Related Links: Action on Hearing Loss
Common Ear Disorders
When a foregin antigen enters the inner ear, it is first processed by immunocompetent cells which reside in and around the endolymphatic sac. Once the foreign antigen has been processed by these immunocompetent cells, these cells secrete various cytokines which modulate the immune response of the inner ear. For example, TNF-alpha may play a key role in the initiation and amplification of the immune response. One result of this cytokine release is to facilitate the influx of inflammatory cells which are recrutied from the systemic circulation. These systemic inflammatory cells enter the cochlea via diapedesis through the spiral modiolar vein and its tributaries, and begin to participate in antigen uptake.
Autoimmune inner ear disease (AIED): is a rare disorder appearing in both adults and children that often involves a bilateral disturbance of the audio and vestibular functions of the auris interna. Up to one-third of pateints with AIED also suffer from a systemic autimmune illness, such as inflammatory bowel disease, and rheumatoid arthritis. In AIED the immune system itself begis to damage the delcate inner ear tissues.
Transtympanic administration of the monoclonal antibody against TNF alpha (infliximab) has been shown to result in hearing improvement and reduced disease relapses in patients suffering from autoimmune inner ear disease (AIED) (Wijk, Audiol Neurotol 2006).
Meniere’s Disease: is an idiopathic condition characterized by sudden attacks of vertigo, nausea and vomiting that may last for 3-24 hours, and may subside gradually. Progressive hearing loss, tinnitus and a sensation of pressure in the ears accompanies the disease through time. The cause of Menier’es disease is unknown but is probably related to an imbalance of inner ear fluid homeostasis, including an increase in production or a decrease in reabsorption of innear ear fluid.
The aetiology and pathogenesis of Meniere’s disease remains unknown (Greco, Autoimmunity Reviews, 11, 2012). Intratympanic injection of gentamicin into the middle ear has been used to treat Meniere’s disease. Gentamicin is toxic to the sensory cells of the balance system and thus supresses the vertigo in these patients by partically ablating their vestibular system. There are also cinical reports related to the local applicaiton of glucocorticoids for Menieres disease.
Meniere’s Syndrome: displays similar symptoms as Meniere’s disease and is attributed as a secondary affliction to another disease process such as thyroid disease or inner ear inflammation due to syphillis infection.
Otitits media (OM) (infection of the middle ear): is an inflammatory disorder of the auris media which includes actue otitis media (AOM), otitis media with effusion (OME) and chronic otitis media. Alhtough adults are susceptible to OM (middle ear infections) children are particularly at risk because their relatively short auditory canals can more easily be closed by inflammation. Fluid can then become trapped behind the tympanic membrane (eardrum), which can cause severe pain as well as provide microbes with an inviting environment. Acute otitis media is linked to the activity of pathogenic bacteria commonly found in the indigenous microbiota of the naso-pharyngeal cavity. Quantitatively, the most important pathogens are Streptococcus pneumonia (35%), non-typeable Haemophilus influenzae (30%) and Moraxella catarrhalis (10%). For this reason, acute otitis media is commonly treated by the adminsitration of antibiotics especially in infants. But this has led to development of resistance to commonly prescribed antibiotics. It has been known for some time that human milk has a protective effect against otitis media and this is thought to be due to specific immunoglobulins in the milk such as seretory IgA antibodies in the milk. Bruessow teaches a composition suitable for treatmnet of otitis media by IgA derived from mature bovine milk.
OM susceptibility is multifactorial and complex, including environmental, microbila and host factors. Bacteria infection accounts for a large percentage of OM cases, with more than 40% of cases attributed to Streptococcus pneumoniae infection. Regardless of the causative agent, increases in cytokine production, including interleukins and TNF, have been observed in the effluent media of individuals afflicted with OM. Because OM can be cuased by a virus, bacteria or both, it is often difficult to identify the exact cause and thus the most appropriate treatment. Treatment opicns in the auris media include treatment with antiboitocis. Pre-treatment with TNF-alpha inhibitors in experimental LPS induced OM animal models have been shown to suppress development of OM.
Sensorineural hearing loss (SNHL): is one of the most prevalent disabilities. Sound stimuli are received by auditory hair cells (HCs) in the bony, snail-shaped cochlea, followed by transduction of the sound stimuli by the HCs to neural signals. Spiral ganglion neurons (SGNs) which are auditory primary neurons, are located in the central bony axis of the cochlea and responsible for transmitting auditory signals to the central auditory system. The cochlea is connected to the tympanic cavity by the round window membrane (RWM). Excessive noise, ototoxic drugs, genetic disorders and aging all contribute to the causes of SNHL.
Vestibular Neuronitis: is characterized by sudden vertigo attacks and may be cause by inflammation of the nerve to the semiicircular canals likely cause by a virus.
Sensorineural Hearing Loss (SHL): occurs when the components of the inner ear or accompanying neural components are affected and/or inflamed. Sensory hearing loss may be hereditary, or it may be caused by acoustic trauma (e.g., very loud nocies), a viral infection, drug-induced or Meniere’s disease. Many studies have focused on finding novel therapeutic molecules that can be used in treatment of SNHL. Despite such research, the translation into useful therapeutic clinical agents has yet to be achieved. However, clinical trials are in progress. For example, gelatin hydrogels are being used for sustained delivery of insulin-like growth factor 1 (IGF-1). Hepatocyte growth factor (HGF) also has been shown to significantly reduce noise exposure. (Inaoka, Acta Oto-Laryngologica, 2009).
Presbycusis: or age-related hearing loss, occurs as a part of normal agining, and occurs as a result of degeneration of the receptor cells in the spiral organ of Corti in the inner ear. Other causes may also be attributed to a decrease in a number of nerve fibers in the vestibulocochlear nerve, as well as a loss of flexibility of the basilar membrane in the cochlea. There is currently no known cure for permanent hearing damage as a result of presbycusis or excessive noise.
Itinnitus: is the perception of sound without external acoustic timulation and is a very common inner ear disorder.