Dennis P. O'Leary

Autorotation Test Abnormalities of the Horizontal and Vertical Vestibulo-Ocular Reflexes in Panic Disorder

Patients with panic disorder often describe dizziness as a disturbing symptom, with more severe episodes reported than in other psychiatric populations. Nineteen patients diagnosed as having a panic disorder were tested for vestibulo-ocular (VOR) abnormalities with the Vestibular Autorotation Test (VAT), a computerized test of the high-frequency (2 to 6 Hz) VOR. The patients were unselected for the presence or absence of balance disorders. Results showed VOR abnormalities, relative to a normal population, in the horizontal and/or vertical VORs of all 19 patients. Vestibulo-ocular reflex asymmetries were commonly present. Because the VAT tested the VOR over a frequency range encountered during common daily activities, the observed abnormalities could result in a perceptually moving visual field (oscillopsia). We hypothesize that the resulting experience of a visual-vestibular disturbance—perhaps in a biologically or psychologically predisposed individual—is catastrophically misinterpreted, leading to more bodily symptoms and anxiety. These could then contribute to more misinterpretation in a positive feedback sense, ultimately leading to a panic attack.

Active Head-Movement Analysis of Cisplatin-Induced Vestibulotoxicity

The vestibulo-ocular reflex (VOR) acts to maintain a clear and stationary image of the visual world during movements of the head. Accurate measurement of the VOR is therefore an important clinical method for evaluation of the vestibular system. We applied a new method of computerized vestibular testing, the Vestibular Autorotation Test (VAT), which is based on 18 seconds of active head movements. The VAT was used to prospectively study the horizontal VOR of nine patients with cancer who were being treated with cisplatin. Patients were instructed to move their heads in the horizontal plane in synchrony with audible clicks of a linearly increasing frequency range, from 0.5 to 6.5 Hz. Electro-oculographic (EOG) eye movements and head velocity were monitored and digitized to compute horizontal VOR gain and phase from 2 to 6 Hz. Patients were tested with the VAT before the initial cisplatin treatment, and then before each subsequent cisplatin treatment. The pretreatment gains and phases were compared with those obtained after the final cisplatin treatment. Results showed decreased VOR gains at 3.1 Hz, 3.9 Hz, and 5.1 Hz, and increased phase lags at 3.1 Hz and 3.9 Hz. We conclude that VAT analysis of the horizontal VOR at frequencies 3 to 5 Hz is useful for detection and monitoring of cisplatin vestibulotoxicity.

Vestibular Autorotation Testing of Meniere's Disease

Ten patients with previously confirmed diagnosis of acute-stage Menieres disease were tested with the Vestibular Autorotation Test (VAT), a portable computerized test that measures the higher-frequency vestibulo-ocular reflex (VOR) to compute gain and phase. Patients were asked to fixate on a target and move their heads in synchrony with a computer-generated, sweep-frequency audible cue (0.5 to 6.0 Hz) through an 18-second test epoch. Head movements in both horizontal (yaw) and vertical (pitch) planes were used separately to test horizontal and vertical VORs, respectively. All subjects easily performed the VAT. Results of the horizontal tests were within normal limits for both gain and phase. The vertical gain was markedly high throughout the 2 to 6 Hz range. Mean vertical phase lags were reduced at higher frequencies. These results imply that the vertical VORs of acute-stage Menieres patients are hypersensitive to the faster vertical head movements that occur commonly in dally activities.

Vestibular autorotation test asymmetry analysis of acoustic neuromas

The vestibular autorotation test (VAT) measures the vestibulo-ocular reflex (VOR) response from 2 to 6 Hz, during 18 seconds of active head movements, while the patient attempts to fixate on a wall-mounted target. A new method of measuring eye velocity asymmetry from VAT data is presented, based on computer estimation of the 0th harmonics of discrete Fourier spectra over short segments of digital eye and head velocity records. Eye asymmetries greater than a 3% normal range are shown to be directionally correlated with the side of the lesions in patients with unilateral labyrinthectomies. Among patients with a diagnosis of acoustic neuroma, who were tested preoperatively with the VAT, nine of nine patients showed eye asymmetries greater than 3% toward the side of the neuroma. Those patients with acoustic neuromas who have sufficiently vigorous high-frequency head responses showed mean percentages of eye asymmetry that were linearly correlated with the size of the acoustic neuroma. These results suggest that VAT high-frequency asymmetry provides a useful method of diagnostic evaluation of the side and extent of unilateral peripheral lesions.

Clincal Use of Pseudorandom Binary Sequence White Noise in Assessment of the Human Vestibulo-Ocular System

White noise rotational stimulation has been used to evaluate the human vestibulo-ocular response for 30 normal subjects over the frequency range from 0.02 to 1.6 Hz and is being extended to characterize response of patients having documented abnormalities. For clinical use, the white noise stimulus has the advantages of shortening the test time by presenting all stimulus frequencies simultaneously, and being well-tolerated by both normal subjects and patients alike. Cross spectral calculations which compare the computer reconstructed slow phase eye velocity response to the pseudorandom acceleration stimulus yield a set of linear and nonlinear estimates of the vestibulo-ocular response. Pilot data indicate that a classification of the disease state can be made using this set of estimates. This classification will be presented and discussed.

Computerized screening of the human vestibulospinal system.

The vestibular nerve projects rostrally via the ascending medial longitudinal fasiculus (MLF) to eventually supply the ocular muscles and also projects caudally via the descending MLF to eventually supply the spinal and limb musculature. Electronystagmographic techniques are designed to evaluate only portions of the vestibulo-ocular and oculomotor systems. Vestibular lesions affecting only the caudal vestibular nerve distributions or lesions affecting both neural distributions, therefore, cannot be objectively assessed except for the vestibulo-ocular component. A promising recording technique for the evaluation of the vestibulospinal system has been developed and tested in the Raymond E. Jordan Human Vestibular Systems Laboratory. A comparison of two data analysis techniques in normal subjects, unilateral vestibular lesion patients and patients with unilateral lesions of the cerebellar hemispheres have provided pilot data which indicate that the vestibulospinal stability test technique holds considerable promise for both research and clinical evaluation of the human vestibulospinal system.

Autorotation Test of the Horizontal Vestibulo-Ocular Reflex in Meniere's Disease

Sixty-four patients with the diagnosis of Menieres disease were tested at the House Ear Clinic with an active head-rotation test system, the Vestibular Autorotation Test (VAT). The VAT is a portable, computerized test that measures the horizontal vestibulo-ocular reflex (VOR) with the use of high-frequency (2 to 6 Hz) active head movements to obtain gain and phase. The purpose of this study was to characterize the horizontal VOR at high frequencies in patients with Menieres disease. At frequencies from 5 to 6 Hz, all patients demonstrated horizontal phase greater than 180 degrees and 85% showed abnormal VAT results. The most common patterns were decreased gain or increased phase values, or both, relative to normative data. No significant differences in the degree of abnormality in gain and phase were noted among groups of patients when the patients were clinically staged. We conclude that, in our test population of patients with Menieres disease, the VAT shows common gain and phase patterns and abnormalities of the horizontal VOR. This may contribute to high retinal image velocities, which render the patient unable to stabilize retinal images during locomotion (visual field image slip), in as many as 85% of the patients tested, regardless of clinical stage. Such high-frequency testing can reveal abnormalities of the horizontal VOR not apparent from conventional vestibular testing. Thus VAT provides additional information about the functioning VOR when combined with the present vestibular test battery. (OTOLARYNGOL HEAD NECK SURG 1993;109:399–412.)

Comparison of Vestibular Autorotation and Caloric Testing

The two most common stimuli of the vestibular system for diagnostic purposes are caloric and rotational head movements. Caloric stimulation, by delivering thermal energy to the lateral semicircular canal, is a well-studied method of vestibular testing, and its clinical usefulness has been established. Vestibular autorotation testing uses high-frequency (2 to 6 Hz), active head movements to stimulate the horizontal and vertical vestibulo-ocular reflex to produce measurable eye movements that can be used to calculate gain and phase. We compared the alternate bilateral bithermal caloric results with the vestibular autorotation test results obtained from 39 patients with peripheral vestibular disorders and from 10 patients with acoustic neuroma. In the peripheral disorder group, only 2 of 14 patients with equal caloric response (<20% reduced vestibular response) had a normal vestibular autorotation test result. No patients with a reduced vestibular response greater than 21% had a normal vestibular autorotation test result. In the acoustic neuroma group, four patients had a normal reduced vestibular response, but all patients had an abnormal vestibular autorotation test result. We conclude that testing both the horizontal and vertical vestibulo-ocular reflexes in their physiologic frequency range with the vestibular autorotation test provides additional information that could be missed by conventional caloric testing. Therefore high-frequency rotational testing is a valuable addition to the vestibular test battery.

Predictive Monitoring of High-frequency Vestibulo-ocular Reflex Rehabilitation Following Gentamicin Ototoxicity

Nine patients exposed to gentamicin ototoxicity were tested with active head movements to determine their high-frequency (2-6 Hz) horizontal and vertical vestibulo-ocular reflex (VOR) responses. Results showed a common pattern documenting patients reports of oscillopsia during walking: gains of 0.5 or less, and phases less than 180 degrees. A subset of these patients undergoing exercise rehabilitation therapy were tested repeatedly during follow-up visits to monitor changes in their VORs. VOR improvements toward reduced oscillopsia were correlated with patients reported reduction of symptoms. Each patients VOR changes over time were monitored with a quantitative least-squares method which predicted results of the next test, based on trends from three or more previous tests. The method was tested by comparing predicted results with actual test results, following the next test. Preliminary results show relatively accurate predictions up to 6 weeks in advance of actual tests, at least when trends of recent, previous tests were in a consistent direction. We conclude that predictive monitoring of changing VOR states can be useful for continuing, or modifying, the course of vestibular rehabilitation therapy, by providing quantitative prediction estimates of future results.

The first demonstration that a subset of women with hyperemesis gravidarum has abnormalities in the vestibuloocular reflex pathway

OBJECTIVEnThe vestibular system is a major pathway to nausea and vomiting, and the vestibuloocular reflex (VOR) is a central component; its function can be studied using the vestibular autorotation test (VAT). We hypothesize that women with hyperemesis gravidarum (HG) may have VOR abnormalities.nnnSTUDY DESIGNnWomen with HG were compared with women without HG using the VAT. Horizontal and vertical VOR gains and phases were evaluated at 3 frequency ranges: low (2.0 to 3.5 Hz), medium (greater than 3.5 to 5.0 Hz), and high (greater than 5.0 to 6.0 Hz) during pregnancy and postpartum.nnnRESULTSnTwenty women with HG and 48 unaffected women were evaluated in early pregnancy. Women with HG had higher horizontal gains at all 3 frequency ranges. Horizontal phase differences were also observed at medium frequencies. No VAT differences were noted postpartum.nnnCONCLUSIONnWomen experiencing HG had a higher mean VOR horizontal gain and lower horizontal phase when compared with unaffected women.