Dizziness and problems with balance are common, with a high proportion of the population being affected by one or both at some time in their lives. Although problems are more likely to occur in the elderly, disorders affecting the ability to maintain upright stance can occur at any age.
Vertigo is the sensation that the individual or the environment is moving when both are still, which typically results from an imbalance in the vestibular system. Lightheadedness, or feeling faint, can result from a number of causes. Oscillopsia, the inability to maintain clear vision when moving, is most often the consequence of a bilateral vestibular loss. Unsteadiness and gait ataxia can be multifactorial in origin. Regardless of the cause, as anyone who has experienced any of these symptoms will attest, they can be unsettling at best, and completely disabling at worst.
Because of the complexity of the systems that are involved in maintenance of postural control and balance, as well as the number of disorders that can cause symptoms of dizziness and unsteadiness, arriving at the correct diagnosis can be challenging. Furthermore, development of a treatment plan often involves consultation with a number of professionals.
Based upon years of experience with this patient population, it is clear to me that the evaluation of patients with dizziness and balance complaints must involve a team approach including audiologists, physicians, and in many cases, physical therapists. The integration of information from each team member is important.
Since Audiology and the Vestibular Testing Center (VTC) are both divisions within the Department of Otolaryngology Head and Neck Surgery at the University of Michigan, staff members typically collaborate on the evaluation of patients who are referred to our institution for complaints related to equilibrium. Most of the patients we see have chronic symptoms and many have been evaluated elsewhere prior to being referred to us. In many cases, they have been seen in a number of locations by various combinations of specialists, and although most have been given a diagnosis of some sort, they are typically frustrated by the ongoing nature of their symptoms, and by the fact that previous intervention has not resulted in a "cure."
Because most of the patients we see have complicated medical histories or other variables that might affect the clarity of their diagnosis and/or treatment plan, we have developed a unique approach to managing patient flow. Specifically, we see patients only on physician referral, and all of the referrals come in through the VTC, where we obtain information from the referring physician as well as from the patient prior to scheduling appointments. In our institution, the staff in the VTC serve as the gatekeepers to the neurotologists, and audiological and balance function testing is completed prior to the patients' appointments with them.
As the assistant director of the VTC, I am responsible for deciding which appointments are scheduled for each patient. At the time of the initial contact with the referring physician, we ask for some basic information including what questions the physician would like help in answering, the preliminary diagnosis when one exists, whether the physician would like the patient to see one of our neurotologists, and whether we have permission to have the patient see our physical therapist when the symptoms suggest that therapy might be useful.
From the patient, we are interested in knowing when the symptoms first began, the specific nature of the symptoms (e.g., dizziness, unsteadiness, hearing loss, tinnitus, headache) as well as whether they are continuous or episodic. When the symptoms are episodic, we are also interested in knowing whether they occur spontaneously or are provoked by changes in body position or movement, as well as when the symptoms occurred most recently. Finally, we ask about whether the patient has been evaluated for this condition before, and if so, when, by whom, and what tests were performed. If audiological or vestibular testing has been performed recently, we request copies of the raw data.
When all of the information has been compiled, I review it before deciding what appointments will be scheduled for the patient. Specifically, the patient might be scheduled for an audiological evaluation, balance function testing, an initial vestibular physical therapy evaluation, and an appointment with one of our neurotologists. Having testing completed prior to the physician visit facilitates efficient care. In addition, in cases in which vestibular physical therapy is warranted, completion of a trial of therapy often precedes that appointment as well. With this system, valuable physician time is used most productively, and the number of trips for the patient to the medical center is minimized.
The audiological tests are an important part of the evaluation, and the test results provide valuable puzzle pieces that contribute to the diagnosis. Specifically, in addition to the audiogram, acoustic immittance test results, including tympanometry, determination of acoustic reflex thresholds, and an assessment of reflex decay, provide information regarding the status of the middle ear system and the auditory and facial nerves.
Electrocochleography (ECoG) can provide objective evidence of hydrops, a condition that is associated with Ménière's disease, and is useful in cases where there is a question about the differential diagnosis, or when monitoring the current status is important. For example, ECoG has been used to evaluate the treatment effect of the Meniett device in patients suffering from MŽ nire's disease.
Auditory brainstem response (ABR) testing provides information about the status of the auditory nerve, and vestibular evoked myogenic potentials (VEMPs) (which are muscle potentials that are recorded from the sternocleidomastoid muscle in response to sounds) provide objective evidence of various vestibular disorders, including superior semicircular canal dehiscence. For these reasons, all of the patients referred through the VTC are seen for audiological testing, including special tests when appropriate.
In the VTC, we also use a test battery approach to evaluating our patients. Not only are we interested in contributing to the medical diagnosis, we strive to provide treatment that will improve the quality of life for our patients. As a result, in addition to completing a thorough evaluation of the patients' vestibular and oculomotor systems via videonystagmography (VNG) and rotational testing, we also provide an evaluation of each patient's functional postural control ability through the use of the modified Clinical Test of Sensory Organization and Balance (CTSIB) or dynamic posturography. When the patient reports ongoing unsteadiness or a gait disturbance, or when there is a concern about fall risk, our physical therapist also performs a complete balance assessment, including a gait assessment.
Four Clinical Scenarios
The following four clinical scenarios illustrate some of the ways in which audiological and balance function test data are integrated in our setting to facilitate making an appropriate medical diagnosis or contributing to treatment decisions or prognosis estimates:
- A 44-year-old male presented with complaints of visual disturbance when talking on the phone with his right ear or when drying or scratching that ear with his finger. The patient also reported some episodic unsteadiness. Initial audiological testing revealed a mild conductive hearing loss bilaterally, although greater in the right ear, with normal tympanograms and absent acoustic reflexes. Given the hearing loss, the initial possible diagnoses included otosclerosis versus superior semicircular canal dehiscence. In addition to routine balance function testing (VNG, rotational testing, posturography), the neurotologist requested that we record eye movements while applying pressure in the ear via pneumatic otoscopy and that VEMPs be recorded. Positive pressure applied in the right ear resulted in clear torsional or rotary nystagmus, which was enhanced when gazing to the right. Pressure in the left ear did not result in any eye movement. In addition, a prominent VEMP response was recorded with a 65 dBnHL click into the right ear, whereas no clear response was evident with sound in the left ear at 85 dBnHL.
Both tests supported the diagnosis of superior semicircular canal dehiscence on the right, which was later confirmed with CT. The patient underwent surgical correction of the defect. Postoperatively, the patient reported improvement in his symptoms, and application of pressure in the right ear yielded minimal torsional nystagmus. At his most recent follow-up visit, the patient reported that he is back to running, competing in cycling races, and climbing. Not only did the appropriate diagnosis and treatment enable him to work in his profession as a cartographer, but he is able to participate fully in the recreational activities that are so important to his quality of life.
- A 34-year-old firefighter presented with a sudden onset of vertigo, nausea, and vomiting three weeks prior to testing, as well as a 2-3 month history of headache. The initial preliminary presenting diagnosis was benign paroxysmal positional vertigo (BPPV). For that reason, the patient was initially seen by our vestibular physical therapist, at which time he reported that when he was in bed and rolled onto his left side, he felt as though his head was moving. He also reported experiencing disturbed vision with head movement.
The initial evaluation revealed the presence of persistent torsional nystagmus following rapid positioning into a supine position with head turned right or left (the Hallpike maneuver), which is not characteristic of BPPV. Although torsional nystagmus is associated with that diagnosis, it has a latent period before its onset, and it decays over time. In addition, the response is not typically the same for maneuvers to both the right and left sides. With this patient, the nystagmus did not fatigue, nor did it change direction with change in side.
In spite of the uncharacteristic findings, the physical therapist attempted to perform a particle repositioning maneuver, which resulted in severe nausea and vomiting. The physical therapist alerted the referring physician to the possibility of a central nervous system disorder. Subsequently, audiological testing revealed normal hearing sensitivity bilaterally with normal tympanograms but absent acoustic reflexes in the left ear. ABR testing revealed abnormal responses bilaterally, with normal wave I-III latency but abnormal III-V and I-V interpeak latencies in the right ear, suggesting abnormal neural conduction. In the left ear, the absolute latency of Wave I was normal, with significantly prolonged interpeak latencies (I-III, III-V and I-V) and poor waveform morphology.
Although vestibular testing revealed some evidence of vestibular system involvement, the most striking results were the evidence that the patient was unable to suppress the vestibulo-ocular reflex (VOR) with visual fixation in rotational testing as well as evidence that he was unable to smoothly track a sinusoidal visual target. Both of these findings suggest cerebellar involvement. Based on our communication with the referring physician, an MRI was ordered, which unfortunately revealed a large mass in the brainstem including the pons and the medulla, more on the left than on the right, and extending into the cerebellum. The tumor was presumed to be a glioma, which is being treated with radiation therapy.
The patient was seen recently for repeat MRI to monitor the tumor growth. The tumor has not decreased in size, but it has not grown either, which is good news. Although the tumor is inoperable, the communication among the patient's health care providers and the speed with which the diagnosis was made and treatment initiated may have saved the life of this patient. Certainly, it has slowed the progression of his disease, enabling him to enjoy the things and people that matter most to him.
- A 53-year-old female was referred to the University of Michigan with a diagnosis of a left acoustic neuroma that was confirmed with MRI. In this case, the audiological and balance function testing we performed were not involved in the diagnosis. Rather, the results were used by the neurotologist in making a decision about whether to attempt hearing preservation and in estimating prognosis.
Audiometric testing revealed a mild to moderate sensorineural hearing loss in the left ear with excellent word recognition ability. Acoustic immittance testing yielded entirely normal results including negative acoustic reflex decay. Both transient and di stortion product otoacoustic emissions were present bilaterally, suggesting preserved outer hair cell function. ABR testing revealed normal responses in the right ear with a prolonged I-III interpeak latency in the left ear. VNG testing revealed a 57% left caloric weakness with otherwise normal findings. In this case, all of the results suggested that the tumor was most likely arising from the superior branch of the vestibular nerve, increasing the likelihood that hearing might be preserved. Obviously, preserved hearing is important for this patient's quality of life.
- A 39-year-old male who was previously diagnosed with bilateral Ménière's disease returned to the department because of new symptoms, including spontaneous falls. Audiometric testing revealed an asymmetrical sensorineural hearing loss, moderate in the right ear with good word recognition ability and moderate to profound in the left ear with no preserved word recognition ability.
Audiological and balance function testing were important to the initial diagnosis. Specifically, the patient's ECoG results in both ears revealed elevated summating potential to action potential (SP/AP) amplitude ratios that are characteristic of the hydrops that is present in Ménière's disease. Furthermore, serial testing revealed elevated SP/AP amplitude ratios that were stable over time. Caloric testing at that time suggested a significant right caloric weakness, with robust responses present in both ears.
With the patient's new symptoms, the issue was not one of diagnosis but of treatment. Whereas medical management had been effective in alleviating symptoms until recently, it appeared to be failing. It was important to the neurotologist, therefore, to determine which ear was causing the current problems in order to decide how best to treat it.
Repeat vestibular testing suggested the continued presence of a relative right weakness, as well as some indication of incomplete physiological and functional compensation and ongoing bilateral involvement. When the current test results were compared with the results obtained in 2002, there was evidence that both ears were becoming weaker. Of interest, however, is the suggestion from the data that there was more change in the left ear than in the right. Whereas the patient had robust caloric responses bilaterally in 2002, the most recent responses are considered to be consistent with a borderline bilateral weakness. It is also noteworthy that whereas the left ear was originally the better hearing ear, the function in that ear had decreased to the point of being of little use.
Ultimately, given the evidence of bilateral involvement with the apparent relative decreased performance in the left ear, the neurotologist decided to treat the left ear. The patient recently received his first treatment of intratympanic gentamicin in the left ear. The goal of the treatment is to quiet the activity of the left ear in hopes of stopping the drop attacks. The patient will return for follow-up in 4-6 weeks, at which time caloric testing will be repeated in order to assess change in vestibular function in the left ear. The decision about further injections will be based on the patient's symptoms. The goal is to preserve as much function as is possible in order to minimize the severity of a bilateral weakness, while providing a therapeutically effective dose. Once the drop attacks have been eliminated, vestibular physical therapy will be initiated to treat any symptoms resulting from the bilateral vestibular loss.
As an audiologist who is involved solely in the evaluation and management of patients having dizziness and other symptoms of disequilibrium, I have come to appreciate the importance of collaboration and the use of a team approach. It is clear from our experience, that the interaction of audiological and balance function test data is essential to providing optimal care for our patients. Without each person contributing to this team effort, our patients would not receive the quality of care to which they, and we, have become accustomed.