Bedside evaluation of profound unresponsiveness: FOUR score and GCS, pupillary/corneal/caloric reflex examination, herniation syndrome recognition, confounder clearance, and Death by Neurologic Criteria (BD/DNC) evaluation.
Profound acute coma (unresponsiveness to all noxious stimuli with eye closure) and loss of brainstem cranial nerve reflexes represent the most severe catastrophic spectrum of neuro-critical illness. The immediate bedside objectives are: (1) Recognize and emergently treat impending transtentorial/tonsillar herniation; (2) Rule out basilar artery occlusion ('Locked-In' syndrome) and reversible metabolic/toxic mimics; (3) Systematically clear confounders; and (4) Evaluate for Death by Neurologic Criteria (BD/DNC) when irreversibility is established.
Caution
Dangerous Diagnosis Not to Miss: Transtentorial (Uncal) Herniation (unilateral fixed dilated pupil, decerebrate posturing) requiring immediate hyperosmolar bolus and emergent neurosurgical decompression; Acute Basilar Artery Thrombosis (distinguishable by preserved vertical eye movements and intact cortical consciousness on EEG); and hypothermia/pharmacologic paralysis mimicking whole-brain death.
FOUR Score & Glasgow Coma Scale (GCS):
Pupillary Light Reflex (CN II/III): Test with strong light; fixed midposition (4–6 mm) or fixed dilated pupils indicate midbrain tectal/parasympathetic failure.
Corneal Reflex (CN V/VII): Touch cornea with sterile swab; evaluates pontine integrity.
Oculocephalic ('Doll's Eyes', CN III/VI/VIII): Rotate head horizontally; eyes moving opposite to head movement indicates intact pontine/midbrain reflex arcs (test only after clearing cervical spine).
Oculovestibular (Cold Caloric Test, CN III/VI/VIII): Irrigate EAC with 50 mL ice-cold water after confirming intact tympanic membranes; tonic conjugate deviation toward cold ear indicates intact brainstem.
Pharyngeal & Tracheal Reflexes (CN IX/X): Gag on posterior pharyngeal touch; cough on deep carina endotracheal suctioning.
If signs of acute herniation (dilating pupil, Cushing triad [bradycardia, hypertension, irregular breathing], decerebrate extensor posturing):
Immediate Hyperosmolar Therapy: Administer 3% Hypertonic Saline (250–500 mL IV bolus over 10–15 min) OR Mannitol 20% (1.0–1.5 g/kg IV bolus over 15–20 min).
Elevate Head of Bed: 30° with neck in neutral midline position to maximize jugular venous drainage.
Brief Hyperventilation: Target PaCO2 30–35 mmHg as a temporary bridge to induce cerebral vasoconstriction while preparing the operating room (avoid prolonged hyperventilation).
Stat Neurosurgical Consult: Immediate CT head and emergent surgical decompression (decompressive hemicraniectomy, EVD, clot evacuation).
Caution
Common Diagnostic Trap: Confusing spinal cord reflexes (e.g. triple flexion of lower limbs, abdominal reflexes, or Lazarus sign) with cerebral motor responses. Spinal reflexes originate from the isolated spinal cord and do NOT indicate brain viability or invalidate brain death; educate bedside staff and families.
Brain Death / DNC: 2023 AAN/AAP/CNS/SCCM guideline, apnea testing on/off ECMO, and donor management.
Altered Consciousness: FOUR score, GCS, and structural coma differential.
Intracranial Hypertension: Tiered ICP algorithms, EVD management, and hyperosmolar therapy.
Ischemic Stroke: Basilar artery occlusion, malignant MCA infarction, and hemicraniectomy.
Severe TBI: Marshall/Rotterdam CT classifications and brain trauma foundation protocols.
Evidence status
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From 'analgesia-first' multimodal pain control and light sedation targeting to daily SAT/SBT coordination, delirium screening, and early mobility.
From acute GCS drop and herniation emergency measures to emergent CT, neurocritical intervention, and death by neurologic criteria determination.
From emergent first-line benzodiazepine administration to second-line IV non-sedating AEDs and continuous cEEG anesthetic burst suppression.
From securing the basics to categorizing structural, toxic-metabolic, infectious, and seizure-related causes.
2023 AAN/AAP/CNS/SCCM consensus guideline: prerequisites, brainstem reflex examination, apnea testing on and off ECMO, valid ancillary tests, plus separate post-declaration donor-management principles.
ARAS neuroanatomy, structural vs toxic-metabolic coma, the comprehensive Coma Exam (pupils, cold calorics, posturing), FOUR score, and CAM-ICU delirium.
Monro-Kellie doctrine, ICP waveforms (P2>P1, Lundberg A-waves), CPP targets (60–70 mmHg), herniation syndromes, and the 4-tier BTF management protocol.
Core vs penumbra dynamics, ASPECTS & CT perfusion, Tenecteplase/Alteplase thrombolysis, DAWN/DEFUSE 3 extended thrombectomy, BP targets, and malignant MCA hemicraniectomy.
Spontaneous ICH vs Aneurysmal SAH, INTERACT-2/ATACH-2 blood pressure targets, emergency anticoagulant reversal, ENRICH minimally invasive evacuation, ISAT coiling, and Nimodipine for delayed cerebral ischemia.
Severe TBI neurocritical care: prevent hypoxemia/hypotension, treat intracranial hypertension, individualize ventilation/CPP, use evidence-based short antiseizure prophylaxis when chosen, and escalate surgery when indicated.