Normal subject postural sway during the romberg test

Original Contributions Am J Otolaryngol 3:309-318, 1982

Normal Subject Postural Sway during the Romberg Test F. OWENBLACK,M.D., F.A.C.S.,* CONRADWALL, III, PH.D.,t HOWARDE. ROCKETTE, JR., PH.D.,$ ANDRUSSELLKITCH,B.S.w 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. (Key words: Postural sway; Romberg test.)

Romberg, 1in 1853, introduced a test to demonstrate the effect of luetic posterior column disease u p o n h u m a n u p r i g h t p o s t u r e control. Throughout the intervening 128 years, the Romberg test has been used with minor modifications for the clinical assessment of patients with dysequilibrium or ataxia from both sensory and motor disorders. ~ Although m a n y attempts have been made to record and quantify normal and abnormal human movement during performance of the Romberg test, 2-9 we could not identify a quantitative study of normal subjects that could serve as a data base for clinical use. M a n y m e a s u r e s , all w i t h i m p o r t a n t limitations, have been used for describing human postural sway usually-in the anterior-posterior or left-right anatomic planes (i.e., the two cartesian planes analyzed separately). Average displacement and velocity do not accurately reflect

oscillating body movement because positive and negative values cancel. Mean square, root mean square, and phase plane calculations yield more accurate measures of sway, which can be used to characterize some mechanical components of postural control, but these methods do not permit analysis of frequency-dependent characteristics of postural sway. Power spectral analysis of normal and abnormal human postural sway has been reported by several investigators over the past decade. 1~ For adult normal subjects, Nashner 16 demonstrated that Fourier coefficients in the lower frequency range (0.01 to 0,1 Hz) increased relatively more than higher-frequency components when visual orientation cues were not available. Our preliminary studies in normal subjects indicated that the major changes from one test condition to another, including eye closure, appeared to be reflected most prominently in total energy of the waveform, and that normal subjects did not yield significant peaks in power spectraY Njiokiktjien and De Rijke, 2 Aggashyan et el.,12 and Dichgans et al. 14 have reported frequencydependent postural sway abnormalities in patients with cerebellar disorders and proprioceptive deficits. Before advocating the more complicated power spectral analysis for assessment of postural sway and for identification of abnormal sway patterns, a thorough investigation of a less complicated method seemed appropriate. The primary objective of this study was to determine the statistics of normal adult human

From the Raymond E. Jordan Human Vestibular Testing Laboratory, Department of Otolaryngology, University of Pittsburgh School of Medicine, Eye and Ear Hospital of Pittsburgh, Pittsburgh, Pennsylvania 15213. Received February 26, 1982. Accepted for publication May 6, 1982. Supported by a grant #NS13286 from the United States Department of Health, Education and Welfare, Public Health Service, National Institutes of Health. * Associate Professor, Department of Otolaryngology. t Research Assistant Professor, Department of Otolaryngology, r Associate Professor of Biostatistics. w Research Assistant. Address correspondence and reprint requests to Dr. Black: Neurootology, Good Samaritan Hospital and Neurological Science Institute, 1015 N.W. Twenty-second Avenue, Portland, Oregon 97210.

0196-07091821090010309 $02.00 (~Z)W, B. Sounders Co, 309

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ANTERIOR

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Figure 1. Diagrammatic summary of the recording technique and data analysis. Schematic of the force platform and graphic demonstration of the sampling technique as viewed from above. The subject's center-of-force displacement was calculated from the output of piezoelectric crystals coupled beneath the platform and sampled at 10 Hz. The centroid (C) of the displacement area was determined and polar vector amplitude (r,) calculated from the centroid to each data point).

LEFT

postural control during the Romberg test as estimated by scaled mean squared displacement recorded from a fixed-force platform. The results provided a normal data base for study of abnormal human populations. The method employed permitted the option of frequency analysis. MATERIALS AND METHODS

Subjects

American Journal of Qtolaryngology

310

Normal subjects were solicited from the following sources: 1} persons who passed industrial employment physical examinations, which i n c l u d e auditory and r o t a t i o n a l v e s t i b u l a r screening examinations; 2) individuals, school populations, and civic groups; and 3) persons taking University of Pittsburgh Athletic Department physical examinations. Every prospective subject with a history of 1) drug intake within 72 hours prior to assessment for this project, 2} ear operation, 3) ataxia, or 4) vertigo (spatial disorientdtion), and all subjects who had 5) musculoskeletal abnormalities were rejected. Those persons in whom any combination of otologic, neurologic, rotational vestibular or audiometric examinations showed abnormalities were removed from the "normal" subject group. Rotation tests results that deviated more than 2 SD from normal data reported previously is were considered abnormal. Pure-tone audiometric thresholds (averaged for 0.5, 1.0, and 2.0 kHz) greater than 30 dB ISO and speech discrimination scores less than 80 per cent were considered abnormal. Prior to examination and testing of any subject, an informed consent in compliance with the "Institutional Guide to DHEW Policy on Protection of Human Subjects" (National Institutes of Health publication 72-102, US Government Printing Office, 1971) was obtained.

Subjects were solicited to represent the largest possible range of ages, with equal numbers of males and females for each age decade. Intersubject variability was very large in the youngest and oldest age groups. We also encountered greater instability ih subjects less than 20 and more than 50 years of age, a finding previously reported by Sheldon. 19This report, therefore, includes only findings in adult subjects between the ages of 20 and 49 years. To d e t e r m i n e test-retest variability, an additional 12 normal subjects, six men and six w o m e n ranging in age from 20 to 32 years, underwent Romberg tests daily over five consecutive days.

Apparatus The apparatus and recording methods have been described, 17 Briefly, a piezoelectric force plate (Kistler Model 9261A) interfaced to a microprocessor (Digital Equipment Corporation, LSI 11) was used to record forces projected vertically to the platform by a standing subject. The amplified outputs of the four vertical-force sensors were connected to the computer's A/D converter and were sampled ten times per second, giving a Nyquist frequency of 5 Hz. Initial analysis of power spectra of data sampled at higher rates showed no significant data beyond 5 Hz, insuring that no frequency aliasing occurred. 2~ Continuous display of center-of-force calculations before and during the testing procedure on the computer display enabled the technician to position the subject at the approximate center of the platform before each trial.

Summary of Test Procedure After removing shoes, the subject was instructed to stand as rigidly as possible on the

BLACKET AL force platform in the standard (feet together) or t a n d e m (heel-to-toe) foot position with eyes open or closed, Four maneuvers were recorded: 1) feet together (standard Romberg), eyes open (SREO); 2) feet together, eyes closed (SREC); 3) feet heel-to-toe (tandem Romberg), eyes open (TREO); 4) feet heel-to-toe, eyes closed (TREC). During each trial the subject was asked to perform the ]endrassik maneuver, 21'22 i.e,, hooking curled hands b y the fingers and laterally extending both arms under isometric tension to stabilize upper torso and neck joints. These ins t r u c t i o n s t e n d e d to m i n i m i z e u p p e r b o d y movements and stiffened axial body muscles in an effort to force the subject to control body sway mainly by exerting torque about the ankle joints. Torque exerted on the foot can be measured by a force platform. Knee, hip, head, and arm movements cannot be measured by a force platform, but asymmetric movements about these joints can significantly affect body sway estimates. The instruction set was, therefore, important to insure projection of the major body center-of-force displacements through the subjects' feet to the recording platform. If visible knee or pelvis flexion occurred, or if lateral spinal bowing was necessary to maintain Romberg position stability, the trial result was discarded and the trial repeated once after instructions were repeated. Each subject was tested using two 15-second trials per maneuver (eight trials total). A relatively short (15-second) trial period was selected to make possible comparison of the results with the results from abnormal subjects, who cannot consistently complete longer recording trialsY

Data Analysis Sampled force-platform data were read by the computer program for each trial separately. The instantaneous center-of-force displacements (r) were calculated in the x and y directions. Mean displacement values of x and y coordinates were subtracted from instantaneous values and the resulting zero mean data converted to polar coordinates (Figs. 1 and 2): r = (x 2 + y2) I12 and 0 = tan-' (y/x) Fluctuations in the polar center-of-force displacement were calculated and were expressed as mean squared displacement (MSD). Fluctuations in r were characterized by a scaled mean

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squared estimate. This estimatewas obtainedby summing the discretepower spectral estimate,23 which was scaled such that a sinusoidal waveform of peak amplitude A would have a corresponding spectral peak of magnitude A~. The mean squared value was chosen because it is proportional to energy expended in many other systems, The different expenditures of energy needed to maintain postural stability while performing the standard tandem Romberg maneuvers appeared to be the most characteristic quantitative change from one test condition to another. Distribution histograms of the scaled MSD values were constructed (Fig. 3). Statistical analysis (chi-squared test for multiple unrelated samples) was performed to test for uniformity of populations sampled (male versus female and age decades). Cumulative percentiles were calculated. Confidence intervals were calculated for selected percentiles of the pooled data. The effects of repeated trials w e r e analyzed using the Wilcoxon matched-pair signed-rank test. The "minimal difference" (lower value from the two eyes-closed trials minus the lower value from the two eyes-open trials) was determined for both standard and tandem maneuvers. Distribution histograms for "minimal difference" were also generated. Finally, to determine test-retest reliability, coefficient of variation w a s calculated using each of 12 normal subject's better trial for each of the four maneuvers performed on five consecutive days.

Volume 3 Number 5 September ] 982

311

POSTURAL SWAY

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BLACKET AL Pooled Mean Squared Displacement (MSD) Data

TABLE I.

90 PSRCENT

PERCENTILE

5Oth

75th

95th

57 54

91 89

166 170

375 439

240-533 355-558

142 128

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368 303

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1,492 1,033

25th Standard Remberg test, eyes open Trial 1 Trial 2 Standard Romberg test, eyes closed Trial 1 Trial 2 Tandem Romberg test, eyes open Trial 1 Trial 2 Tandem Romberg test, eyes closed Trial 1 Trial 2

TABLE 2.

CONFIDENCE INTERVAL RANGE OF 95th PERCENTILE

543

1,273-1,915 896-1,926

Intertrial Group Comparisons of Mean Squared Displacement (MSD) Values

AVERAGEMSD INCREASE OR

WILCOXON TEST

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Trial 2

DECREASEOFMSD

P (Two-TAILED)

130 288

143 265

Increase Decrease

0.418 0.048

168 510

143 424

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0.017 0.008

Standard Rombergtest Eyes open Eyes closed Tandem Rombergtest Eyes open Eyes closed

RESULTS

Effects of Sex and Age Decade, Ages 20-49 One hundred and thirty-two subjects between the ages of 20 and 49 years satisfied the criteria for n o r m a l subjects. Initially, subjects were grouped into three age decades, 20-29, 30-39, and 4 0 - 4 9 years. The MSD values for the two sexes and the three decades were plotted as distribution histograms. Distributions for the two sexes and the three age decades appeared to be virtually identical w h e n compared by maneuver. A chi-squared test 24 was applied to data from either sex and from each of the three age decades to determine whether the preliminary grouping according to sex and decades could be considered to represent equivalent samples drawn from the same population. For purposes of the chi-squared test, h i s t o g r a m bin w i d t h s were selected so that zero-frequency (empty) bins did not occur. The tandem Romberg manuever with the eyes open, trial 1, yielded the only significant difference (P

< 0.05) obtained for the between-sexes comparison. For all other maneuvers and trials, P values were not significant, ranging from 0.18 for the eyes-closed tandem maneuver, trial 1, to 0.6 for the standard Romberg test with the eyes closed, trial 2. Because only the first tandem maneuver, eyes-open trial demonstrated a statistically significant difference between sexes, and because the second such trial yielded a P value of 0.33, the former result was considered spurious. For age decade comparisons, P values ranged from 0.30 to 0.885. Subject, sex, and age, therefore, did not have a statistically significant effect upon seven of eight Romberg test trials for normal subjects between the ages of 20 and 49 years. The MSD data from subjects of both sexes, ages 20 through 49 years inclusive, were therefore pooled, histograms were constructed (Fig. 3) and percentile values were calculated for the two trials of each maneuver. Ninety per cent confidence intervals based on the order statistics 2'~ were also calculated for the 95th percentiles (Table 1). The upper 90 per cent confidence limits at the 95th percentile for all maneuvers and trials were less than the 100th percentile.

Volume 3 Number 5 September 1982 313

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FOOTPOSITION

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50th

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157

453

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704

Intermaneuver Group Comparisons The distribution mode values were approximately the same for both standard Romberg tests and the eyes-open t a n d e m maneuver, but a marked increase in MSD occurred during the eyes-closed tandem maneuver, reflecting the more difficult postural control maneuvers necessitated by the more unstable heel-to-toe foot position, particularly with eyes closed.

Intertrial Group Comparisons American Journal of Qtoloryngology

314

Examination of scatter plots suggested that most normal subjects had reductions of MSD values during trial 2 relative to trial 1 for all maneuvers except for the standard test with the

eyes open. The 25th percentile MSD values were consistently lower for the second trial than for the first (Table i). For the 95th percentile, on the other hand, MSD values increased slightly for the standard Romberg test but decreased for the tandem maneuver. The Wilcoxon matched-pair, signed-rank test 24 was applied to test the null hypothesis that there was no change between trials of the same maneuver for the normal group as a whole. The rejection region for the null hypothesis was two-tailed (no predicted direction of change); the rejection limit was P = 0.05 (Table 2). A statistically insignificant increase in MSD estimates during the second trial occurred for the eyes-open standard maneuver, i.e., the null h y p o t h e s i s was accepted. For the other three maneuvers, however, there were significant decreases in MSD second-trial estimates, i.e., the null hypothesis was rejected.

Eyes Closed vs. Eyes Open Performance Visual deprivation w i d e n e d the MSD distribution as compared with the eyes-open recording condition (compare top and bottom rows of Fig. 3-4). Mean MSD values w i t h the eyes closed approximately doubled for the standard Romberg test and increased by a factor of 3 for the t a n d e m m a n e u v e r relative to the corresponding eyes-open maneuvers. The Wilcoxon test was a p p l i e d to compare e y e s - o p e n and eyes-closed Romberg test performances as estimated by MSD. For the entire group, MSD values i n c r e a s e d ( c o r r e s p o n d i n g to an i n c r e a s e in energy expenditure needed to maintain stable posture) upon visual deprivation (P < 0.05). This is shown also in Table 2. In order to q u a n t i t a t e f u r t h e r the strong stabilizing influence of visual information upon Romberg test posture control, the performance of each participant was examined by comparing the difference between the better (lower MSD value) eyes-dosed trial for a given maneuver and the better (lower MSD value) eyes-open trial. [Minimal difference = (lower MSD, eyes closed) - (lower MSD, eyes open).] Figure 4 shows the distribution histograms for this "minimal difference." The "minimal difference" increased in 90 per cent of subjects for the standard Romberg test and in 92 per cent of subjects for the tandem maneuvers. The r e m a i n i n g subjects demonstrated a decrease for eyes-closed as compared with eyes-open MSD estimates. Percentiles for this "minimal difference" measure are listed in Table 3.

BLACKET AL

Variance of Repeated Romberg Tests Repeatability of the Romberg test measures was determined for 12 normal subjects, each tested for five consecutive days. The coefficient of variation (CV) was calculated for each subject using the better (lower MSD value) of the two trials for each of the four maneuvers. The CV (standard deviation divided by the mean value) was selected to characterize variability of repeated measurements because the method normalizes the data on the mean value. The CVs were averaged over the 12 subjects to characterize group variabilities for each maneuver. They ranged from 0.14 to 0.86 and suggest a high degree of variability (Table 4). Repeatability was also characterized in terms of percentile MSD values. The percentile variability "normalized" about the 50th percentile is shown for the group in Table 4. The percentage MSD value was then extrapolated relative to the 50th percentile. The percentile variation ranges for individuals were quite wide (from the 21st percentile to the 74th percentile) except when a subject's average percentile performance remained below the 50th percentile. However, all of the 12 subjects performed within the group normal range (95th percentile or below) during the five consecutive daily tests. None of the subjects demonstrated an order effect, and there was no monotonic trend in MSD values over the five-day period. DISCUSSION

Pooled Data The absence of statistically significant differences between age decades and between males and females for seven of eight trials permitted pooling of data from all subjects, aged 20-49 years. The larger population that resulted from pooling also permitted the use of percentile data with relatively small confidence intervals (CI) at the 95th percentile. The upper 90 per cent confidence limits at the 95th percentile were well below the 100th percentile. The 95th percentile is considered the normal/abnormal cut-off for most clinical laboratory data. The CI limits at the 95th percentile give an estimate of the variance, which is especially important for population data with positively skewed distributions. Thus, the clinician has the choice of being very conservative, ff he so chooses, by setting normal limits at the highest 90 per cent CI range of the ghth percentile (Table 1). Intersubject variances

for subjects younger than 20 years old and older from 50 years old were too large to permit pooling of their data.

Distribution Skew for Normal Subjects About 20 per cent of subjects accounted for an upward (positive) skew in normal subject distributions. There is no adequate standard test for the human vestibulospinal function that can be used as a basis of comparison with our data. Vestibular criteria for normality were, therefore, based upon horizontal canal vestibule-ocular rotational responses (VOR). There is a possibility that our sample included asymptomatic (compensated} abnormal subjects with partial vestibular lesions not affecting the horizontal canal VOR system. The posturographic test procedure may be sensitive enough to detect such abnormalities, but they may remain undetected by the patient, clinical examiners, and available screening techniques. Nashner (personal communication) has encountered a similar positive skew in about 25 per cent of his "normal" subject population, and suspects that these subjects are vestibular-deficient, because they cannot maintain normal upright posture when forced to use only vestibular input (i.e., when ankle joint and visual inputs are nulled with respect to body sway).

Increased Sway Displacement for the Tandem Romberg Test The increased MSD (i.e., the decrease in pastural stability) during the eyes-closed tandem maneuver has been attributed to the reduction of the support surface in the left-right axis when the feet are in the tandem position. Another possible explanation for the marked differences between sway amplitude during the eyes-closed tandem maneuver and sway amplitudes during the other maneuvers that should be explored is the relative sensitivity of the sensory input systems, particularly the vestibular system, to detect left-right versus anterior-posterior sway. We have observed marked asymmetries in lateral sway detection and sway amplitude in subjects with unilateral vestibular disturbances (unpublished data), but could locate no published quantitative data from normal subjects for comparison.

Intertrial Variability Low repeat-test variability is desirable if a quantitative Romberg test is to be used to

Volume 3 Number 5 September 1982

315

POSTURAL SWAY

TABLE 4.

Variability of Daily

Romberg

FEET TOGETHER

Variance Best subject 9 Range Mean W o r s t subject Range Mean

Eyes Open

Eyes Closed

0.42 • 0.16

0.45 -4- 0.16

0.42 -+ 0.2

0.39 _+ 0,13

2 1 - 5 9 percentile

2 1 - 7 4 percentile

2 3 - 7 1 percentile

31-68 percentile

6-33 14

1-14 8

2-16 8

2-8 3

23 - 9 0 61

9-80 41

7-73 35

21-83 53

Test-Retest Variabifity

of

Otolaryngology 316

HEEL--ToE POSITION

Eyes Closed

monitor or otherwise track patient responses to treatment or to track progression of disease. A comparison of first versus second trials demonstrated a significant second-trial improvement (decreased MSD) for every maneuver except the eyes-open standard Romberg test (Table 2). The observations may have practical importance because virtually all vestibular-deficient subjects record increased second-trial MSD values for all maneuvers (Black et al., unpublished data). A repeated trial paradigm may be of value in separating normal from abnormal subjects, given the statistically significant decrease in MSD values for the eyes-closed standard test and both tandem maneuvers. Reasons are obscure for the slight increase in second-trial eyes-open standard test MSD values and the significant improvements in MSD (MSD reductions) for the other maneuvers. Fatigue does not provide a plausible explanation; with increasing fatigue a progressive decrement (increase of MSD values) would be anticipated for each sequential Romberg maneuver and trial.

American Journal

Results

Open

Eyes Coefficient of variation (average -+ SD)

Test

The 12 subjects who underwent daily tests s h o w e d high variability, but d e m o n s t r a t e d neither consistent improvements nor consistent decrements in MSD measures from day to day. None of these 12 subjects recorded MSD values above the 90th percentile of our normal distribution. Our findings were somewhat different in this respect from those reported by Holliday and Fernie, 2~ who tested 29 healthy volunteers for 15 consecutive working days. Most of their subjects improved consistently upon daily testing, but some subjects did not. S w a y velocity was used by Holliday and Fernie as a measure of postural sway during longer (60 second) trials with eyes open and with eyes closed. For most subjects, sway velocity gradually decreased within the first five days, reaching an asymptote

of 25 per cent of the initial value at five days (maximum 34 per cent at 15 days). Murray et el. 27 reported correlation coefficients greater than 0.77 from repeated same-day measures of postural sway. Since Murray et al. e m p l o y e d different r e c o r d i n g a n d analysis methods to study a smaller population of 24 adult men, their results m a y not be directly compared with our data. Our results from repeated daily tests suggest that test-retest variability for a given subject is proportional to MSD, i.e., the greater the MSD, the greater the test-retest variability. This hypothesis should be tested using both normal and abnormal~subjects. Results of such studies will have a direct bearing u p o n the design and clinical usefulness of a quantitative Romberg test in an abnormal population.

Effects of Visual Cues upon Romberg Test Stability Wilcoxon test results statistically confirmed the observed increases in MSD values w h e n the subjects' eyes were closed. The increased MSD values with eyes closed as compared with eyes open for most normal subjects support findings of others '2'~'14'2s and confirm the strong influence of visual orientation cues on h u m a n upright posture control. The strong stabilizing influence of vision u p o n normal h u m a n postural control is reflected in both the standard Romberg test and the tandem maneuvers, but is more marked for the more difficult tandem maneuver. The eyesclosed/eyes-open MSD ratios are approximately 2 and 3 for the standard test and t a n d e m maneuvers, respectively. However, the assumption that the eyes-closed performance will always yield values higher than those obtained with the eyes open did not hold true in about 10 per cent of normal subjects performing the standard Reinberg test and 8 per cent of the subjects performing the t a n d e m maneuver. This m a y explain failure of Leroux and coworkers 13to demonstrate

BLACK ET AL

a significant effect of vision upon posturaI stability in 20 young firemen. Thus, fixed force platform measures of eyes-open versus eyesclosed Romberg tests can be employed te demonstrate differences in population responses but cannot be applied to all individuals. Reasons for these individual differences would be purely speculative, but is possible that the subjects whose eyes-closed MSD values are greater than eyes-open values might rely more on proprioceptive or vestibular input than u p o n visual cues fer optimal pestural stabilization. What impact this finding may have en use of the Romberg test clinically must be d e t e r m i n e d by studying abnormal patient populations under well-defined conditions. From a comparison of our results with those of recently reported experiments that employed roughly similar tests and analysis methods, we conclude that intertrial and repeat-test variability probably depends upon such variables as the postural task, instruction set, length of recording trial (fatigue), and resolution of recording technique.

eyes-open and eyes-closed tandem Romberg tests statistically significant changes (lower MSDs) were recorded from the second trials for normal subjects. 4. Upon repetition of the Romberg test over five consecutive days, another 12 normal subjects demonstrated a large variability, but all individual subjects' results remained within the 90th percentile of normal group distributions. 5. Mest normal subjects recorded lower MSD values when visual cues were permitted as compared with recordings obtained with the eyes closed for both standard and tandem Romberg tests. However, about 10 per cent of normal subjects recorded lower MSD scores with the eyes closed,

CONCLUSIONS

References

The following conclusions may be drawn frem a study of fixed-platform standard and tandem Romberg test responses from 132 normal subjects: 1. There was no statistically significant effect of age decade upon normal adult Romberg test results from 20 through 49 years of age. Recordings of the Romberg test results from subjects older than 50 and younger than 20 years old demonstrated high intersubject variances, which prevented systematic description in a normal data base (i.e., prevented pooling of data for c o m p a r i s o n of populations). Unless further studies can identify, control, and resolve sources of these variances, clinical application and interpretation of results of the Romberg test in the younger (less than 20) and older (more than 50) age groups should be performed with caution. Until this problem is resolved, each laboratory should establish its own norms for age groups less than 20 and more than 50 years old. Reports should specifically state the percentile levels and corresponding confidence interval ranges used as normal and abnormal limits. 2. In the 2 0 - 4 9 - y e a r age population, there was no statistically significant difference bet w e e n Romberg test r e s p o n s e s of men and women. 3. There was no statistically significant difference between two trials for the standard Romberg test with the eyes open. For the standard Romberg test with the eyes closed and for both

1. Romberg MH: Manual of Nervous Diseases of Man. London, Sydenham Society, 1853, pp 395-401 2. Njiokiktjlen Ch, De Rijke W: The recording of Romberg's test and its application in neurology. Agressologie 13(C):1-7, 1972 3. Fernie GR, Holliday P]: Postural sway in amputees and normal subjects. J Bone Joint Surg 60:895-898, 1978 4. Kapteyn TS, de Wit G: Posturography as an auxiliary in vestibular investigation. Acta Otolaryngol 73: 104-111, 1972 5. Stribley RF, Abers JW, Tourtellotte WW, et ah A quantitative study of stance in normal subjects. Arch Phys Med Rehabil 55:74-80, 1974 6. Sugano H, Takeya T: Measurement of body movement and its clinical application. Jpn I Physiol 20:296-308, 1970 7. Terekhov Y: A system for the study of man's equilibrium. Biomed Eng 9:478-480, 1974 8. Terekhov Y: Stabilometry as a diagnostic tool in clinical medicine. Can Med Assoc ) 115:631-633, 1976 9. de Wit G: Stabilometry as an auxiliary in investigations of patients with vestibular disturbances. Agressologie 14:27-31, 1973 10. BenseI CK, Dzendolet E: Power spectral density analysis of the standing sway of males. Percept Psychophys 4(5):285-288, 1968 11. Scott DE, Dzendolet E: Quantification of sway in standing humans. Agressologie 13(B):35-40, 1972 12. Aggashyan R-V, Gurfinkel V-S, Mamasakhlisov, G-V, et ah Changes in spectral and correlation characteristics of human stabilograms at muscle afferentation disturbance. Agressologie 14(D);5-9, 1973 13. Leroux J, Baron JB, Bizzo G, et ah Power spectrum density of lateral and antere-posterior spontaneous motions of the center of gravity of the man standing up. Agressologie 14(C):57-63, 1973 14. Dichgans J, Maurit.z KH, Allure JHJ, et ah Postural sway in normals and stactic patients: analysis of the stabilizing and destabilizing effects of vision. Agressologie 17:15-24, 1976 15. Soames R-W, Atha J, Harding R-H: Temporal changes in the pattern of sway as reflected in power spectral density analysis. Agressologie 17(B):15-20, 1976

Acknowledgments. Computer programs were written by Alison Hunt and Ber-Name Lin. Mary Ann Czerniewski and Sharon Simon prepared the manuscript and Scott Brown provided technical aid.

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POSTURAL SWAY 16. Nashner LM: Sensory feedback in human posture control. Thesis, Centre for Space Research, Massachusetts Institute of Technology, Cambridge, 1970 17. Black FO, Wall D Ill, O'Leary DP: Computerized screening of the human vestibulospinal system. Ann Otol Rhinol Laryngol 87:853-861, 1978 18. Wall C III, Black FO, O'Leary DP: Clinical use of pseudorandom binary sequence white noise in assessment of the human vestibule-ocular system. Ann Otol Rhinol Laryngol 87:845-852, 1978 19. Sheldon JH: The effect of age on the control of sway. Gerontol Clin 5:129-138, 1963 20. Bendat JS, Piersol AG: Random Data: Analysis and Measurement Procedures. New York, Wiley International Press, 1971, pp 322-329 21. Laskiewicz A: Erno Jendrassik's maneuver in otological practice. Acta Otolaryngol 63:238-244, 1967 22. Gurfinkel V-S, Alexeef M, Elnar G, et ah Variations de l'ectivite tonique posturale et du reflexe achileen sons

23. 24. 25. 26. 27. 28.

l'influence du calcul mental et d'une manoeuvre derivee do celle de Jendrassik, Agressologie 13(B):6368, 1972 Jenkins GM, Watts DG: Spectral Analysis and Its Applications. San Francisco, Holden-Day, 1968, pp 21-23 Seigel S: Nonparametric Statistic for the Behavioral Sciences. New York, McGraw-Hill, 1956 Hogg RV, Craig AT: Introduction to Mathematical Statistics. New York, MacMillan, 1965 Holliday P~, Fernie GR: Changes in the measurement of postural sway resulting from repeated testing. Agressologie 20:225-228, 1979 Murray NIP, Seireg AA, Sepic SB: Normal postural stability and steadiness: quantitative assessment. J Bona Joint Surg 57-A: (Part 1), 510-516, 1975 Dichgans J, Brandt T: Visual-vestibular interaction: effects on self-motion perception and postural control, in: Handbook of Sensory Physiology. Volume VIII. New York, Springer-Verlag, 1978, pp 787-792

COMMENTARY This manuscript reports important work which is a first, tile accurate measurement of pastural sway in normal individuals and a careful statistical description of the findings. There is a good deal of interest in vestibular spinal testing for clinical purposes, and this article is an important contribution to fundamental information. Quite often clinicians go ahead and do things and attribute their findings to disease without any accurate information of normal function, and Dr. Black a n d his colleagues have provided important data. HUGHO. BARBER,M.D. Department of Otolaryngology Sunnybrook Medical Centre 2075 Bayview Avenue Toronto, Ontario M4N 3M5 Canada

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