Internal Medicine/Dizziness and Vertigo

Understanding Dizziness
Dizziness is a complex and multifaceted symptom that patients often use to describe various sensations, including vertigo, light-headedness, faintness, and imbalance. To better comprehend the nature of dizziness, it's essential to distinguish among these sensations.

Causes of Dizziness
Dizziness can have a multitude of underlying causes, and understanding these causes is crucial for accurate diagnosis and effective treatment. One primary category of dizziness is vestibular dizziness, which includes vertigo (a spinning or whirling sensation) and imbalance. Vestibular dizziness may arise from peripheral disorders affecting the inner ear's labyrinths or vestibular nerves, or it can result from disruptions in central vestibular pathways within the brain.

Acute unilateral lesions in the vestibular system can lead to vertigo due to a sudden imbalance in input from the two labyrinths. Conversely, bilateral lesions can result in imbalance and unsteadiness, especially when the head is in motion, causing a phenomenon known as oscillopsia. Presyncopal dizziness is another category, occurring when conditions like cardiac dysrhythmia, orthostatic hypotension, or medication side effects lead to insufficient blood supply to the brain.

Apart from vestibular causes, dizziness can stem from nonvestibular sources such as gait disorders, anxiety, and sensory neuropathy. Differentiating among these causes is a critical aspect of diagnosing dizziness accurately.

Evaluation and Diagnosis
The assessment of patients presenting with dizziness demands a meticulous approach. Several questions should be considered during the evaluation process: Is the dizziness dangerous, possibly resulting from conditions like arrhythmia or transient ischemic attack? Is it genuinely vestibular in nature? If it is vestibular, can we determine whether it is peripheral or central?

A comprehensive history-taking and a thorough physical examination can provide valuable insights into the nature and potential causes of dizziness. Given that patients often struggle to articulate their symptoms accurately, clinical history should not solely rely on the patient's description of the sensations. Instead, clinicians should delve into various aspects of the dizziness experience, including the number of episodes, their duration, any triggering factors, and accompanying symptoms.

History
In assessing dizziness, the patient's history plays a pivotal role. Vertigo, for instance, can be an alarming symptom that often indicates an acute vestibular issue. However, the clinical presentation largely depends on factors like whether the vestibular lesion is unilateral or bilateral and whether it has developed acutely or gradually.

Gathering a detailed history is especially critical in the presence of episodic dizziness. Differentiating between brief, intermediate, and prolonged episodes is vital, as this can help in narrowing down potential causes. For instance, brief episodes of dizziness lasting only seconds may be indicative of benign paroxysmal positional vertigo (BPPV) or orthostatic hypotension, while longer episodes measured in minutes might warrant consideration of transient ischemic attacks of the posterior circulation.

Symptoms accompanying vertigo can offer valuable clues. Unilateral hearing loss and other acute aural symptoms such as ear pain, pressure, fullness, or new tinnitus usually point to a peripheral cause. However, central lesions can also manifest with hearing-related symptoms, but typically only when the lesion affects specific anatomical areas. Other symptoms like double vision, numbness, or limb ataxia may suggest involvement of the brainstem or cerebellum.

Examination
In addition to the detailed history, a thorough examination is essential in evaluating dizziness. The neurologic examination assumes particular significance in this context. During the examination, special attention should be directed towards assessing eye movements, vestibular function, and hearing.

Examination of eye movements encompasses observing the range and symmetry of eye movements in both eyes. Peripheral eye movement disorders, such as cranial neuropathies or eye muscle weakness, usually result in disconjugate movements, meaning that the movements differ between the two eyes. Assessing pursuit (the ability to smoothly track a moving target) and saccades (the ability to accurately shift gaze between two targets) can provide insights into the presence of central pathology, often implicating the cerebellum.

Aligning the two eyes can be tested using a cover test. This involves alternately covering each eye while the patient fixates on a target, allowing the examiner to observe any corrective saccades. Vertical misalignment of the eyes may indicate a brainstem or cerebellar lesion.

Nystagmus, an involuntary back-and-forth movement of the eyes, is another crucial aspect of the examination. Nystagmus is often of the jerk type, characterized by a slow drift in one direction (slow phase) followed by a rapid saccadic movement in the opposite direction (quick phase or fast phase) that resets the eye position. Different types of nystagmus can provide valuable diagnostic information. For example, downbeat nystagmus (vertical nystagmus with downward fast phases) and gaze-evoked nystagmus (horizontal nystagmus that changes direction with gaze) are characteristic of lesions in the cerebellar pathways, while peripheral lesions typically cause unidirectional horizontal nystagmus.

To enhance the detection of peripheral vestibular nystagmus, clinicians may employ Frenzel eyeglasses or infrared video goggles, which limit the patient's ability to use visual fixation to suppress nystagmus.

Ancillary Testing
Depending on the clinical presentation and examination findings, ancillary tests may be employed to further investigate the underlying cause of dizziness. Audiometry is a valuable tool, especially when vestibular disorders are suspected. Unilateral sensorineural hearing loss is often indicative of a peripheral disorder, such as vestibular schwannoma.

Videonystagmography involves recording spontaneous nystagmus, if present, and measuring positional nystagmus. Caloric testing and video head-impulse testing assess the responses of the various semicircular canals within the inner ear. Vestibular evoked potentials are used to evaluate otolith reflexes. In some cases, the evaluation may extend to include recording saccades and pursuit to assess central ocular motor function.

Neuroimaging, typically in the form of MRI, is recommended when central vestibular disorders are suspected. In particular, patients with unexplained unilateral hearing loss or vestibular hypofunction should undergo MRI to rule out conditions like vestibular schwannoma.

Treatment Approaches
The treatment of vestibular symptoms largely depends on the underlying diagnosis. It's important to note that simply suppressing dizziness with medications is often insufficient and may even impede the recovery process. Therefore, tailoring the treatment to the specific vestibular disorder is crucial.

For instance, in cases of acute prolonged vertigo, such as vestibular neuritis, patients experience constant vertigo, nausea, vomiting, and oscillopsia due to a sudden imbalance in vestibular inputs. Treatment options for such conditions may include glucocorticoid therapy, although its effectiveness remains a topic of debate. Antiviral medications may be considered in specific situations, such as when there's evidence of herpes zoster oticus (Ramsay Hunt syndrome). However, vestibular suppressant medications should be avoided after the initial stages of treatment to prevent hindrance of central compensation. Encouraging patients to resume normal activity as soon as possible and providing vestibular rehabilitation therapy can accelerate recovery.

Benign Paroxysmal Positional Vertigo (BPPV)
BPPV is a common cause of recurrent vertigo characterized by brief episodes, usually lasting less than a minute. These episodes are invariably triggered by changes in head position relative to gravity, such as lying down, rising from a supine position, or tilting the head upward. Rolling over in bed is a classic trigger for BPPV and can help differentiate it from orthostatic hypotension.

The root cause of BPPV lies in free-floating otoconia, tiny calcium carbonate crystals, dislodged from the utricular macula within the inner ear. These crystals find their way into the semicircular canals, typically the posterior canal, where gravity induces their movement, leading to vertigo and nystagmus. Repositioning maneuvers, like the Epley maneuver, are employed to guide these crystals out of the semicircular canals, effectively treating BPPV.

Vestibular Migraine
Vestibular migraine is a relatively common yet often underdiagnosed cause of episodic vertigo. This condition may involve vertigo without a severe headache or with only a mild headache. The duration of vertigo episodes can vary, lasting from minutes to hours, and some individuals may experience prolonged periods of disequilibrium. Motion sensitivity, especially in response to visual motion like watching movies, is a characteristic feature. Vestibular migraine is typically treated with medications commonly used for migraine prophylaxis, and antiemetic drugs may provide relief during acute attacks.

Ménière’s Disease
Ménière’s disease is characterized by episodic attacks of vertigo, hearing loss, and aural symptoms like ear pain, pressure, and fullness. Notably, low-frequency hearing loss and these aural symptoms set Ménière’s disease apart from other peripheral vestibulopathies and vestibular migraine. Audiometry during an attack often reveals a characteristic asymmetric low-frequency hearing loss. Initial treatment for Ménière’s disease often involves diuretics and sodium restriction. If attacks persist, more invasive treatments like injections of glucocorticoids or gentamicin into the middle ear may be considered. In severe cases, surgical procedures like vestibular nerve section or labyrinthectomy may be necessary.

Vestibular Schwannoma
Vestibular schwannomas, also known as acoustic neuromas, and other tumors in the cerebellopontine angle typically present with slowly progressive unilateral sensorineural hearing loss and vestibular hypofunction. These patients usually do not experience vertigo because the gradual loss of vestibular function is compensated for by central mechanisms. However, diagnosis often occurs only when significant hearing loss becomes apparent. Vestibular examination in these cases may show deficient responses to the head impulse test but without prominent nystagmus. Patients with unexplained unilateral sensorineural hearing loss or vestibular hypofunction should undergo MRI to check for the presence of a schwannoma.

Bilateral Vestibular Hypofunction
Bilateral vestibular hypofunction presents unique challenges. Patients with this condition typically do not experience vertigo due to the simultaneous loss of vestibular function on both sides, resulting in a lack of asymmetry in vestibular input. Instead, they may complain of balance problems, particularly in low-light conditions, and oscillopsia during head movement. Bilateral vestibular hypofunction can occur idiopathically and progress gradually, be associated with neurodegenerative disorders, or be induced iatrogenically by ototoxic medications. Various other underlying causes, such as autoimmune diseases or peripheral polyneuropathy, can also lead to bilateral vestibular hypofunction. In such cases, both vestibular loss and impaired proprioception contribute to the balance issues. Patients with bilateral vestibular hypofunction benefit from vestibular rehabilitation therapy but should avoid vestibular suppressant medications.

Central Vestibular Disorders
Central vestibular disorders are often associated with lesions affecting vestibular pathways within the brainstem and cerebellum. These lesions can result from various conditions, including ischemic or hemorrhagic strokes, demyelination, tumors, and neurodegenerative diseases. Distinguishing between central and peripheral causes of vertigo is crucial because central vertigo can be a medical emergency, potentially indicating life-threatening conditions like stroke or hemorrhage. To confirm or rule out central vestibular disorders, brain MRI is a valuable diagnostic tool, and patients with suspected central vestibular issues should undergo a comprehensive neurological evaluation.

Psychosomatic and Functional Dizziness
Psychological factors can significantly influence chronic dizziness. Dizziness can sometimes manifest as a somatic symptom of underlying psychiatric conditions like major depression, anxiety disorders, or panic disorder. In other cases, individuals with primary vestibular disorders may develop anxiety and autonomic symptoms as comorbidities, leading to conditions like persistent postural-perceptual dizziness (PPPD). These patients typically experience chronic dizziness that fluctuates over three months or longer, worsens while standing, and intensifies in complex visual environments. Although there might be a history of acute vestibular disorders, neuro-otologic examinations and vestibular testing often appear normal or indicative of compensated vestibular deficits, suggesting that the ongoing dizziness is not primarily related to vestibular pathology. Anxiety disorders are frequently comorbid in these patients, contributing significantly to their morbidity. Treatment approaches for PPPD include pharmacological therapy with selective serotonin reuptake inhibitors (SSRIs), cognitive-behavioral psychotherapy, and vestibular rehabilitation. Vestibular suppressant medications should generally be avoided.

Treatment Strategies for Dizziness
Effective treatment of dizziness involves a multifaceted approach that considers the underlying cause, the patient's specific symptoms, and their overall health. Tailoring treatment to address these factors is essential for achieving successful outcomes.

Medications for Symptomatic Relief
While addressing the root cause of dizziness is paramount, medications can provide symptomatic relief, especially during acute episodes. Here, we delve into the medications commonly used:

1. Antihistamines: Drugs like meclizine, dimenhydrinate, and promethazine are often employed to manage vertigo symptoms. These medications exert their effects by blocking histamine receptors, thereby reducing overstimulation of the inner ear's vestibular system. They can alleviate symptoms such as nausea, vomiting, and vertigo. However, their use should be cautious due to potential side effects like drowsiness, dry mouth, and impaired cognitive function.

2. Benzodiazepines: Diazepam and clonazepam, both belonging to the benzodiazepine class of drugs, can help alleviate vertigo symptoms, particularly in cases of psychosomatic dizziness. These medications have anxiolytic and muscle-relaxing properties, which can be especially useful when dizziness is associated with anxiety. However, they should be prescribed judiciously, considering the risk of dependence and sedation.

3. Anticholinergic (Scopolamine): Transdermal scopolamine patches are commonly used to prevent and treat motion sickness, which can induce dizziness. These patches slowly release the medication through the skin, offering a more sustained effect compared to oral formulations. They work by inhibiting the action of acetylcholine, a neurotransmitter involved in balance and motion sickness. Patients should be educated on proper patch application and potential side effects, such as dry mouth and blurred vision.

4. Antimigrainous Drugs: For patients diagnosed with vestibular migraine, prophylactic antimigraine medications may be prescribed. These drugs, which include beta-blockers, calcium channel blockers, and anticonvulsants, aim to reduce the frequency and severity of migraine-associated vertigo episodes. Treatment choices should be based on the patient's specific migraine profile and medical history.

5. Selective Serotonin Reuptake Inhibitors (SSRIs): Patients with persistent postural-perceptual dizziness (PPPD), often characterized by chronic dizziness and disequilibrium, may benefit from SSRIs. These antidepressant medications can help manage the anxiety and autonomic symptoms frequently seen in PPPD. Psychotherapy, especially cognitive-behavioral therapy, may complement pharmacological treatment for this condition.

Vestibular Rehabilitation Therapy (VRT)
Vestibular rehabilitation therapy is a cornerstone in the management of various vestibular disorders. This structured, exercise-based approach aims to promote central adaptation processes, compensate for vestibular loss, and reduce symptoms related to dizziness. Key components of VRT include:

1. Gaze Stabilization Exercises: These exercises help patients improve their ability to maintain visual focus while their head is in motion. By reducing oscillopsia (perceived bouncing or instability of the visual field), patients can regain a sense of stability during daily activities.

2. Balance Training: Balance exercises challenge patients to improve their postural control and reduce the risk of falls. These exercises often progress from simple static balance tasks to more complex dynamic activities.

3. Habituation Exercises: In cases where dizziness is exacerbated by specific movements or visual environments, habituation exercises can desensitize the vestibular system. Patients gradually expose themselves to these triggers to reduce their sensitivity over time.

4. General Conditioning: Improving overall physical fitness can complement VRT, as enhanced fitness can aid in managing dizziness and improving overall well-being.

Specific Treatments for Underlying Causes
Tailored treatments may be necessary for specific vestibular disorders:

1. Benign Paroxysmal Positional Vertigo (BPPV): This common condition, characterized by brief vertigo triggered by head position changes, can often be effectively treated with repositioning maneuvers like the Epley maneuver or the Semont maneuver. These maneuvers guide dislodged calcium carbonate crystals out of the semicircular canals, providing relief.

2. Ménière’s Disease: Initial treatments for Ménière’s disease may involve diuretics and dietary sodium restriction. If symptoms persist and become disabling, more invasive options like intratympanic injections of medications or surgical procedures such as vestibular nerve section or labyrinthectomy may be considered.

3. Vestibular Schwannoma: The management of vestibular schwannoma may involve a "wait-and-scan" approach for slow-growing tumors. For larger or symptomatic tumors, surgical resection or radiation therapy (stereotactic radiosurgery) may be recommended, depending on the patient's age, overall health, and tumor characteristics.

4. Bilateral Vestibular Hypofunction: Treatment strategies for bilateral vestibular hypofunction often focus on vestibular rehabilitation therapy. Patients learn to adapt to the loss of vestibular input, improving balance and minimizing symptoms. Identifying and addressing any underlying causes, such as medication-induced vestibular loss, is crucial.

5. Central Vestibular Disorders: The management of central vestibular disorders depends on the underlying cause, which may include stroke, demyelination, or tumors. In cases of acute central vertigo, rapid diagnosis and intervention are crucial. Treatment may involve addressing the underlying condition, managing symptoms, and providing rehabilitation as needed.

Medications for Vertigo
A closer look at medications used for vertigo treatment, including dosages, indications, and considerations:

Antihistamines:

1. Meclizine: Typically administered at doses of 25 to 50 mg, three times daily, meclizine is commonly prescribed for symptomatic relief of vertigo associated with various vestibular disorders.

2. Dimenhydrinate: At a dosage of 50 mg, one to two times daily, dimenhydrinate can effectively alleviate vertigo symptoms. It is often used for motion sickness.

3. Promethazine: Promethazine can be administered at doses of 25 mg, two to three times daily, and is particularly useful for managing vertigo associated with nausea and vomiting. In some cases, it can also be administered rectally or intramuscularly.

Benzodiazepines:

1. Diazepam: Typically prescribed at doses of 2.5 mg, one to three times daily, diazepam helps alleviate vertigo symptoms and anxiety associated with certain vestibular disorders.

2. Clonazepam: At a dosage of 0.25 mg, one to three times daily, clonazepam is another benzodiazepine used to manage vertigo and associated anxiety.

Anticholinergic:

1. Scopolamine (Transdermal): Scopolamine is available in the form of a transdermal patch for motion sickness prevention. It should be applied to a clean, dry area of skin behind the ear at least four hours before the antiemetic effect is desired. The patch should be replaced every three days. Notably, its use is primarily for motion sickness and may not be suitable for all types of vertigo.

Other Medications:

1. Diuretics and Low-Sodium Diet: Ménière’s disease often responds well to diuretics (e.g., hydrochlorothiazide) and dietary sodium restriction. These interventions aim to reduce excess endolymphatic fluid buildup in the inner ear.

2. Antimigrainous Drugs: Patients with vestibular migraine may benefit from medications commonly used to prevent migraine attacks, such as beta-blockers (e.g., propranolol), calcium channel blockers (e.g., verapamil), and anticonvulsants (e.g., topiramate).

3. Selective Serotonin Reuptake Inhibitors (SSRIs): SSRIs like sertraline and fluoxetine are useful for managing persistent postural-perceptual dizziness (PPPD) and associated anxiety. The choice of SSRI and dosage should be individualized based on the patient's specific needs and considerations.

It is important for healthcare providers to weigh the benefits and potential side effects of these medications carefully, considering the patient's overall health, comorbidities, and medication interactions.

Conclusion
Dizziness is a common and often challenging symptom encountered in clinical practice. Its multifaceted nature, encompassing various sensations and potential causes, necessitates a meticulous evaluation and a tailored treatment approach. Through a comprehensive understanding of the underlying mechanisms, thorough history-taking, careful examination, ancillary testing, and targeted treatments, healthcare providers can effectively address the diverse array of dizziness-related complaints presented by their patients.