How does EEG contribute to evaluating coma or altered mental status?

• A. Detects nonconvulsive seizures or status; helps differentiate structural vs metabolic etiologies; guides prognosis.
• B. Measures blood pressure variations.
• C. Visualizes brain tissue directly.
• D. Replaces CT scan for all emergencies.

Answer: (A)

EEG in coma evaluation is used to uncover hidden electrical activity abnormalities, differentiate likely causes, and guide prognosis and treatment.

Nonconvulsive seizures can occur in coma without obvious convulsive movements. Continuous EEG monitoring can detect ongoing seizure activity that would otherwise be missed, allowing timely initiation or adjustment of antiseizure treatment.

EEG patterns help distinguish structural from metabolic or diffuse processes. Global slowing or triphasic waves often suggest metabolic or toxic etiologies, while focal abnormalities, asymmetry, or specific discharges can point toward a structural lesion such as a hemorrhage, infarct, or mass effect.

Prognostically, certain EEG features correlate with outcomes. For example, diffuse suppression or burst-suppression patterns and lack of reactivity generally indicate a poorer prognosis, whereas preserved reactivity and more continuous activity can be more favorable.

EEG complements imaging and bedside monitoring but does not measure blood pressure, does not directly visualize brain tissue, and does not replace CT or MRI in emergencies.