INTRODUCTION {Back to Outline}
Click here for CHAPTER OUTLINE
My new chapter on The Auditory System - all you ever wanted to know ( and more ) about Central Auditory Disorders
Dr. Tim Hains Northwestern University
Invisible Illnesses and Disabilities, by Sharon E. Smith
General Information for Patients - A member of this group, Francis Janton, is a former houseofficer of mine
Vestibular Disorders Association
Dr. Terry McMillan's Pages
Serious Poem from a Dizziness Sufferer
Humorous Poem about Dizziness
My Chapter on Ototoxicity
My Lecture on Bad VertigoEXAMINATION OF THE DIZZY PATIENT
Directed Neuro-Otologic Examination
DIFFERENTIAL DIAGNOSIS OF VERTIGO AND DIZZINESS
BPPV (Benign Positional Paroxysmal Vertigo)
Other Peripheral Vestibular Conditions
Brainstem Ischemia and Infarction
Cerebello-Pontine Angle Tumors
MULTIPLE SENSORY ABNORMALITIES
LABORATORY EVALUATION OF DIZZINESS (TESTS)
THERAPY FOR PERIPHERAL VESTIBULAR DISORDERS
Medical Therapy for Peripheral Vestibular Disorders
Surgical Therapy for Peripheral Vestibular Disorders
THERAPY FOR SYSTEMIC AND CENTRAL VESTIBULAR DISORDERS
Surgical Therapy for Central Vestibular Disorders
Basic Office Examination of Hearing
Speech Reception Threshold (SRT)
Brainstem Auditory Evoked Potentials
THERAPY FOR AUDITORY DISORDERS
INTRODUCTION
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Neuro-otology is a subspecialty that encompasses disorders of the peripheral and central auditory and vestibular systems. Neuro-otology is a field similar to neuro-ophthalmology in that it is defined by its practitioners. Most neuro-otologists have come from the field of otolaryngology. The focus has been on the organ that is presumably abnormal, that is, the ear. This emphasis resembles the early history of neuro-ophthalmology, which concentrated primarily on the eye; only later when central visual and ocular motor connections and symptomatology were considered, the field began to involve those dealing with the brain, namely neurologists. Similarly, neuro-otology initially concentrated upon the primary functions of the ear, vestibular and auditory, without reference to central auditory processing within the central nervous system (CNS) or to those neurologic conditions which could produce unsteadiness, dizziness, vertigo, as well as alterations in hearing. When the multiple symptoms of dizziness or disequilibration are considered, it is clear that there are neurological and systemic conditions that can produce disorders of balance. Thus, neurologists have become increasingly involved in the evaluation of patients reporting dizziness. Just as retinal disorders remain primarily the province of the ophthalmologist, so hearing disorders, which are primarily peripheral, remain largely the province of the otolaryngologist.
We have divided this chapter into two major sections: the first on vestibular disorders, and the second on auditory disorders. Each section reviews the essential aspects of the history and the office examination. Because vestibular symptoms are often accompanied by auditory complaints, neurologists who choose to deal with dizzy patients should be familiar with both vestibular and auditory testing. Therefore, we include a brief review of pertinent tests for vestibular and auditory disorders. Finally, we introduce therapeutic strategies for patients with dizziness and hearing loss.
VESTIBULAR DISORDERS {Back to Outline}
HISTORY{Back to Outline}
Vertigo, strictly defined, refers to an hallucination of movement. When the symptom
complex is of spinning or rotation, the cause is almost always the inner ear or peripheral vestibular
system. Although it is true that some patients experience a definite sense of environmental spin or
self-rotation, the majority do not present solely with true spinning vertigo. The most common
complaint is one of dizziness, a term that represents a variety of symptoms (Table 1):
| Vertigo | Bouncing | |
| Unsteadiness | Falling | |
| Imbalance | Swimming | |
| Spinning | Staggering | |
| Floating | Weaving | |
| Fainting | Moving | |
| Lightheadedness | Passing out | |
| Swaying | Tilting | |
| Twisting | Listing | |
| Blurry vision | Rocking | |
| Disorientation | Oscillating | |
| Poor equilibrium | Rolling |
The examiner should elicit an exact description of what the patient is experiencing. Is it a spinning sensation that could be characterized as vertigo, pointing to the peripheral vestibular apparatus? Is it a sensation of falling without rotation? Is it a sensation of unsteadiness or imbalance? Is there a particular direction in which the patient tends to fall? When the patient's complaint is actually of incoordination or clumsiness, the cause may be cerebellar dysfunction or peripheral neuropathy. When the symptom complex is of "lightheadedness" or "swimmy-headedness," the examiner should think of presyncope or syncope and consider systemic factors such as postural hypotension, vasodepressor syncope, or cardiac arrhythmia.
After trying to define the true qualitative nature of the symptom complex, one must proceed to a consideration of temporal factors. Is the patient's experience a continuous one? Are there episodes of severe symptomatology with symptom-free intervals? If the symptoms are episodic, do they occur only when the patient is upright?
Patients often have difficulty describing their symptoms. Initially, it is important that patients provide their own description before the examiner biases the outcome by suggesting descriptive phrases. Some patients are asked to describe their symptoms without using the word dizziness cannot further characterize the symptoms.
In addition to determining whether the symptom complex is episodic, one should define duration, length of symptoms, and any associated complaints such as tinnitus, hearing loss, double vision, slurred speech, numbness, or paralysis. A history of episodic disequilibration accompanied by diplopia, slurred speech, perioral numbness, dimming of vision, and occasional drop attacks would suggest transient vertebrobasilar ischemia (Troost-1995, Bradley-Daroff Chapter 18). Are there associated symptoms such as headache, and have these occurred at earlier times in life? If the patient had experienced severe episodes of imbalance in early life, followed by occipital or generalized headaches, especially throbbing, the history would be suggestive of basilar artery migraine. Did the dizziness follow head trauma, a systemic illness accompanied by aminoglycoside antibiotic therapy, or a mild upper respiratory infection? Episodic positional vertigo with brief episodes of spinning while turning over in bed is suggestive of a common condition, benign paroxismal positional vertigo (BPPV) (Troost & Patton, 1992). Did the symptom complex occur following ear surgery or infection, deep-sea diving, or a concussive blow to the ear? Such a history, with or without hearing loss, would suggest a perilymph fistula.
There are a significant number of patients whose balance disorder is aggravated or even caused by anxiety. If the symptom of disequilibration or dizziness is of long duration, it is often difficult to tell whether the symptom complex is caused by anxiety or depression or whether the anxiety or depression are secondary to the dizziness. One always tries to make a positive diagnosis of a neurosis or chronic anxiety disorder based upon other symptomology and historical information. There may be a history of previous episodes of serious depression or anxiety attacks, and these should be elucidated before arriving at the conclusion that dizziness is secondary to anxiety.
Neurologists and neuro-otologists follow a large number of patients with chronic vertiginous sensations who remain undiagnosed. These patients complain of constant or intermittent disequilibration, often aggravated by position change, as well as by visual stimuli such as moving traffic, patterned wallpaper, or by passing food displays in supermarkets. Many of these patients have become agoraphobic; they hesitate to leave their homes, and particularly fear driving a car that will be passed by other automobiles. Some of these persons have had a single attack of acute peripheral vestibulopathy but have never made appropriate central compensation or adapted to their peripheral abnormality. Although mechanisms for compensation remain unclear, the majority of patients, particularly those younger than 30, rapidly recover from an acute peripheral vestibulopathy. Elderly patients or patients with a previously existing intrinsic brainstem abnormality, will rarely make adequate compensation for an acute peripheral vestibulopathy. These patients continue to complain of severe disequilibration and have exacerbated symptoms with a variety of visual inputs. They often have completely normal examinations and vestibular tests.
Figures 1 and 2 illustrate what might happen following an acute peripheral vestibular
abnormality.
Figure 1:
Figure 1 (Left) Vestibular afferent input during normal horizontal head rotation to the right.
Increased firing rate from right peripheral vestibular apparatus. Ocular deviation
shows slow phase deviation to the left. VN = vestibular nuclei. (Adapted from Baloh
1984 and Daroff 1977). (Right) Acute left peripheral vestibulopathy with resultant
acute vertiginous sensation simulating head rotation to the right. Slow phase ocular
deviation to the left (small arrow) and fast phase of nystagmus to the right (bold
arrow) and away from the side of the peripheral vestibular injury.
Figure 2:
Figure 2 (Left) Normal adaptation for prior left peripheral vestibulopathy. Despite a reduced
firing rate from the left side, the central nervous system (CNS) has compensated for
the disparity and there is no nystagmus or vertigo. (Right) Abnormal compensation
for prior left peripheral vestibulopathy. The patient continues to experience
vertiginous sensations and may have nystagmus with a fast phase to the right (solid
arrow).
In some individuals, as diagrammed in the right-hand panel of Figure 2, there is
decreased ability to compensate for peripheral vestibular abnormality. One possibility would be a
congenital inability to make CNS compensation, but others include: (1) an acquired central inability
to compensate due to CNS lesions as from multiple sclerosis or previous brainstem stroke, (2) a
fluctuating peripheral vestibular problem, as in Meniere's disease, (3) relative inactivity without
much afferent input, and (4) a peripheral vestibular apparatus providing inaccurate, although non-fluctuating afferent information. Careful history taking may reveal childhood meningitis, a remote
head injury, or particular susceptibility to motion sickness in childhood. An explicit search during
history taking should be made to define these possibilities.
EXAMINATION OF THE DIZZY PATIENT {Back to Outline}
Every patient with a disorder of equilibration or true vertigo should have a screening general physical examination. Patients who exhibit symptoms suggesting presyncope or actual syncope must have particular attention paid to their cardiovascular system. Not only should patients have their blood pressure measured in the resting, sitting, and standing position, but they also should have their blood pressure measured at 1 minute intervals up to 5 minutes after assuming the upright position, as delayed postural hypotension is not uncommon. Exercise-induced hypotension is an important observation and should lead to consideration of conditions such as the Shy-Drager syndrome, diabetic autonomic neuropathy, and cardiac defects such as aortic stenosis and obstructive cardiomyopathy. Whenever episodic symptomatology is associated with a question of alteration of consciousness or lightheadedness, particular attention should be paid to the possibility of cardiac dysrhythmia. Most patients with cardiac dysrhythmias do not report associated sensations of irregular heartbeat, thumping in the chest, or fluttering, however, examination may reveal an irregular cardiac rhythm or cardiac murmur.
During the general examination, attention should be paid to systemic conditions that could give rise to a general feeling of malaise or weakness interpreted by the patient as a disorder of balance. Conditions leading to sudden syncope may be revealed on the general physical examination. Patients with suspected extracranial vascular disease not only should have the head and neck auscultated for bruits, but also should have a general examination of the peripheral vascular system, including the cranial and carotid pulses and evaluation for signficant varicose veins that may lead to venous pooling and hypotensive episodes.
The neurological examination should be directed by the patient's history. In patients with clear-cut episodic vertigo, the neurological examination will usually be normal with the exception of the ocular motor findings to be described. However, when the patient's symptom complex is more vaguely defined and includes disequilibration or unsteadiness, particular attention must be paid to examination of the motor system, reflexes, sensation, and cerebellar function.
All patients with undiagnosed disorders of equilibration, however described, should have a complete neurological examination. Portions of the neurological examination will be described briefly, followed by suggestions of which entities might cause abnormality.
Mental Status Examination{Back to Outline}
Signs of diffuse alteration in consciousness may suggest overmedication, metabolic encephalopathy, or an acquired dementing process. Focal disturbances in intellectual function, such as a subtle aphasia, may lead to the consideration of multi-infarct dementia with accompanying brainstem infarctions, or of a mass lesion in the dominant hemisphere.
Cranial Nerve Examination{Back to Outline}
Alterations in visual sensory function can be a primary or exacerbating cause of disequilibration. Even the recent addition of a new refractive correction, particularly lenses for presbyopia, may be an added or primary cause of imbalance. Visual field defects such as unsuspected bitemporal or homonymous field defects from infarcts or tumors may cause patients to run into objects or feel disoriented in space. The presence of papilledema or absent venous pulsations on fundoscopy should be an immediate clue to raised intracranial pressure. Altered corneal sensation can be the clue to a previously unsuspected cerebellopontine angle mass. Simple auditory screening tests may reveal a previously unsuspected hearing loss and should always lead to formal audiological testing. Abnormalities on examination of cranial nerves IX through XII raise the differential diagnosis of multiple cranial neuropathies caused by collagen vascular disease, tumors of the base of the skull, or nasopharyngeal carcinoma.
Ocular Motor Examination{Back to Outline}
The presence of spontaneous or induced nystagmus is of critical importance in the diagnosis of peripheral, central, or systemic causes of imbalance. Nystagmus types of particular note are described in the section on the directed neuro-otologic examination. Defective downward gaze is often the first sign of progressive supranuclear palsy a condition often accompanied by disequilibration. The presence of asymmetrical slowing of the adducting eye indicating an internuclear ophthalmopleglia is a subtle but important clue to the presence of brainstem multiple sclerosis, brainstem infarction, or mass lesion of the posterior fossa.
Motor System Examination{Back to Outline}
The examination of motor function can reveal focal or diffuse weakness indicative of CNS or neuromuscular disorders. A subtle hemiparesis may be the true cause of the patient's balance complaint. Diffuse hyperreflexia reflects cerebral or spinal cord dysfunction and, in combination with cerebellar abnormality, might lead to the diagnosis of a spinocerebellar degeneration.
Sensory System Examination{Back to Outline}
Examination of sensation can reveal a significant peripheral neuropathy leading to a diagnosis of diabetes or toxic neuropathy. Selective loss of sensory modalities conveyed by the posterior column such as proprioception and vibration, may indicate that the patient has vitamin B12 deficiency or early tabes dorsalis. Such patients are relatively steady during the Romberg test with eyes open, but rapidly lose balance and fall in any direction when visual compensation is eliminated by eye closure.
Cerebellar System Examination{Back to Outline}
Obvious limb or body ataxia should be an immediate clue to the CNS abnormality as the cause for the patient's imbalance. Unsteadiness during Romberg testing with eyes open and only slight exaggeration on eye closure indicates a cerebellar abnormality. Cerebeller dysfunction is usually accompanied by abnormality during gait testing or even difficulty maintaining balance while seated. Patients with symptomatic peripheral vestibulopathy tend to fall toward the side of the abnormality during eye closure with the head straight ahead. Unilateral limb ataxia is almost always an indicator of focal posterior fossa abnormality, such as infarct, demyelination, abscess, or tumor.
Directed Neuro-otologic Examination{Back to Outline}
A directed neuro-otologic examination should be performed, particularly when there are abnormalities of the auditory, ocular motor and vestibular systems. Audiological testing is discussed later. During the neurological examination, there may be subtle signs of peripheral vestibular dysfunction indicated by nystagmus. On external examination the nystagmus fast phase is away from the ear with the vestibular abnormality. During the funduscopic examination, particular attention should be paid to the movement of the optic disc. A rhythmical subtle horizontal slow and fast component nystagmus is frequently present in patients with new peripheral vestibular dysfunction. The nystagmus is brought out by reducing fixation during the funduscopic examination. For example, with the patient staring at a dimly lit target in the distance, the presence of a slow ocular drift to the left and a fast phase to the right of the optic disc should indicate to the examiner that the patient has a subtle left beating nystagmus in the primary position. The findings indicate a right peripheral vestibular abnormality. Fast upward rhythmic vertical movement of the optic disc seen during funduscopic examination signifies the presence of downbeat nystagmus. The examiner should then search carefully for the presence of downbeat nystagmus during examination of oblique and downward gaze. The need to search for presence of any type of nystagmus during the directed neuro-otologic examination cannot be overemphasized. The directed neuro-otologic examination should include a detailed otoscopic examination of the external auditory canal and the tympanic membrane. The presence of a retracted or scarred eardrum suggests prior middle ear infection. The presence of a blue mass behind the tympanic membrane points to a glomus jugular tumor.
The patient should be tested for balance during standing, walking, and turning, and for the presence of past-pointing. Past-pointing is a tendency for the repetitively elevated and lowered outstretched fingers to drift unidirectionally. Past-pointing is a clear indication of tonic imbalance in the vestibular system. If during Romberg testing the patient tends to fall in a certain direction, can this direction be altered by changing head position? The ability to alter the direction of the fall during Romberg testing by head turning indicates a peripheral vestibular abnormality. For example, a patient with an acute left peripheral vestibulopathy will tend to fall to the left during eye closure with the head straight ahead, but will fall backwards (toward the abnormal ear) with the head turned left, and will fall forward during eye closure when the head is turned to the right.
The physician should test for the presence of an intact vestibulo-ocular reflex (VOR), and observe whether the patient is able to maintain steady ocular fixation during funduscopic examination as the head is gently rotated from side to side. The patient with an intact VOR can still maintain fixation on distance objects during head turn. The absence of this ability produces an apparent nystagmus, most easily observed during funduscopic examination, which is good evidence for a defective VOR. A different test of vestibulo-ocular control is for the patient to fix on his or her own thumb while rotating the head in the same direction. During this maneuver, the patient must suppress the vestibulo-ocular response in order to permit combined head and eye tracking. The loss of this ability may be a subtle clue to cerebellar system dysfunction. The patient should also be examined for the presence of nystagmus when visual fixation is reduced by wearing of Frenzel glasses, which blur the patient's vision. The lenses also magnify the eye allowing better detection of low amplitude nystagmus.
If the patient has no cervical problems, a head-shaking test can be performed. The patients are asked to shake their head rapidly twenty times back and forth while wearing Frenzel glasses. Then the patient is observed to determine whether there is any primary position horizontal nystagmus. The maneuver may bring out a latent nystagmus indicating vestibular imbalance. The fast phase of the nystagmus would be away from the ear with the peripheral vestibulopathy. {Back to Outline}
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