Nonoperatively treated type A spinal fractures: mid-term versus long-term functional outcome.

This study focuses on the mid-term (four years) and long-term (ten years) functional outcome of patients treated nonoperatively for a type A spinal fracture without primary neurological deficit. Functional outcome was measured using the visual analogue scale spine score (VAS) and the Roland-Morris disability questionnaire (RMDQ). The 50 patients included were on average 41.2 years old at the time of injury. Four years post injury, a mean VAS score of 74.5 and a mean RMDQ score of 4.9 were found. Ten years after the accident, the mean VAS and RMDQ scores were 72.6 and 4.7, respectively (NS). No significant relationships were found between the difference scores of the VAS and RMDQ compared with age, gender, fracture sub-classification, and time between measurements. Three (6%) patients had a poor long-term outcome. None of the patients required surgery for late onset pain or progressive neurological deficit. Functional outcome after a nonoperatively treated type A spinal fracture is good, both four and ten years post injury. For the group as a whole, four years after the fracture a steady state exists in functional outcome, which does not change for ten years at least after the fracture.

Return to work and quality of life in severely injured patients.

BACKGROUND: Little is known about the long-term consequences of severe injuries in terms of return to productivity and quality of life. METHODS: In this study we focused on the return to work status and quality of life in 53 severely injured patients (AIS/ISS > or = 16, mean ISS 24, range 16 - 54), mean age 37 years, one to two years after the injury. Questions were asked concerning employment in the past and at present. Quality of life was measured by means of the Sickness Impact Profile (SIP) questionnaire. Injury-related parameters were analysed in order to study their relation with disablement. RESULTS: Of those patients who survived their injuries, 87% had resumed their former work. Only 10% of the patients received disability benefits. A mean SIP-total score of 6.7 was found, the mean SIP-physical score was 5.9 and the mean SIP-psychosocial score was 6.9. "No disability" (SIP score < or = 3) was found in 55% of the patients, whereas 11% of the patients reported "severe disability" (SIP score > or = 20). Age was a significant predictor of disablement (odds ratio 1.07). The Injury Severity Score (ISS), the length of hospital stay and the number of diagnoses did not predict disablement. CONCLUSIONS: Although the results were obtained in a relatively small sample size, the return to work rate in the surviving severely injured patients appears to be excellent. The quality of life is good; the majority of patients are not disabled. Age (and not the ISS) seems to be a significant predictor of disablement.

Functional outcome 5 years after non-operative treatment of type A spinal fractures.

This study was conducted to study the functional outcome after non-operative treatment of type A thoracolumbar spinal fractures without neurological deficit. Functional outcome was determined following the International Classification of Functioning, Disability and Health, measuring restrictions in body function and structure, restrictions in activities, and restrictions in participation/quality of life. All patients were treated non-operatively for a type A thoracolumbar (Th11-L4) spinal fracture at the University Hospital Groningen, The Netherlands. Thirty-three of the eighty-one selected patients agreed to participate in the study (response-rate 41%). Respondents were older than non-respondents (mean 50.5 years vs. 39.2 years), but did not differ from each other concerning injury-related variables. Patients with a neurological deficit were excluded. Treatment consisted either of mobilisation without brace, or of bedrest followed by wearing a brace. Restrictions in body function and structure were measured by physical tests (dynamic lifting test and bicycle ergometry test); restrictions in activities were measured by means of questionnaires, the Roland Morris Disability Questionnaire (RMDQ) and Visual Analogue Scale Spine Score (VAS). Restrictions in participation/quality of life were assessed with the Short Form 36 (SF-36) and by means of return to work status. Thirty-seven per cent of the patients were not able to perform the dynamic lifting test within normal range. In the ergometry test, 40.9% of the patients performed below the lowest normal value, 36.4% of the patients achieved a high VO(2)-max. Mean RMDQ-score was 5.2, the mean VAS-score was 79. No significant differences between patients and healthy subjects were found in SF-36 scores, neither were differences found between braced and unbraced patients in any of the outcome measures. Concerning the return to work status, 10% of the subjects had stopped working and received social security benefits, 24% had arranged changes in their work and 14% had changed their job. We conclude that patients do reasonably well 5 years after non-operative treatment of a thoracolumbar fracture, although outcome is diverse in the different categories and physical functioning seems restricted in a considerable number of patients.

Sagittal range of motion after a spinal fracture: does ROM correlate with functional outcome?

Literature regarding the effect of a spinal fracture and its treatment in terms of resulting spinal range of motion (ROM) is scarce. However, there is need for data regarding sagittal spinal ROM, since many patients who sustain a spinal fracture are concerned about the back mobility they will have after treatment. In addition, the relationship between ROM and impairment is not clear. The literature gives conflicting results. To study spinal ROM after a spinal fracture, we measured thoracolumbar ROM in operatively and non-operatively treated patients (n=76, average 3.7 years follow-up) as well as controls (n=41). In order to study the relation between ROM and subjective back complaints, we calculated the correlation between thoracolumbar ROM and scores derived from the VAS spine score and RMDQ. To assess impairment after a spinal fracture, we compared RMDQ and VAS scores between operatively and non-operatively treated patients and healthy controls. Operatively treated patients were found to have lower thoracolumbar ROM than controls (56.7 degrees vs 70.0 degrees , respectively; p<0.01). There was no difference between operatively treated and non-operatively treated patients (56.7 degrees vs 62.7 degrees , respectively); nor was a difference found between non-operatively treated patients and controls. Correlation between ROM and subjective impairment was very weak and only significant for ROM and RMDQ scores in the whole study group (rho= -0.25; p<0.01). Patients were more impaired than controls, there was no difference between operatively and non-operatively treated patients (VAS score 76.3 vs 72.6; RMDQ score 4.5 vs 4.4, respectively). We conclude that patients treated operatively for a thoracolumbar spinal fracture have a lower thoracolumbar ROM than controls. Spinal ROM, however, does not influence impairment. A spinal fracture results in impairment, no matter what therapy is chosen.

Spinal mobility: sagittal range of motion measured with the SpinalMouse, a new non-invasive device.

INTRODUCTION: In this paper the SpinalMouse, a new computerised external device for measuring sagittal spinal range of motion (ROM), was tested for inter-rater reliability and use in clinical practice. MATERIALS AND METHODS: To assess inter-rater reliability, two investigators each measured 111 subjects. RESULTS: Correlation coefficients were found to be r=0.90 for flexion, r=0.85 for extension and r=0.90 for total inclination. Intra-class coefficients were 0.95 for flexion, 0.92 for extension and 0.95 for total inclination. A poor agreement (kappa=0.22) was found for the presence of outliers from normal values for intersegmental ROM. CONCLUSION: We conclude the device is a useful, reliable tool for measuring sagittal spinal ROM in clinical practice, considering the small load it confers on patients and the short amount of time the measurement involves. The SpinalMouse might be more accurate after following the recommendations we make.

Contributions of object- and space-based mechanisms to line bisection errors.

In two experiments, normal adults divided a horizontal line segment and an equal spatial interval that did not contain a line into eight equal-appearing segments by means of successive bisections. In the first experiment, subjects' average initial bisections erred to the left of objective center for both stimuli. Their subsequent bisections produced similar errors for the line-present stimulus, as the bisection of each progressively smaller line segment was placed to the left of true center. However, this pattern did not occur when bisecting the empty interval. The finding that the presence of a line influences bisection errors implicates an 'object-based' mechanism in the genesis of line bisection errors and suggests that this mechanism varies in its operation with visual field location. In the second experiment, subjects successively bisected longer line and interval stimuli which were presented either centered on the subjects' midlines or displaced to the right or left. Bisections tended to be placed farther to the left for the left stimuli and farther to the right for the right stimuli, with little or no bias for the centrally located stimuli. Repeated measures with the centrally located stimulus demonstrated strong individual differences in bisection biases. Errors were also found to be correlated for the line-present and line-absent stimuli in both experiments, suggesting the additional contribution of a mechanism that is not object-based.

Why do pitched horizontal lines have such a small effect on visually perceived eye level?

In two experiments, visually perceived eye level (VPEL) was measured while subjects viewed two-dimensional displays that were either upright or pitched 20 degrees top-toward or 20 degrees top-away from them. In Experiment 1, it was demonstrated that binocular exposure to a pair of pitched vertical lines or to a pitched random dot pattern caused a substantial upward VPEL shift for the top-toward pitched array and a similarly large downward shift for the top-away array. On the other hand, the same pitches of a pair of horizontal lines (viewed binocularly or monocularly) produced much smaller VPEL shifts. Because the perceived pitch of the pitched horizontal line display was nearly the same as the perceived pitch of the pitched vertical line and dot array, the relatively small influence of pitched horizontal lines on VPEL cannot be attributed simply to an underestimation of their pitch. In Experiment 2, the effects of pitched vertical lines, dots, and horizontal lines on VPEL were again measured, together with their effects on resting gaze direction (in the vertical dimension). As in Experiment 1, vertical lines and dots caused much larger VPEL shifts than did horizontal lines. The effects of the displays on resting gaze direction were highly similar to their effects on VPEL. These results are consistent with the hypothesis that VPEL shifts caused by pitched visual arrays are due to the direct influence of these arrays on the oculomotor system and are not mediated by perceived pitch.

Effects of alcohol on exogenous precueing of attention.

OBJECTIVE: Transient visual events cause a rapid allocation of attention to the event location. We studied the effect of alcohol on this aspect of attention. METHOD: Subjects responded to targets presented either left or right of fixation and the time between target presentation and response (reaction time: RT) was measured both before and after ingestion of either alcohol or a placebo. Transient cues were presented prior to each target presentation. Cues were, variously, a brightening of either the box in which the target was to occur ("valid"), the box on the opposite side of the display from where the target was to occur ("invalid") or the fixation stimulus ("neutral"). The interval between cue and target presentation (stimulus onset asynchrony: SOA) was variously 50, 100, 150 or 800 msecs. RESULTS: At short SOAs, RT was faster to targets presented following valid cues relative to the other cues. At 800 msecs the opposite pattern was found. Alcohol selectively slowed RT only following neutral or invalid cues at short SOAs. CONCLUSIONS: Alcohol does not disrupt the normal attentional allocation to visual transients. It may delay the subsequent response to events at other locations, however.

Role of feedback in formation of acute tolerance to alcohol.

OBJECTIVE: The contributions of feedback to formation of acute ethanol tolerance were studied during performance of a task that allowed practice in the absence of feedback about performance accuracy. METHOD: The perceptual instability of the seen environment during head movement (apparent concomitant motion, ACM) and the vestibulo-ocular reflex (VOR) were measured before and after alcohol ingestion. In separate conditions, eight (six female) subjects were either deprived or not deprived of normal vision of the laboratory during the portion of the experiment following onset of alcohol ingestion. RESULTS: Alcohol caused ACM in the direction opposite head rotation to increase in both sessions. The degree of ACM increase was greater during sessions in which visual feedback was prevented than in sessions in which subjects could see the surroundings. The increase in ACM was accompanied by a decrease in gain of the VOR which was relatively larger in the no-feedback condition. In addition, ACM returned to normal (pre-alcohol ingestion) values more rapidly during sessions in which subjects received visual feedback. CONCLUSIONS: The results suggest that feedback is an important component in forming acute tolerance to alcohol, independent of task practice.

Dual adaptation of apparent concomitant motion contingent on head rotation frequency.

Perceived movement of a stationary visual stimulus during head motion was measured before and after adaptation intervals during which participants performed voluntary head oscillations while viewing a moving spot. During these intervals, participants viewed the spot stimulus moving alternately in the same direction as the head was moving during either .25- or 2.0-Hz oscillations, and then in the opposite direction as the head at the other of the two frequencies. Postadaptation measures indicated that the visual stimuli were perceived as stationary only if traveling in the same direction as that viewed during adaptation at the same frequency of head motion. Thus, opposite directions of spot motion were perceived as stationary following adaptation depending on head movement frequency. The results provide an example of the ability to establish dual (or "context-specific") adaptations to altered visual-vestibular feedback.

Relative spatial expansion and contraction within the Müller-Lyer and Judd illusions.

The shaft portions of Müller-Lyer (M-L) figures, one-ended M-L figures, Judd figures, and their respective control (tails-up) figures were divided by subjects into eight equal-appearing intervals by means of successive bisections. For most of the control stimuli the length of the left half of the shaft tended to be overestimated relative to the length of the right side. For the tails-out version of the M-L figure, there was relative overestimation of segments of the shaft adjacent to the tails, while for the tails-in version there was relative underestimation of these segments. These results indicate that the distortion of perceived length in the M-L illusion is not distributed evenly along the shaft. For the one-ended M-L figures the apparent overestimations and underestimations extended further along the shaft than for the standard figures. For the Judd figure perceived length varied systematically along the length of the shaft from underestimation near the tails-in end of the figure to overestimation near the tails-out end. These results are contradictory to the hypothesis that the M-L illusion results from inappropriate size scaling produced through the operation of size-constancy mechanisms, since this conjecture would predict uniform expansion or contraction. The results are compared with findings that localization responses are accurate for M-L figures but biased for one-ended M-L figures and Judd figures.

Effects of lorazepam on the distribution of spatial attention.

Reaction time (RT) to stimulus events was assessed for 2 tasks with different spatial attention demands before and after receiving either a placebo or lorazepam (1 mg). In 1 task (onset), 12 participants responded to the onset of 1 of 5 potential dot targets contained within either a small or large area. In the other task (offset), all 5 targets were illuminated and 12 participants responded to the offset of 1 of them. In the onset task, lorazepam slowed RT equally for both the large and small display areas. In the offset task, substantial impairment was found with the large but not the small display area. Results are consistent with the hypothesis that lorazepam interferes with the processes involved in the movement of spatial attention. The possibility that lorazepam selectively impairs the disengage component of attentional movement is discussed.

Adaptation to altered visual-vestibular feedback: mechanisms of maintenance and recovery.

Adaptation of perceived movement during head motion (apparent concomitant motion, ACM) and the subsequent elimination of adaptation were studied in two experiments. During the adaptation phase of both experiments, subjects performed voluntary 1-Hz head oscillations for 6 min while fixating a stimulus moving either in the same (with) direction as or the opposite (against) direction of head movements. In Experiment 1, ACM adaptation was measured following either a 1- or a 4-min delay after the adaptation phase. Results indicated some loss of adaptation during the additional 3-min delay, demonstrating a tendency of the system linking head and image to return to its preadaptation state following removal of an adaptation stimulus. In Experiment 2, subjects viewed a stimulus after adaptation that appeared to move minimally in the same manner as the adaptation stimulus during 3 min of head oscillations. No loss of adaptation was measured in these subjects between the beginning and the end of the 3-min interval. In another condition, subjects viewed a stimulus that appeared to move alternately in the same direction as and in the opposite direction of the adaptation stimulus during a similar 3-min interval following adaptation. ACM adaptation was substantially reduced during this 3-min interval. These results implicate two mechanisms that operate to either maintain or eliminate the short-term adaptation. One is passive and operates in the absence of visual feedback to eliminate the short-term adapted state, and the other responds to postadaptation visual feedback.

An effect of alcohol on the distribution of spatial attention.

OBJECTIVE: Previous research on the effects of alcohol on visual performance led us to the prediction that alcohol should interfere with the distribution of visual spatial attention. This prediction was examined in two experiments that measured the effect of alcohol on reaction time (RT) for tasks that differed in visual spatial attention requirements. METHOD: In the first experiment, 48 adult volunteers (33 female) responded to either the onset or offset of one of five potential targets without alcohol to determine the relative demands on attention of stimulus onset and offset. The spatial extent of the five-target display was also varied. In the second experiment, the effect of alcohol was determined for both the onset and the offset tasks in 12 adult volunteers (nine female). RESULTS: The offset task was found to place greater demands on spatial attention as the increase in display area result in relatively greater increases in RT. Alcohol increased RT in the offset task for the larger, but not the smaller, display, and there were no significant effects of alcohol for the onset task. CONCLUSIONS: The results indicate that alcohol impairs performance on tasks that place greater demands on visual spatial attention and likely disrupts the ability to shift attention from one spatial locus to another during serial search.

Accuracy and adaptation of reaching and pointing in pitched visual environments.

Visually perceived eye level (VPEL) and the ability of subjects to reach with an unseen limb to targets placed at VPEL were measured in a statically pitched visual surround (pitchroom). VPEL was shifted upward and downward by upward and downward room pitch, respectively. Accuracy in reaching to VPEL represented a compromise between VPEL and actual eye level. This indicates that VPEL shifts reflect in part a change in perceived location of objects. When subjects were provided with terminal visual feedback about their reaching, accuracy improved rapidly. Subsequent reaching, with the room vertical, revealed a negative aftereffect (i.e., reaching errors that were opposite those made initially in the pitched room). In a second study, pointing accuracy was assessed for targets located both at VPEL and at other positions. Errors were similar for targets whether located at VPEL or elsewhere. Additionally, pointing responses were restricted to a narrower range than that of the actual target locations. The small size of reaching and pointing errors in both studies suggests that factors other than a change in perceived location are also involved in VPEL shifts.

Is there dissociation of perceptual and motor responses to figural illusions?

Open-loop reaching for locations within figural illusions was measured in three experiments. The experiments differed with respect to whether subjects were provided a visible target toward which to direct their reaching or were required to form a mental representation of the intended target. In the first experiment, subjects' reaching errors for vertices of a Müller-Lyer figure were similar to those for a nonillusory control stimulus. In experiment 2, subjects' errors while reaching to the imaginary bisector of the Judd illusion were consistent with the presence of an illusion of bisector location. However, when a bisector line was added to the Judd figure, reaching errors were similar to those obtained with a control figure. In experiment 3, subjects' open-loop reaching at the perceived midpoint of a triangle was biased toward its illusory perceptual midpoint. When a mark was placed at the midpoint between a vertex and the opposite side, reaching errors were similar to those obtained with a control figure. The results of the experiments indicate that hand-eye coordination is biased in the direction of illusions of bisector location only when no target is present at the intended goal of the reaching response and subjects are required instead to form a mental image of the target. Under these conditions, reaching responses appear to utilize the spatial map of the visual system, and are influenced by figural illusions of bisector location. The present data can be understood without invoking the notion of visual-motor dissociation.

The role of retinal versus perceived size in the effects of pitched displays on visually perceived eye level.

Visually perceived eye level (VPEL) was measured while subjects viewed two vertical lines which were either upright or pitched about the horizontal axis. In separate conditions, the display consisted of a relatively large pair of lines viewed at a distance of 1 m, or a display scaled to one third the dimensions and viewed at a distance of either 1 m or 33.3 cm. The small display viewed at 33.3 cm produced a retinal image the same size as that of the large display at 1 m. Pitch of all three displays top-toward and top-away from the observer caused upward and downward VPEL shifts, respectively. These effects were highly similar for the large display and the small display viewed at 33.3 cm (ie equal retinal size), but were significantly smaller for the small display viewed at 1 m. In a second experiment, perceived size of the three displays was measured and found to be highly accurate. The results of the two experiments indicate that the effect of optical pitch on VPEL depends on the retinal image size of stimuli rather than on perceived size.

The effect of alcohol on the vestibulo-ocular reflex and apparent concomitant motion.

Measures of the vestibulo-ocular reflex (VOR) and apparent concomitant motion (ACM), the apparent motion of stationary visual stimuli during head motion, were obtained during sessions in which subjects consumed either alcoholic or placebo beverages. Both VOR and ACM remained constant throughout the placebo sessions. During sessions in which alcohol was consumed, the gain of the VOR was reduced and there was an increased tendency to see ACM in the direction opposite head motion. The effects of alcohol on ACM were greatest 50 min following cessation of drinking, near the maximum of the blood alcohol concentration (BAC). ACM measures then returned towards baseline, whereas the BAC measures remained elevated. VOR gain alterations paralleled the BAC measures. Therefore, reduction of VOR gain with alcohol produces an increase of ACM, but the ACM changes are relatively transient when compared with the altered VOR gain.

Up-down asymmetry in vertical induced motion.

Induced motion (IM) is the illusory movement of an object in the direction opposite to the real motion of adjacent detail. One theory of IM suggests that it results, in part, from suppression of optokinetic nystagmus (OKN) by fixational (smooth-pursuit) effort. In several studies an asymmetry in human vertical OKN has been reported, with upward optokinetic stimulation eliciting higher OKN gain than downward motion. This provides a test of the nystagmus-suppression theory of IM. If suppression of OKN contributes significantly to IM, upward inducing stimuli should result in a greater magnitude of the illusion than should downward stimulus motion. Additionally, the asymmetry of vertical OKN should become more pronounced at higher stimulus velocities. Therefore, the asymmetry of vertical IM should be greater at higher inducing-stimulus velocities. Twelve subjects viewed a large, random-dot stimulus, which moved either upward or downward at a velocity of 10, 40, or 70 deg s-1. Subjects fixated a horizontally moving laser spot and adjusted a rod to match the apparent slope of the motion path of the spot. IM magnitude was derived from these measures. Mean IM velocity was significantly higher with upward than with downward stimulation, and the difference was maximal at velocities of 40 and 70 deg s-1. The results are discussed within the context of the nystagmus-suppression theory and other theories of IM.

The relationship between vestibulo-ocular reflex plasticity and changes in apparent concomitant motion.

The vestibulo-ocular reflex (VOR) and the apparent motion of a spot stimulus fixated during head movement (apparent concomitant motion, ACM) were measured before and after an adaptation period during which subjects attempted fixation of a stimulus which moved either in the same or opposite direction as head oscillations. Movements of the head were voluntary and paced by a metronome at either 0.5 or 2.0 Hz during the 4 min adaptation period. Pre- and post-adaptation measures of VOR and ACM were obtained for both frequencies of head oscillation. VOR and ACM were altered similarly by the period of exposure to correlated head and stimulus motion. Viewing a stimulus moving in the same direction as head motion resulted in decreased VOR gain and increased ACM in the opposite direction as head motion. Viewing a stimulus moving opposite head motion resulted in increased VOR gain and increased ACM in the same direction as head movement. Differences between pre- and post-measures tended to be maximal at the adaptation frequency, but transferred to a lesser degree to the other frequency. The results indicate that changes in motor and perceptual systems are related, and are consistent with the proposal that VOR gain is a determinant of ACM.