Abstract
The impact of language impairment on the clinical assessment of patients suffering from disorders of consciousness (DOC) is unknown or underestimated and may mask the presence of conscious behavior. In a group of DOC patients (n = 11; time post-injury range: 5–252 months), we investigated the main neural functional and structural underpinnings of linguistic processing, and their relationship with the behavioral measures of the auditory function using the Coma Recovery Scale-Revised (CRS-R). We assessed the integrity of the brainstem auditory pathways, of the left superior temporal gyrus and arcuate fasciculus, the neural activity elicited by passive listening of an auditory language task, and the mean hemispheric glucose metabolism. Our results support the hypothesis of a relationship between the level of preservation of the investigated structures/functions and the CRS-R auditory subscale scores. Moreover, our findings indicate that patients in minimally conscious state minus (MCS−): (1) when presenting the auditory startle (at the CRS-R auditory subscale) might be aphasic in the receptive domain, being severely impaired in the core language structures/functions; (2) when presenting the localization to sound might retain language processing, being almost intact or intact in the core language structures/functions. Despite the small group of investigated patients, our findings provide a grounding of the clinical measures of the CRS-R auditory subscale in the integrity of the underlying auditory structures/functions. Future studies are needed to confirm our results that might have important consequences for the clinical practice.
Highlights
Severe brain injury might result in disorders of consciousness (DOC), a spectrum of conditions comprising coma, vegetative state (VS), and minimally conscious state (MCS)
In MCS patients, distinct behaviors at the Coma Recovery Scale-Revised (CRS-R) auditory function subscale might be sustained by different neurofunctional profiles
Our results support the hypothesis that MCS− patients presenting the auditory startle might be aphasic in the receptive domain, independently from the level of cerebral metabolism and, from the level of consciousness [30]
Summary
Severe brain injury might result in disorders of consciousness (DOC), a spectrum of conditions comprising coma, vegetative state (VS), and minimally conscious state (MCS). [3] The presence of cognitive deficits, may mask the presence of conscious behaviors when using these standardized approaches [4] leading to possible misdiagnosis. In this context, aphasia is one of the main confounding factors in the behavioral assessment of these patients [4]: among 13 CRS-R items [2] used to classify DOC patients in MCS, almost 80% relies on the presence of preserved language comprehension. A proof of concept that language disorders might lead to misdiagnosis in DOC patients showed that a consistent percentage of fully aware patients with aphasia (up to 54%) did not reach the maximal CRS-R total score and that patients with global aphasia were prone to have a diagnosis underestimating their level of consciousness [5]
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