From Ear Anatomy and Physiology to Hearing Disorders and Meniérè’s Disease

14 dicembre 2016
Versione stampabile

Luogo:  Polo Scientifico e Tecnologico “F. Ferrari” – Via Sommarive 5, Aula A107 
Ore 16:00

  • Relatore: Giuseppe Nicolò Frau (Direttore UO di Otorinolaringoiatria Ospedale Santa Maria del Carmine, Rovereto)

Abstract:
The ear isn’t just the hearing organ. It is a complex system of parts that not only allows humans to hear, but also makes it possible to stand and walk. The ear’s function is to transmit and transduce sound to the brain through the parts of the ear: the outer ear, the middle ear and the inner ear. In fact two functions combine into this small organ, hearing and balance in some diseases, as Meniérè’s, both this functions are affected. Meniérès disease (MD) is a long term, progressive condition affecting the balance  and hearing parts of the inner ear. Is a  multifactorial disorder where the combined effect of genetics and environmental factors probably determine the onset of the disease. Symptoms are acute attacks of vertigo (episodes typically last from 20 minutes up to 4 hours), tinnitus, increasing deafness and a feeling of pressure in the ear. Usually, the hearing loss involves mainly the lower pitches, but over the years, hearing loss often becomes permanent and affects tones of all pitches. The incidence is between 1:1000 and 1:2000 of the population; depending on the source. Both sexes are equally affected and it can occur at any age. About 7-10% of sufferers have a family history of the disease. The cause of Meniere's disease isn't understood and many factors are thought to be involved in the development of the condition. It is associated with the accumulation of endolymph in the cochlear duct and the vestibular organs in histopathological studies, although endolymphatic hydrops (EH) per se does not explain all clinical features. Factors that affect the fluid, which might contribute to Meniere's disease, include: • Improper fluid drainage, perhaps because of a blockage or anatomic
abnormality • Abnormal immune response • Allergies • Viral infection • Genetic predisposition • Head trauma • Migraines Because no single cause has been identified, it's likely that Meniere's disease results from a combination of factors. Reasonable possibilities are obstruction of endolymphatic outflow at the endolymphatic duct level, increased production of endolymph, or reduced absorption of endolymph caused by a dysfunctional endolymphatic sac or other unknown factors. The relationship between these factors and the progression of the disease however remains unclear. Recently the new light on the meningeal and CNS lymphatics has put a new actor into the play. Immunologists have long believed that the central nervous system (CNS) lacks lymphatic vessels and have struggled to understand how lymphocytes access and exit the brain. Louveau et al. now describe the existence of functional lymphatic vessels that run parallel to the dural sinuses of the meninges. The discovery of these lymphatics is likely to have far-reaching consequences for our understanding of immune responses in the CNS and perhaps of MD. MD treatment is necessary when the patient is suffering repetitive attacks of vertigo or severe hearing loss. The goal of treatment is to block the vertigo attacks and restore hearing. They need to be individualized since MD may present in many different ways in different There are three main types of therapy: Diet, different pharmacologic treatments and surgery. Part of treatment may be also a Vestibular rehabilitation therapy that is sometimes used to help with the imbalance that can plague people between attacks or after destructive treatments. Its goal is to help retrain the ability of the body and brain to process balance information. When successful, this can help a person regain confidence in the ability to move about. Low salt diet and avoiding excitants as caffeine together with drinking high volumes of water are the main dietary regimens. The more used medicines are special antihistamines as betahistine that is thought to increase the blood flow around the inner ear, diuretics and corticosteroids. Surgical treatments may be divided in office procedures as intratympanic injections of drugs and ventilation tubes and major surgical procedures. Among the first we can divide a conservative treatment with injection of steroids from a destructive procedure where injecting a drug called gentamicin through your eardrum into the middle ear we give a very high concentration of the drug next to the affected inner ear.
This drug works by damaging the nerve endings that send signals of balance down the vestibular nerve. A ventilation tube can work alone reducing the pressure in the inner ear or as part of a Pressure pulse treatment (Meniett® device). This is a machine which generates a pulse of pressurized air into the ear canal. Major surgical procedures can be divided in conservative as Endolinphatic Sac decompression. This is an operation to reduce the pressure of the fluid in the labyrinth. And destructive procedures as: •Vestibular nerve section. This means that the nerve of balance is cut - which stops the abnormal signals of balance being sent to the brain. •Labyrinthectomy.
This means totally destroying the inner ear. The big disadvantage of this is that the hearing part of the inner ear is destroyed in addition to the balance part. So,  the operated ear will be totally deaf. A recent evolution of this is to associate a posterior labyrinthectomy, where only the vestibular part is destroyed with a cochlear implantation to restore the hearing.

UNITN Host:  E. F. Toro - eleuterio.toro [at] unitn.it