Manifestations of multiple sclerosis (MS) in the sense of hearing and balance, such as sudden hearing loss and dizziness, but also a foreign body sensation, are among the side effects of multiple sclerosis. In this article, we explain the basics of hearing and balance and shed light on how these can be affected by multiple sclerosis.

The human ear and the audio-vestibular system

The human ear consists of an outer ear and an inner ear, in which the audio-vestibular system is located. The audio-vestibular system is responsible for hearing and balance. It consists of the auditory part, which is responsible for hearing, and the vestibular part, which is responsible for balance and spatial orientation.

hearing

The auditory part of the audio-vestibular system comprises the outer ear, which picks up sound and transmits it to the middle ear. In the middle ear, more specifically on the back of the eardrum, there are three ossicles, the ossicle chain: hammer, anvil and stirrup. When a sound or sound in the form of a sound wave hits the eardrum, it vibrates and transmits it to the ossicle chain. The ossicles are used to amplify and transmit sound to the cochlea. The cochlea is filled with fluid and contains hair sensory cells. These cells convert sound waves into electrical signals, which are then transmitted via the auditory nerve to the brain, where they are perceived as sounds. The cochlea therefore converts mechanical movements into an electrical nerve signal, which the human being processes as heard.

equilibrium

The vestibular part of the system comprises the structures in the inner ear that are responsible for balance and spatial orientation. These include the semicircular canals, which register head and body movements, as well as the vestibular organs, which register linear acceleration and gravity. This information is transmitted to the brain to maintain balance and enable spatial orientation.

‍

auditory nerve

The nerves of the auditory organ and the organ of balance combine to form the auditory nerve. This enters the brain stem and is converted into cranial nerve nuclei. From there, the signal goes towards the cerebral cortex. Since it is important for hearing and balance that signals are transmitted quickly, nerve cells are isolated with myelin all the way from the inner ear to the cerebral cortex. You can think of myelin as an insulating layer around the nerve. The myelin sheath is the basis for rapid transmission of electrical signals.

‍

Hearing problems in multiple sclerosis

Around one in a hundred MS patients report hearing impairment. In most cases, hearing problems occur in the form of sudden hearing loss, including sensorineural hearing loss, sensorineural hearing loss). Here, “sensorineural” means that the cause of the hearing loss lies in the cochlea or the auditory tract. Since the nerve tract is isolated with myelin on the way from ear to cerebrum, it is attacked and de-isolated from time to time as part of multiple sclerosis. This often takes place in the area of the cranial nerve nuclei, the 'switching stations' in the brainstem. However, this can also happen in the temporal lobe. This is the area of the brain where the sense of hearing is processed. But this can not only result in hearing loss, but also tinnitus and a feeling of pressure in the ear.

‍

Balance problems & dizziness in multiple sclerosis

Dizziness describes a feeling of disorientation, fluctuation, dizziness, or the sensation of movement even though no actual movement is taking place. It can include a variety of sensations, including spinning vertigo (the feeling that the environment or your own body is spinning or dizzy), vacillatory dizziness (feeling as though you are swaying or swaying), or uncertainty when walking or standing.

Around one out of three patients complain of dizziness at times during the course of their illness. Causes of dizziness include

• Vestibular causes (disorders of the organ of balance (vestibular organ))
• Causes in the central nervous system (CNS)
• Non-vestibular causes (e.g. cardiovascular disease, muscle weakness or vision problems)

Vestibular causes are divided into central versus peripheral dizziness.

Peripheral vestibular vertigo

Peripheral vestibular vertigo, also known as peripheral vertigo, is a sense of balance that originates in the vestibular organ of the inner ear.

Central vestibular vertigo

Central vestibular vertigo is a form of dizziness caused by disorders in the central nervous system, particularly in the brain. This form of dizziness can also be triggered by multiple sclerosis:
The nerve fibers of the auditory and balance nerves are so-called peripheral nerves until they enter the brainstem. Like the nerve tracts in the CNS, these peripheral nerves are surrounded by a layer of myelin, but this layer of myelin is different from that in the CNS. MS disease primarily attacks the central nerve pathways, i.e. the pathways that transmit information from the peripheral nerves to the cerebral cortex. If an MS lesion now occurs in the nerve tract for the sense of balance, the patient feels dizziness.

Dizziness may be a symptom of multiple sclerosis, but may also be caused by other causes. Since the causes of dizziness require treatment, it is important to document symptoms and discuss them with the treatment provider in order to initiate subsequent examinations if necessary.

‍

Diagnostic methods for hearing and balance disorders: MRI and evoked potentials

There are several options available for examining the sense of hearing and balance. The clinical examination is very important in this regard. MRI diagnostics and so-called evoked potentials can help to better classify the disorders.

MRI examination for multiple sclerosis

An MRI (magnetic resonance imaging) scan is an imaging technique that is used to create detailed images of the body's internal structures. It enables doctors to obtain detailed images of organs, tissues, and anatomical structures such as the brain, spine, joints, muscles, and internal organs. MRI scans are routinely performed on MS patients.

The multiple sclerosis foci are shown in MRI as so-called “white matter hyperintensities (WMH)”, i.e. more signal-intensive regions in the white matter of the brain. White matter is the part of the brain in which the nerve pathways are located. Recent studies indicate that in MS patients, these WMHs were also found in the cochlea and auditory nerve, which may indicate the involvement of these structures in MS. MS is traditionally seen as a disease of the CNS, which is why the infection of peripheral structures sounds surprising at first. The fact that peripheral nerves can also be affected by MS is a relatively new finding and requires further research. The ear problems could therefore be a rare but important early symptom of MS.

Evoked potentials

On the basis of evoked potentials, brain waves can be displayed and transmission via the nerves and nerve pathways can be measured. To do this, electrodes are placed on the patient's skin and acoustic signals are played out. These acoustic signals are then converted into electrical signals in the inner ear, as described above. When healthy, these signals are transmitted at a specific speed. If there is damage on the way between the ear and the cerebral cortex, this electrical signal is delayed. This delay can then be proven in the investigation. In this way, if the auditory tract is damaged, you can determine exactly where the transmission is impaired on the way from the hearing organ to the brain. Evoked potentials are also used to measure other sensory pathways, such as the visual path. The word 'evoked' refers to the fact that during this investigation a stimulus is generated, such as a sound, which is then transmitted to the brain in electrical signals by the sensory organs.

‍

Treatment of auditory tract symptoms

Basically, it is important to discuss any symptoms that arise with the treatment provider, to clarify the causes and to create an optimal treatment on this basis.
Glucocorticoids, which are also used in higher doses in push therapy, are often used to treat auditory symptoms. The treatment of auditory symptoms is only symptomatic here, i.e. it is not the fundamental condition or the disease itself that is being treated, but a symptom. The symptoms often subside on their own or only occur during episodes. If those affected still have hearing problems despite drug therapy, hearing aids can be used.

‍

synopsis

Hearing problems and balance problems such as dizziness can occur with multiple sclerosis. In science, they are also discussed as early manifestations of MS. MRI and evoked potentials can be used to identify the involvement of the inner ear, auditory nerve, or auditory tract. Ear problems are treated with glucocorticoids.