Peripheral Vestibular Disorders - Diagnosis and Its Treatment

Introduction:

Peripheral vestibular disorders are pathologies associated with the vestibular (related to the ear) portion of the eighth cranial nerve (vestibulocochlear nerve). These disorders cause a disturbance in the balance system of the body.

What Is the VIII Cranial Nerve?

Cranial nerves are 12 pairs at the back of the brain. The cranial nerves transfer electrical signals from the brain to different body parts. They are responsible for all sensory and motor functions of the body. The eighth cranial nerve is called the vestibulocochlear nerve. It consists of the vestibular nerve (responsible for maintaining body balance and eye movements) and the cochlear nerve (responsible for hearing). Injury to this nerve will lead to symptoms such as vertigo (spinning of the head), tinnitus (ringing in the ears), nystagmus (rapid involuntary movements of the eyes), and hearing loss.

What Are the Different Peripheral Vestibular Disorders?

The different peripheral vestibular disorders include -

1. Benign Paroxysmal Positioning Vertigo (BPPV).

2. Menière's Disease.

3. Vestibular Neuritis.

4. Bilateral Vestibulopathy.

5. Vestibular Paroxysmia.

6. Superior Canal Dehiscence Syndrome (SCDS).

What Is Benign Paroxysmal Positioning Vertigo?

It occurs in individuals aged 50 or more. It is more commonly seen in females. It mainly occurs due to any ear disorder or damage to the inner organs of the ear due to a significant head injury.

Causes of Benign Paroxysmal Positioning Vertigo:

Benign paroxysmal positioning vertigo is primarily idiopathic (without known cause). But, in some cases, it may occur due to minor or significant head injury, which causes a disturbance in the inner ear apparatus. The internal structures of the ear also play an essential role in causing this disease. The inner ear has an organ called the vestibular labyrinth, which includes three loop-shaped structures that contain fluid and delicate hair-like sensors that monitor the rotation of the head. Other structures called the otolith organs are also present in the ear, which monitor the position of the head concerning gravity. This organ contains otolith crystals that make the person sensitive to gravity. If, for any reason, these crystals get dislodged and move into one of the loops of the vestibular labyrinth. This causes it to become sensitive, and the person feels dizzy when the position of the head changes.

Symptoms of Benign Paroxysmal Positioning Vertigo:

The symptoms of this disorder may appear irregularly and may last for less than a minute -

1. Vertigo is a sensation of spinning the head. The world seems to be spinning around the affected individual.

2. The patient experiences a loss of balance and cannot walk steadily (unstable gait).

3. Nausea and vomiting.

4. Headache and dizziness.

5. Abnormal rhythmic eye movements may also accompany vertigo.

Diagnosis of Benign Paroxysmal Positioning Vertigo:

A detailed patient history combined with specific tests for the eye provides an appropriate diagnosis for this condition.

Positional Testing - Dix–Hallpike Maneuver (examining the right ear).

The patient is seated on a table so that when the patient lies down, the head of the patient will extend out of the table. The physician will check for eye signs when the patient is lying down with the head extending out of the table. There will be signs of nystagmus (rapid uncontrolled eye movements) lasting for a few seconds. This maneuver is completed by seating the patient in a sitting position and observing the eyes for a reversal of nystagmus.

Treatment of Benign Paroxysmal Positioning Vertigo:

• Patients are advised to avoid positions and actions that may induce vertigo.

• Medications are prescribed for symptomatic relief.

• The Liberatory Maneuver of Semont (right ear) - These simple movements can help reduce dizziness. The maneuver consists of the patient sitting on the edge of the bed. Moving the head 45 degrees to the left side. Then lying down on the bed on the right side without changing the direction of the head. Wait in the side-lying position for one minute. Then quickly change the side and lie down on the left side without changing the position of the head. The head must be in a right downward direction. Keep this position maintained for a minute. Get back to the original position slowly and sit there for 10 minutes. The physiotherapist recommends this maneuver for the treatment of benign paroxysmal positioning vertigo. These movements must be performed under the supervision of the physical therapist.

What Is Meniere's Disease or Meniere's Syndrome?

This disease is a combination of symptoms such as -

1. Recurrent spontaneous attacks of vertigo (spinning sensation of the head).

2. Fluctuating hearing loss.

3. Tinnitus (ringing in the ears).

4. Aural fullness (pressure, discomfort, and a feeling of fullness in the ear).

These symptoms are caused by changes in the hydraulic pressure within the inner ear (the pressure exerted by a fluid on a surface or structure). This change in pressure is caused by the loss of electrolytes in the endolymphatic system (endolymph is a clear fluid found in the membranous labyrinth of the inner ear).

Causes of Meniere's disease:

The exact cause of this disease is not known. Meniere's syndrome mainly occurs due to increased pressure within the endolymphatic system. It can also occur as a complication of systemic conditions like -

1. Endocrine problems.

2. Autoimmune diseases.

3. Parasitic infections.

4. Electrolyte imbalance.

5. Medications.

6. Trauma.

Diagnosis of Meniere's Disease:

Endolymphatic hydrops is a pathological hallmark of Meniere's disease. Visualization of endolymphatic hydrops is done by high-resolution MRI (magnetic resonance imaging) after transtympanic injection of gadolinium (gadolinium is a contrast material that improves the clarity of the pictures or images of the internal body structures, and it is injected through the eardrum into the inner ear space).

Treatment Strategies for Meniere's Disease:

Medications are proven to help manage this condition.

1. Gentamicin - Intratympanic (inside the middle ear) application of gentamicin has promising results. Gentamicin is an antibiotic that damages the inner ear and the balance organ when applied behind the eardrum. This therapy reduces the episodes of vertigo but may result in hearing loss.

2. Steroid Medications - Transtympanic administration of glucocorticoids like Dexamethasone and Solumedrol. This treatment option is not as effective as gentamicin therapy.

3. Betahistine - This drug helps reduce the intensity and frequency of vertigo attacks and tinnitus and improves hearing loss.

What Is Vestibular Neuritis?

It is a disease of the inner ear caused due to inflammation or swelling of the vestibular portion of the vestibulocochlear nerve (responsible for regulating the head position and maintaining balance). It is characterized by severe sudden onset vertigo, nystagmus (rapid involuntary eye movements), nausea and vomiting, and difficulty in balance. Vestibular neuritis may be caused by a reactivation of herpes simplex virus one infection.

Diagnosis of Vestibular Neuritis:

A vestibular specialist will perform various in-office tests to diagnose the condition -

Head Impulse Test - This test checks the ability of the patient to maintain focus on objects during rapid head movements. It causes severe vertigo and nystagmus in patients having vestibular neuritis; hence, it is a reliable test for diagnosing this condition.

Treatment of Vestibular Neuritis:

The treatment of this disease mainly comprises treating the symptoms and reducing their severity which includes -

1. Medications are prescribed for controlling nausea and vomiting. If the vomiting is severe, the patient is admitted to the hospital, and IV fluids(intravenous fluids are specially formulated fluids that are injected continuously into the vein to treat dehydration) are administered to treat dehydration caused by vomiting.

2. Vestibular suppressants are a group of drugs that are used to reduce dizziness. These drugs must not be taken for more than three days as it has severe side effects and may delay recovery.

3. Steroid therapy may also be used in some cases.

4. Antiviral drugs are used if the symptoms are caused by herpes simplex virus infection.

What Is Bilateral Vestibulopathy?

Vestibulopathy is mainly a disorder caused by damage to the inner ear. Bilateral vestibulopathy is when both ears are affected, and it causes symptoms on both sides of the body. As a result, the patient has difficulty balancing the body, leading to an unsteady gait (walking). Patients may even experience episodes of vertigo that may get worse in the dark, blurred vision while walking, and also experience oscillopsia (an illusion of objects moving around while, in reality, they are not). Bilateral vestibulopathy highly affects the quality of life as it affects functions like walking and vision. However, it has a good prognosis, symptoms are relieved in maximum cases, and recurrence is rare.

Diagnosis of Bilateral Vestibulopathy:

The symptoms of an unsteady gait and decreased vision are classic for bilateral vestibulopathy. The vestibule-ocular reflex is checked to confirm the diagnosis of this disease. The following tests are carried out -

1. Rotatory Chair Test - This is the gold-standard test to confirm the diagnosis. The patient is seated in a computerized rotational chair in a small dark room. A seat belt and head strap are used to prevent falls. A pair of infrared goggles are given to the patient. The patient wears them while the chair is in motion. These infrared goggles record eye movements during the test. Different sub-tests are done to identify whether the dizziness is due to vestibular dysfunction or a central nervous system disorder.

2. The Head-Impulse Test - This test checks the ability of the patient to maintain focus on objects during rapid head movements.

3. The Caloric Test - It is used to assess the functioning of the vestibular system (responsible for normal movement and balance).

Treatment Plan For Bilateral Vestibulopathy:

1. Vestibular function is recovered with the help of physical therapy.

2. Medications that have been proven helpful in treating vertigo, for example, steroids, non-steroidal anti-inflammatory drugs, and antihistamines, will worsen bilateral vestibulopathy.

3. Vestibular implants can be beneficial.

What Is Vestibular Paroxysmia?

It comprises spontaneous, recurrent, short-lasting attacks of vertigo. The episodes of vertigo last for a few seconds to minutes. Ear signs, such as tinnitus (ringing in the ears), are absent. The common cause of this disease is damage to the vestibular nerve (VIII cranial nerve). The patients experience vertigo, oscillopsia, and unstable gait, similar to other vestibular disorders.

Diagnosis of Vestibular Paroxysmia:

1. The diagnosis of vestibular paroxysms is dependent on the symptoms experienced by the patient.

2. MRI scan (magnetic resonance imaging) helps identify the damage to the vestibular nerve.

Medications Useful in Treating This Disorder:

1. Carbamazepine is the drug of choice in treating this disorder.

2. Low doses of anticonvulsant medications (Carbamazepine) help improve symptoms.

What Is Superior Canal Dehiscence Syndrome (SCDS)?

Superior canal dehiscence syndrome can cause problems with hearing and balance. Dehiscence is the splitting or bursting open of organs or tissues and exuding out material. In superior canal dehiscence syndrome, the bone's opening covers the inner ear's semicircular canals. This can also be a congenital (inborn developmental disorder) problem. The bone surrounding the canals can be abnormally thin since its development and can cause this disease.

Symptoms of Superior Canal Dehiscence Syndrome:

• Simple, loud sounds can cause the patient to feel like the world is wobbling down.

• Autophony is a common phenomenon associated with this disorder. Autophony means hearing the sound of oneself. For example, sounds such as breathing, heartbeats, and blood flowing in the body can be heard by the patient, and when the patient talks, they can listen to themselves from inside the ear.

Diagnose of Superior Canal Dehiscence Syndrome:

• Hearing tests are helpful for the diagnosis of this disease. The neurotologist performs them.

• The vestibular-evoked myogenic potential is another diagnostic test. It is a sound generator that checks reactions in the neck and eye muscles.

• Thin-slice computed tomography (CT scan) is also done to check the condition of the bone, but this may give the false appearance of dehiscence, even if the bone is thin but intact.

Treatment Plan for Superior Canal Dehiscence Syndrome:

• Patients are educated on how to avoid the triggers that will cause the symptoms. For example, to avoid places with loud noises or undertake any activities that can worsen the symptoms.

• A certified vestibular physical therapist will suggest exercises that improve balance and reduce the risk of falling.

• Patients who have a severe disability may require surgery to correct the dehiscence. The prognosis of this surgery is good, but some patients may experience hearing loss after surgery.

Conclusion:

Most peripheral vestibular disorders have a good prognosis due to the suitable diagnostic methods available. Newer diagnostic techniques are being developed, improving this disease's prognosis. Medications combined with physical therapy provide the best results by improving the quality of life of affected individuals. Patients debilitated by these disorders may require surgery, which has promising results and helps improve function.