Table 2.

Electrophysiological markers with pros and cons for use in prognostication.

Category	Markers	Pro	Con
cEEG	Isoelectric, low-voltage; Burst and suppression, Epileptiform pattern (not always reliable); Absence of EEG reactivity.	Directly provide measurement of neuronal activities; Low financial cost, bedside and non-invasive monitoring; EEG reactivity and continuity have been validated as critical factors in predicting recovery or poor outcome.	Confounded by subjective interpretation by neurologists; Affected by external factor, i.e., medications and sedation; Not able to provide detailed information about the degree of injury.
Quantitative EEG (qEEG)	Burst suppression, continuous low voltage or flat trace EEG background and seizure pattern; Absence of aEEG continuous normal voltage (CNV) pattern; The lower values obtained from other qEEG measurement are associated with poor outcome.	Simpler, objective and accurate prognostication; Do not need neurologists’ interpretation.	Most qEEG markers (i.e., CRI and Entropy-base qEEG) lacks clinical data, or larger patient groups (i.e., aEEG) which needs further clinical study and can only regard as a complementary criterion in prognostication; Conflicting results (i.e., BIS) of prognostic ability.
SSEPs	Bilateral absence of N20 potentials.	Provide direct information about the degree of functional damage of somatosensory pathway; Most accurate marker of poor outcome prognosis; Most robust to sedation.	Only limited to studying the presence or absence of N20; The prognostic value of good outcome is inconclusive.
Quantitative SSEPs (qSSEPs)	The lower qSSEP values are associated with poor outcome .	Do not require experts’ interpretation; Allow researchers to choose the time period of interest; Objectively provide not only prediction of bad outcome but good outcome.	qSSEP techniques lack clinical validation.
Other EPs	The absence of mismatch negative (MMN) waves in evoked-related auditory evoked potentials (ERPs); The disorder of auditory discrimination capabilities.	Provide direct information about the degree of functional damage of different neurologic pathway.	Their prognostic abilities have not been validated on TH-treated patients.