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Efficacy of Traumatic Brain Injury Rehabilitation: Interventions of QEEG-guided Biofeedback, Computers, Strategies, and Medications

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Abstract

The onset of cognitive rehabilitation brought with it a hope for an effective treatment for the traumatic brain injured subject. This paper reviews the empirical reports of changes in cognitive functioning after treatment and compares the relative effectiveness of several treatments including computer interventions, cognitive strategies, EEG biofeedback, and medications. The cognitive functions that are reviewed include auditory memory, attention and problem solving. The significance of the change in cognitive function is assessed in two ways that include effect size and longevity of effect. These analyses complement the previously published meta-reviews by adding these two criteria and include reports of EEG biofeedback, which is shown to be an effective intervention for auditory memory.

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Authors and Affiliations

  1. The Brain Foundation, Ste. 2a, 2509 Park Avenue, South Plainfield, NJ, 07080, USA

    Kirtley E. Thornton & Dennis P. Carmody

  2. Institute for the Study of Child Development, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, NJ, 08903, USA

    Dennis P. Carmody

Authors
  1. Kirtley E. Thornton
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  2. Dennis P. Carmody
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Correspondence to Kirtley E. Thornton.

Appendix A. Calculation of Effect Size

Appendix A. Calculation of Effect Size

Effect size is a way of quantifying the size of the difference between two groups (Coe 2000). It quantifies the effectiveness of a particular intervention relative to some comparison and answers the question of how well does the intervention work. An effect size (ES) of zero means that the mean scores of two groups are identical, while an ES of 1 indicates that the mean scores of one group are superior to a second group by a value of one standard deviation. Some examples of other effect sizes show the overlap in the distributions of scores. An ES of 0.20 indicates that the treatment moved a subject from the 50th percentile to the 58th percentile, while an ES of 0.50 means that the subject is now performing at the 69th percentile, and an ES of 0.80 means that the subject is now performing at the 79th percentile.

Olejnik and Algina (2000) describe the history of methods for calculating effects size. Cohen’s effect size (1969), d, was the first commonly recognized effect size. It represented mean differences in units of common population standard deviation. Glass et al. (1981) proposed a modification of the Cohen d where the common standard deviation was replaced with the standard deviation of the control group. Hedges (1981) suggested that a better estimate of effect size would use the pooled variance and standard deviation rather than the standard deviation of one of the groups. There are also differences in the literature on which estimate of variance to use. Typically the variance of the control group is used, which represents the population. Others argue for a pooled estimate when there is no control group but rather two treatment groups and the population variance is unknown. As indicated by Coe (2000), when using the pooled standard deviation to calculate the effect size, which generally gives a better estimate than the control group SD, it is slightly biased and gives a value slightly larger than the true population value. This bias is corrected using a formula (Hedges and Olkin 1985), p. 80).

While Cohen (1988), p. 25) warned that he arbitrarily chose values to classify the interpretation of size of the effect, many studies continue to interpret an effect size of .2 as a small effect, a .5 as a medium effect, and a .8 is a large effect (Coe 2000). The interpretation is improved by using confidence intervals that provide a range of values around the effect size to determine the likelihood of the effect size occurring due to chance. Greater accuracy of the effect size is more likely when based on a large sample rather than a small sample. If the confidence interval includes the value of zero, then the effect size is statistically equivalent to no effect. If the confidence interval does not include the value of zero, then the effect size is statistically significant.

In the effect size analysis of the interventions for TBI, we included research reports that provided the statistics necessary to obtain an effect size. These statistics included the means and standard deviations of the treatment and control groups. In the studies where there was no control group, then we used the means and standard deviations of the pre-treatment and post-treatment scores of the treatment group.

We provide an example of how we obtained the effect size and confidence intervals for three interventions that addressed memory. Kerner and Acker (1985) treated 12 subjects with TBI using a memory retraining software and showed improved memory scores for the treatment group (M = 34.75, SD = 12.53) compared to 12 subjects in a control group (M = 30.42, SD = 11.41). The pooled standard deviation is 11.98. The effect size, using Hedge’s bias correction for sample size, is 0.35 with a 95% confidence interval of −0.46 to 1.16. Using Cohen’s terms, the effect size of 0.35 is small to moderate. However, the confidence interval includes the value of zero, making the effect size not statistically different from zero. The conclusion, using the effect size and 95% confidence interval, is that the memory retraining software intervention is no different than the control group treatment.

In a second example, Schoenberger et al. (2001) treated 12 TBI subjects with 25 sessions of Flexyx Neurotherapy System. Immediate and delayed memory scores were obtained using the Rey’s Auditory Verbal Learning Test (AVLT). Six subjects were treated first for five to six weeks while six were in a wait-list control group. Then the six subjects in the wait-list group received treatment. We can assess the effect size for the treatment by using pre- and post- treatment scores for the entire group of 12 subjects. There was no significant effect size for immediate memory score. The pre-treatment scores (M = 10.50, SD = 2.11) were no different than the post-treatment scores (M = 10.17, SD = 1.90), ES = − 0.16 with a 95% confidence interval of −0.96 to 0.64. The authors reported a significant effect (p < .10) for treatment with a significant improvement in the delayed memory scores between pre-treatment (M = 9.67, SD = 2.39) and post-treatment scores (M = 11.08, SD = 2.54); however the ES was 0.55 with a 95% confidence interval ranging from −0.26 to 1.37.

In the third example, on data reported in this paper, 19 subjects with TBI were given QEEG treatment. Their pre- and post-treatment scores were compared to a control group of 15 subjects. The TBI subjects improved their scores on paragraph recall from pre-treatment (M = 8.75, SD = 4.51) to post-treatment (M = 24.46, SD = 7.25), in addition the ES was 2.61 with a 95% confidence interval ranging from 1.87 to 3.47. The confidence interval does not include the value of zero. Clearly the treatment was effective.

Appendix B Sample sizes and durations of interventions

Intervention

Reference

Number subjects

Number sessions

Computer

Kerner and Acker (1985)

12

12

Gray and Robertson (1992)

31

17.5

Ruff et al. (1994)

15

20

Park et al. 1999

23

20

Niemann et al 1990

29

36

Strategies

Ryan and Ruff, (1988)

20

132

Freeman et al. (1992)

6

15

Cicerone et al. (1996)

20

6 months

Novak et al. 1996

22

20

Milders et al. (1998)

13

12

Fasotti et al. (2000)

12

7.4

Laatsch and Stress (2000)

16

Mean of 32

Quemada et al. (2003)

12

120

Kaschel et al. (2002)

12

30

Stephens (2006)

10

20

Salazar et al. (2000)

120

67 in hospital treatment

53 home treatment

32

Medications

McDowell et al. (1998)

24

Subjects tested twice––with placebo and with Bromocriptine

Whyte et al. (2004)

19 Ss completed some tasks

Subjects tested twice––with placebo and with Methylphenidate

 

9 Ss completed all tasks

 

León-Carrión et al. (2000)

10

Cytidinediphosphocholine for 3 months

Fann et al. (2001)

15

Sertraline for 8 weeks

Eyes Closed QEEG

Tinius and Tinius (2000)

16

20

Standard QEEG

Stephens (2006)

6

20

Modified QEEG

Keller (2001)

12

10

Schoenberger et al. (2001)

12

25

Activation QEEG

Thornton and Carmody (2005)

7

80

Thornton and Carmody, this article, paragraph recall

19

54

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Thornton, K.E., Carmody, D.P. Efficacy of Traumatic Brain Injury Rehabilitation: Interventions of QEEG-guided Biofeedback, Computers, Strategies, and Medications. Appl Psychophysiol Biofeedback 33, 101–124 (2008). https://doi.org/10.1007/s10484-008-9056-z

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