Standard EEG in diagnostic process of prolonged disorders of consciousness

• Standard EEG can complement behavioral diagnosis of disorders of consciousness.
• EEG activity and reactivity differ in vegetative and minimally conscious state.
• In anoxic patients EEG features are more severely impaired and less discriminative.

ObjectiveThis cross-sectional study assessed the ability of standard EEG in distinguishing vegetative state (VS) from minimally conscious state plus (MCS+) or MCS minus (MCS−), and to correlate EEG features with aetiology and level of responsiveness assessed by Coma Recovery Scale-Revised (CRS-R).MethodsWe analyzed background EEG activity and EEG reactivity to eye opening and closing and to tactile, acoustic, nociceptive stimuli and Intermittent Photic Stimulation (IPS) in 73 inpatients (VS = 37, MCS− = 11, MCS+ = 25), with traumatic (n = 21), vascular (n = 25) or anoxic (n = 27) aetiology.ResultsAll patients, but one, showed abnormal background activity. EEG abnormalities were more severe in VS than in MCS+ or MCS−, and in anoxic than other aetiologies. MCS+ patients with normal or Mildly Abnormal background activity showed higher scores on CRS-R than patients with moderate to severe EEG abnormalities. Reactivity to IPS, and acoustic stimuli was significantly more frequent in MCS+ and MCS− than in VS patients.ConclusionsEEG features differ between VS and MCS− or MCS+ patients and can provide evidence of relative sparing of thalamocortical connections in MCS+ patients. In anoxic patients EEG organization is more severely impaired and provides less discriminative diagnostic information.SignificanceConventional EEG can help clinicians to disentangle VS from MCS patients.