We present a case report of a patient who suffered from an acute cochleovestibular deficit after topical application of potassium iodide solution into the left ear. Although the vestibular symptoms progressively disappeared, severe sensorineural hearing loss persisted after treatment with hyperbaric oxygen therapy and intravenous administration of corticosteroids and vasodilating agents. The mechanisms of ototoxicity after topical application of solutions are discussed with emphasis on the particular features of the present case: a patulous Eustachian tube syndrome and the presence of a tympanostomy tube in the left ear.