sudden deafness

Hearing loss is a sudden loss of hearing with no recognizable external cause.

Possible causes of sudden hearing loss according to the DGHNO guideline “sudden hearing loss” depending on the type of sensorineural hearing loss (IOS):

Hearing loss with high-frequency hearing loss
Depending on the extent of the hearing loss, the probable hearing loss of the sloping or steep drop in the sound threshold in the high frequency range or the inner ear tympanic depression is an insufficiency of the outer hair cells (inner ear hearing loss (IOS) up to approx. 50 dB hearing loss) and/or the inner hair cells (IOS from approx. 60 dB hearing loss).
Hearing loss with low-frequency hearing loss
Based on clinical and animal data, the hearing loss in the low frequency range is probably due to endolymphatic hydrops. A local circulatory disorder of the lamina spiralis with hypoxic tissue damage and disturbance of electrolyte homeostasis is also conceivable.
Hearing loss with pancochlear hearing loss
As all frequencies are affected, even minor hearing losses are subjectively perceived as severe. The main cause of the disease is a functional impairment of the stria vascularis and/or the supplying vessels in the sense of a circulatory disorder and tissue hypoxia.
Hearing loss with mid-frequency hearing loss
The fundamentals of the rare trough-shaped lowering of the tone threshold in the medium frequency range have hardly been investigated. Causes discussed include local circulatory disorders in the area of the lamina spiralis ossea with hypoxic damage (oxygen deficiency) of the organ of Corti and genetic defects.
Hearing loss with deafness / hearing loss bordering on deafness
This form of hearing loss is characterized by the extent of the hearing loss, which usually affects all frequencies. This could be due to a (thrombotic/embolic) occlusion of the common cochlear artery or the spiral modiolar artery with hypoxic strial insufficiency.
Other
This refers to sound threshold curves that can neither be categorized in the groups already mentioned nor assigned to specific IOS types. Its cause is unknown. In a broader sense, this group also includes strongly fluctuating (fluctuating) hearing thresholds and sudden hearing loss with progression of hearing loss under therapy, e.g. due to changes in cerebrospinal fluid pressure and/or immunopathological mechanisms.

What can cause a sudden onset of inner ear hearing loss?
In general, sudden hearing loss is equated with the term acute idiopathic sensorineural hearing loss. The term idiopathic means that the hearing loss has occurred without a recognizable cause. According to a guideline of the German Society for Otorhinolaryngology, Head and Neck Surgery (DGHNO), acute idiopathic sensorineural hearing loss, also known as sudden deafness, is defined as “sudden, usually unilateral sensorineural hearing loss of cochlear origin of varying degrees of severity up to deafness, without an identifiable cause. Dizziness and/or ringing in the ears are also possible” (awmf online, 2009, No. 017/010, Guideline for sudden hearing loss of the German Society for Ear, Nose and Throat Medicine, Head and Neck Surgery). In very few cases can a cause of acute hearing loss be found. A basic distinction is made between hearing loss caused in the inner ear (cochlear), behind the inner ear (retrocochlear) and hearing loss caused in the brain (central). This means that various causes can lead to sudden hearing loss and these causes can come from a wide variety of sources. Looking at the causes of sensorineural hearing loss, Ménière’s disease with endolymphatic hydrops and perilymphatic fistula is a possible cause of acute sensorineural hearing loss. Perilymph fistula is a leakage of inner ear fluid (perilymph) between the inner ear and the middle ear. This is possible, for example, if pressure (barotrauma) causes a tear in the membrane of the round window (entrance port between the middle ear and the inner ear). Drugs that are toxic to the ear (ototoxic drugs) can also cause permanent or temporary damage to the inner ear. These include medications such as furosemide, which is given for high blood pressure or kidney disease, or salicylates, which are used in pain therapy (e.g. aspirin). These can temporarily damage the ear. If the ear is damaged by chemotherapeutic agents (aminoglycosides, cytostatics such as cisplatin) or medication for tuberculosis, the damage is usually reversible. Injuries to the cervical spine, loud acoustic effects such as explosions or significant noise exposure can also cause temporary or permanent damage to the inner ear. Rare diseases of the immune system, such as sarcoidosis or Cogan’s syndrome, can also damage the inner ear. Even rarer are genetic diseases (e.g. Pendred syndrome or Usher syndrome), which can have damaging consequences for the inner ear structures. Inflammation of the inner ear (labyrinthitis) can also occur in infections caused by Lyme disease, measles or mumps infections. If an inflammation of the middle ear is very severe, the inner ear can also be damaged. This is possible in the sense of labyrinthitis or as a result of meningitis. Infections can also damage the auditory nerve. This is referred to as retrocochlear hearing loss. Such infections can be caused, for example, by herpes zoster oticus or other infections such as Borrelia burgdorferi (Lyme borreliosis) or sexually transmitted diseases (lues with the pathogen Treponema pallidum). In very rare cases, HIV can lead to hearing loss. Parasites, e.g. a disease caused by Toxoplasma gondii, can also cause an inner ear infection. If the cause lies in the blood vessels, hearing loss can be caused by an undersupply of blood to the ear due to a blockage (vasospasm) of the supplying inner ear artery (internal auditory artery). A variety of causes, such as heat stress, allergic or psycho-emotional triggers, can cause a change in vascular and blood flow. Bleeding into the inner ear or changes in the large vessels supplying the ear, such as the vertebral artery or basilar artery, are also cited as possible causes of hearing loss.

Can sudden hearing loss be caused by stress?
In practice, we are often asked whether psychological (mental) or physical (bodily) stress can trigger a sudden hearing loss. In fact, fine tissue examinations showed that damaging changes were detectable in the supporting cells of the inner ear. These changes can lead to cell death (necrosis) or slow death (apoptosis). In the event of pathological activation of degradation processes, certain messenger substances (cytokines) are released (IL-1Beta or TNF-Alpha) together with other stress-typical proteins. If these substances are only released for a limited time, the hearing threshold recovers. However, if the activation is prolonged, it results in a permanent loss of the outer hair cells. (Adams JC, Otol Neurotol 2002, 23 (3): p 316-22; Adams et al. Neuroscience 2009 ; 160 (2), p 530-9; Merchant SN, Adams JC and Nadol Jr, Otol Neurotol 2005, 26 (2), p 151-60).