374.3 🏥 內科專科考前版

374.3.1 Mechanistic Deep Dive

374.3.1.1 Reticular Activating System (RAS)

  • Brainstem origin (rostral pons, midbrain)
  • Diffuse cortical projections via thalamus
  • Cholinergic, noradrenergic, serotonergic, histaminergic, orexinergic
  • Lesions cause coma if bilateral

374.3.1.2 Glymphatic System

  • CSF-interstitial fluid exchange
  • Clears waste during sleep
  • Disrupted in disorders of consciousness

374.3.1.3 Default Mode Network

  • Resting state network
  • Disrupted in coma, VS
  • Recovery markers

374.3.2 Recent Trials & Updates

374.3.2.1 Post-Anoxic Prognostication

  • Multimodal approach
  • After 72 hr off sedation, normothermic
  • NSE > 60 ng/mL: poor
  • EEG suppression/burst-suppression: poor
  • Absent N20 on SSEP: poor
  • Diffuse cortical edema on MRI: poor
  • Avoid premature withdrawal

374.3.2.2 Targeted Temperature Management (TTM)

  • TTM trial (33 vs 36°C) — equivalent
  • TTM2 (33 vs 37.5°C) — no benefit at 33
  • Active fever prevention preferred

374.3.2.3 Anti-NMDA-R Encephalitis

  • Young women
  • Psychiatric → seizures → movement → autonomic → coma
  • Often paraneoplastic (ovarian teratoma)
  • Immunotherapy + tumor

374.3.2.4 Wernicke Encephalopathy Dose

  • 500 mg IV TID × 3 days, then 250 mg IV daily × 5 days, then oral 100 mg
  • Older guidelines used lower doses

374.3.3 High-Yield Specialist Points

374.3.3.1 Pseudo-Coma (Functional)

  • Resistance to eye opening
  • Eyes look away from examiner
  • Reverse Doll’s eyes
  • Normal EEG
  • Suggest psychogenic

374.3.3.2 Akinetic Mutism

  • Awake but no movement/speech
  • Frontal lobe lesions (bilateral)
  • Mesial frontal/anterior cingulate

374.3.3.3 Coma Mimics

  • Locked-in syndrome
  • Akinetic mutism
  • Catatonia
  • Severe Guillain-Barré
  • Psychogenic

374.3.3.4 Toxidromes

Toxidrome Features
Opioid Pinpoint pupils, hypoventilation, coma
Anticholinergic Dilated pupils, dry, hot, urinary retention, tachycardia, hallucinations
Cholinergic (organophosphate) SLUDGE, pinpoint pupils, fasciculations
Sympathomimetic Dilated, tachy, HTN, diaphoresis
Sedative-hypnotic Slurred, ataxia, coma

374.3.3.5 Antidotes

  • Opioid: naloxone
  • BZD: flumazenil (controversial)
  • Acetaminophen: NAC
  • Methanol/ethylene glycol: fomepizole
  • Anticholinergic: physostigmine
  • β-blocker: glucagon
  • CCB: calcium, glucagon, high-dose insulin/glucose
  • Iron: deferoxamine
  • Salicylate: alkalinization, HD
  • Methemoglobinemia: methylene blue
  • Cyanide: hydroxocobalamin

374.3.3.6 Status Epilepticus → Coma

  • After convulsive activity stops
  • May continue NCSE (8-37% of post-CSE)
  • cEEG essential

374.3.3.7 Catatonia

  • Stupor or excitement
  • Posturing, waxy flexibility, mutism
  • Many causes (psychiatric, medical, drug)
  • Treatment: lorazepam, ECT

374.3.3.8 Functional Imaging in Disorders of Consciousness

  • fMRI: command following
  • PET: metabolic activity
  • May reveal “covert consciousness” in some labeled UWS

374.3.4 Pearls

  • Coma vs UWS vs MCS vs locked-in distinction
  • Bilateral hemispheric (toxic-metabolic) >> brainstem causes
  • GCS for severity
  • Pupils + eye movements key for localization
  • Decerebrate worse than decorticate
  • Empiric thiamine before glucose
  • CT head emergent + comprehensive labs + tox + ABG
  • LP after imaging if meningitis suspected
  • Brain herniation patterns: uncal, central, tonsillar, subfalcine
  • Locked-in: ventral pontine, preserved vertical gaze + awareness
  • Post-anoxic prognostication: multimodal at 72 hr off sedation