Brain Death Anatomy and Physiology

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Brain DeathAnatomy and Physiology

• Joel S. Cohen, M.D.
• Associate Professor of Clinical Neurology
• Albert Einstein College of Medicine

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Historical Perspective

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

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Historical Perspective

• 1959 Coma depasse Mollaret and Goulon
• 1968 Irreversible Coma/Brain Death Harvard
  Medical School Ad Hoc Committee
• 1981 Uniform Determination of Death Act -
  Presidents 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

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Brain Death Current Consensus

• Absent Cerebral Function
• Absent Brainstem Function
• Apnea

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Normal Brain Anatomy
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Normal Brain Anatomy
Cerebral Cortex
Reticular Activating System
Brain Stem
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Cerebral Cortex

• Cognition
• Voluntary Movement
• Sensation

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Brain Stem
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Brain Stem

• Midbrain
• Cranial Nerve III
• pupillary function
• eye movement

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Brain Stem

• Pons
• Cranial Nerves IV, V, VI
• conjugate eye movement
• corneal reflex

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Brain Stem

• Medulla
• Cranial Nerves IX, X
• Pharyngeal (Gag) Reflex
• Tracheal (Cough) Reflex
• Respiration

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Reticular Activating System

• Receives multiple sensory inputs
• Mediates wakefulness

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Causes of Brain Death
Cerebral Anoxia
Normal
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Causes of Brain Death
Normal
Cerebral Hemorrhage
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Causes of Brain Death
Subarachnoid Hemorrhage
Normal
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Causes of Brain Death
Normal
Trauma
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Causes of Brain Death
Meningitis
Normal
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Mechanism of Cerebral Death
ICPgtMAP is incompatible with life
Increased Intracranial Pressure
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Conditions Distinct From Brain Death

• Persistent Vegetative State
• Locked-in Syndrome
• Minimally Responsive State

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Persistent Vegetative State

• Normal Sleep-Wake Cycles
• No Response to Environmental Stimuli
• Diffuse Brain Injury with Preservation of Brain
  Stem Function

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Locked-in Syndrome
Ventral Pontine Infarct

• Complete Paralysis
• Preserved Consciousness
• Preserved Eye Movement

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Minimally Responsive State
Static Encephalopathy

• Diffuse or Multi-Focal Brain Injury
• Preserved Brain Stem Function
• Variable Interaction with Environmental Stimuli

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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 gt 32 C

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Brain Death Neurological Examination

• Coma
• Absent Brain Stem Reflexes
• Apnea

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Coma

• No Response to Noxious Stimuli
• Nail Bed Pressure
• Sternal Rub
• Supra-Orbital Ridge Pressure

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Absence of Brain Stem Reflexes

• Pupillary Reflex
• Eye Movements
• Facial Sensation and Motor Response
• Pharyngeal (Gag) Reflex
• Tracheal (Cough) Reflex

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Pupillary Reflex
Pupils dilated with no constriction to bright
light
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Eye Movements
Occulo-Cephalic Response Dolls Eyes Maneuver
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Eye Movements
Oculo-Vestibular Response Cold Caloric Testing
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Facial Sensation and Motor Response

• Corneal Reflex
• Jaw Reflex
• Grimace to Supraorbital or
• Temporo-Mandibular Pressure

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Apnea Testing

• Prerequisites
• Core Body Temperature gt 32 C
• Systolic Blood Pressure 90 mm Hg
• Normal Electrolytes
• Normal PCO2

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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 lt 90, PO2 saturation
  decreases, or cardiac dysrhythmia observed

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Confounding Clinical Conditions

• Facial Trauma
• Pupillary Abnormalities
• CNS Sedatives or Neuromuscular Blockers
• Hepatic Failure
• Pulmonary Disease

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Observations Compatible with Brain Death

• Sweating, Blushing
• Deep Tendon Reflexes
• Spontaneous Spinal Reflexes- Triple Flexion
• Babinski Sign

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Confirmatory Testing

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

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Confirmatory Testing
EEG
Normal
Electrocerebral Silence
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Confirmatory Testing

• Cerebral Angiography

Normal
No Intracranial Flow
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Confirmatory Testing

• Technetium-99 Isotope Brain Scan

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Confirmatory Testing

• MR- Angiography

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Confirmatory Testing
Transcranial Ultrasonography
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Confirmatory Testing

• Somatosensory Evoked Potentials

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• 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