This content focuses on some of the less common causes of dizziness in the adult. The diseases have been divided into the 2 broad categories of those causing chronic symptoms and those causing episodic symptoms. Presented here are the unusual causes of chronic disequilibrium in the adult, including bilateral vestibular loss, progressive supranuclear palsy, spinocerebellar ataxias, and mal de debarquement. Also discussed are the unusual causes of episodic disequilibrium in the adult, including psychogenic disequilibrium, vestibular paroxysmia, episodic ataxia, vestibular seizures, and cervicogenic vertigo.
This content focuses on some of the less common causes of dizziness in the adult. The diseases have been divided into the 2 broad categories of those causing chronic symptoms and those causing episodic symptoms. Presented here are the unusual causes of chronic disequilibrium in the adult, including bilateral vestibular loss, progressive supranuclear palsy, spinocerebellar ataxias, and mal de debarquement. Also discussed are the unusual causes of episodic disequilibrium in the adult, including psychogenic disequilibrium, vestibular paroxysmia, episodic ataxia, vestibular seizures, and cervicogenic vertigo.
Bilateral vestibular loss
Epidemiology
Bilateral vestibular loss is uncommon. In some cases the cause is known. In other cases, the condition seems to be idiopathic. These patients tend to be older adults.
Pathophysiology
The percentage of idiopathic cases of bilateral vestibular loss varies from 21% to 51%. Of the remaining cases, the most common etiology is ototoxicity, accounting for 17% to 66%, with gentamicin being the most common ototoxic agent. Other causes include bilateral (usually sequential) vestibular neuritis and autoimmune inner ear disease. The underlying pathophysiology is either dysfunction of the peripheral vestibular receptors (as in gentamicin ototoxicity) or dysfunction of the vestibular nerve (as in vestibular neuritis).
Typical Presentation
The common complaints are dizziness and oscillopsia (“jumpy vision” with each step or when driving in a car that goes over a bump). Patients will also be very dependent on their vision for maintaining balance, so falls will often result when trying to walk in the dark, or when closing the eyes in the shower. Depending on the cause, the chronology of symptoms is variable. In idiopathic cases, the development of symptoms may be insidious. In gentamicin ototoxicity, the onset of symptoms usually occurs within several weeks of starting intravenous gentamicin.
Physical Examination
Patients’ gait and station will be obviously unsteady on physical examination. They fail unsighted tandem Romberg stance. On dynamic visual acuity testing, they typically lose 4 or more lines of visual acuity during active head rotation compared with acuity when the head is stationary. On fundoscopy, if the head is similarly oscillated, the retinae appear to move (rather than staying entirely steady).
Diagnostic Testing
The gold standard test for bilateral vestibular loss is rotary chair testing, which shows the combination of low vestibulo-ocular reflex (VOR) gain and increased phase lead (more so in the lower frequencies) on sinusoidal harmonic oscillation, and low response gains and time constants on step velocity testing. Vestibular evoked myogenic potentials are absent. Caloric responses, including those to ice water, are absent. Computerized dynamic posturography shows a constellation of abnormalities collectively referred to as a “vestibular” sensory pattern, as well as an “ankle dominant” pattern (especially in test conditions 4–6) on strategy analysis. Magnetic resonance imaging of the brain and internal auditory canals is usually normal, although when the etiology involves vestibular neuritis, there may be mild enhancement of the vestibular nerves on T1 post-contrast imaging (in contrast to vestibular schwannoma which enhances more intensely).
Treatment
Treatment is generally limited to physical therapy for vestibular rehabilitation. These patients can improve, but retain significant dependence on vision and proprioception for balance.
Progressive supranuclear palsy and other atypical parkinsonisms
Parkinson disease and the other parkinsonian disorders often involve disequilibrium at some point in the course of the disease. Idiopathic Parkinson disease is by far the most common pathology in this family of diseases, but will usually have come to the attention of a neurologist long before referral to a subspecialty clinic of balance disorders. The other diseases in this family include progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome), multiple systems atrophy, corticobasal ganglionic degeneration, and dentatorubropallidoluysian atrophy. Of these, progressive supranuclear palsy (PSP) was selected for discussion because it often presents with disequilibrium early in the course of the disease and may elude diagnosis initially, or be misdiagnosed as idiopathic Parkinson disease.
Epidemiology
The prevalence of PSP has been estimated variably at 1.39 to 6.40 per 100,000. It is more common in men. The age of onset is usually in the fifth through seventh decades.
Pathophysiology
PSP is in a class of neurodegenerative diseases known as “tauopathies.” Histopathologic studies demonstrate accumulation of abnormal tau protein seen as globose neurofibrillary tangles in the prefrontal cortex, globus pallidus, substantia nigra, and subthalamic nucleus.
Typical Presentation
By the time the diagnosis is made, symptoms have often been present for several years. Often the initial presentation will be a complaint of unsteadiness or falling, typically backward. Descending stairs sometimes poses a particular challenge. By the time of diagnosis, patients have usually developed some degree of dysphagia. Patients with PSP frequently seem to be oblivious to their deficits and consequently exhibit poor judgment regarding their ability to ambulate and to negotiate stairways. As the disease advances, patients become progressively immobilized and are eventually confined to a wheelchair, and then to a bed. The mean disease duration from the first onset of symptoms until death is 8.0 ± 4.1 years. Patients usually die within approximately 5 years of being diagnosed, with death typically resulting from the usual diseases affecting immobilized patients (aspiration, infections, thromboembolism, etc).
Physical Examination
There is usually axial hypertonia manifesting as truncal and neck stiffness (often with tonic hyperextension), although distracting maneuvers (such as having the patient open and close the hands) may be required to elicit this sign. The extremities usually have normal tone initially and lack the resting tremor of Parkinson disease, although as the disease advances, symmetric appendicular hypertonia may develop. Facies eventually become masked, although in contradistinction to Parkinson disease, the tone of the periorbital musculature tends to produce the appearance of a “frightened stare.” Oculomotor examination shows obvious slowing of voluntary vertical saccades, although reflexive vertical saccades may initially be preserved; more subtle findings include convergence insufficiency and square wave jerks. Later in the disease, horizontal saccades are also affected. Cognitive evaluation reveals a mild to moderate dementia with apathy and executive dysfunction.
Diagnostic Testing
Videonystagmography corroborates and quantifies the clinical oculomotor examination. Caloric responses are normal. Rotatory chair testing sometimes exhibits “hang-up” at the extremes of lateral gaze on optokinetic testing. Vestibular evoked myogenic potential amplitudes are often reduced out of proportion to age. Midbrain atrophy can be noted on MRI.
Treatment
Only symptomatic treatment is available. Medication for idiopathic Parkinson disease (such as carbidopa-levodopa [Sinemet]) may bring about a modest, transient therapeutic response that is never sustained.
Progressive supranuclear palsy and other atypical parkinsonisms
Parkinson disease and the other parkinsonian disorders often involve disequilibrium at some point in the course of the disease. Idiopathic Parkinson disease is by far the most common pathology in this family of diseases, but will usually have come to the attention of a neurologist long before referral to a subspecialty clinic of balance disorders. The other diseases in this family include progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome), multiple systems atrophy, corticobasal ganglionic degeneration, and dentatorubropallidoluysian atrophy. Of these, progressive supranuclear palsy (PSP) was selected for discussion because it often presents with disequilibrium early in the course of the disease and may elude diagnosis initially, or be misdiagnosed as idiopathic Parkinson disease.
Epidemiology
The prevalence of PSP has been estimated variably at 1.39 to 6.40 per 100,000. It is more common in men. The age of onset is usually in the fifth through seventh decades.
Pathophysiology
PSP is in a class of neurodegenerative diseases known as “tauopathies.” Histopathologic studies demonstrate accumulation of abnormal tau protein seen as globose neurofibrillary tangles in the prefrontal cortex, globus pallidus, substantia nigra, and subthalamic nucleus.
Typical Presentation
By the time the diagnosis is made, symptoms have often been present for several years. Often the initial presentation will be a complaint of unsteadiness or falling, typically backward. Descending stairs sometimes poses a particular challenge. By the time of diagnosis, patients have usually developed some degree of dysphagia. Patients with PSP frequently seem to be oblivious to their deficits and consequently exhibit poor judgment regarding their ability to ambulate and to negotiate stairways. As the disease advances, patients become progressively immobilized and are eventually confined to a wheelchair, and then to a bed. The mean disease duration from the first onset of symptoms until death is 8.0 ± 4.1 years. Patients usually die within approximately 5 years of being diagnosed, with death typically resulting from the usual diseases affecting immobilized patients (aspiration, infections, thromboembolism, etc).
Physical Examination
There is usually axial hypertonia manifesting as truncal and neck stiffness (often with tonic hyperextension), although distracting maneuvers (such as having the patient open and close the hands) may be required to elicit this sign. The extremities usually have normal tone initially and lack the resting tremor of Parkinson disease, although as the disease advances, symmetric appendicular hypertonia may develop. Facies eventually become masked, although in contradistinction to Parkinson disease, the tone of the periorbital musculature tends to produce the appearance of a “frightened stare.” Oculomotor examination shows obvious slowing of voluntary vertical saccades, although reflexive vertical saccades may initially be preserved; more subtle findings include convergence insufficiency and square wave jerks. Later in the disease, horizontal saccades are also affected. Cognitive evaluation reveals a mild to moderate dementia with apathy and executive dysfunction.
Diagnostic Testing
Videonystagmography corroborates and quantifies the clinical oculomotor examination. Caloric responses are normal. Rotatory chair testing sometimes exhibits “hang-up” at the extremes of lateral gaze on optokinetic testing. Vestibular evoked myogenic potential amplitudes are often reduced out of proportion to age. Midbrain atrophy can be noted on MRI.
Treatment
Only symptomatic treatment is available. Medication for idiopathic Parkinson disease (such as carbidopa-levodopa [Sinemet]) may bring about a modest, transient therapeutic response that is never sustained.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
