Cross-spectral analysis of cerebral autoregulation after mild traumatic brain injury

Severe traumatic brain injury (TBI) disrupts cerebral autoregulation (CAR), which may increase the risk of secondary neuronal damage in victims with large fluctuations in blood pressure (BP). CAR is also impaired in mild TBI. Given that mild TBI accounts for up to 70% of cases, this issue needs to be addressed. Physiological and non-invasive methods are now required to study CAR without the sharp fluctuations in blood pressure that underlie CAR tests. The cross-spectral analysis of fluctuations between cerebral blood flow and blood pressure discussed in the article is truly non-invasive and physiological. Forty-eight victims with mild traumatic brain injury were studied. CAR was assessed using two methods. The cuff test was used as a control method to assess autoregulation (RoR). Non-invasive cross-spectral analysis with phase shift (PS) detection was performed. The RoR values were normal, but there were cases within the group with varying severity of symptoms of the acute period of mild TBI. For example, the RoR was significantly higher (p < 0.001) in 32 patients with regression of symptoms than in 16 with persistence of symptoms. Their RoR and PS indicated a violation of the CAR, which required correction of the treatment. It was found that in 1/3 of the patients with mild TBI, a different state of CAR required individual tactics. RoR and PS correlated well.