at the beginning, oftener during the course or after the termination of mumps. There may be with it some pain and considerable tinnitus. 408. Syphilis is accused often as a cause of labyrinthine disease, but according to personal experience, as well as published reports in literature, the localization in the labyrinth is really very rare in the acquired form of the disease. It is apparently more frequent in congenital syphilis, occurring in females more than in males, and usually between the ages of eight to twenty years. Congenital syphilis localizing itself in the labyrinth coincides often with or follows syphilitic keratitis, and the subjects generally show the malformation of the upper incisor teeth known as Hutchinson's teeth. In the acquired form a few casual observations have shown the labyrinth filled with an inflammatory non-purulent exudate, presumably preceded by syphilitic disease of the blood-vessels. Autopsies at a later stage have shown osseous transformation of the labyrinth with disappearance of the nerve-fibers. The labyrinthine affection in both the acquired and the congenital forms may assume the apoplectic type, or may in an acute manner destroy rapidly the hearing without vertigo. In other instances the affection has been of a slower character and some times did not proceed to complete deafness. As a rule, it is double-sided. Specific treatment has had no positive effect in most instances. In the slower forms it is not even possible to arrest the disease with certainty. Sometimes, however, moderate recovery has been observed, which by some surgeons has been attributed to the use of pilocarpin in addition to specific treatment. 409. A typical labyrinthine affection is a frequent unfortunate outcome of cerebrospinal meningitis. Its percentage varies somewhat with the type of the disease. After severe epidemics of cerebrospinal meningitis its victims constitute a large part of the deaf-mutes of the locality. The disease, as well as its labyrinthine complication, occurs principally in children. Its beginning is usually overlooked on account of the severity of the primary disease and the somnolence or coma so frequently present. As the patient recovers, he finds himself completely deaf and generally distressingly dizzy. The vertigo improves, the staggering gait becomes steadier, after a while incoordination occurs only under trying circumstances, but the deafness remains. Postmortems have shown the lesion to be a suppurative inflammation extending along the auditory nerve into the labyrinth and destroying both the trunk of the nerve and its ends. A primary inflammation of the labyrinth with fever, headache, dizziness, and deafness has been described by Voltolini in children. This affection, however, is now generally believed to be an abortive form of cerebrospinal meningitis. CHAPTER XLVII. DISEASES OF THE AUDITORY NERVE.-DEAF MUTISM. 410. Anatomy of the Auditory Nerve.-The eighth cranial nerve pursues a short course from its emergence at the side of the medulla oblongata underneath the pons to the internal meatus in the middle of the posterior surface of the petrous pyramid. It is joined by the seventh or facial nerve in its course, which leaves it in the depth of the internal meatus to pass over the vestibule into the Fallopian canal. The auditory nerve consists of two branches really representing separate nerves, the cochlear branch or posterior lateral root, and the vestibular nerve, or anterior median root. The independence of these two branches is shown both by their separate peripheral distribution and their separate central course. Besides, the vestibular nerve receives its medullary investment earlier during embryonic life than the cochlear nerve. The cochlear nerve-fibers pass through the spiral ganglion in the interior of the modiolus. The first neuron of this nerve consists of the fibers in the lamina spiralis, peripheral to the spiral ganglion. The second neuron begins in the latter and terminates in the anterior or ventral and posterior or dorsal auditory nuclei in the medulla. Thence the further path is by means of fibers in the trapezoid body and striæ acusticæ, which, decussating, pass forward in the lateral inferior fillet (lemniscus) to the posterior corpora quadrigemina. Through the subthalamic region and posterior part of the internal capsule they finally reach the cortex of the temporal lobe, in which they terminate. The vestibular nerve is interrupted by a ganglion in the internal meatus, whence its fibers enter the vestibule and ampullæ. The nerve ends. in a dorsal nucleus in the floor of the fourth ventricle. Its subsequent connections have been traced into the cerebellum, but are not yet completely known. 411. Affections of the auditory nerve central to the labyrinth are quite rare and are oftener seen by neurologists than by otologists. As in labyrinthine disease, the deafness is characterized by impairment of bone-conduction as well as air-conduction, but, unlike the latter, it is stated that the perception of the highest notes does not suffer first. Tinnitus is, as a rule, not so pronounced as in labyrinthine disease or is even absent. The deafness, too, is not necessarily-indeed, rarely-associated with vertigo. The diagnosis, however, must be based largely on other concomitant nervous symptoms. The auditory nerve trunk suffers from degeneration in a small proportion of patients with tabes. The atrophy is of the same character as the lesion of the optic nerve, which latter, however, is much more common. It is not certain whether there ever occurs a true neuritis of the auditory nerve, except as a complication of adjoining inflammatory processes. Deafness, sometimes one-sided, does occur when basilar disease, localized meningitis, or especially syphilitic disease involves the auditory nerve, but all this is very rare. The intracerebral nerve path may suffer from hemorrhagic effusions, tumors, and abscesses. On the basis of the involvement of the auditory nerve, a localizing diagnosis cannot be made, since its symptoms have been observed in consequence of disease of the cerebellum, as well as of the corpora quadrigemina, subthalamic region, internal capsule, and temporal lobe. When the process is distinctly one-sided, it is the opposite ear which becomes deaf. This has a special bearing in the case of abscesses of otitic origin situated in the temporal lobe. Besides actual deafness disease of the temporal lobe may result in what has been termed word-deafness, or amnesic aphasia. The patient hears, but does not understand the significance of the words. He can repeat the words mentioned, but he cannot recall the words for independent speech. This mental deafness is observed only when the left temporal lobe is diseased in right-handed subjects, or vice versâ. 412. Purely functional deafness occurs at times in hysteria. Neurologists often find that in hysteric subjects unilateral anesthesia extends into the meatus up to the drumhead and is accompanied by a one-sided reduction of hearing, of which the patient is not conscious. The hearing can be restored by suggestive influences, such as electricity or metallotherapy. More striking, however, is the occasional occurrence of sudden absolute. bilateral deafness in hysteric subjects, usually due to emotions or viciously concentrated attention and sometimes. accompanied by speechlessness. The absence of vertigo, of nausea, and of subjective noises distinguishes the hysteric deafness from Ménière's disease. Under suggestive influences hysteric deafness may disappear as suddenly as it occurred, while otherwise it may last indefinitely. DEAF-MUTISM. the re 413. Since speech is normally dependent upon tention and repetitions of auditory impressions, a child born deaf cannot learn to speak in the normal way. Even after speech has been learned it is again forgotten if deafness supervenes before a certain age. This agelimit is about the seventh year, being somewhat variable with the intelligence of the child. It is only after the auditory centers have become fully developed that the impressions once stored up in them remain permanent without fresh additions. Deaf-mutes are either born deaf or have become so during early childhood. Both classes are about equal in number. The proportion of deaf-mutes to the total population is 66 in 100,000 in this country, and varies in Europe from 43 in Holland to 245 in 100,000 in Switzerland. Males predominate slightly over females. Among the determining conditions heredity is to be mentioned |