374 Ch 373. Coma and Altered Consciousness

Coma = pathological state of unconsciousness — eyes closed + unaware + unarousable + no purposeful movement；arousal (wakefulness, brainstem reticular activating system — RAS) + awareness (content, cerebral cortex) — both must be preserved for consciousness；two anatomic causes: (1) bilateral cerebral hemispheric dysfunction (toxic/metabolic, bilateral structural, post-anoxic), (2) brainstem dysfunction at midbrain/pons/upper medulla (RAS lesion)；toxic-metabolic >> structural in frequency (drugs, alcohol, glucose, electrolytes, hepatic/uremic, hypoxia, hypoglycemia, hypothermia, sepsis)；examination focus: GCS + pupils (size, reactivity) + eye movements (oculocephalic doll’s eyes, oculovestibular calorics) + motor response + brainstem reflexes；spectrum of altered consciousness: confusion → drowsiness → stupor → coma; persistent vegetative state (UWS — unresponsive wakefulness syndrome) vs minimally conscious state (MCS) vs locked-in syndrome (preserved awareness + horizontal gaze + vertical eye movement preserved, due to ventral pontine lesion)；brain death = irreversible loss of all brain function including brainstem (Ch374)。