To combine functional assessment of auditory and sensory pathways using Auditory Brainstem Reflex (ABR) and Somatosensory Evoked Potential (SSEP), respectively, with the microstructural integrity of these pathways using MRI Diffusion Tensor Imaging (DTI) and its correlation with outcomes in disorders of consciousness (DoC). 

Prognostication of long-term outcomes after acute brain injury is challenging. Advanced imaging and electrophysiological biomarkers carry the premise to be used for prognosticating functional recovery by demonstrating preserved brain networks in seemingly unresponsive patients.

In a prospective study, 50 comatose acute brain injury patients were recruited. SSEP and ABR were performed all patients in the Neuroscience ICU; of these, 20 patients and 3 healthy subjects had MRI DTI with fractional anisotropy (FA). Glasgow Outcome Scale-Extended was used to assess recovery 12-months after injury.

Among the 50 patients, the median age was 44 (IQR 63-32.5), 18% were females and 57% Hispanic; 41 (82%) had TBI, 6 (12%) ICH, and 3 (6%) SAH. When patients had bilateral SSEP and ABR, 62% were functionally independent (defined as GOSE >3, independent for at least 8 hours a day) by 12 months. When bilateral SSEP were absent, 10% of patients had recovery by 12 months. When bilateral ABR were absent, no recovery was seen by 12 months. When SSEP was present unilaterally, FA was worse on the contralateral corticothalamic, medial lemniscus, and spinothalamic tracts. Lateral lemniscus FA was marginally higher with bilateral present ABR (left, mean 0.33; right, mean 0.28) when compared to any dysfunction of ABR (left, mean 0.30; right, mean 0.26).

SSPE and ABR presence and absence strongly correlated with recovery by 12-month after injury. Dysfunction of these evoked potentials correlated with disruption of microstructural integrity of the relevant circuits as measured by DTI, showing congruence structurally and functionally. Together, these tools may be valuable to the prognostication in coma.