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Biomedical subjects

R J Tusa

Publications and source records attributed to R J Tusa.

At least 19 recordsLinked to original sources
PubMed1996

Complications of the canalith repositioning procedure.

OBJECTIVE: To describe the conversion of benign paroxysmal positional vertigo involving the posterior canal into benign paroxysmal positional vertigo involving the anterior or horizontal canals after treatment using the canalith repositioning maneuver. DESIGN: Retrospective study of outcome. SETTING: Outpatient clinic. PATIENTS: Consecutive sample of 85 patients diagnosed as having benign paroxysmal positional vertigo affecting the posterior canal. Identification of posterior canal involvement was based on the observation of the direction of the vertical component of nystagmus after the Hallpike-Dix maneuver. INTERVENTION: Canalith repositioning maneuver. MAIN OUTCOME MEASURE: Eye movements were observed about 1 week after the treatment. The direction of nystagmus elicited after movement of the patient into the Hallpike-Dix position indicated which canal was involved in the patients who had not responded to treatment. RESULTS: Of the 85 patients studied who originally had posterior canal benign paroxysmal positional vertigo, five (6%) had anterior canal (n=2) or horizontal canal (n=3) positional vertigo after undergoing this maneuver. CONCLUSION: Careful observation of the direction of the nystagmus is necessary for correct identification of which canal is involved in patients who do not respond to the initial treatment using the canalith repositioning maneuver.

Adult↗
PubMed1996

Development of an inventory for dizziness and related factors.

Dizziness is an extremely common complaint of patients, yet often goes unexplained after medical evaluation, which can lead to inappropriate treatment. There is a lack of psychometrically sound self-report instruments that measure dizziness and related factors. This study describes the application of factor analytic procedures with 184 dizzy patients' responses to develop the Dizzy Factor Inventory (DFI), a 44-item inventory divided into three sections and modeled after the Multidimensional Pain Inventory. The first section consists of symptom factors, the second concerns responses of significant others to the dizzy patient, and the third section assesses activity level. This inventory groups symptoms into empirically distinct factors that could be related in clinical and research applications to physiological and psychological processes, and could be useful for treatment planning and measuring treatment progress. Factors derived with dizzy patients are compared to factors found with chronic pain patients.

Activities of Daily Living↗
PubMed1996

The contribution of the vertical semicircular canals to high-velocity horizontal vestibulo-ocular reflex (VOR) in normal subjects and patients with unilateral vestibular nerve section.

We have examined to what extent the vertical semicircular canals contribute to the nonlinearity of the horizontal VOR imposed by the driving of primary vestibular afferents into inhibitory cutoff at high velocities of head rotation (Ewald's second law). The gain (eye velocity/head velocity) of the horizontal component of the VOR with the head pitched down 30 degrees and pitched up 30 degrees was examined during constant-velocity rotations in normal subjects and patients following unilateral vestibular nerve section. In normal subjects, VOR gain decreases as chair velocity increases from 60-300 degrees/s when the head is pitched up, but VOR gain remains constant when the head is pitched down. This finding implies that the mechanism by which the gain of the horizontal VOR gain remains constant at all velocities of rotation depends upon the pattern of labyrinthine stimulation. Following unilateral nerve section, we found that the directional preponderance (DP) in horizontal VOR depends upon whether the head is pitched up 30 (mean asymmetry = 5%) or pitched down 30 degrees (mean asymmetry = 20%). This is what is expected based on the degree to which the lateral and vertical semicircular canals sense horizontal head acceleration with the head in different degrees of pitch. Hence, following unilateral vestibular lesions, the DP of horizontal VOR gain is most easily elicited at high velocities of head rotation and with the head pitched down 30 degrees. Evidence for DP at the bedside using the "head-shaking nystagmus" technique may be optimally elicited with the head pitched down 30 degrees.

Acceleration↗
PubMed1995

Visual system abnormalities in adrenomyeloneuropathy.

We studied the visual system in 59 men with adrenomyeloneuropathy. Pattern-reversal visual evoked potentials, magnetic resonance imaging, and clinical examination revealed that visual pathways are affected in 63% of patients, involving the optic discs, optic nerves, lateral geniculate bodies, optic radiations, and parietooccipital cortex. This indicates both primary demyelination of the optic nerves and discs, and more diffuse involvement of postchiasmal structures.

Adrenoleukodystrophy↗
PubMed1995

Refractive error and axial length in a primate model of strabismus and congenital nystagmus.

PURPOSE: To evaluate the development of refractive error and axial length in a primate model of sensory strabismus and nystagmus. METHODS: Four macaque monkeys had alternating tarsorraphy beginning within 24 hours of birth. One eye was closed for 25 days, and when it opened, the second eye immediately was closed for the next 25 days. Cycloplegic refractions and axial lengths were determined prospectively for three animals for 1 year or more. These data were compared to those of three unsutured control macaques raised under otherwise similar conditions. RESULTS: Each experimental animal developed exotropia and nystagmus. The first occluded eyes were significantly more hypermetropic than the control eyes at 1 month of age (+7.25 D +/- 1.95 D versus +1.92 D +/- 1.27 D; P < 0.02) and remained significantly more hypermetropic throughout the study. The second occluded eyes were more hypermetropic than the control eyes at 1 month (+2.42 D +/- 2.13 D versus +1.92 D +/- 1.27 D; P = 0.20), but less hypermetropic than the first occluded eyes. The rate of emmetropization was slightly faster for the first occluded eyes than for the control eyes (-0.12 D/month compared to -0.03 D/month). The mean axial length measurements of the experimental and control eyes were the same at 1 month, and their rates of change over time were identical. CONCLUSIONS: Persistent hypermetropia was produced by a brief period of reverse neonatal eyelid closure in a model of congenital-like nystagmus. It is suggested that infantile lid closure, nystagmus, or amblyopia after neonatal visual disruption may be associated with a failure of normal emmetropization.

Animals↗
PubMed1994

Prospective study of central nervous system function in amateur boxers in the United States.

Active amateur boxers from six US cities were studied in 1986-1990 to determine whether changes in central nervous system function over a 2-year interval (as evaluated by tests of perceptual/motor function, attention/concentration, psychomotor speed, memory, visuoconstructional ability, and mental control, measures of ataxia and brain-stem auditory evoked potentials, and electroencephalography) were associated with degree of participation in amateur boxing. A total of 484 participants were examined at baseline; 393 (81.2%) were examined 2 years later. At baseline, 22% of the participants had not yet competed in a bout; 9% had never competed in a bout by the second examination. Exposure was defined by number bouts, sparring-years, and sparring with a professional boxer. Very few statistically significant odds ratios were found between exposure and change in function. Significant tests of trend were found between the total number of bouts incurred before the baseline examination and changes in memory, visuoconstructional ability, and perceptual/motor ability. The significant trends for change in function in the latter two domains were primarily due to performance on the Block Design test, which was common to both test domains. No statistically significant associations were found between more recent bouts (after the baseline visit) and any functional domains, nor between bouts or sparring and any other outcome measures. The significant trends with past bouts, but not more recent bouts, may reflect the need for a long latency period before effects are manifest. Alternatively, given changes in safety practices, the observed association may be related to more severe exposure from bouts that occurred before 1986, when new safety measures were imposed.

Adolescent↗
PubMed1994

Dizziness in childhood.

There is a scant literature regarding vestibular evaluation of children with complaints of dizziness or vertigo. Considerable time and effort are expended on the problem and prevention of hearing loss in children, yet we often ignore concurrent or subsequent vestibular disorders. This neglect could be due to several factors, perhaps the most common being the fact that vertiginous crises in childhood are often attributed to problems of behavior or incoordination. In this article, we offer an approach to the dizzy child based on presenting symptoms. We discuss features of the history, examination, and laboratory evaluation key to determining the cause of dizziness. Finally, we discuss management, which varies according to the diagnosis.

Brain Injuries↗
PubMed1994

Longitudinal study of brainstem auditory evoked responses in 87 normal human subjects.

We evaluated the reproducibility of brainstem auditory evoked responses (BAERs) in 87 normal individuals in a longitudinal study by estimating the correlation coefficients and variability of the interpeak intervals and the V/I amplitude ratio between trials on the same day and between sessions spaced 2 years apart. The highest correlation coefficients occur for the I-V interpeak interval between trials on the same day. The coefficients for the I-III and III-V intervals are lower, due to the variability of wave III. The correlations between ears done on the same day are lower still and are similar to measures obtained from the same ear at a 2-year interval. BAERs are more variable than previously believed between ears and over time, but not in a manner that is clinically significant and can be used longitudinally as a measure of neurologic disease. Finally, we provide the sample size required to detect a significant change in interpeak intervals.

Acoustic Stimulation↗
PubMed1994

Characteristics of postural stability in patients with aminoglycoside toxicity.

Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity was characterized by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to sudden translational and rotational (pitch) perturbations of the support surface. We found our patients had increased sway on sensory tests in which either visual or somatosensory cues were altered and were unable to maintain their balance when both visual and somatosensory cues were altered compared to age-matched normal subjects. The amount of vestibular loss, as inferred from the VOR Tc, accounted for a significant amount of A-P sway on test 4 in which somatosensory cues were altered. The frequency response of anterior-posterior sway in the BVL group suggests that they use more hip movements than do normal subjects to maintain postural stability. The responses of BVL patients to sudden translations of the support surface did not differ from those of normal subjects. More BVL patients lost their balance, however, on the initial trial of the toes-up rotational perturbation of the support surface than did normal subjects.

Adult↗
PubMed1993

Single treatment approaches to benign paroxysmal positional vertigo.

OBJECTIVE: To determine the effectiveness of two different physical therapy approaches for benign paroxysmal positional vertigo. DESIGN: Randomized study. SETTING: Outpatient clinic. PATIENTS: Consecutive sample of 60 patients with benign paroxysmal positional vertigo. INTERVENTION: Patients received either a single treatment based on the hypothesis that the vertigo and nystagmus of benign paroxysmal positional vertigo are due to debris adhering to the cupula of the posterior semicircular canal (cupulolithiasis) or a single treatment based on the hypothesis that the debris is free floating in the long arm of the posterior canal (canalithiasis). Patients were reevaluated 1 to 2 weeks after the treatment and again 4 to 6 months later. OUTCOME: Treatment outcome was classified as either asymptomatic, more than 70% improved as rated by the patient, or no change. RESULTS: The treatment designed for cupulolithaisis resulted in remission of vertigo and nystagmus in 70% of the patients and in improvement of the symptoms in another 20%. The treatment designed for canalithiasis resulted in remission of vertigo and nystagmus in 57% of the patients and in improvement in another 33%. There was no statistically significant difference between treatments. CONCLUSIONS: These single-treatment approaches are equally effective treatments for benign paroxysmal positional vertigo. Further studies are needed to look at the long-term effectiveness of these treatments.

Adult↗
PubMed1993

Visual evoked potentials in adrenoleukodystrophy: a trial with glycerol trioleate and Lorenzo oil.

Adrenoleukodystrophy is an X-linked metabolic disorder with very-long-chain fatty acid (VLCFA) accumulation and multifocal nervous system demyelination, often with early involvement of visual pathways. Dietary therapy with glycerol trioleate and glycerol trierucate (Lorenzo oil) diminishes VLCFA levels. In a study of patients with the adrenomyeloneuropathy phenotype of adrenoleukodystrophy, we used pattern-reversal visual evoked potentials to evaluate visual pathways before and after treatment. Of 108 patients tested, all 26 women and 68 of the 82 men had normal potentials at baseline. Seventy patients were retested at 1 year, at which time VLCFA levels were markedly diminished. Of them, the responses in the 10 men who showed abnormalities at baseline remained abnormal; the latencies in 4 men with initially normal responses became abnormal. No patients improved. There were no correlations between disease duration prior to treatment, baseline P100 latencies, VLCFA levels, or the change in P100 latencies and VLCFA levels after dietary treatment for 1 year. Pattern-reversal visual evoked potentials were abnormal in 17% of the men with adrenoleukodystrophy, and there was no evidence that reduction of VLCFA levels improved or retarded visual pathway demyelination.

Adolescent↗
PubMed1993

Abnormal eye movements in Creutzfeldt-Jakob disease.

We report 3 patients with autopsy-proven Creutzfeldt-Jakob disease who, early in their course, developed abnormal eye movements that included periodic alternating nystagmus and slow vertical saccades. These findings suggested involvement of the cerebellar nodulus and uvula, and the brainstem reticular formation, respectively. Cerebellar ataxia was also an early manifestation and, in 1 patient, a frontal lobe brain biopsy was normal at a time when ocular motor and cerebellar signs were conspicuous. As the disease progressed, all saccades and quick phases of nystagmus were lost, but periodic alternating gaze deviation persisted. At autopsy, 2 of the 3 patients had pronounced involvement of the cerebellum, especially of the midline structures. Creutzfeldt-Jakob disease should be considered in patients with subacute progressive neurological disease when cognitive changes are overshadowed by ocular motor findings or ataxia.

Aged↗
PubMed1993

Neurophysiologic and clinical correlations of epileptic nystagmus.

Epileptic nystagmus (EN) is a rare sign of seizure activity. We describe eight patients with horizontal EN and hypothesize that the frequency of ictal discharge, anatomic localization of ictal activity, and level of consciousness determine its occurrence and mechanism. We believe that EN is due to epileptic activation of a cortical saccade region; in each case, quick phases were generated away from the side of the focus, and both quick and slow phases were totally confined to the field contraversive to the seizure focus.

Adult↗
PubMed1992

Spontaneous nystagmus and gaze-holding ability in monkeys after intravitreal picrotoxin injections.

1. Eye movements were measured in three rhesus monkeys after monocular intravitreal injections of picrotoxin, a gamma-aminobutyric acid (GABA) antagonist. The effects of this drug were tested when the animals were in a completely dark room, when they performed a smooth pursuit task, and when they viewed either a stationary pattern or a full-field optokinetic pattern rotating horizontally. 2. Between 15 and 20 min after the injection, a sustained conjugate spontaneous nystagmus developed in the dark, with the slow-phase movement in the temporal-to-nasal direction with respect to the injected eye. Peak slow-phase velocity ranged from 15 to 45 degrees/s. The nystagmus persisted for at least 1 h but stopped by the next day. 3. In a well-lit room, the nystagmus was completely suppressed, even during monocular viewing with the injected eye. When the lights were turned off, the slow-phase velocity of the spontaneous nystagmus slowly increased to a steady-state level within 70-120 s. 4. Horizontal smooth pursuit eye movements to a 1 degree target light moving in front of the animal +/- 20 degrees to either side of center of gaze at constant speeds were normal. Target speeds ranging from 15 to 60 degrees/s for both monocular and binocular viewing conditions were used. Binocular and monocular optokinetic nystagmus (OKN) to a full-field drum rotating at a constant velocity (5-90 degrees/s) were also normal. The initial pursuit and steady-state components of OKN were measured, as well as the velocity-storage component (optokinetic after nystagmus, OKAN).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Middle latency auditory evoked potentials in temporal lobe disorders.

Middle latency auditory evoked potentials (MAEP) were recorded in 30 normal subjects and in 19 age-matched patients with temporal lobe lesions. MAEP appeared to be differentially affected by the specific structures involved within the temporal lobe. In the majority of patients with lesions involving the auditory area and/or auditory radiation, Na-Pa amplitude was significantly reduced over the involved hemisphere. No similar reduction in amplitude was noted in subjects with lesions not involving the auditory structures within the temporal lobe. We also observed a shift in a Pa latency over the involved hemisphere in patients with temporal lobe lesions involving the auditory structures. This latency shift was less pronounced than the amplitude reduction. The generators of MAEP in humans are discussed according to these findings and to the available literature. Normal intersubject variability of the conventional amplitude measures, and the occasional myogenic contamination of the response, limits establishing reliable criteria for abnormality that can be applied clinically for the diagnosis of patients with temporal lobe disorders.

Acoustics↗
PubMed1991

Early visual deprivation results in persistent strabismus and nystagmus in monkeys.

To understand to what extent visual-pattern deprivation during infancy results in strabismus and nystagmus, the authors examined the long-term consequences of this type of deprivation in monkeys during the first 50 days of life. Three cynomolgus and three rhesus monkeys had the eyelids sutured closed within 24 hr of birth. At 25 days of age, the eyelids were opened, and the eyelids of the fellow eye were sutured closed for an additional 25 days (reverse-eyelid suture). When the eyelids were opened at 50 days of age, each monkey was found to have 20-30 delta of exotropia and nystagmus, which persisted for the duration of the study (1 yr). The cynomolgus monkeys developed a monocular 8-10 Hz pendular nystagmus in the eye sutured first. The rhesus monkeys developed a conjugate nystagmus with both jerk and pendular components. The slow phases often had velocity-increasing profiles. The rhesus monkeys also had a superimposed latent component to the nystagmus found during monocular viewing. One additional rhesus monkey was examined after 55 days of binocular-eyelid suturing. This monkey also developed exotropia and nystagmus resembling that of the other rhesus monkeys. These findings suggest that early pattern vision in monkeys is necessary for the development of normal ocular alignment and gaze-holding ability.

Animals↗
PubMed1990

Ipsiversive eye deviation and epileptic nystagmus.

We studied an 11-year-old boy with focal seizures in the right temporo-occipital cortex. During the seizure, there was a 1- to 2-second period of ipsiversive (rightward) conjugate eye deviation, followed by 10 to 15 seconds of horizontal jerk nystagmus with slow phases that were directed to the right and appeared linear. The patient was conscious throughout the seizure. These findings fit the description of epileptic nystagmus. We postulate that the eye deviation and slow phases of the nystagmus in this patient were induced by epileptic activation of a cerebral smooth pursuit pathway originating from temporoccipital cortex.

Child↗