Detecting the Potential for Consciousness in Unresponsive Patients Using the Perturbational Complexity Index

Area of Science:

• Neuroscience
• Neurology
• Clinical Neurophysiology

Background:

• Behavioral assessment of prolonged disorders of consciousness (DOC) is challenging.
• Brain-based diagnostic methods are needed for accurate evaluation.
• The perturbational complexity index (PCI) shows promise in detecting consciousness.

Purpose of the Study:

• To validate the reliability of PCI in a new cohort of severely brain-injured patients.
• To assess PCI's effectiveness in differentiating between unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS).
• To explore the potential of PCI in identifying covert consciousness.

Main Methods:

• Collected data from 24 severely brain-injured patients (11 UWS, 12 MCS, 1 emergence from MCS).
• Measured PCI using electroencephalography (EEG) responses to transcranial magnetic stimulation (TMS).
• Compared individual PCI values against a validated empirical cutoff (PCI*).

Main Results:

• PCI correctly identified 11 out of 12 MCS patients (92% sensitivity) as conscious.
• Most UWS patients (64%) exhibited low PCI values, consistent with unresponsiveness.
• A subset of UWS patients (36%) showed high PCI values, suggesting potential covert consciousness.

Conclusions:

• PCI reliably differentiates between UWS and MCS patients.
• TMS-EEG assessment using PCI is a valuable tool for DOC evaluation.
• PCI may help identify patients with covert consciousness who are misdiagnosed behaviorally.