Transient tinnitus is an experience that almost every adult has. It is an auditory hallucination caused by auditory dysfunction. Those who exceed the physiological limit become symptoms.If it develops into persistent severe tinnitus, it will not only interfere with normal life and sleep, but also induce cardiovascular disease, digestive disorders, anxiety and depression.
Understanding the classification, incidence and mechanism of tinnitus and other related issues are essential for the cognition and treatment of tinnitus.
Tinnitus caused by cochlear lesions can be classified as organic tinnitus, and those caused by non-cochlear lesions should be classified as functional tinnitus.According to the characteristics of tinnitus, it can be divided into subjective tinnitus (referred to as tinnitus) and heterosensory tinnitus.The former can be felt by others and cannot be heard by others, which is very common in clinical practice; the latter can be heard by others and is rare in clinical practice. The basis of its occurrence is related to myoclonus or vascular malformations.The tinnitus of patients with conductive deafness is mostly low-pitched, such as the roar of machines, air blows, and the sound of running water. The tinnitus of patients with sensorineural hearing loss is mostly high.The tone is like a cicada.Tinnitus can be caused by lesions in adjacent tissues of the ears or systemic lesions.Anxiety, fatigue, or emotional excitement can easily induce tinnitus, and the hearing of such tinnitus patients may be completely normal when they go to the doctor, and no substantial lesions can be found locally or throughout the body.
Tinnitus can be unilateral or bilateral, and the pitch can be high or low, such as cicadas, machine roars, or siren sounds. Most or most patients with persistent tinnitus are accompanied by hearing impairment.The author’s statistics on outpatient tinnitus patients in the past 10 years show that persistent severe tinnitus patients with completely normal hearing have a significant and continuous increase trend. The tinnitus of such patients is also called primary tinnitus.
It is generally believed that the abnormal sensory perception of the auditory nerve caused by various reasons, the displacement of the relative relationship between the tectorial membrane and the hair cells, etc. are related to the occurrence of tinnitus.Tinnitus related to sensorineural hearing loss may be due to the loss or change of the normal spontaneous activity of cells in the damaged part of the cochlea, or the auditory nerve’s ability to filter afferent signals is weakened.
The triad of tinnitus, hyperacusis and hearing loss (especially common after brain trauma) is a disease with a common pathophysiological basis. Its occurrence is based on the dysfunction of cochlear hair cells. The first is to cause the transmission of acoustic signals to the auditory center. The second is hearing. Decrease, the auditory center accepts and may reshape the acoustic signals with abnormal conduction. This neuroplasticity can increase the amount of acoustic signals received by the auditory center, causing auditory hypersensitivity; receiving hallucinated sound signals, causing tinnitus.The auditory center receives the hallucinatory sound signal and induces the reorganization of the auditory center itself, which aggravates the hearing impairment.
Dysfunction of the temporomandibular joint can stimulate the ear-temporal nerve, open the somatosensory bypass, and induce increased excitability of the dorsal cochlear nucleus, thereby changing the plasticity of the auditory nerve and leading to tinnitus.Therefore, according to the current understanding of serotonin regulation of nerve excitability and plasticity, reducing the tension of serotonergic nerves can aggravate tinnitus, and improve the function of temporomandibular joint or/and enhance the excitability of serotonergic nerves , It helps prevent the formation of tinnitus memory loops.
Therefore, for persistent severe tinnitus, local and systemic causes should be examined first, and then targeted treatment should be taken based on the results of the examination. (Sun Aihua, Department of Otolaryngology, Shanghai Changzheng Hospital)