Preservation of Brain Activity in Unresponsive Patients Identifies MCS Star

Objective Brain-injured patients who are unresponsive at the bedside (ie, vegetative state/unresponsive wakefulness syndrome - VS/UWS) may present brain activity similar to patients in minimally conscious state (MCS). This peculiar condition has been termed non-behavioural MCS or MCS*. In the present study we aimed to investigate the proportion and underlying brain characteristics of patients in MCS*. Methods Brain F-18-fluorodeoxyglucose Positron Emission Tomography (FDG-PET) was acquired on 135 brain-injured patients diagnosed in prolonged VS/UWS (n = 48) or MCS (n = 87). From an existing database, relative metabolic preservation in the fronto-parietal network (measured with standardized uptake value) was visually inspected by three experts. Patients with hypometabolism of the fronto-parietal network were labelled VS/UWS, while its (partial) preservation either confirmed the behavioural diagnosis of MCS or, in absence of behavioural signs of consciousness, suggested a diagnosis of MCS*. Clinical outcome at 1-year follow-up, functional connectivity, grey matter atrophy, and regional brain metabolic patterns were investigated in the three groups (VS/UWS, MCS* and MCS). Results 67% of behavioural VS/UWS presented a partial preservation of brain metabolism (ie, MCS*). Compared to VS/UWS patients, MCS* patients demonstrated a better outcome, global functional connectivity and grey matter preservation more compatible with the diagnosis of MCS. MCS* patients presented lower brain metabolism mostly in the posterior brain regions compared to MCS patients. Interpretation MCS* is a frequent phenomenon that is associated with better outcome and better brain preservation than the diagnosis of VS/UWS. Complementary exams should be provided to all unresponsive patients before taking medical decisions. ANN NEUROL 2021

Automated summary

A study investigated brain activity in non-responsive brain-injured patients, finding that a significant proportion of them showed partial preservation of brain metabolism, labeled as MCS*. Patients with MCS* had better outcomes, global functional connectivity, and grey matter preservation compared to those with VS/UWS. MCS* patients had lower brain metabolism in posterior brain regions compared to MCS patients.