Introduction
The main cause of reduced hearing due to sudden deafness is suspected to be a circulatory disorder of the blood in the inner ear with accompanying reduced supply of hair cells. The hair cells are the sensory cells of the inner ear, which are responsible for converting the sound stimulus into an electrical stimulus. From the hair cells, the impulses are then passed on via the auditory nerve to the brain, where the sound and tone can then be perceived as perceived. In order to maintain the function of the hair cells, it is absolutely necessary that these cells are supplied with blood and thus with oxygen. If there is a disturbance in the blood circulation in the area of the inner ear, a loss of function with the described hearing disorders occurs.
Causes
The reasons why this clinical picture leads to a circulatory disorder are not proven, but it is assumed that there are many different causes for a blood deficiency in the inner ear. These include the following: If the blood changes its flow habits (viscosity), coagulation in the blood vessel can occur more quickly with accompanying occlusion (embolism) of the vessel. The prerequisite is that the flow rate of the blood is reduced.
This happens when the blood becomes more viscous, which is the case, for example, when the daily fluid intake is reduced. Older people are particularly at risk here. Blood coagulation disorders can also lead to premature blood clotting and thus cause vascular occlusion.
It is assumed that the acute hearing loss is a minor stroke or infarction of the inner ear. The causes are similar to those of a heart attack or major stroke. Patients who suffer from the typical symptoms of a stroke (dizziness, possibly headaches, paralysis, etc.)
often have reduced hearing in one or both ears. It is assumed here that in addition to the blood clot blocking a vessel of the brain, a small clot also obstructs the vessel of the inner ear. Arteriosclerosis, the thickening of the vessel wall by fats and non-degradable glycerides, which causes heart attacks, is also held responsible for the cause of sudden deafness.
This can happen if the cholesterol level is permanently too high, lack of exercise, overweight or diabetes mellitus. Noise can also be a possible cause of sudden hearing loss. However, the underlying mechanisms are not yet fully understood.
One explanation lies in the direct effect of noise on the inner ear. In order for us to be able to hear, hair cells in the inner ear must be deflected to varying degrees depending on the pitch and volume of the sound. Figuratively speaking, this can be imagined by a lawn on which the blades of grass are deflected by the wind.
If the hair cells are constantly deflected by noise, their metabolism increases and they need more nutrients and oxygen. If the noise persists over a longer period of time without a break for regeneration, the metabolism will eventually be exhausted and the hair cells can no longer be adequately supplied. The consequence is the irreparable loss of hair cells.
As the deterioration progresses, the hearing performance also diminishes. A further explanatory approach puts the psychological burden of noise in the foreground. If the affected person cannot escape the noise, he or she perceives it as stress.
It automatically becomes tense and reacts by releasing hormones, which lead to increased blood pressure due to a narrowing of blood vessels. Normally this reaction of the body is very useful, because stress requires a willingness to act. However, if the blood pressure rises too much, the blood circulation can be impaired in some cases.
One possibility is that the vessels leading to the inner ear become too narrow. The result is an undersupply of blood to the inner ear, which results in a ringing in the ears or hearing loss. If this condition persists for too long, it can lead to a sudden loss of hearing with further symptoms.
Although there is no evidence of this, stress is often blamed for the hearing loss. This is probably due to the fact that sudden deafness also occurs frequently in patients who are either in an acutely stressful situation or suffer from a chronic stress situation. One explanation is the high release of adrenaline during a stressful situation.
Adrenaline has the task of raising the blood pressure accordingly. This is done by narrowing the blood vessels.If the vessels become too narrow and reduce their diameter, the hair cells of the inner ear may also be undersupplied with blood (similar effect of a heart attack). Damage to the inner ear or hair cells can also always be caused by injuries and trauma.
It is therefore particularly important to ask the patient about recent falls or accidents. It is also possible that infections can cause hearing loss. These infections can also be otherwise inconspicuous and can only affect the inner ear.
For this reason, diagnosis proves to be difficult. Pathogens can be mumps viruses, herpes viruses, HIV or adenoviruses. Therefore, the physician should ask the patient about any accompanying illness at the moment and the weeks and months before each cause study.
Inflammation of the middle ear (otitis media) can also cause sudden hearing loss. The reason for this is an inflammatory accumulation of fluid in the inner ear, which hinders the transmission of sound from outside to inside. A cold can simulate a sudden loss of hearing.
As a rule, however, there is no functional disorder of the inner ear. Only the symptoms of these independent diseases can overlap. Both diseases can lead to a feeling of pressure in the ear, dizziness and hearing loss.
In contrast to sudden deafness, however, a cold does not cause a circulatory disorder in the inner ear. Rather, it is the inflammatory swollen mucous membrane in the throat area that leads to a ventilation problem in the middle ear. This in turn results in a feeling of pressure in the ear and hearing loss.
In the case of a cold, dizziness is also not caused by a functional impairment of the organ of equilibrium in the inner ear, but by the paranasal sinuses, which are usually filled with secretions and exert a strong pressure on the cranial structures. In principle, all vascular situations can cause a sudden loss of hearing. Not to be forgotten is also damage to the support and growth of the spinal column, especially the cervical spine, which, due to corresponding bending, can cause pressure to be exerted on the vessels that supply the ear with blood and oxygen.
Functional disorders of the cervical spine itself can have various causes. One possibility would be muscular tension in the cervical and neck area, which impairs supply structures that move from the back towards the ear. Hardened muscle parts can press on blood vessels or nerves and thus manipulate the supply to the inner ear, which can manifest itself symptomatically in a sudden loss of hearing.
Direct injury to the inner ear due to muscle tension is unlikely, but whiplash injury is conceivable. A twisting of the cervical spine during an accident can therefore be another possible cause. If there is no acute accident and bony changes can still be detected, age-related wear and tear can be seen as a possibility for a narrowing of blood vessels or nerve cords in the direction of the ear.
For the attending physician, the patient’s description and posture are usually decisive, so that he or she examines the cervical spine more closely as a possible cause of a sudden hearing loss. If the patient indicates a unilateral ear noise and shows an abnormal posture or muscularity of the cervical region, the cervical spine is in most cases quickly exposed as the cause. In principle, all autoimmune diseases that affect the vessels in the body can also cause sudden deafness.
Here, too, typical accompanying signs of the patient’s sudden hearing loss should be investigated. A patient suffering from the so-called arteritis temporalis, for example, usually also complains of severe throbbing headaches. The diagnosis is confirmed by blood tests and the identification of autoantibodies, which are found in the blood in such a case.
The possibility of a tumor in the area of the auditory nerve as the cause of hearing loss must always be considered. Although this cause of sudden hearing loss is quite rare, it should not be disregarded. In the case of a tumor disease, the so-called acoustic neuroma is described as the most common tumor causing sudden deafness.
The diagnostic tool of choice here is magnetic resonance imaging (MRI) of the head. Occasionally, major neurological diseases can trigger the symptoms of sudden deafness. In addition to the stroke described above, multiple sclerosis (MS) and meningitis should also be mentioned.In many cases, the sudden hearing loss on one side is simply due to ear contamination caused by increased lard production or improper cleaning with cotton swabs (earwax plug is pushed into the ear canal).
