On classification capability of neural networks: a case study with otoneurological data

We investigated the capability of multilayer perceptron neural networks and Kohonen neural networks to recognize difficult otoneurological diseases from each other. We found that they are efficient methods, but the distribution of a learning set should be rather uniform. Also it is important that the number of learning cases is sufficient. If the two mentioned conditions are satisfied, these neural networks are similarly efficient as some other machine learning methods. The conditions are known in the theory of neural networks [1,2], but not often taken seriously in practice. Both networks functioned as well, excluding the case with several input variables, where the Kohonen neural networks surpassed the perceptron.

Sensorineural hearing loss after vibration: an animal model for evaluating prevention and treatment of inner ear hearing loss

Sensorineural hearing loss following a variety of acoustic trauma, including middle ear surgery, is well known. Current literature, which points to the deleterious influence of noise on the inner ear during surgery, has yet to assess the influence of vibration generated by the burr. The purpose of the study reported here was to establish an animal model that mimics drilling and can be used to explore methods of hearing loss prevention and treatment. A specially developed electromagnetic vibrator was calibrated and used in 59 guinea pigs to induce hearing loss. Both young and old guinea pigs were used. The bony external ear canal of guinea pigs were exposed to vibration or sound of varying duration and intensity. The vibration of the temporal bone and noise level in the middle ear were measured. Electrocochleography was recorded to evaluate the hearing loss. Among the young animals, 90% developed a significant threshold shift (TS > 20 dB), when vibrated with 250 Hz at an intensity of 6.2 m/s2 for 15 min. An average of 42 dB TS was observed. With 10 min exposure 63% showed a TS. The older animals vibrated for 5 min developed the same TS (mean TS 34 dB) as the young animals when vibrated for 10 min. The vibration-induced TS showed no recovery within 3 days of observation. In the contralateral ear 4 out of 5 animals showed TS > 20 dB. When exposed to sound levels exceeding the vibration-generated sound in the middle ear (119 dB at 250 Hz) only 2 out of II animals (18%) showed TS. The frequency of TS and level of TS were significantly greater in the vibrated animals than in sound-only exposed animals (p < 0.01). The degree of vibration-induced TS in the present animal model could be controlled by vibration intensity and duration. The older animals were more susceptible to vibration-induced inner-ear damage than younger animals. This model will be used in further studies to find methods for prevention and treatment of hearing loss during ear surgery.

Clinical picture of vestibular schwannoma

PURPOSE

To characterize the clinical picture with vestibular schwannoma, we retrieved 122 patients with vestibular schwannoma from the vestibular unit of the Helsinki University Central Hospital.

PROCEDURES

The patients filled out a questionnaire concerning their symptoms, earlier diseases, accidents, and the use of tobacco and alcohol. This information was then completed with results of audiometric, neurotologic and imaging studies. The data were prospectively stored to the database of neurotologic expert system called ONE.

RESULTS

The average tumor size was 21 mm. Most of the patients had hearing loss (94%) and tinnitus (83%) but only half of them (49%) had vertigo attacks. The most common initial symptom was hearing loss combined with tinnitus (34%, n=44). Vertigo only was the initial symptom for 12 patients. The mean duration of a vertigo attack was from 5 min to 4 h and the intensity of the attack was regularly mild (37%) or moderate (32%). The vertigo of the vestibular schwannoma patients differed from vertigo in other diseases by the absence (63%) or low intensity (18%) of nausea. Spontaneous nystagmus was present in 56 patients (46%), and caloric asymmetry (>25%) was observed in 66% (n=69). Caloric asymmetry increased with tumor size. The prevalence of headache was 18% (n=21). Sudden slips seldom (7%) occurred.

CONCLUSION

Hearing loss and tinnitus are the main symptoms of vestibular schwannoma. Only half of patients have vertigo. Screening to detect vestibular schwannoma is more yielding in sudden deafness patients rather than in patients with Meniere's disease.

Increased retinal image velocity after vestibular lesion

The vestibulo-ocular reflex stabilizes gaze during head movements by producing compensatory eye movements. Retinal image velocity (RIV) is defined as the difference between the eye and head velocities. The RIV of 20 vestibular schwannoma (VS) patients and 17 healthy controls was measured with a head autorotation test. The head autorotation test had a sensitivity of 80% and a specificity of 88%. The mean RIV (degree/second) +/- 95% confidence intervals of the VS patients in the 5 frequency bands of 1 to 5 Hz was respectively 4.8 (4.2 to 5.5), 11.5 (8.6 to 14.4), 21.7 (15.5 to 27.9), 25.2 (17.1 to 33.4), and 26.1 (13.1 to 39.1). The RIV of the VS patients was asymmetrically larger on the operated side (P<0.05) in the frequency band of 1 Hz. The mean RIV was significantly (P<0.05) larger in the VS patients than in the controls in the frequency bands of 1 to 4 Hz. The vestibulo-ocular reflex is inaccurate after VS surgery; but the inaccuracy may not lead to the occurrence of any symptoms.

Usefulness of imputation for the analysis of incomplete otoneurologic data

The usefulness of imputation in the treatment of missing values of an otoneurologic database for the discriminant analysis was evaluated on the basis of the agreement of imputed values and the analysis results. The data consisted of six patient groups with vertigo (N=564). There were 38 variables and 11% of the data was missing. Missing values were filled in with the means, regression and Expectation-Maximisation (EM) imputation methods and a random imputation method provided the baseline results. Means, regression and EM methods agreed on 41-42% of the imputed missing values. The level of agreement between these and the random method was 20-22%. Despite the moderate agreement between the means, regression and EM methods, the discriminant functions were similar and accurate (prediction accuracy 83-99%). The discriminant functions obtained from the randomly imputed data were also accurate having prediction accuracy 88-97%. Imputation seems to be a useful method for treating the missing data in this database. However, a lot of data was missing in otoneurologic tests, which are likely to be of less importance in the diagnosis of vertiginous patients. Consequently, the disagreement of the methods did not affect clearly the discriminant analysis, and, therefore, future research requires more complete data and advanced imputation methods.

Postoperative headache after surgery for vestibular schwannoma

Postoperative headache was studied among 251 patients who underwent operation for vestibular schwannoma. A questionnaire based on the McGill Pain Questionnaire and the Finnish Pain Questionnaire was sent to the patients. Twenty-one expressions describing postoperative headache were extracted with a factor analysis. The pain intensity was expressed on a visual analog scale, and the risk factors for postoperative headache were evaluated. Immediately after the operation, 154 subjects reported headache. Eighty-nine of the patients had had headache before operation, whereas 65 patients experienced headache only after operation. An average of 8.9 years after surgery, 93 patients still reported headache. Headache was a major problem for 27 subjects; 18 of the 27 had suffered from headache before operation. A retrosigmoidal approach, postoperative gait problems, preoperative headache, and small tumor size predicted postoperative problems with headache. When headache is present before operation, it tends to continue after operation, and if headache continues for 1 year, it usually persists without being reduced.

Analysis of eustachian tube function by video endoscopy

OBJECTIVE

Human eustachian tubes (ET) were inspected in vivo endoscopically, and video recordings were made for careful slow-motion analysis of normal physiologic function.

SETTING

Ambulatory office in a tertiary referral center.

SUBJECTS

Thirty-four adults, 17 with no history of ET dysfunction (2 of whom had tympanic membrane perforations), 17 with known ET dysfunction.

INTERVENTIONS

Transnasal endoscopic examination of the nasopharyngeal opening of the eustachian tube during rest, swallowing, and yawning.

MAIN OUTCOME MEASURES

Video analysis of ET opening movements.

RESULTS

Normal ETs had four consistent sequential movements: (1) palatal elevation causing passive, then active, rotation of the medial cartilaginous lamina; (2) lateral excursion of the lateral pharyngeal wall; (3) dilation of the lumen, caused primarily by tensor veli palatini muscle movement beginning distally and inferiorly, then opening proximally and superiorly; and (4) opening of the tubal valve at the isthmus caused by dilator tubae muscle contraction. Dysfunctional ETs had intraluminal edema, polyps, or minimal muscle movement.

CONCLUSIONS

Slow-motion endoscopic video analysis may be a useful new technique for the study of eustachian tube physiology. Consistent muscle movement patterns were demonstrated in normal subjects but were absent in abnormal subjects. More studies of normal and abnormal patterns are needed to establish useful clinical correlates.

Modelling oculomotor data with decision tree induction

We studied relationships between oculomotor test results and the site of lesion in the data set containing patient cases with operated cerebello-pontine angle tumour, operated hemangioblastoma, infarction of cerebello-brainstem or Meniere's disease and control subjects. Several classification models were generated by decision tree induction to find parameter combinations which are efficient in classification. The studied data were characterised by missing values and scarcity of example cases. This study suggested that decision tree induction can be a useful method even in problematic real world classification tasks. Models generated by decision tree induction and evaluated by an expert physician may give information that is beneficial for research.

Treatment of missing values with imputation for the analysis of otologic data

Usefulness of imputation in the treatment of missing values in an otologic database was studied. Missing values were filled in with means (ME), regression (LR) and Expectation-Maximization (EM) imputation methods. A random imputation method (RA) provided baseline results. ME, LR and EM methods agreed on 41-42% of the imputed missing values. The level of agreement between these and RA method was 20-22%. Despite the moderate agreement, discriminant functions were similar and accurate (prediction accuracy 83-99%) for each diagnosis. A lot of data were missing in otoneurotologic tests which have less weight in the diagnosis of vertiginous patients. Consequently, the disagreement of the methods did not affect discriminant analysis. Inputation seems to be a useful method to treat missing data in this database, but future research requires more complete data and advanced imputation methods.

[Future cure of hearing disorders? Gene therapy and stem cell implantation are possible new therapeutic alternatives]

Hearing loss is a very common disorder; nearly 10 per cent of the population is affected. Recently, a few findings such as the roles of neurotrophins, nitric oxide, reactive oxygen species and glutamate receptors in the peripheral hearing system have been highlighted. In this review, focus is set on possible mechanisms of peripheral hearing disorders, and on recent advances to prevent and treat hearing loss. Clinically useful treatment strategies, especially gene therapy and the use of embryonic stem cells, are particularly stressed.

Production of diagnostic rules from a neurotologic database with decision trees

A decision tree is an artificial intelligence program that is adaptive and is closely related to a neural network, but can handle missing or nondecisive data in decision-making. Data on patients with Meniere's disease, vestibular schwannoma, traumatic vertigo, sudden deafness, benign paroxysmal positional vertigo, and vestibular neuritis were retrieved from the database of the otoneurologic expert system ONE for the development and testing of the accuracy of decision trees in the diagnostic workup. Decision trees were constructed separately for each disease. The accuracies of the best decision trees were 94%, 95%, 99%, 99%, 100%, and 100% for the respective diseases. The most important questions concerned the presence of vertigo, hearing loss, and tinnitus; duration of vertigo; frequency of vertigo attacks; severity of rotational vertigo; onset and type of hearing loss; and occurrence of head injury in relation to the timing of onset of vertigo. Meniere's disease was the most difficult to classify correctly. The validity and structure of the decision trees are easily comprehended and can be used outside the expert system.

Decreased vestibulo-ocular reflex gain of vestibular schwannoma patients

OBJECTIVE

The vestibulo-ocular reflex (VOR) stabilizes gaze during head movements by producing compensatory eye movements. Gain of the VOR can be defined as the difference between the eye and corresponding head movement amplitudes. The objective of the study was to compare the gain of postoperative vestibular schwannoma (VS) patients with that of healthy controls.

METHODS

The gain of 19 vestibular schwannoma (VS) patients and 100 healthy controls was measured with a head autorotation test (HART) in the five frequency bands of 1-5 Hz. It was computed as the ratio of the amplitude of the eye position signal to the amplitude of the head position signal. The mean gain was compared between the VS patients and healthy subjects in each frequency band by using an analysis of variance with statistical significance pre-defined as P < 0.05.

RESULTS

The HART was abnormal in 58% of the VS patients, whose mean gains in the five frequency bands of 1-5 Hz were 0.85, 0.79, 0.72, 0.64 and 0.60, respectively. The mean gains of the VS patients were significantly (P < 0.05) smaller than those of the controls in all the frequency bands.

CONCLUSIONS

The deficit of the VOR gain seems to prevail in more than a half of postoperative VS patients, although this inaccuracy of compensatory eye movements may not lead to the occurrence of any symptoms. However, in these patients a potential threat to gaze stability exists.

Decision tree induction in the diagnosis of otoneurological diseases

Expert systems have been applied in medicine as diagnostic aids and education tools. The construction of a knowledge base for an expert system may be a difficult task; to automate this task several machine learning methods have been developed. These methods can be also used in the refinement of knowledge bases for removing inconsistencies and redundancies, and for simplifying decision rules. In this study, decision tree induction was employed to acquire diagnostic knowledge for otoneurological diseases and to extract relevant parameters from the database of an otoneurological expert system ONE. The records of patients with benign positional vertigo, Meniere's disease, sudden deafness, traumatic vertigo, vestibular neuritis and vestibular schwannoma were retrieved from the database of ONE, and for each disease, decision trees were constructed. The study shows that decision tree induction is a useful technique for acquiring diagnostic knowledge for otoneurological diseases and for extracting relevant parameters from a large set of parameters.

Discovering diagnostic rules from a neurotologic database with genetic algorithms

Data on patients with Meniere's disease, vestibular schwannoma, traumatic vertigo, sudden deafness, benign paroxysmal positional vertigo, or vestibular neuritis were retrieved from the database of otoneurologic expert system ONE for the development and testing of a genetic algorithm (GA). The accuracy of the diagnostic rules in solving the test cases was 81%, 91%, 92%, 95%, 96%, and 98% for the respective diseases. The best rules retrieved from the GA were described by a set of questions with the most likely answers. The most important questions concerned the duration of hearing loss and the occurrence of head injury. The validity and structure of the rules created with a GA can be analyzed in detail. For rare diseases, some other reasoning process can be used, for example, case-based reasoning.

Otoneurological expert system for vertigo

We have developed an otoneurological expert system (ONE) to aid the diagnostics of vertigo, to assist teaching and to implement a database for research. The ONE database is set to harvest data on patient history, signs and test results necessary for diagnostic work with vertiginous patients. A method based on pattern recognition was used in the reasoning process. Questions about symptoms, signs and test results are weighted and scored for each disease and the most likely disease is recognized from defined disease profiles. Missing information and uncertainties are solved with a method resembling fuzzy logic. ONE was validated by comparing diagnoses assessed by physicians with those provided by the system. It proved to be a valid decision-maker by solving 65% of the cases correctly, while the physicians' mean was 69%. To improve ONE further, a follow-up should be implemented for the patients, since diagnosing sudden deafness and Meniere's disease during the first visit is often impossible. We aim to obtain new information on diseases involving vertigo by applying adaptive computer applications, such as genetic algorithms, to the reasoning process.

Smoking as a risk factor in sensory neural hearing loss among workers exposed to occupational noise

The effect of smoking on hearing was investigated among 199 professional forest workers and 171 shipyard workers. The effect of age on hearing was corrected with Robinson's model for an audiologically screened population. The exposure of the subjects to noise and their history of tobacco smoking were examined, with special reference to blood pressure and occupational Raynaud's phenomenon. Smoking without the presence of any other risk factors did not increase the risk for sensory neural hearing loss, but smoking in combination with elevated blood pressure and occupational Raynaud's phenomenon put workers at higher risk for hearing loss than any of these factors alone.

Comparison of two head autorotation tests

The head autorotation test is a novel method for studying the high-frequency vestibuloocular reflex without heavy machinery to generate whole-body rotation. Despite many studies with the test, the method is far from standardized, and no comparison has been made of different versions of the test. The objective of this study was to compare the vestibuloocular reflex of 100 healthy subjects measured simultaneously with two versions of the head autorotation test. Gain, phase, asymmetry, and the frequency bands reached were determined in the frequency bands of 1, 2, 3, 4, and 5 Hz. The gain measured with both tests was close to unity (range 0.95-1.04) from 1 to 4 Hz and about 0.9 at 5 Hz. In the test developed by Vorteq the phase lagged (-7 to -21 degrees) in all the frequency bands, and it differed significantly from the phase lead of 2 to 5 degrees that was measured by the other test. The asymmetry measured with the Vorteq test increased continuously from 1.5% (1 Hz) to 5.7% (5 Hz). The results of the tests showed intersubject variation, which was larger in the higher frequency bands. In conclusion, the high-frequency vestibuloocular reflex of healthy subjects can be quantified with active head oscillation. Both tests produced similar gain results, but the phase results differed systematically. Thus, the results of different head autorotation tests may not be directly comparable.

Postural compensation after intratympanic gentamicin treatment of Menière's disease

We have treated 93 patients with severe Menière's disease with gentamicin (GM) applied with 1 to 4 or intratympanic injections in a prospective study. The patients were tested at frequent intervals and followed up for two years. Postural stability was evaluated on posturography. Unsteadiness and gait between attacks, working capacity and vertigo were scored. Before commencing the treatment 47 of the patients complained from moderate to severe postural instability. After treatment moderate to severe postural instability was met in 19 patients. Initially the sway velocity was 27 mm/s on average being significantly worse than in referents. Two weeks after treatment the sway velocity increased to 33 mm/s. Thereafter the sway velocity slowly started to decline to 31 mm/s after two years. Patients with severe attacks of rotatory vertigo had a good postural outcome with GM treatment. In logistic regression analysis the most significant risk factor for poor recovery after GM treatment was severely reduced gait before commencing the treatment with odds ratio of 2.0. Subjectively, after two years, the patients rated their postural stability significantly improved when compared to pretreatment values. The good subjective rating of postural stability is related to postural training program where in the absence of attacks, the patients have learned to cope with daily tasks.

Effect of intratympanic gentamicin on hearing and tinnitus in Meniere's disease

OBJECTIVE

The objective of this study was to examine the effect of intratympanically applied gentamicin (GM) (30 mg/mL) on hearing and tinnitus in patients with intractable Meniere's disease.

STUDY DESIGN

A prospective study was conducted on 93 subjects treated with intratympanically applied GM. The mean pure-tone average (PTA) at speech frequencies was measured before the treatment and after 2 weeks, 1 month, 3 months, 6 months, 1 year, and 2 years after injections. Tinnitus was surveyed with a questionnaire. The mean duration of Meniere's disease was 9.8 years (range, 1-33 years).

PATIENTS

The study group consisted of 28 men and 65 women. The mean age was 50.9 years (range, 19-74 years).

RESULTS

The mean PTA at speech frequencies for the group worsened from 60 dB to 68 dB, which was statistically significant. Ten ears were deafened. The mean tinnitus handicap score before treatment was 2.92; 2 years after treatment, it was 2.26, indicating significant abatement of tinnitus during the course of the treatment.

CONCLUSIONS

The authors found that the average frequency of deafening was 10% and it was dose dependent. GM caused alleviation of tinnitus in the majority of the patients.

Comparison of two head autorotation tests

The head autorotation test is a novel method for studying the high-frequency vestibuloocular reflex without heavy machinery to generate whole-body rotation. Despite many studies with the test, the method is far from standardized, and no comparison has been made of different versions of the test. The objective of this study was to compare the vestibuloocular reflex of 100 healthy subjects measured simultaneously with two versions of the head autorotation test. Gain, phase, asymmetry, and the frequency bands reached were determined in the frequency bands of 1, 2, 3, 4, and 5 Hz. The gain measured with both tests was close to unity (range 0.95–1.04) from 1 to 4 Hz and about 0.9 at 5 Hz. In the test developed by Vorteq the phase lagged ( − 7 to − 21 ∘ ) in all the frequency bands, and it differed significantly from the phase lead of 2 to 5 ∘ that was measured by the other test. The asymmetry measured with the Vorteq test increased continuously from 1.5% variation, which was larger in the higher frequency bands. In conclusion, the high-frequency vestibuloocular reflex of healthy subjects can be quantified with active head oscillation. Both tests produced similar gain results, but the phase results differed systematically. Thus, the results of different head autorotation tests may not be directly comparable.

Postural compensation after intratympanic gentamicin treatment of Meniere's disease

We have treated 93 patients with severe Meniere's disease with gentamicin (GM) applied with 1 to 4 or intratympanic injections in a prospective study. The patients were tested at frequent intervals and followed up for two years. Postural stability was evaluated on posturography. Unsteadiness and gait between attacks, working capacity and vertigo were scored. Before commencing the treatment 47 of the patients complained from moderate to severe postural instability. After treatment moderate to severe postural instability was met in 19 patients. Initially the sway velocity was 27 mm/s on average being significantly worse than in referents. Two weeks after treatment the sway velocity increased to 33 mm/s. Thereafter the sway velocity slowly started to decline to 31 mm/s after two years. Patients with severe attacks of rotatory vertigo had a good postural outcome with GM treatment. In logistic regression analysis the most significant risk factor for poor recovery after GM treatment was severely reduced gait before commencing the treatment with odds ratio of 2.0. Subjectively, after two years, the patients rated their postural stability significantly improved when compared to pretreatment values. The good subjective rating of postural stability is related to postural training program where in the absence of attacks, the patients have learned to cope with daily tasks.

Effects of atropine and scopolamine on bradycardia and emetic symptoms in otoplasty

OBJECTIVE

To assess the effects of unilateral or bilateral otoplasty on bradycardia and postoperative nausea and vomiting (PONV) and the efficiency of transdermal scopolamine in the prophylaxis of PONV.

STUDY DESIGN

Post hoc assessment of the data from a double-blind, randomized study.

METHODS

Fifty otoplasty patients were studied; half of them received randomly and in double-blind fashion a transdermal therapeutic system (patch) of scopolamine (TTS-scopolamine) as prophylaxis against PONV before general anesthesia. The placebo group received atropine 10 microg x kg(-1) intravenously during induction.

RESULTS

The scopolamine-treated patients suffered more from moderate peroperative bradycardia (8/25; P < .05) than the atropine-treated patients (1/25). Two patients wearing a half of the TTS-scopolamine patch needed intravenous atropine. After unilateral otoplasty, none of the TTS-scopolamine-treated patients and 50% of the atropine-treated patients suffered from PONV. After bilateral operation, the respective incidences were 39% and 81% (P < .01). After unilateral otoplasty no patient needed droperidol, but after bilateral otoplasty, 12 of 19 of the atropine-treated and 4 of 18 (P < .05) of the scopolamine-treated patients needed droperidol. The mean numbers of doses of droperidol were 0.8+/-0.9 and 0.3+/-0.6 (P < .05), respectively. Two additional patients, wearing half of the TTS-scopolamine patch, suffered from mild central anticholinergic syndrome.

CONCLUSION

TTS-scopolamine offers effective prophylaxis against PONV (auriculoemetic reflex), but does not protect from bradycardia (auriculocardiac reflex) in otoplasty. Cutting of the TTS-scopolamine patch may lead to undesirable side effects.

Paediatric facial paralysis caused by Lyme borreliosis: a prospective and retrospective analysis

The incidence of Lyme borreliosis (LB) was studied prospectively in 49 children (< 17 years of age) with 50 episodes of acute FP. In addition, 43 children with a history of FP (average follow-up of 5.2 y) were studied retrospectively for the outcome of FP and for the symptoms and signs of late LB. In the prospective study, 17 (34%) patients with FP proved to have acute LB. They all received antibiotic treatment and their FP had a favourable outcome. In the retrospective study the patients had had FP before the diagnostic tests for LB were available. Thus, none of the 43 patients had been diagnosed to have, or treated for, LB. The outcome of their FP had generally been favourable. None of them had any signs of late LB at the follow-up visit. Our results indicate that LB is a frequent cause of acute paediatric FP in an endemic area. In addition our data suggests that FP caused by LB in children has a favourable prognosis, even when left untreated.

One-footed and externally disturbed two-footed postural control in patients with chronic low back pain and healthy control subjects. A controlled study with follow-up

STUDY DESIGN

A study of postural control during one-footed and externally disturbed two-footed stance among healthy control subjects and patients with chronic low back pain at the beginning of a functional back restoration program and 6 months later at follow-up examination.

OBJECTIVES

To study postural control cross-sectionally among control subjects and patients with low back pain, and to evaluate the effects of functional restoration on the postural control parameters in a follow-up examination.

SUMMARY OF BACKGROUND DATA

Deficits of motor skills and coordination have been reported in association with musculoskeletal disorders. It has been found that patients with chronic low back pain have impaired psychomotor control, but the impairment is reversible with successful low back rehabilitation. It is insufficiently known how functional activation and intensive physical training affect postural control.

METHODS

Sixty-one healthy volunteers (32 men, 29 women) and altogether 99 patients with low back pain participated in the study. Sixty-eight patients (33 men, 35 women) had moderate and 31 (18 men, 13 women) had severe low back pain. Postural stability was measured with a force platform. In two-footed stance, vibration stimulation on calf and back muscles was used to disturb the balance. Center point of force-velocity (cm/sec), average position shift in anteroposterior direction (cm), and maximal position shift in lateral direction (cm) were used as the parameters.

RESULTS

Reliability of all tests was acceptable. Center point of force-velocity was the most sensitive parameter and the one-footed measurement the most sensitivetest for evaluating postural stability. At the beginning, the patients with severe low back pain had poorer one-footed postural control compared with the control subjects (P = 0.0003). The subgroup of patients with moderate low back pain participated in the restoration program. The outcome of the restoration program was considered good if the disability because of low back pain (Oswestry index) decreased during the restoration program and poor if the disability increased or did not change. The one-footed postural stability remained primarily at the same level as the initial results in the control and good outcome groups, but became significantly poorer in the poor outcome group. The difference between poor outcome and control groups was statistically significant (P = 0.04).

CONCLUSIONS

Impaired postural stability seems to be one factor in multidimensional symptomatology of patients with chronic low back trouble. Postural stability is easily disturbed in case of impairment in strength, coordination, or effective coupling of muscles in the lumbar and pelvic area. Patients with chronic low back pain seem to experience impairment in these functions, which should be taken into consideration when back rehabilitation programs are planned.