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Brain Death Anatomy and Physiology. Joel S. Cohen, M.D. Associate Professor of Clinical Neurology Albert Einstein College of Medicine. Historical Perspective. Prior to the advent of mechanical respiration, death was defined as the cessation of circulation and breathing .

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brain death anatomy and physiology
Brain DeathAnatomy and Physiology

Joel S. Cohen, M.D.

Associate Professor of Clinical Neurology

Albert Einstein College of Medicine

historical perspective
Historical Perspective

Prior to the advent of mechanical respiration, death was defined as the cessation of circulation and breathing

historical perspective3
Historical Perspective
  • 1959 Coma de’passe’ Mollaret and Goulon
  • 1968 Irreversible Coma/Brain Death Harvard Medical School Ad Hoc Committee
  • 1981 Uniform Determination of Death Act - President’s Commission for the Study of Ethical Problems in Medicine
  • 1994 American Academy of Neurology Guidelines for the determination of Brain Death
  • 2005 NYS Guidelines for Determining Brain Death
brain death current consensus
Brain Death Current Consensus
  • Absent Cerebral Function
  • Absent Brainstem Function
  • Apnea
normal brain anatomy6
Normal Brain Anatomy

Cerebral Cortex

Reticular Activating System

Brain Stem

cerebral cortex
Cerebral Cortex
  • Cognition
  • Voluntary Movement
  • Sensation
brain stem9
Brain Stem


Cranial Nerve III

  • pupillary function
  • eye movement
brain stem10
Brain Stem
  • Pons
  • Cranial Nerves IV, V, VI
    • conjugate eye movement
    • corneal reflex
brain stem11
Brain Stem
  • Medulla

Cranial Nerves IX, X

      • Pharyngeal (Gag) Reflex
      • Tracheal (Cough) Reflex
  • Respiration
reticular activating system
Reticular Activating System
  • Receives multiple sensory inputs
  • Mediates wakefulness
causes of brain death
Causes of Brain Death

Cerebral Anoxia


causes of brain death14
Causes of Brain Death


Cerebral Hemorrhage

causes of brain death15
Causes of Brain Death

Subarachnoid Hemorrhage


causes of brain death17
Causes of Brain Death



mechanism of cerebral death
Mechanism of Cerebral Death

ICP>MAP is incompatible with life

Increased Intracranial


conditions distinct from brain death
Conditions Distinct From Brain Death
  • Persistent Vegetative State
  • Locked-in Syndrome
  • Minimally Responsive State
persistent vegetative state
Persistent Vegetative State
  • Normal Sleep-Wake Cycles
  • No Response to Environmental Stimuli
  • Diffuse Brain Injury with Preservation of Brain Stem Function
locked in syndrome
Locked-in Syndrome

Ventral Pontine Infarct

  • Complete Paralysis
  • Preserved Consciousness
  • Preserved Eye Movement
minimally responsive state
Minimally Responsive State

Static Encephalopathy

  • Diffuse or Multi-Focal Brain Injury
  • Preserved Brain Stem Function
  • Variable Interaction with Environmental Stimuli
brain death neurological examination
Brain Death Neurological Examination

Clinical Prerequisites:

  • Known Irreversible Cause
  • Exclusion of Potentially Reversible Conditions
    • Drug Intoxication or Poisoning
    • Electrolyte or Acid-Base Imbalance
    • Endocrine Disturbances
  • Core Body temperature > 32° C
brain death neurological examination24
Brain Death Neurological Examination
  • Coma
  • Absent Brain Stem Reflexes
  • Apnea

No Response to Noxious Stimuli

  • Nail Bed Pressure
  • Sternal Rub
  • Supra-Orbital Ridge Pressure
absence of brain stem reflexes
Absence of Brain Stem Reflexes
  • Pupillary Reflex
  • Eye Movements
  • Facial Sensation and Motor Response
  • Pharyngeal (Gag) Reflex
  • Tracheal (Cough) Reflex
pupillary reflex
Pupillary Reflex

Pupils dilated with no constriction to bright light

eye movements
Eye Movements

Occulo-Cephalic Response

“Doll’s Eyes Maneuver”

eye movements29
Eye Movements

Oculo-Vestibular Response

“Cold Caloric Testing”

facial sensation and motor response
Facial Sensation and Motor Response
  • Corneal Reflex
  • Jaw Reflex
  • Grimace to Supraorbital or

Temporo-Mandibular Pressure

apnea testing
Apnea Testing


  • Core Body Temperature > 32° C
  • Systolic Blood Pressure ≥ 90 mm Hg
  • Normal Electrolytes
  • Normal PCO2
apnea testing32
Apnea Testing

1. Pre-Oxygenation

  • 100% Oxygen via Tracheal Cannula
  • PO2 = 200 mm Hg

2. Monitor PCO2 and PO2 with pulse oximetry

3. Disconnect Ventilator

4. Observe for Respiratory Movement until PCO2 = 60 mm Hg

5. Discontinue Testing if BP < 90, PO2 saturation decreases, or cardiac dysrhythmia observed

confounding clinical conditions
Confounding Clinical Conditions
  • Facial Trauma
  • Pupillary Abnormalities
  • CNS Sedatives or Neuromuscular Blockers
  • Hepatic Failure
  • Pulmonary Disease
observations compatible with brain death
Observations Compatible with Brain Death
  • Sweating, Blushing
  • Deep Tendon Reflexes
  • Spontaneous Spinal Reflexes- Triple Flexion
  • Babinski Sign
confirmatory testing
Confirmatory Testing

Recommended when the proximate cause of coma is not known or when confounding clinical conditions limit the clinical examination

confirmatory testing36
Confirmatory Testing



Electrocerebral Silence

confirmatory testing37
Confirmatory Testing

Cerebral Angiography


No Intracranial Flow

confirmatory testing38
Confirmatory Testing

Technetium-99 Isotope Brain Scan

confirmatory testing39
Confirmatory Testing

MR- Angiography

confirmatory testing40
Confirmatory Testing

Transcranial Ultrasonography

confirmatory testing41
Confirmatory Testing

Somatosensory Evoked Potentials

Concern for man and his fate must always form the chief interest of all technical endeavors. Never forget this in the midst of your diagrams and equations.

Albert Einstein