Tinnitus and Other Subjective Phenomena—and the Hearing Process

Abstract

Disease, intoxications and injuries cause subjective phenomena of hearing that shed much light on the mechanism of hearing, and on the causes of deafness. Paralysis of the tensor tympani muscle arising from injury to the fifth cranial nerve causes dysakusia for low frequencies—a condition in which high intensities produce discomfort or actual pain. Hyperacousis, or increased acuteness of hearing, in which the loudness of sound is accentuated, follows injuries to the facial nerve paralyzing the stapedius muscle. Affections of these middle ear muscles by myasthenia gravis, or other diseases which give rise to muscular fibrillations, cause roaring, “boiler factory” tinnitus. In the absence of the ear drum, high intensities of low frequencies cause vertigo and falling. These phenomena parallel in many respects animal experimental findings such as those reported by Drs. Wever and Bray; and indicate that the middle ear mechanism serves primarily as a sound impedance that protects the inner ear, rather than as a specialized sound conductor. Tinnitus of inner ear origin may be caused either by anemia, congestion, allergy or spasm of blood vessels. Intoxication by quinine, aspirin and other salicylates, and ergot are among the most frequent causes of these types of tinnitus and deafness. They act by causing spasm of the blood vessels. The incidence of progressive deafness could be considerably reduced by restriction of these drugs. Increased pressure of the perilymph on the inner ear gives rise to tinnitus which is readily cleared up by spinal tap and by medical therapy designed to keep the pressure down. Hallucinations of hearing often characterize disease of the brain involving the central nervous mechanism of hearing.