Nervous and mental diseases . ear is represented on both sides of the brain, but also principallyupon the opposite side. The auditory center for speech, however, in right-handed individuals is practically confined to the left temporal lobe, thedestruction of which produces word-deafness, or a loss of spoken-wordmemories. At its peripheral termination the auditory nerve enters thecribriform opening in the internal meatus. The auditory portion is dis-tributed to the cochlea and the organ of Corti. The labyrinthian portionis distributed to the vestibule and ampullae of the semicircular c
Nervous and mental diseases . ear is represented on both sides of the brain, but also principallyupon the opposite side. The auditory center for speech, however, in right-handed individuals is practically confined to the left temporal lobe, thedestruction of which produces word-deafness, or a loss of spoken-wordmemories. At its peripheral termination the auditory nerve enters thecribriform opening in the internal meatus. The auditory portion is dis-tributed to the cochlea and the organ of Corti. The labyrinthian portionis distributed to the vestibule and ampullae of the semicircular canals. Irritation of the auditory portion of the eighth nerve ismarked by auditory hyperesthesia, by increased acuteness of hearing {hyper-acousis), and by tinnitus. It must be understood that continued irrita-tion of the auditory apparatus may result in diminished or lost function,just as overstimulation of any tissue or organ finally produces weaknessand involution. It follows that tinnitus, for example, is often found with. Fig. 50.—Diagram of a section showing the ori-gin of theeighth cranial nerve. V, YtMil>ular por-tion ; 0, cochlear portion ; W, accessory of Wiis-berg; A, accessory nucleus ; T, acousiic tubercle;R, restiform body; NC, nucleus of Clarke (afterBrissaud). 130 DISEASES OF THE CRANIAL NERVES. defective hearing. Hyperesthesia is frequently present in excitable andnervous persons. Migraine and all forms of pain often render thesufferer more sensitive to sudden noises, especially of high pitch, butactual hyperacousis is rare. In meningitis, acute mania, and under theinfluence of some stimulant drugs, such as alcohol, opium, anesthetics,Indian hemp, and eaffein, the special sense of hearing is at times actuallyexalted. It is also conceivable that an irritant lesion of the auditorycortical centers might give rise to hyperacousis, and perhaps this is alsothe explanation of some hallucinations of hearing and sometimes of therare auditory aurse of epilepsy. The
Size: 1495px × 1671px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1900, bookidnervousmentald00chu
