, Institute of General Physiology, University of Pavia, Via Forlanini, 6, 127100 Pavia, Italy. Tel: +39-382-507608; Fax: +39-382-507527; E-mail: [email protected]
Abstract: It is well known that most episodes of benign paroxysmal positional vertigo (BPPV), even in untreated, recover spontaneously in 2 to 6 weeks. In the present study, we put forward the hypothesis that this is mainly due to the fact that endolymph, owing to its low calcium content (20μM) is able to dissolve otoconia. To support this, the fate of frog saccular otoconia immersed in normal endolymph (Ca2+ content 20μM) and in Ca2+-rich endolymphatic fluids (up to 500μM) was studied by observing the crystals at regular intervals for 3 weeks. The results demonstrated that normal endolymph can dissolve otoconia very rapidly (in about 20 hours). When the endolymphatic Ca2+ content was increased (50 to 200μM) otoconia dissolution time was slowed down (about 100 to 130 hours, respectively) and completely stopped when the endolymphatic Ca2+ content was of 500μM. The present results therefore suggest that the major process involved in the spontaneous recovery of BPPV episodes is the capability of the endolymph to dissolve dislodged otoconia.
