fMRI activation with an “affective speech” paradigm in vegetative and minimally conscious states: applicability and prognostic value.

Vegetative state (VS) and minimally conscious state (MCS) are considered different clinical entities but their differential diagnosis remains challenging. Some VS patients can show an MCS-like activation in functional magnetic resonance imaging (fMRI) studies that seems to predict recovery from VS. We studied fMRI activation with an affective speech paradigm in a cohort of non-communicative brain-injured individuals consecutively admitted to a post-acute neurorehabilitation facility in five years. Among 93 eligible subjects, 65 met the clinical criteria for VS and 28 for MCS. Because of exclusion criteria, activation studies were performed in only 30 cases out of 93 and analysed in only 24 (about ¼ of the eligible cases): 19 VS and five MCS patients. The passive acoustic stimulus consisted in a familiar voice narrating a significant episode in the patient's life, administered by nonmagnetic earphones. All the MCS patients showed an activation spread to secondary associative cortices but also 52.7% of the VS patients displayed an "atypical" large-scale activation pattern. Regarding the clinical outcome, 80% of the patients with large-scale network activation (LSNA) had some recovery of consciousness. Our results confirm that the VS patients with LSNA at fMRI study have potential for further recovery of consciousness, whereas no patient without activation or only typical activation improved. fMRI study with an affective speech paradigm, when applicable, seems to have a valuable prognostic value in VS patients, even if there are major limitations in terms of applicability.