Different Varieties of Tinnitus Aurium.—I. Tinnitus caused by obstruction of the normal sound-vibrations in their outward passage through the middle ear and external canal; tidal tinnitus, so called from a resemblance to the noise of the ocean. Such obstructions may exist in the middle-ear cavity, as thickening of the soft tissues of the middle ear, exudations and adhesions, as found in chronic catarrh, or in the external canal, as impacted cerumen, a swollen canal, etc. The effect of such obstruction would be to interrupt the normal sound-vibrations and cause them to be reflected back again to impress for a second time the auditory nerve-elements, causing an abnormal and therefore recognized condition. This is the most frequent variety of tinnitus, and for the reason that it is produced by the more ordinary ear diseases.
II. Tinnitus caused by abnormal sound-vibrations produced either by increase or by decrease of intra-labyrinthine pressure. In a normal condition the auditory nerve-elements are subjected to a given intra-labyrinthine pressure; now, if this pressure be altered (either by being increased or diminished) an abnormal condition ensues, and is noted as such.
a. Tinnitus produced by increased intra-labyrinthine pressure may be caused by increase of the intra-labyrinthine fluids (by effusions, hemorrhages, etc., as in Menière's disease), or can be caused by increase in the amount of blood flowing through the arteries and veins of the internal ear. In either case there will result an increase of pressure that is exerted on the auditory nerve-elements. Also, another result of such increase of pressure on the arteries of the labyrinth would be to throw them into more active pulsation, and so cause greater movement on the intra-labyrinthine fluids. These abnormal vibrations impinging on the auditory nerve-endings would be noticed as such, and give rise to tinnitus of a pulsating character corresponding to the movements of the pulsating vessels. Such a condition is noticed in an eyeball afflicted by glaucoma, or can be artificially produced by finger-pressure on a normal eye. The veins of the retina will be first thrown into movement, and as the pressure increases the arteries will show marked pulsation. Why should not a similar set of conditions in the internal ear produce similar results?
b. Tinnitus produced by a lessened intra-labyrinthine pressure may be caused either by loss of intra-labyrinthine fluid or by a lessened blood-supply to the internal ear. The latter cause being the most frequent, a familiar example of this would be the tinnitus experienced by a fainting person, a common sensation being a swimming head accompanied with strange whizzing noises in the ears. The tinnitus of anæmia is of this class, and frequently of the pulsating variety. Another explanation might be given: an anæmic heart murmur might be conveyed along the blood-vessels as through a speaking-tube, and in that way impress the auditory nerve. In this variety of tinnitus it is supposed that the sound-conducting apparatus of the middle and external ear is normal; if any obstruction exists, it would cause increase of tinnitus of this variety.
III. Tinnitus caused by a diseased condition of the auditory nerve, either in the part lying between the internal ear and brain or in the brain-centre itself—pure subjective tinnitus. Here we enter upon a subject obscure from the fact that so little pathological research has been made in this direction; but, reasoning from analogy, why cannot the auditory nerve be subject to as many diseased conditions as the optic nerve, where the ophthalmoscope has clearly shown the existence of neuritis, atrophy, and many other pathological changes, caused, it may be, by disease of the retina, or it may exist as an inflammation of the nerve itself exterior to the eyeball, or it may be due to a brain tumor pressing on the optic nerve or optic tracts, also basilar meningitis? Gummata, osseous growths, etc. have in turn caused optic neuritis; finally, lesions at the optic nerve-endings in the brain itself have caused well-defined pathological changes in the optic nerve, which by the aid of the ophthalmoscope are recognized. Now, if these changes exist in the optic nerve, why may not the same conditions be present in connection with the auditory nerve, although from its anatomical location they are not capable of demonstration, as in the case of the optic nerve? And, as in the latter phosphene symptoms are common, due to nerve-irritation, so in irritation of the auditory nerve tinnitus would be developed, but of a subjective character. (In this connection it is not out of place to remark that in obscure internal ear disease examination of the optic nerve will often give valuable information toward clearing up the ear complication.) This variety of tinnitus may in some cases be due to a reflex nerve-irritation.
Finally, tinnitus may be noticed in cases of inflammation of the middle ear where fluid has collected, and is caused by the bursting of air-bubbles in their passage through this fluid, the air gaining access to the middle ear by way of the Eustachian tube. Tinnitus so produced resembles a bubbling or crackling sound. Hinton draws attention to certain cases where the tympanic membrane has lost its normal elasticity and become stiff, any movement of such a membrane causing a crackling sound. Also, there are some cases of tinnitus produced by foreign bodies being deposited on the tympanic membrane, such as cerumen, pieces of hair, etc., making a rustling or rasping noise.
Tinnitus produced by abnormal contractions of the tensor tympani or stapedius muscles has been thought to exist. Tinnitus may be intermittent or continuous. It also has an endless variety of sound, from one almost unrecognizable to a roar so loud as to render the patient nearly distracted.
Location of the Tinnitus.—Those varieties due to a diseased external or middle ear locate the sound, as a rule, in the ear itself. Subjective tinnitus is often located in the frontal and occipital regions; often also in the ear itself. It is also to be noted that marked tinnitus may be associated with a low degree of deafness, and the converse is true: slight tinnitus may be associated with a high degree of deafness.
PROGNOSIS.—The removal of tinnitus depends entirely upon the cause of it and the possibility of its removal. Continuous tinnitus is always to be regarded as a more pronounced symptom than the intermittent form.
The TREATMENT will be directed to the removal of the cause. If the disease is located in the external canal or middle ear, or in a diseased condition of the naso-pharynx, these irritating causes should be removed by treatment already laid down in previous pages. The treatment of subjective tinnitus will be guided by the same principles. Determine the cause and seek for its removal. As to whether any particular drugs exist peculiarly adapted to the removal of tinnitus, I would say that in tinnitus of a subjective character or due to nerve-irritation the bromides are indicated in appropriate doses. Inflation of the middle ear with air impregnated with ether (a few drops of ether dropped into a Politzer air-bag and the inflation made by the Politzer method), at intervals of three or four days, in some cases proves of benefit.