Linda L. Davis

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.

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.)

Monoclonal antibodies as prognostic indicators in patients with squamous cancer of the oral cavity and oral pharynx

Prior work in our laboratory has shown that the expression of an epithelial antigen identified by the monoclonal antibody A9 is amplified in squamous carcinoma cell lines and that the intensity of expression is related to aggressive cell growth in vitro and in the nude mouse (1). To determine if alterations in expression of normal epithelial antigens are related to the biological behaviour of squamous cell carcinoma in man, the expression of the A9 antigen and of normal A, B and H blood group antigens in primary tumor tissue sections from 41 patients with cancer of the oral cavity and oral pharynx was analyzed. The majority of these patients had stage III (19/41) or stage IV (17/41) tumors. Antigen expression was analyzed with respect to traditional histologic features and disease-free survival. Median follow-up was 13 months (range 1—53 months). Disease-free survival was decreased (median 8.7 months) in patients with tumors that had high A9 expression compared to patients with low A9 expression (p =. 132...

Spectral analysis of low-frequency, active-head vestibulo-ocular reflex responses.

Useful medical diagnostic information has been reported from low-frequency rotational testing of the horizontal vestibulo-ocular reflex (VOR) of patients with vestibular disorders. Servocontrolled rotating systems have been used as the only practical method to generate stimuli over lower VOR frequency response ranges, the decade from 0.01 to 0.1 Hz. Active head movements have been used for testing the human VOR at higher frequencies, exceeding 0.5 Hz. We examined whether active head movements could be used also to test the VORs of subjects over lower frequency ranges, extending to 0.02 Hz. We used a swept-frequency, active head movement protocol to generate a broad-band stimulus. Eye position was recorded with electro-oculography. Head velocity was recorded with a rotational sensor attached to a head band. Six individual test epochs from human subjects were concatenated to form complex, periodic waveforms of head and eye velocity, 75 seconds in duration. Broad-band cross-spectral signal processing methods were used to compute horizontal VOR system characteristics from these waveforms extending from 0.02 to 2 Hz. The low-frequency VOR data appeared to originate from amplitude modulation of high-frequency active movements, acting as carrier signals. Control experiments and processing of simulated data from a known system excluded the possibility of signal processing artifacts. Results from six healthy subjects showed low-frequency gains and phase values in ranges similar to those from published rotational chair studies of normal subjects. We conclude that it is feasible to test the human VOR over extended low-frequency ranges using active head movements because of amplitude modulation of the head and eye signals.