Balance was tested with a dual-plate force platform during quiet standing as well as during weight shifting using visual feedback. Whcrcas quiet standing is ...
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Identification of Static and Dynamic Postural Instability Following Traumatic Brain Injury Alexander C. H. Geurts, MD, PhD, Gerardus M. Ribbers, MD, Johannes A. Knoop, MS, Jacques van Limbeek, MD, PhD ABSTRACT. Geurts ACH, Ribbers GM, Knoop JA. Limbeek J van. Identification of static and dynamic postural instability following traumatic brain injury. Arch Phys Med Rehabil 1096; 77535)~44. Objective: Quantitative evaluation of static and dynamic aspccts of postural instability as a long-term consequence of traumatic brain injury (TBI). Design: Experimental two-group design. Setting: Outpatient rehabilitation department. Patients and Other Participants: From a consecutive sample of TBI patients at least 6 months after trauma, 20 subjects were selected who complained of reduced gross motor skills but showed no sensorimotor impairments in a standard neurological examination (1 I men, 9 women; mean age, 36.2 2 10.7 years). Thirteen patients had sustained mild, 2 moderate, and 5 severe TBI. Twenty healthy controls were matched for age and gender. Intervention: None. Main Outcome Measures: A dual-plate force platform recorded the amplitude and velocity of the center-of-pressure fluctuations in the anteroposterior (AP) and lateral (LAT) sway directions during quiet standing. Also. the speed and fluency of weight shifting using visual feedback was registered. Both balance tasks were combined with an arithmetic task, whereas quiet standing was also tested with visual deprivation. Results: Compared to controls, TBI patients showed an increase of over 50% in AP and LAT sway, and a weight-shifting speed 20% lower. Dual-task interference was never significant. Visual deprivation was most detrimental for the TBI patients, particularly for LAT sway control. Conclusion: A long-term overall reduction in both static and dynamic control of posture can bc present after TBI, even in patients without clear neurological deficits. Force-plate recordings can identify such (latent) balance problems. Visual deprivation during quiet standing appears a simple, sensitive test for postural instability related to sensory integration deficits. 0 1996 by the Americun Congress of Rehabilitation Medicine ond the American Academy of Physical Medicine and Rehabilit&ion
T
RAUMATIC BRAIN INJURY (TBI) is an important cause of disability at all ages. Unlike the severely head-injured, those who have sustained mild TBI often receive little attention Front the t~panmrnt of Kesearch and Developmenr (Dr\. Geurts. Rihhcrs. Kncwp. and van I.imheek). Ihe Depanmenl of Kehahilitation Medune (Drs. (;uns. Krhhcrs. and van Limhcek). and the Department of Clinical Ncuropcycholq!y (Dr. Knoop), Sinr Maaflensklinirk. NiJmegen. The Nelherlands. Suhmrtted fur publication April 24. IYYS. Accepted in revised form January I Y. IYY6 I)r\. Cicurl\ and Rihhers are currently afliliated with Rchahilrlation Cenler Kqndam. Kottrrdam. The Nrlherlanda. No c~~mmsrcial pariy having a dwxt linancial mtercs~ in the results of the rexarch aupponrng Ihir ariicle has or will confer a lxnefir upon [he authors or qx~n any organrzalmn wrth which the authors are aswcraled. Keprmr requesr\ 10 Dr. Alexander C. H. Gcurts. Kchabilitation Cemer Rijndam. IT) Rex 17 IX I. WOI KD Rorterdam. l’hc Netherlands. 1’ IYYh hy [he American Congress 01 Rehahililarion Medrcine and the American Academy 01 Physical Medicrne and Kehahilitation OMW)3-YYY~/‘~h~707-3J’~3%3.00/0
to their impairments and disabilities. There is growing evidence, however, that even years after mild TBI, cognitive, affective, and behavioral functions may bc altered, leading to disabilities at work, school, or in social relations.‘.’ In this study, the cmphasis is on sensorimotor impairments adding to the aftermath of TBI, in particular loss of standing balance. Indeed, postural instability and impaired gross-motor skills are common complaints after TBI.‘-5 Earlier studies have shown that an able-bodied and TBI population can be discriminated by using quantitative body sway measures obtained from force-platform recordings.5.h Such measures are sufficiently reliable and valid to detect both interindividual and intraindividual differences in balance performance.‘.’ A relation between the severity of head trauma and body sway has been suggested, which becomes increasingly clear under complex conditions (ie, visual deprivation or conllict, impaired somatesthesis).‘.‘.“~‘~’ Postural problems seem to he most evident in the cast of deep parenchymal brain damage (eg, to the basal ganglia, brain stem or cerebellum)‘.h or focal cerebral lesions (eg, hemiparesis).5 This study differs from previous work because it focuses on TBI patients who persistently complain of impaired gross-motor skills several months or years after their head trauma, but who do not show sensorimotor deficits in a standard neurological examination. The majority of these patients sustained mild TBI as assessed by the initial Glasgow Coma Scale.“’ The main questions are: (1) Can postural instability be objectilicd in this subgroup of TBI patients by using quantitative force-platform recordings, and (2) if so, what tasks, conditions, and parameters are most sensitive? Whereas severe postural dyscontrol will not easily bc overlooked when neurological deficits arc evident, postural instability in patients without clear sensorimotor impairments will often remain clinically unnoticed or doubted. Indeed, there is a large observer variation in the clinical assessment of standing balance even among experienced raters.” Balance was tested with a dual-plate force platform during quiet standing as well as during weight shifting using visual feedback. Whcrcas quiet standing is normally a highly automatic activity, the latter task requires attention-invested control. Because many TBI patients experience postural instability during complex integrative actions, both tasks were combined with a concurrent arithmetic task to obtain insight into the automaticity of postural control. The idea behind such a dual-task procedure has been extensively discussed elsewhere.” ” Quiet standing was also tested with visual deprivation to detect sensory integration deficits.“ 6x We hypothesized that if postural instability could be identified in comparison with controls, it would be most apparent in the dual-task and visual-deprivation conditions. METHODS Subjects During a period of one and a half years, posturographic measurements were recorded from all consecutive subjects who visited a specialized outpatient unit of a rehabilitation center Arch
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Rehabil
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POSTURAL
Table Pt. 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20
Age o’r)
SW
GCS*
38 46 45 45 38 46 45 23 36 25 28 35 44 35 31 24 15 22 50 53
F F M F M M F F M F M M M F M M M M F F
14 15 14 15 15 14 15 14 14 14 14 14 14 13 13
Lowest Glasgow Coma Scale” ’ Time since head trauma. * For medical-legal purpose. l
score
after
INSTABILITY
1: Characteristics
of Traumatic
CT/Ml71
Severity
Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Positive Positive Negative Negative Positive Positive Positive
Phys Med Rehabil
Vol77,
July
1996
Brain
TBI,
Geurts
Injury
Group
Time’ imo)
Mild Mild Mild Mild Mild Mild Mild Mild Mild Mild Mild Mild Mild Moderate Moderate Severe Severe Severe Severe Severe
6 72 9 24 12 33 14 9 17 41 15 24 10 36 17 26 50 9 112 36
(N = 201 CalJS3 Traffic Fall Violence Traffic Traffic Fall Fall Traffic Fall Traffic Traffic Traffic Traffic Traffic Traffic Traffic Traffic Traffic Fall Traffic
accident
accident accident
accident accident accident accident accident accident accident accident accident accident accident
Reason for Consult Medical Medical Vocational Medical Vocational Medical Medical Medical Vocational Medical Vocational Disability Medical Medical Medical Medical Disability Vocational Vocational Medical
care care assessment care assessment care care care assessment care assessment assessment’ care care care care assessment’ assessment assessment care
hospitalization.
for advice regarding long-term TBI-related disabilities. The patients’ reasons for seeking clinical consultation are listed in table 1. Each subject had sustained a direct traumatic impact at the head and had suffered a period of impaired consciousness and/or post-traumatic amnesia after the injury. All subjects had been hospitalized for at least 24 hours. The primary diagnosis obtained from the neurological records was always TBI. The cause of injury as well as the time period elapsed since the head trauma are also listed in table 1. Only TBI patients who (among other symptoms) complained of postural instability or gross-motor “clumsiness” since their head trauma were included. The following exclusion criteria were applied: (1) clinically abnormal muscle strength, muscle tone, sensation, coordination, balance (two-legged standing, feet together, with eyes opened and closed), and gait (including heelto-toe walking), as well as visual, vestibular, or oculomotor impairments detectable by standard neurological examination,” (2) vertigo (defined as paroxysmal rotational dizziness), (3) preexistent neurological or psychiatric disease, (4) a history of skull fractures, (5) established cervical injury, (6) musculoskeletal abnormalities, and (7) medication affecting balance. Electronystagmography or caloric vestibular tests were not performed. Thus, 20 patients (11 men, 9 women) were included. The mean age at examination was 36.2 2 10.7 (range 15 to 53) years. The mean time since the trauma was 28.6 t- 25.7 (range 6 to 112) months. The lowest Glasgow Coma Scale (GCS) score obtained afrer hospitalization ranged from 3 to 15 (mean, 12). Focal abnormalities on initial computed tomography (CT) or magnetic resonance imaging (MRI) were found in 5 subjects. Thirteen patients had sustained “mild” (GCS range 13 to 15) and 5 “severe” (GCS range 3 to 8) TBI.lh Two patients with an initial GCS score of 13, both of whom did not achieve a score of 15 within 3 days and had CT or MRI abnormalities, were classified as “moderate” TBI (table 1). The 4 patients with a GCS score of 15 either had suffered no impaired consciousness but only post-traumatic amnesia or their consciousness had normalized between the time of injury and time of admission. The control group consisted of 20 healthy volunteers who were matched for age (mean age 36.1 -C 10.4 years) and gender. They were recruited from various socioeconomic layers of personnel of a rehabilitation center.
Arch
AFTER
Equipment Postural control was measured with a firmly secured force platform consisting of two aluminum plates, each placed on three force transducers” (hysteresis and nonlinearity of
