Topics and Speakers Jose Fayad, MD
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Synopsis
The ear is not only responsible for hearing but also for our sense of balance. In this lecture, Dr Jose Fayad discusses the ear's anatomy, its functional organization, what can go wrong when certain parts are perforated, detection of hearing loss, treatment of the same, and disorders of the vestibular system.
The ear is composed of three compartments: the outer ear, the middle ear, and the inner ear. The outer ear is called the pinna or auricle. It is the part that the patient can see and it serves no major role in hearing. The middle ear starts with the tympanic membrane, or eardrum, which separates the outer ear and ossicles from the outer ear. If the tympanic membrane were to be perforated by injury or disease, mild hearing loss might occur. It also begins the conversion of sound waves into vibrations for the ossicles. The ossicles are composed of the malleus, incus, and stapes, and their main function, in turn, is to convert sound into vibrations for the inner ear. When these vibrations reach the inner ear, which is filled with inner fluids, they create waves within these fluids. When the organ of Corti, which is located here, receives these waves, the stereocilia within it move, creating voltage changes in the cells located there. These electric signals are transmitted to the vestibulocochlear nerve, which translates them as understandable sound to the brain. If the organ of Corti were to be lost, the result would be complete deafness.
Regarding testing for loss of hearing or deafness, Dr Fayad broaches the topic of audiometry, speech tests, and detection of otoacoustic emissions and juxtaposes them to ear lesions and their resulting effects on hearing loss, decibel-wise. The human range of hearing is roughly 120 dB, with sounds above 90dB (such as a jet engine), resulting in permanent hearing damage. If ossicles were lost, you would experience about 55 db hearing loss, also known as conductive hearing loss. Treatments for hearing loss include costly implantable hearing aids, cochlear implants, and bone-anchored hearing applicances (BAHAs); their pros and cons are addressed.
Dr Fayad concludes with the ear's role in balance and posture, which is the function of the vestibule, the region of the inner ear made up of the convergence of three semicircular canals and two organs known as the the saccule and utricle. The canals are responsible for information about angles and different planes, whereas the saccule and utricle are responsible for horizontal and vertical planes. Examining the state of the vestibular system involves caloric testing and posturography. If injury or disease were to assault the vestibular system, conditions such as Meniere's disease (a disease characterized by periodic episodes of rotatory vertigo or dizziness; low-frequency hearing loss; tinnitus; and a sensation of "fullness" or pressure in the ear) and benign positional vertigo may occur. The lecture finishes with suggestions for treatments of such diseases and conditions.
