Sensorineural deafness is caused by damage to the hair cells of the spiral apparatus, the auditory nerve, the auditory conduction pathway, or neurons at all levels, resulting in impaired sound perception and nerve impulse conduction, as well as cortical deficits. There are many kinds of symptoms of sensorineural deafness.
1. Congenital deafness
Congenital deafness is a hearing impairment that exists at birth or shortly after birth. It can be divided into two main categories according to the cause.
(1) Hereditary deafness refers to sensorineural deafness caused by genetic or chromosomal abnormalities.
(2) Non-hereditary congenital deafness: Viral infectious diseases such as rubella, mumps, influenza, or systemic diseases such as syphilis, diabetes, sepsis, or heavy application of ototoxic drugs in the mother during early pregnancy can cause fetal deafness.
2.Deafness in the elderly
It is a manifestation of the aging process of the human body in the auditory organs. Its age of appearance and rate of development varies from person to person. The common feature of clinical manifestation is bilateral symmetrical deafness with slow involvement of middle and low frequencies, accompanied by persistent high-pitched tinnitus. Most have loudness reverberation and disproportionate speech recognition to pure tone audiometry results.
3.Deafness of infectious origin
Sensorineural deafness is caused by or complicated with various acute and chronic infectious diseases. The pathogenic microorganisms or their toxins enter the inner ear through channels such as blood circulation and perivascular nerve spaces in the inner ear canal, destroying the tissue structure of different parts of the ear. Clinical manifestations are unilateral or bilateral progressive deafness with or without symptoms of vestibular involvement. In some cases, the deafness is mild or involves only the high tone audio. In this type of deafness, the milder cases recover on their own with the recovery of infectious diseases, but sometimes they continue to worsen, leading to persistent deafness.
4.Deafness caused by systemic diseases
The main causes are hypertension and arteriosclerosis. The mechanism of deafness may be related to impaired blood supply to the inner ear, increased blood viscosity, and flocculation of lipid metabolism in the inner ear. The clinical manifestation is bilateral symmetrical high-frequency sensorineural deafness with persistent high-pitched tinnitus.
5.Drug-related deafness
Deafness is caused by the misuse of certain drugs or long-term exposure to certain chemicals. There are nearly 100 kinds of drugs known to have ototoxicity. Commonly used are aminoglycoside antibiotics such as streptomycin, kanamycin, neomycin and gentamicin; salicylic acid analgesics; antimalarial drugs such as quinine and chloroquine; antitumor drugs such as vincristine and cisplatin; tab diuretics such as furosemide and etanercept; thalidomide preparations such as thallium. In addition, copper, phosphorus, arsenic, benzene, carbon monoxide, carbon dioxide, carbon tetrachloride, alcohol, tobacco and other poisoning.
The mechanism of damage to the inner ear by drugs is not yet clear and depends on the toxicity, dose and course of treatment of the drug itself, in addition to the individual sensitivity. Clinically, deafness and tinnitus coexist with vertigo and balance flocculation. The deafness is bilaterally symmetrical sensorineural, mostly progressing from high to medium and low frequencies. The degree of vestibular involvement may vary from side to side and does not correlate with the degree of deafness.
6. Traumatic deafness
The clinical manifestation is mostly bilateral severe high-frequency neurological deafness or mixed deafness with high-pitched tinnitus and vertigo and balance flutter. The symptoms can be relieved after several months, but it is difficult to recover completely.
7.Sudden deafness
It refers to severe sensorineural deafness that occurs instantaneously and suddenly without any obvious cause. It is currently thought to occur in association with impaired blood supply to the inner ear or viral infection. Unilateral onset is the most common clinical condition. Deafness is usually preceded by high-pitched tinnitus, and about half of the patients have vertigo, nausea, vomiting and a feeling of heaviness and numbness around the ear. Hearing impairment is more severe, with a steeply descending high-frequency or horizontal curve. Vestibular function is normal or diminished. There is a tendency of self-healing, but most cases cannot obtain complete recovery.
8.Autoimmune deafness
Asymmetric, fluctuating, progressive sensorineural deafness that occurs bilaterally at the same time or sequentially, mostly in young adults. Most of the deafness reaches its severity in a few weeks or months, and the condition may sometimes fluctuate. The vestibular function is progressively involved in succession. Patients feel dizzy and have a sense of shaking without nystagmus.