Detecting the Potential for Consciousness in Unresponsive Patients Using the Perturbational Complexity Index.
Level 4 - case-series / case-control
Diagnostic cross-sectional study in a small clinical cohort without a healthy reference group.
PubMed 33260944 · doi:10.3390/brainsci10120917
What was done
Researchers evaluated the diagnostic utility of the perturbational complexity index (PCI)—which measures electroencephalographic (EEG) responses to transcranial magnetic stimulation (TMS)—in an independent cohort of 24 patients with severe brain injuries. The sample included 11 patients with unresponsive wakefulness syndrome (UWS), 12 in a minimally conscious state (MCS), and 1 emerging from MCS. Individual maximum PCI values were compared against an empirical cutoff (PCI*) and resting EEG.
What was found
Maximum PCI values exceeded the PCI* cutoff in 11 MCS patients, resulting in a sensitivity of 92%. In the UWS cohort, 7 patients (64%) displayed low-complexity PCI values (≤ PCI*), whereas 4 patients (36%) exhibited high-complexity PCI values.
Why it matters
This study independently replicates the capacity of TMS-EEG perturbational complexity to assess consciousness, indicating that over one-third of behaviorally unresponsive patients may retain covert cortical complexity.
Limits
The sample size was small (n = 24), and the abstract provides no longitudinal outcomes to verify whether high PCI scores in unresponsive patients predict behavioral recovery.