374.1 🎓 醫孞生版

374.1.0.1 📌 䞀頁重點

374.1.0.1.1 Definitions

374.1.1 Consciousness

  • Arousal (wakefulness)
    • Brainstem RAS (midbrain → pons → upper medulla)
    • Diffuse cortical projections
  • Awareness (content)
    • Cerebral cortex
    • Thalamic projections

Both required for consciousness.

374.1.2 Spectrum

  • Alert: normal
  • Confused: disoriented, slow
  • Drowsy/lethargic: arousable but lapses
  • Stuporous: difficult to arouse, minimal response
  • Coma: unarousable, no purposeful response

374.1.3 Persistent Disorders

  • Vegetative state (Unresponsive Wakefulness Syndrome — UWS):
    • Eyes open
    • Sleep-wake cycles
    • No awareness
    • No purposeful response
    • Reflexes preserved
    • Persistent (1 month) → permanent (3 months non-traumatic, 12 months traumatic)
  • Minimally Conscious State (MCS):
    • Some signs of awareness
    • Inconsistent
    • Better prognosis than UWS
  • Locked-In Syndrome:
    • Awake + aware
    • Quadriplegic
    • Anarthric
    • Preserved: vertical eye movements + blinking + sometimes horizontal
    • Ventral pontine lesion (often basilar artery occlusion)
    • Devastating but consciousness intact
374.1.3.0.1 Etiology — Two Anatomic Causes

374.1.4 1. Bilateral Cerebral Hemispheric Dysfunction

  • Toxic/Metabolic (most common):
    • Drugs (opioids, BZDs, alcohol, anesthetics, sedatives, anticonvulsants)
    • Alcohol intoxication or withdrawal
    • Hypoglycemia, hyperglycemia (HHS, DKA)
    • Hyponatremia, hypernatremia
    • Hypercalcemia, hypocalcemia
    • Hypothyroid (myxedema), thyroid storm
    • Adrenal insufficiency
    • Hepatic encephalopathy
    • Uremia
    • Hypoxia, hypercapnia (CO2 narcosis)
    • Hypothermia, hyperthermia
    • Sepsis
    • Wernicke encephalopathy (thiamine deficiency)
  • Bilateral Structural:
    • Bilateral large strokes
    • SAH with diffuse vasospasm
    • Diffuse axonal injury
    • PRES
  • Diffuse:
    • Post-anoxic (cardiac arrest)
    • Meningitis, encephalitis
    • Seizure/post-ictal

374.1.5 2. Brainstem Dysfunction (RAS)

  • Midbrain → pons → upper medulla
  • Pontine hemorrhage (often)
  • Brainstem infarct (basilar artery)
  • Brainstem tumor
  • Central pontine myelinolysis (osmotic demyelination)
  • Compression from posterior fossa mass

374.1.6 Unilateral Hemispheric

  • Usually does NOT cause coma
  • UNLESS mass effect → herniation → brainstem compression
374.1.6.0.1 Examination

374.1.7 General

  • Vital signs
  • Skin (cyanosis, jaundice, rash)
  • Smell (alcohol, ketones)
  • Trauma (raccoon eyes, Battle sign, hemotympanum, CSF leak)
  • Stigmata of liver disease, IVDU

374.1.8 Glasgow Coma Scale (GCS)

  • Eye opening (1-4): spontaneous, to voice, to pain, none
  • Verbal (1-5): oriented, confused, inappropriate, incomprehensible, none
  • Motor (1-6): obeys, localizes, withdraws, flexor, extensor, none
  • Total 3-15
  • GCS ≀ 8 → consider intubation
  • Confounded by intubation, sedation, intoxication

374.1.9 Pupils

Size + Reactivity: | Finding | Suggests | |———|———-| | Bilateral pinpoint reactive | Pontine hemorrhage, opioids, organophosphate, neurosyphilis | | Bilateral mid-position fixed | Midbrain lesion | | Bilateral fixed dilated | Severe anoxia, brain death, atropine, cocaine, late herniation | | Unilateral fixed dilated | CN III compression (uncal herniation, PCA aneurysm) | | Reactive in metabolic | Mostly preserved in metabolic |

374.1.10 Eye Movements

Oculocephalic (“Doll’s Eyes”): - Turn head; eyes move opposite direction - Present in coma = intact brainstem - Absent = brainstem dysfunction (or normal awake) - DO NOT perform if cervical injury possible

Oculovestibular (Cold Calorics): - Confirm intact tympanic membrane - Cold water in ear → eyes deviate TOWARD cold ear (COWS in awake — fast phase OPPOSITE) - In coma: only slow phase → eyes deviate toward cold - Absent = brainstem dysfunction - More sensitive than doll’s eyes

Gaze: - Conjugate deviation toward lesion (cortical stroke) - Conjugate deviation away from lesion (pontine stroke or seizure) - Skew deviation: brainstem - Forced downgaze: thalamic, dorsal midbrain (Parinaud)

374.1.11 Motor Response

Localizes to pain: cortex intact Withdraws: spinal/subcortical Decorticate posturing (flexor): above red nucleus (severe cortical/subcortical injury) Decerebrate posturing (extensor): below red nucleus (brainstem injury) — worse No response: severe diffuse dysfunction

374.1.12 Brainstem Reflexes

  • Pupillary
  • Corneal
  • Gag
  • Cough
  • Oculocephalic / oculovestibular
  • Spontaneous breathing pattern

374.1.13 Breathing Patterns

  • Cheyne-Stokes: crescendo-decrescendo (cerebral, HF)
  • Central neurogenic hyperventilation: rapid + deep (midbrain)
  • Apneustic: pause at full inspiration (lower pons)
  • Ataxic (Biot): irregular (medullary — pre-arrest)
374.1.13.0.1 Workup

374.1.14 Initial (Often Simultaneous with Exam)

  • Glucose (immediate)
  • ABG
  • Electrolytes (Na, Ca, Mg)
  • BUN/creatinine
  • LFTs, ammonia
  • TFTs, cortisol
  • CBC
  • Coagulation
  • Toxicology screen + alcohol + salicylates + acetaminophen
  • Blood + urine cultures if sepsis suspected
  • Pregnancy
  • CK
  • Lactate

374.1.15 Empiric Therapy in Coma

  • Thiamine 100 mg IV (before glucose if possible)
  • Glucose 50 mL D50W if low or unmeasured
  • Naloxone if opioid suspected
  • Flumazenil controversial (risk of seizure)

374.1.16 Imaging

  • CT head emergent (rule out hemorrhage, herniation)
  • MRI brain if CT negative (better for infarct, encephalitis, demyelination)
  • CTA/MRA if posterior fossa stroke suspected

374.1.17 LP

  • After imaging
  • If meningitis/encephalitis suspected
  • Get cell count, protein, glucose, gram stain, culture, viral PCR

374.1.18 EEG

  • Non-convulsive status epilepticus
  • Encephalopathy patterns
  • Prognosis after cardiac arrest
  • Brain death (electrocerebral silence — adjunctive)

374.1.19 Additional

  • LP autoimmune (NMDA-R, etc.)
  • Heavy metals
  • Genetic
  • Specific tests
374.1.19.0.1 Specific Causes — Common Patterns

374.1.20 Opioid Overdose

  • Pinpoint pupils
  • Hypoventilation
  • Coma
  • Naloxone IV/IM/IN

374.1.21 Hypoglycemia

  • Diaphoresis early
  • Altered LOC
  • Focal deficits possible (mimics stroke)
  • D50W

374.1.22 Hepatic Encephalopathy

  • Asterixis (with arms outstretched)
  • Triphasic waves on EEG
  • Hyperammonemia (not always sensitive)
  • Lactulose + rifaximin

374.1.23 Uremic Encephalopathy

  • Myoclonus, asterixis
  • Improves with dialysis

374.1.24 Wernicke Encephalopathy

  • Triad: ophthalmoplegia + confusion + ataxia (only 16% have all)
  • Thiamine deficiency
  • Alcoholism, malnutrition, bariatric surgery, hyperemesis
  • IV thiamine before glucose

374.1.25 Post-Anoxic Coma

  • Cardiac arrest survivors
  • Prognosis assessment after 72 hr (without sedation, normothermic)
  • NSE, EEG, SSEP, MRI

374.1.26 Septic Encephalopathy

  • Common in ICU
  • Multifactorial
  • Treat sepsis

374.1.27 CO2 Narcosis

  • COPD with O2 administration
  • Acute or chronic hypercapnia
  • BiPAP, careful O2

374.1.28 Carbon Monoxide Poisoning

  • Cherry red (rare)
  • Co-oximetry (SpO2 misleading)
  • 100% O2, hyperbaric if severe

374.1.28.1 🩺 床邊速查

  • Coma = unarousable + unaware + eyes closed + no purposeful movement
  • Two causes: bilateral hemispheric (toxic-metabolic >> structural) vs brainstem RAS
  • Locked-in: ventral pontine, preserved vertical gaze
  • GCS for severity
  • Pupils: pinpoint = pontine/opioid; unilateral dilated = uncal herniation
  • Oculocephalic + oculovestibular: assess brainstem
  • Motor: decorticate (above red), decerebrate (below red — worse)
  • Empiric: thiamine → glucose → naloxone
  • CT head + labs + ABG + tox + glucose
  • Wernicke: thiamine before glucose