The neurovascular complexity index as a potential indicator of traumatic brain injury severity: A case series study

BACKGROUND: Multimodal monitoring of brain physiology following a traumatic brain injury (TBI) shows promise as a strategy to improve management and outcomes of TBI patients within civilian and military trauma. Valid and reliable measures of different aspects of brain physiology following a TBI could prove critical to accurately capturing these changes. METHODS: Using a case-series design with a healthy control group comparison, we evaluated a new proprietary algorithm called the neurovascular complexity index (NCI) using transcranial Doppler to noninvasively obtain measures of cerebral blood flow variability (CBFV). Baseline NCI data from 169 healthy control participants were compared to 12 moderate-to-severe TBI patients. RESULTS: TBI patients exhibited significantly greater mean and variability in NCI scores than healthy controls (F=195.48; p<0.001). The mean absolute deviation (MAD) of NCI scores increased significantly and in a monotonic fashion with severity of injury, where healthy controls exhibited a small MAD of 0.44, moderate TBI patients had a higher MAD of 4.20 and severe TBI patients had a MAD of 6.51 (p<0.001). CONCLUSION: Advancement in multimodal monitoring of TBI patients is important in reducing the potential risk of secondary injury. This study reports results indicating that a new non-invasive quantifiable assessment of TBI based on a noninvasive measure of CBFV shows potential for continuous monitoring and early identification of brain-injured patients, deployable in far-forward military environments, to better inform individualized management. LEVEL OF EVIDENCE: Case series, level IV.