Vestibular disease
Isolated otolith dysfunction
This information is intended as a general introduction to this topic. As everyone is affected differently by balance and dizziness problems, you should speak to your doctor for individual advice.
For reasons of better readability, the generic masculine is used and the simultaneous use of the language forms male, female and diverse (m/f/d) is dispensed with. Unless otherwise indicated, the personal designations used in this patient information refer to all genders.
What is isolated otolith dysfunction?
Otolith dysfunction is a generic term for one or more disorders involving the macular organs (sacculus and utriculus). People with otolith dysfunction often have one or more disorders involving another part of the vestibular system.
New research suggests that some people may have isolated otolith dysfunction. The usual definition of isolated otolith dysfunction is abnormal function of the macular organs despite normal function of the semicircular canals. Currently, isolated otolith dysfunction is not an officially recognized vestibular disorder. The diagnosis is still controversial.
The macular organs are part of the vestibular system in the inner ear. This system consists of 10 structures - 3 semicircular canals and 2 macular organs in each ear. The information from these balance sensors is transmitted from the inner ear to the brain via the vestibulocochlear nerve (8th cranial nerve). The brain processes this information so that you can remain upright when standing or moving.
The three semicircular canals - the anterior, posterior and horizontal - are at right angles to each other. They function like a gyroscope to detect different types of rotational movements of the head (e.g. when you bend down to pick something up or turn your head to look over your shoulder).
The macula organs consist of two sac-like structures, the sacculus and the utriculus. The macular organs detect gravity and movement in all directions. They signal to the brain when your head is tilted. This helps you to stay upright and balanced when walking. The macula organs also detect changes in speed during linear movements (linear acceleration) - for example, when you accelerate or brake in a car. The utriculus is located horizontally in the inner ear and mainly perceives horizontal movements. The sacculus is located vertically and mainly perceives vertical movements. The sacculus also provides information about the position of your head, even if it is not moving.
The otoliths have the shape of crystals of a chandelier and hang on the walls of the macular organs. They are microscopic crystals of calcium carbonate that lie on a gelatinous membrane. When you tilt your head, the crystals accelerate in relation to the hair cells on which they lie. The upper and lower parts of the hair cells move in opposite directions (shear force). This movement is recognized by the hair cells and sent to your brain as information about your head position and movement.
New research suggests that the macula organs may also play a role in spatial orientation (where your body is in relation to your surroundings) and memory.
Summary
- Is a collective term for one or more disorders involving the macular organ (sacculus and utriculus).
- The otoliths transmit information about the position and movement of the head from the inner ear to the brain.
- Otolith dysfunction can either occur in isolation or involve a problem with another part of the vestibular system, particularly the semicircular canals.
- Symptoms of isolated otolith dysfunction include a misdirected sense of non-rotating (non-twisting) movements, tilting movements and falling attacks.
- Two vestibular function tests are used to examine the otoliths.
- Vestibular rehabilitation therapy to activate the otoliths appears to be helpful.
- Researchers are still investigating how best to define, diagnose and treat isolated otolith dysfunction.
What causes isolated otolith dysfunction?
How the function of the utriculus and/or sacculus is affected, while other parts of the vestibular system - in particular the semicircular canals - are not affected, is currently unknown.
The researchers suspect, among other things:
- Due to the different blood and nerve supply, a vestibular disorder can only affect one part of the vestibular mechanism in the inner ear, e.g. the macular organs
- Viral damage to the utriculus and/or sacculus without affecting other parts of the inner ear, including the semicircular canals
- Selective hydrops (fluid accumulation) of the utriculus and/or sacculus
- The anatomical structure of the macular organs can make them more sensitive to head trauma than the more resistant structure of the cupula of the semicircular canals
Comorbidities with other disorders
Otolith dysfunction can either occur in isolation or involve a problem with another part of the vestibular organ, particularly the semicircular canals. Vestibular disorders that can lead to macular organ dysfunction include:
- Benign paroxysmal positional vertigo (BPLS)
- Meniere's disease
- Head trauma, including mild traumatic brain injury (TBI)
- Persistent postural-perceptual dizziness (PPPD)
- Acoustic neuroma
- Vestibular neuritis
In many cases, the cause of otolith dysfunction is unknown (idiopathic).
The symptoms of isolated otolith dysfunction are not yet clearly defined. Subjective symptoms possibly caused by macular organ dysfunction include:
- Misdirected sensation of non-rotating (non-spinning) movement - Descriptions include feelings of:
- Rocking or swaying, like on a boat
- Walking on sponges, cushions or uneven ground
- The ground shifts or breaks away from under you
- Float
- Can be pushed or pulled forwards, backwards or sideways
- Leaning to one side when standing or sitting upright
- Confusion of top and bottom (inversion illusion)
- Imbalance during a rapid change in walking speed or when changing from a sitting to a standing position
- Sensitivity to changes in the speed of movement in a vehicle, e.g. in stop-and-go traffic
- Sensitivity to upward and downward movements, e.g. when riding in an elevator
- Recurrent sudden falls that seem to happen for no reason (so-called fall attacks or tumarkin seizure)
- Blurred vision with head movements
Diagnosis of isolated otolith dysfunction
Currently, there is no consensus on the diagnostic criteria for isolated otolith dysfunction. Some researchers propose diagnostic criteria based on symptoms and clinical tests, which are divided into definite isolated otolith dysfunction and probable isolated otolith dysfunction.
In most cases, functional disorders of the macular organs are examined by a neuro-otologist or ENT doctor specializing in vertigo.
These specialized doctors will take a thorough medical history, perform a neurological examination and various tests to assess the function of your vestibular system.
Two special tests are currently used to assess the macular organs:
- cVEMP (Cervical Vestibular Evoked Myogenic Potential) test (assesses the sacculus)
- oVEMP (Ocular Vestibular Evoked Myogenic Potential) test (assesses the utriculus)
Abnormal VEMP results in both ears may be due to non-vestibular causes. For example, VEMP responses are affected by the aging process and results may be inaccurate in individuals over the age of 65.
The subjective visual vertical/horizontal (SVV/SVH) test also evaluates the utriculus; however, brain lesions can influence the results.
Two tests to rule out a functional disorder of the semicircular canal are likely to be performed. These are the caloric test and the video head impulse test. Some abnormal results may lead to some people being incorrectly diagnosed with isolated otolith dysfunction when the semicircular canals are affected.
Treatment of isolated otolith dysfunction
Therapy option
Vestibular rehabilitation therapy appears to be useful, although it has not been well studied in the context of isolated otolith dysfunction. Vestibular rehabilitation therapy is an exercise-based therapy.
For most people, vestibular rehabilitation therapy helps to strengthen the connection between the body, eyes, brain and inner ear. During vestibular rehabilitation therapy, your symptoms are deliberately provoked in a safe and controlled way to allow your brain to adapt. The overall goal is to improve your quality of life by getting used to your condition, reducing your symptoms and improving your overall function.
Research shows that rehabilitation programs are most effective when they are individually adapted. The type, frequency and intensity of effective exercises will vary from person to person. A certified IVRT® Dizziness and Vestibular Therapist can help you develop a
What happens next?
What you can expect in the future.
There is still a lot we don't know about isolated otolith dysfunction. Researchers are still investigating the cause, how many people suffer from it and how best to define, diagnose and treat it.
In order to keep this patient information as short as possible, we have not included a detailed list of references. However, this can be requested at any time at info@ivrt.de.
