Auditory and Cognitive Factors Associated with Speech-in-Noise Complaints following Mild Traumatic Brain Injury

Abstract

Background: Auditory complaints following mild traumatic brain injury (MTBI) are common, but few studies have addressed the role of auditory temporal processing in speech recognition complaints.

Purpose: In this study, deficits understanding speech in a background of speech noise following MTBI were evaluated with the goal of comparing the relative contributions of auditory and nonauditory factors.

Research design: A matched-groups design was used in which a group of listeners with a history of MTBI were compared to a group matched in age and pure-tone thresholds, as well as a control group of young listeners with normal hearing (YNH).

Study sample: Of the 33 listeners who participated in the study, 13 were included in the MTBI group (mean age = 46.7 yr), 11 in the Matched group (mean age = 49 yr), and 9 in the YNH group (mean age = 20.8 yr).

Data collection and analysis: Speech-in-noise deficits were evaluated using subjective measures as well as monaural word (Words-in-Noise test) and sentence (Quick Speech-in-Noise test) tasks, and a binaural spatial release task. Performance on these measures was compared to psychophysical tasks that evaluate monaural and binaural temporal fine-structure tasks and spectral resolution. Cognitive measures of attention, processing speed, and working memory were evaluated as possible causes of differences between MTBI and Matched groups that might contribute to speech-in-noise perception deficits.

Results: A high proportion of listeners in the MTBI group reported difficulty understanding speech in noise (84%) compared to the Matched group (9.1%), and listeners who reported difficulty were more likely to have abnormal results on objective measures of speech in noise. No significant group differences were found between the MTBI and Matched listeners on any of the measures reported, but the number of abnormal tests differed across groups. Regression analysis revealed that a combination of auditory and auditory processing factors contributed to monaural speech-in-noise scores, but the benefit of spatial separation was related to a combination of working memory and peripheral auditory factors across all listeners in the study.

Conclusions: The results of this study are consistent with previous findings that a subset of listeners with MTBI has objective auditory deficits. Speech-in-noise performance was related to a combination of auditory and nonauditory factors, confirming the important role of audiology in MTBI rehabilitation. Further research is needed to evaluate the prevalence and causal relationship of auditory deficits following MTBI.

Figure 1

Group mean audiograms for the young, matched, and MTBI groups. The young group is represented by the dotted line, the matched group is represented by the dashed line, and the MTBI group is represented by the solid line. The standard deviation around each point is marked with a vertical bar.

Figure 2

Individual thresholds for the speech-in-noise tests for young, matched, and MTBI group listeners. Listeners in each group are represented by a unique symbol. For the Match and MTBI groups, symbols correspond to those in Table 1. Horizontal bars represent group means and error bars represent the standard deviation. The horizontal dashed line represents the cutoff above which speech recognition in noise is considered abnormal in each test.

Figure 3

Individual results for the SRM task presented in collocated (left panel) and spatially separated (center panel) noise conditions. Each point represents the dB target to masker ratio at the listeners’ estimated 50% threshold. The benefit of spatial separation in dB is shown in the right panel. Listeners in each group are represented by a unique symbol, and the symbols correspond to those used in Table 1. Group mean scores are shown with horizontal bars and vertical bars show the SD. The dashed line represents the cutoff for abnormal performance as defined by two SD worse than the YNH mean.

Figure 4

Individual results of the four psychoacoustic tests for each group. Listeners are represented by a different symbol in each group and the symbols correspond to those used in Table 1. Group mean and SD are shown with horizontal bars. Horizontal dashed line represents normal limits as defined by 2 SD worse than YNH mean thresholds.

Figure 5

The proportion of listeners who performed in the abnormal range for a given number of tests. Abnormal was defined by clinical normative data for the QuickSIN and WIN tests, and two SD worse than the YNH mean for all other tests. The top panel shows the proportion of listeners in integer bins, and the lower panel shows the proportion who had abnormal results on two or fewer tests versus more than two tests. Groups are separated by lightness, with the young group represented by the light grey bars, the matched group in medium grey bars, and the MTBI group in dark grey bars. Note that none of the listeners in the YNH group were abnormal on greater than two tests.