F. Owen Black

Normal subject postural sway during the Romberg test.

Analysis of fixed force platform recordings of Romberg tests performed by 132 normal subjects demonstrated no statistically significant sex or age effect for adults aged 20 through 49 years. There was a strong stabilizing influence of vision upon postural control in most, but not all, normal subjects. Comparison trials showed no statistically significant differences between trials for the standard Romberg eyes-open maneuver. However, a significant improvement was demonstrated for the second trial for all other Romberg maneuvers. Tests repeated over a period of five consecutive days yielded results with large variances within normal limits and no systematic individual or group trends. Normal percentiles and confidence intervals for the 95th percentile were calculated for use as a normal data base. These percentile distributions derived from a relatively large population of normal subjects provide a normal statistical base for comparison with postural sway from abnormal subjects.

Effects of unilateral loss of vestibular function on the vestibulo-ocular reflex and postural control

Long-term recovery from surgically induced unilateral loss of vestibular function was studied in 14 patients. Seven patients underwent surgical extirpation or section of the vestibular nerve, and seven patients underwent labyrinthectomy without vestibular nerve section. The vestibulo-ocular reflex (VOR) and postural control were evaluated preoperatively and monitored for up to 4 years postoperatively with use of pseudorandom rotation (combined sinusoidal frequencies from 0.009 to 1.5 Hz) and moving platform posturography. Immediately following surgery all patients showed minimal reductions in the VOR gain constant, but marked reduction in the time constant, and marked increase in slow eye velocity bias. Bias returned to normal values within about 10 days, but time constants never returned to normal values. Results of standard Romberg tests in these patients were normal throughout the preoperative and postoperative periods. However, all patients showed marked postural control abnormalities in tests of the ability to maintain balance in unusual sensory environments in the immediate postoperative period. Seventy-five percent of the patients eventually recovered normal postural control. Postural control returned to near baseline performance with a time course similar to that of the VOR bias. However, postural control also continued to improve after the recovery of VOR bias was complete.

Vestibulo-spinal Control Differs in Patients with Reduced Versus Distorted Vestibular Function

Abnormal vestibular function disrupts a subjects reference to gravity (earth) vertical, and prevents resolution of conflicting or inaccurate visual and somatosensory spatial references. However, errors which patients make when attempting to resolve conflicting visual and somatosensory orientation inputs during upright stance differed markedly in patients with (1) symmetric or asymmetric reduced vestibular function, (2) benign paroxysmal positional nystagmus and vertigo, and (3) a combination of distorted and reduced function. Objective characterization of spatial orientation systems and compensatory strategies under altered sensory conditions is an essential first step toward identifying optimal treatment methods for each of these three types of vestibular deficient patients.

What can posturography tell us about vestibular function

Abstract: Patients with balance disorders want answers to the following basic questions: (1) What is causing my problem? and (2) What can be done about my problem? Information to fully answer these questions must include status of both sensory and motor components of the balance control systems. Computerized dynamic posturography (CDP) provides quantitative assessment of both sensory and motor components of postural control along with how the sensory inputs to the brain interact. This paper reviews the scientific basis and clinical applications of CDP. Specifically, studies describing the integration of vestibular inputs with other sensory systems for postural control are briefly summarized. Clinical applications, including assessment, rehabilitation, and management are presented. Effects of aging on postural control along with prevention and management strategies are discussed.

Diagnosis and Management of Drop Attacks of Vestibular Origin: Tumarkin's Otolithic Crisis:

Erroneous signals of vestibular origin can cause sudden falls without warning. Drop attacks of vestibular origin in our experience most commonly occurred in patients with late or end-stage endolymphatic hydrops (usually idiopathic, ie, Menieres disease). Eponymically termed Tumarkins otolithic crisis, drop attacks of vestibular origin must be distinguished from drop attacks due to cardiovascular abnormalities, seizure disorders, vertebral basilar arterial insufficiency (transitory brain stem ischemia), multiple sclerosis, and drug-induced motor control disturbances. The treatment of choice for drop attacks of vestibular origin is either surgical ablation (labyrinthectomy) in the absence of serviceable hearing or middle fossa vestibular nerve section in order to preserve serviceable hearing.

Postural Disturbance in Patients with Benign Paroxysmal Positional Nystagmus

Abnormal vestibular function disrupts postural and ocular muscle control system references to gravity (earth) vertical. Vestibular disorders also prevent satisfactory resolution of normally redundant, but often conflicting, visual and somatosensory spatial references required for normal postural control during active and passive body motion. Using a moving platform and visual surrounds posturography technique to systematically interact visual, somatosensory, and vestibular inputs, it was clearly demonstrated that patients with the benign paroxysmal positional nystagmus type of distorted vestibular function employ an unstable, visually dependent postural sway distinct from the postural instability associated with unilateral or bilateral vestibular functional deficits. These findings have important clinical implications for diagnosis and management of patients with vestibular disorders.

Loss of otolith function with age is associated with increased postural sway measures.

Loss of balance and increased fall risk is a common problem associated with aging. Changes in vestibular function occur with aging but the contribution of reduced vestibular otolith function to fall risk remains unknown. We examined a population of 151 healthy individuals (aged 21-93) for both balance (sway measures) and ocular counter-rolling (OCR) function. We assessed balance function with eyes open and closed on a firm surface, eyes open and closed on a foam surface and OCR during +/-20 degree roll tilt at 0.005 Hz. Subjects demonstrated a significant age-related reduction in OCR and increase in postural sway. The effect of age on OCR was greater in females than males. The reduction in OCR was strongly correlated with the mediolateral measures of sway with eyes closed. This correlation was also present in the elderly group alone, suggesting that aging alone does not account for this effect. OCR decreased linearly with age and at a greater rate in females than males. This loss of vestibular otolith-ocular function is associated with increased mediolateral measures of sway which have been shown to be related to increased risk of falls. These data suggest a role for loss of otolith function in contributing to fall risk in the elderly. Further prospective, longitudinal studies are necessary to confirm these findings.

Postural Stability and Rotational Tests: Their Effectiveness for Screening Dizzy Patients

Results of independently interpreted computerized stationary platform posturography and white noise rotational tests were compared with diagnoses for 110 patients. Using the criterion that an abnormal result from either test classified the subject as abnormal, the sensitivity estimate for the pair of tests was 78% for persons with diagnoses known to result in vestibular dysfunction. The specificity estimate was 90%. Both a vestibulo-ocular and a vestibulo-spinal test were required for effective screening. Consecutive tests performed over five days showed the rotation test to be much less variable than posturography. Rotation testing is therefore preferred for following the performance of patients having disorders thought to cause fluctuating vestibular systems. Interobserver reliability rates were 83% for posturography and 93% for rotation tests.

Quantitative Diagnostic Tests for Perilymph Fistulas

The definitive diagnosis of perilymph fistulas can be made only by tympanotomy, and previous attempts to record vestibular abnormalities based on eye movement recordings have been of limited value because of the inability to isolate vestibular reflexes from visual and proprioceptive contributions to body muscle control. In the past, therefore, tests for suspected perilymph fistulas yielded unacceptably high false—negative and false—positive test results. At the meeting, F. Owen Black, MD, and associates David J. Lilly, PhD, Lewis M. Nashner, DSc, and Robert J. Peterka, PhD, Neurological Sciences Institute, Good Samaritan Hospital and Medical Center, Portland, Ore, reported that a new fistula test based on vestibulospinal reflexes has been developed. This test is based on vestibulospinal responses to sinusoidally modulated air pressures within the external auditory canal. During this test, vision and support-surface orientation references are removed systematically from a standing patient. With only vestibular control of posture available, patients with

Vestibular reflex changes following aminoglycoside induced ototoxicity

The effects of aminoglycoside‐induced changes on the vestibular system were evaluated in three subjects who suffered significant damage over the course of treatment. Measurements of vestibulo‐ocular reflex (VOR) function were made using sinusoidal and pseudorandom rotational stimuli between 0 to 5 days after initiation of drug therapy, during drug therapy, and up to 579 days following drug administration.