Relationship Between Balance and Cognition Following Traumatic Brain Injury
James Mullin, Ph.D.
David Ripley, MD, MS,
Jose Vargas, MD
Robert Godsall, Ph.D.
Sary Korrick, PT
Download Article

Dr. James Mullin, Ph.D. is a clinical neuropsychologist at the Rehabilitation Institute at Northeast Georgia Medical Center. He is a graduate of the clinical psychology program at Central Michigan University, and completed his internship in neuropsychology at Henry Ford Hospital in Detroit, MI. He completed a two-year post doctoral fellowship at Shepherd Center and Emory University Center for Rehabilitation Medicine. Clinical interests include geriatrics, rehabilitation, and psychoeducational intervention with families of brain injury and stroke survivors.

Dr. David Ripley, MD, MS joined the staff of The Shepherd Center in August of 2001, and assumed responsibility as Medical Director of Brain Injury Research and Medical Director of Post-Acute Services. Prior to joining Shepherd, he held a position on faculty of Emory University School of Medicine with a primary appointment in the Department of Rehabilitation Medicine, where he served as Medical Director of Brain Injury Services. Dr. Ripley is a Fellow of the American Academy of Physical Medicine and Rehabilitation. He is Board-Certified in Physical Medicine & Rehabilitation, and licensed to practice medicine in the states of Georgia, Virginia, and Tennessee. He completed medical school and internship at the Medical College of Georgia, and he completed his residency in Physical Medicine & Rehabilitation at Medical College of Virginia Hospital, serving as Chief Resident his final year. He was awarded the Herman J. Flax Education and Leadership award at MCV. Prior to entering medical school, Dr. Ripley received a Master’s degree in Vocational Rehabilitation Counseling from Georgia State University, and worked as a Vocational Rehabilitation Counselor, and he retains Certification as a Rehabilitation Counselor (CRC). He was recently given an appointment as Adjunct Professor in the Department of Counseling and Psychological Services at Georgia State University. His current practice at the Shepherd Center involves providing inpatient and outpatient services to individuals with neurological impairment including brain injury and spinal cord injury, and providing medical oversight and direction of the Shepherd Pathways, the Rehabilitation Day program for individuals with acquired brain injury.

Sary Korrick, PT is a physical therapist at Shepherd Pathways, a post-acute facility specializing in brain injury in Decatur, Georgia. Ms. Korrick is a 1981 graduate of the Ithaca College physical therapy program. She has worked at Shepherd Pathways since it began 5 years ago. She has her competency in vestibular therapy.

Jennifer Coker, MPH is Research Coordinator for the Crawford Research Institute at Shepherd Center. She is currently involved in several research projects at the Shepherd Center, including the Rehabilitation Research Engineering Center (RERC) on Wireless Technologies as well as the RERC on Worksite Accommodations. She was previously Project Coordinator for the Georgia Model Brain Injury System as well as Research Specialist for the Georgia Regional Model Spinal Cord Injury Care System, where she coordinated data collection for several collaborative and site grant projects. Ms. Coker received her MPH in Behavioral Sciences from the Rollins School of Public Health at Emory University in May 2001. She has made over 20 presentations at professional conferences, and has served as a co-author on six published articles.

ABSTRACT

Balance disturbance may affect as many as 70% of people following TBI. Anecdotal evidence suggests that neurocognitive impairment and balance disturbance are both related to severity of outcome, and therefore, should be related to each other. The resultant increased risk for falls can have an impact on a patient’s level of dependency, affecting the amount and type of supervision and assistance that a patient will require. In a patient with decreased insight and impulsivity, the risk for falls can be of paramount concern, and the need for increased supervision is likely to result in considerable stress on the family system. Balance disturbance following closed head injury, as it relates to the risk for falls, is therefore an important component of a clinical assessment. A objective, systematic investigation of balance disturbance is rarely done in the clinical setting, but such an evaluation can provide useful information for making recommendations and providing guidance to family members upon discharge. Our study examined the relationship between balance disturbance, as measured by performance on the Neurocom Balance Master, and conventional neuropsychological measures of attention, memory, language, motor skills, and executive functions. Interestingly, balance variables demonstrated few significant correlations with neuropsychological test variables. This suggests that balance and neurocognitive impairment are separate constructs that need to be addressed individually. A discussion of the implications for assessment, treatment, and family education is presented.

INTRODUCTION

The physical, cognitive, and behavioral changes which occur following a severe traumatic brain injury can result in a significant impact on family functioning (Serio, Kreutzer, & Gervasio, 1995; MacFarlane, 1999). Because the family members often assume the role of caregiver when a patient does not make a complete return to independence, family adjustment can have a major impact on the quality of life of the patient. Family adjustment has been shown to correlate with length and degree of recovery (Serio, et al., 1995), highlighting the need to identify the factors that contribute to family outcome following brain injury.

Although much research has been conducted regarding the effects of neurocognitive and neurobehavioral symptoms on family functioning following TBI, other patient characteristics including dependency and physical limitations have not been adequately addressed. Physical limitations are likely to result in increased caregiver burden due to the increased physical dependence of their loved one (Kosciulek & Lustig, 1998). Balance disturbance and the resultant increased risk for falls are specific factors that have an impact on a patient’s level of dependency, affecting the amount and type of supervision and assistance that a family member will require in order to safely complete activities of daily living. When a patient also presents with neurobehavioral issues such as decreased insight and impulsivity, the risk for falls can be of paramount concern, and can result in considerable stress on the family system.

Due to the potential impact of balance disturbance on a patient’s level of dependence, balance has always been an important component of many rehabilitation programs. However, there has been an increased effort in recent literature to examine and quantify the relationship between balance (sitting or standing) and rehabilitation outcomes. Many of these studies have been based on earlier stroke models that suggested balance as a predictor of level of independence up to five years after discharge. Juneja and associates (1995) examined the relationship of objectively rated balance scores with rehabilitation outcomes, including length of rehabilitation stay and gain in FIM scores. Their findings indicated that balance scores on admission had a moderate to high correlation with the total FIM score and length of rehabilitation stay. More specifically, the ability to sit unsupported accounted for 27 percent of the variance in length of stay when demographic factors were controlled. More recently, Black et al (2000), hypothesized that sitting balance upon initial admission to the inpatient rehabilitation unit would be a predictor of need for assistance at discharge. Their results suggested that the degree of sitting balance dysfunction is a significant predictor of mobility independence upon discharge from rehabilitation, when age or severity of injury are controlled. Balance has also been shown to be related to severity of injury. Greenwald et al. (2001) examined the relationship of balance ratings on admission to demographics, measures of injury severity, and neuroradiological findings. Patients with greater length of coma and longer duration of PTA were more likely to exhibit abnormal sitting balance. In addition, those patients with abnormal pupillary responses were also more likely to be grossly impaired on sitting balance.

Despite the evidence of a significant relationship between balance deficits and rehabilitation outcomes following TBI, few studies have utilized a comprehensive or objective measurement of balance. The Neurocom Balance Master (Neurocom International, 1999) attempts to provide a mulitfactorial, integrated assessment of the inner ear, the visual pathway, proprioception, the cerebellum, and the motor system components of balance. The system provides a standardized, computer-based measurement that measures the patient’s response to the microsecond. The level of accuracy provided by the Balance Master theoretically allows for a more objective and detailed measurement of balance disturbance following TBI. Therefore, the system may have the potential to add to our understanding of the relationship between balance and TBI outcome.

Neuropsychological assessment also provides an objective, comprehensive assessment of neurocognitive impairment following TBI. Research has demonstrated that both balance disturbance and neuropsychological variables are related to functional outcome following traumatic brain injury (Ryan et al., 1992). Therefore, it is hypothesized that neurocognitive impairment and balance dysfunction should be significantly correlated. To our knowledge, no study to date has examined the relationship between an objective computer-based measure of balance disturbance and neuropsychological test performance. Our study examined the utility of the Neurocom Balance Master in examining balance disturbance following closed head injury, and examined the relationship between balance disturbance and conventional neuropsychological measures.

SUBJECTS/MEASURES

The subjects consisted of 45 patients who were admitted for post-acute rehabilitation services at an outpatient day program in metropolitan Atlanta, GA. Admission to the program required that patients participate in at least three hours of therapy per day, be medically stable, and have no severe neurobehavioral problems that would jeopardize the safety of other patients or staff. The subject pool consisted of patients who had sustained traumatic brain injuries, the majority through motor vehicle accidents. All TBI patients were classified with severe injuries based on initial Glasgow Coma Scale score and/or length of coma. The subjects ranged in age from 19 to 56, with a mean age of 32.9 years. The average education of the sample was 12.97 years.

During their course of rehabilitation, the subjects were administered a neuropsychological test battery as part of an interdisciplinary team evaluation. Test batteries were completed 3 weeks to 2 months following the date of injury, with the criteria for testing being an absence of post-traumatic confusion. The measures consisted of the following: Wechsler Memory Scale - Revised (Logical Memory I and II, Visual Reproduction I and II), Digit Span, Finger Tapping, Controlled Oral Word Association Test, Block Design, Symbol Digit Modalities Test, Trail Making Test, and Block Design. Other measures were administered at the time of evaluation, but were not included in the present study. All measures were administered by
a trained, master’s level psychometrist under supervision of a staff neuropsychologist.

At the onset of their outpatient rehabilitation, the subjects’ balance was assessed using the Neurocom Balance Master by a trained physical therapist. The computerized system consists of a force plate on which the client can sit or stand. The platform measures the client’s center of gravity, and the ability of the individual to shift their weight performing various tasks. Through computer measurement, an objective assessment of the patient’s
functional ability is completed. The system provides objective data regarding how well the client uses his sensory systems to maintain his balance (visual, vestibular and somatosensory) as well as what muscle strategy the client is using for the balance task.

The Balance Master is an instrument that uses computer-based technology developed for NASA to assess balance. The system can be used to assess balance deficits, improvement over time, and can also indirectly address stretching, range of motion, and muscle strengthening issues. The therapist can use the balance master to specifically target a client’s area of weakness and design a specific plan of treatment suited for that individual. The system can then provide the client with a variety of situations that challenge their balance. The system has the capacity to assess and give the client feedback including the performance of functional activities such as walking, squatting, turning, and stepping up and over objects. The visual and or auditory feedback helps the client make adjustment in their responses to help them build physical stability, endurance and confidence.

One of the indices that is calculated from the Balance Master make up the Sensory Organization Test. During the assessment, the somatosensory and visual inputs are systematically altered so that inaccurate information is delivered to the subject’s eyes, feet, and joints. Specifically, the sway plate, visual surround, or both are “sway referenced”and the subjects responses are recorded. The score is derived from a comparison of the subject’s sway to a theoretical sway limit of 12.5 degrees. A patient swaying to the limits of stability will receive a lower score, while a subject with no sway will receive a score closer to 100.

The Balance Master System also calculates a Reaction Time index that measures the subject’s response time to the movement of the sway plate. From the patient’s response, the Endpoint Excursion (EPE) and Maximum Excursion (MXE) scores are calculated to measure the endpoint of the subject’s sway. On the two indices, a higher score means that the subjects demonstrated greater sway, indicating poorer balance performance. Greater details of the calculation of the index scores can be found in the Neurocom Balance Master manual.

RESULTS

Table 1 summarizes the mean performance of the patients on the Balance Master variables
that were included in the current study. On the Sensory Organization Test, the subjects had a broad range of performance (38 to 91 out of 100) with a mean performance of 65.23
(S.D. = 14.90). The mean score of the subject sample falls within the impaired range according to the normative manual. The mean Reaction Time was .89 seconds (range - .50 to 1.27; S.D. = .27), which also falls within the impaired range. The mean Endpoint Excursion score was 59.29 (S.D. = 15.97), with a wide range of performance from an index of 30 to 86. The Maximum Excursion score also demonstrated considerable variability, ranging from 37 to 107 (Mean = 72.19; S.D. = 17.44).

The means and standard deviations from the neuropsychological test performance of the subjects were calculated and are presented in Table 2. Despite the homogeneity of the patient population in terms of severity of injury, the subjects demonstrated a wide range of impairment levels on the neuropsychological measures. Tests of sensorimotor functioning and processing speed, including finger tapping, COWAT, Symbol Digit Modalities Test, and Trails were most consistently within the impaired range.

Pearson product-moment correlations were calculated to examine the relationship between the neuropsychological and balance variables. A correlation matrix can be found in Table 3. As expected, many of the neuropsychological measures demonstrated significant intercorrelations. However, in examining the relationship between the neuropsychological variables and the scores from the Balance Master, few significant correlations were documented. The Reaction Time score from the Balance Master correlated positively only with the COWAT. The End-Point Excursion and Maximum Excursion scores were highly intercorrelated (.878). The EPE score was also positively correlated with Visual Reproduction I and II (.640 and .486 respectively), and significant correlations were also documented between the MXE score and Visual Reproduction I and II (.550 and .370 respectively). No other significant correlations were found between balance and neuropsychological variables.

DISCUSSION

The present study was designed to collect pilot data on the utility of the Neurocom Balance Master as applied to a patient population of individuals who have sustained severe traumatic brain injuries. Although most of our subjects performed within the impaired range on the measures generated by the Balance Master, a wide range of overall performance was noted on each test. Outcome data was not collected for this particular study, but the variability in performance among a relatively homogeneous sample suggests that the Balance Master may be useful as a more finely graded predictor of length of rehabilitation, psychosocial, and vocational outcome. The measure may also prove useful as a means to provide family members with more specific and individualized feedback regarding their loved one’s need for assistance with ambulation and mobility in a variety of settings.

The study also examined the relationship between neuropsychological test variables and balance variables, which are both thought to be important predictors of outcome. Interestingly, very few significant correlations were found between the two modalities. Most surprising is the lack of relationship between the balance variables and the neuropsychological measures with a major motor or sensorimotor component, such as Finger Tapping, Trails, and Symbol Digit Modalities. The only consistent correlation between the two modalities was found between the EPE/MXE scores and WMS-R Visual Reproduction. An explanation for this significant correlation is not readily apparent, especially in light of the absence of correlations between balance performance and other motor tasks. Type I error is one possible explanation, but the coefficients are sufficiently high to suggest that the findings may be replicable. It is therefore possible that the Visual Reproduction subtests tap into a constellation of fine motor skills, motor speed and visual perception that share a common factor with the capacity to adjust one’s balance in a complex environment.

The fact that only one significant relationship was found raises several questions. One possible explanation is that balance and neuropsychological measures reflect separate or heterogeneous constructs. In fact, not all of the data in the literature have demonstrated a consistent relationship between balance and outcome following TBI. A study by Wade et al. (1997) found no significant correlations between changes in sway indices and functional assessment. Specifically, there was no relationship between improvements in standing balance and the patient's actual ability to walk. The authors concluded that different mechanisms may underlie postural sway as measured by conventional instruments and actual walking parameters in everyday life. Juneja et al. (1998) also found no relationship between balance assessment and gains in FIM scores over the course of inpatient rehabilitation.

Geurts and colleagues (1996) also suggested that neurological deficits and balance disturbance may not be directly related. The authors conducted a study of patients who complained of impaired gross motor skills several years after head trauma, but who did not have sensory motor deficits on a neurological examination. Their results demonstrated that long-term reduction in postural control can be present after traumatic brain injury, even in patients without clearly defined neurological deficits. Greenwald et al. (2001) also documented that only 30.4 percent of those patients with a length of stay longer than three weeks actually demonstrated impaired sitting balance. These results suggest a significant variability in balance disturbance following TBI, which may account for a lack of correlation. In contrast, neuropsychological impairment is almost universal following moderate to severe traumatic brain injury, especially within the first six months to one year following injury.

Another explanation for the disparity of findings is the heterogeneous etiological factors that result in balance disturbance following TBI. Balance dysfunction can result from a disruption of one of several systems, including the inner ear, the visual pathways, proprioception, the cerebellum, and the motor system (Black et al., 2000). Others have suggested that balance disturbance after TBI is diffuse in nature, resulting in a decreased speed of processing of balance related information secondary to “slowness of subcortical activity and spatiotemporal disruption of postural responses” (Geurts et al., 1996). Disruption of these systems result in difficulties in the timing and activation of muscle contractions, which in turn affect standing balance (Wade et al., 1997). In addition, the generalized muscle weakness resulting from traumatic brain injury can result in disruption of balance. Such a wide range of etiological factors may make it difficult to establish a clear relationship with neurocognitive factors.

In addition, the results may suggest that neuropsychological tests that are commonly used in the inpatient rehabilitation setting may not thoroughly examine the total extent of motor impairments that may be present following traumatic brain injury. Specifically, neuropsychologists may not adequately assess sensorimotor integration or vestibular functions seen in real-world balance disturbance. Black et al. (2000) also suggest that balance difficulties may serve as a moderator variable, and may depend on a number of factors not measured by conventional neuropsychological tests. Lastly, homogeneity of subjects and limited sample size may have also impacted the results of this study.

It has been estimated that as many as 70% of individuals that suffer a TBI will have some degree of balance impairment (Black et al., 2000). An objective, systematic investigation of balance disturbance is rarely done in the clinical setting, but an evaluation as such can provide useful information for making recommendations and providing needed guidance to family members on discharge. In a review of the literature regarding the impact of traumatic brain injury on the family, Perlesz, Kinsella, & Crowe (1999) documented significant increases in marital discord, anxiety, and depression in the months following an injury. Family characteristics have been shown to play an important role, especially the perception of the “burden” placed on them in caring for their loved one. Patient characteristics have also been documented as a predictor of family outcome (Serio, et al., 1995). An increased risk for falls places an extraordinary amount of pressure on the family unit to supervise and to safeguard against possible injury in the brain injured patient. The financial burden of providing a safe environment only adds to the stress that a family must deal with months after such a life-altering event. More research is clearly needed to examine the relationship between balance, neurocognitive impairment, and functional outcome in order to provide better information and support for family members as they deal with the role changes that occur following severe TBI.

REFERENCES

Black, K., Zafonte, R. Millis, S., Desantis, N., Harrison-Felix, C., Wood, D., and Mann, N. (2000). Sitting Balance following brain injury: does it predict outcome? Brain Injury, 14(2), 141-152.

Greewald, B.D., Cifu, D.X., Marwitz, J.H., Enders, L.J., Brown, A.W., Englander, J.S., & Zafonte, R.D. (2001). Factors associated with balance deficits on admission to rehabilitation after traumatic brain injury: A multicenter analysis. Journal of Head Trauma Rehabilitation, 16(3), 238-252.

Geurts, A.C.H., Ribbers, G.M, Knoop, J.A., & van Limbeek, J. (1996). Identificantion of static and dynamic postural instability following traumatic brain injury. Archives of Physical Medicine and Rehabilitation, 77, 639-644.

Juneja, G., Czyrny, J.J., & Linn, R.T. (1998). Admission balance and outcomes of patients admitted for acute inpatient rehabilitation. Journal of Physical Medicine and Rehabilitation, 77, 388-393.

Kosciulek, J.F. & Lustig, D.C. (1998). Predicting family adaptation for brain injury related family stress. Journal of Applied Rehabilitation Counseling, 29(1), 8-12.

MacFarlane, M.M. (1999). Treating brain-injured clients and their families. Family Therapy, 26(1), 13-29.

Perlesz, A., Kinsella, G., & Crowe, S. (1999). Impact of traumatic brain injury on the family: A critical review. Rehabilitation Psychology, 44(1), 6-35.

Ryan, T.V, Sautter, S.W., Capps, C.F., Meneese, W., & Barth, J.T. (1992). Utilizing neuropsychological measures to predict vocational outcome in a head trauma population. Brain Injury, 6(2), 175-182.

Serio, C.D., Kreutzer, J.S., & Gervasio, A.H. (1995). Predicting family needs after brain injury: Implications for rehabilitation. Journal of Head Trauma Rehabilitation, 10(2), 32-45.

Wade, L.D., Canning, C.G., Fowler, V., Felmingham, K.L., & Baguley, I.J. (1997). Changes in postural sway and performance of functional tasks during rehabilitation after traumatic brain injury. Archives of Physical Medicine and Rehabilitation, 78, 1107-1111.

..............................

Premier Outlook is a publication of ResCare Premier. The views and opinions expressed in this publication, outside of the editorial and the About us…. sections, are not necessarily the views and opinions of the publisher and staff of Premier Outlook. The materials presented herein are a service and for information purposes only. We have not screened each individual or organization that appears in this publication. The appearance of an individual or organization in this publication is not intended as an endorsement. We urge all readers of this publication to conduct their own investigation of the products and services identified herein. Premier Outlook reserves the right to refuse or edit articles and publications submitted for consideration. If you would like to comment on our publication, inform us of mistakes or dead links, or suggest relevant links or topics, we would be pleased to hear from you at: editor@premieroutlook.com.

Permission to duplicate, reprint, or electronically reproduce any document in part or in its entirety may be obtained by written consent from the editors.

Copyright © 2002 Premier Outlook. All rights reserved