12/19/2019 Head and Brain Head and Brain Injuries Mehdi Shafieian Department of Biomedical Engineering Amirkabir University of Technology (Tehran Polytechnic) 29th International Course on Transport Planning and Safety December 2019 Traumatic Brain Injuries Physical force causes nerve cells to stretch, tear and pull apart, therefore the brain is unable to relay messages Injury to brain cells affects processing: TBI in the thinking United States remembering seeing control & coordination mood TBI in the world Causes of TBI ADULTS AGED 75 YEARS AND OLDER HAVE THE HIGHEST RATES OF TBI-RELATED HOSPITALIZATION AND DEATH ANNUALLY, AN ESTIMATED THE YEARLY 10 MILLION PEOPLE SUFFER AGGREGATE A TBI EVENT WORLDWIDE INCIDENCE OF TBI HOSPITALIZATION ALMOST HALF A MILLION AND FATALITIES IS EMERGENCY DEPARTMENT VISITS ESTIMATED AT FOR TBI ARE MADE ANNUALLY BY 235 PER 100,000 CHILDREN AGED 0 TO 14 POPULATION 1 12/19/2019 Head Anatomy Skull Scalp Macroscopic Anatomy of Head and Brain Meninges Cerebrum Dura Mater Frontal lobe Microscopic Anatomy Arachnoid Temporal of Head and Brain Pia Mater Lobe Parietal Lobe Mechanisms of Occipital Lobe Traumatic Brain Injury Cerebellum Criteria for Brain Injury Brain Stem Spinal Cord Solid Model of Head/Brain A bit more details Frontal Bone Based on CT and MRI 1 cerebral hemisphere, 2 corpus callosum Parietal Parietal 3 ventricle Bone 4 fornix Bones 5 thalamus 6 pituitary gland 7 pons Temporal 8 medulla oblongata Bone 9 spinal cord 10 cerebellum Sphenoid Occipital 11 midbrain Bone Bone Dura and Brain Brain (Sagittal Section) Frontal Lobe Occipital Lobe Lateral Ventricle Midbrain Cerebellum Temporal Lobe Brain Stem 2 12/19/2019 Meninges and Superficial Cerebral Veins CSF Facts (Coronal Section) Superior Sagittal Sinus 1.The total volume of CSF is 125-150 ml. Scalp 2.Normal resting pressure of the CSF is between 150-180 mm H2O (11-13 mm Hg). Bridging Skull 3.Total production of CSF is about 400-500 ml/day (about .36 Veins Dura Mater ml/min) Arachnoid Mater Pia Mater Note: Blood Pressure (Artery): 100 mm Hg = 13 kPa = 1.9 PSI CSF Pressure: 12 mm Hg = 1.6 kPa = 0.2 PSI Brain Falx Cerebri Subarachnoid Space: Filled by CSF (11-13 mmHg) CSF Functions Vasculature Contribution to Brain Material Properties 1. Protection: the CSF protects the brain from damage by "buffering" the brain. In other words, the CSF acts to cushion a blow to the head and lessen the impact. 2. Buoyancy: because the brain is immersed in fluid, the net weight of the brain is reduced from about 1,400 gm to about 50 gm. Therefore, pressure at the base of the brain is reduced. 3. Excretion of waste products: the one-way flow from the CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain. 4. Endocrine medium for the brain: the CSF serves to transport hormones to other areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they may act. BBB (The Blood-Brain-Barrier) Brain is ANISOTROPIC Corona Radiata In the brain, the endothelial cells fit tightly together and substances cannot pass out of the bloodstream The BBB is semi-permeable; that is, it allows some materials to cross, but prevents others from crossing. 3 12/19/2019 Brain Facts Weight of the human head? Weight of human brain? Microscopic Anatomy of Head and Brain Axon - the long extension of a neuron that carries Neuron nerve impulses away from the body of the cell Cell Body - the cell body of the neuron; it contains Axon Terminals - the hair-like ends of the axon the nucleus (also called the soma) 4 12/19/2019 Dendrites - the branching structure of a neuron Myelin Sheath - the fatty substance that surrounds that receives messages (attached to the cell body) and protects some nerve fibers Node of Ranvier - one of the many gaps in the Nucleus - the organelle in the cell body of the myelin sheath neuron that contains the genetic material of the cell Schwann's Cells - cells that produce myelin - they Neuron Facts are located within the myelin sheath. How many neurons in an adult human brain? Size of the Cell body 15 m 5 12/19/2019 Gray Matter, White Matter Glial Cells Functions Astrocyte (Astroglia) Star-shaped cells that provide physical and nutritional support for neurons: 1) clean up brain "debris"; 2) transport nutrients to neurons; 3) hold neurons in place; 4) digest parts of dead neurons; 5) regulate content of extracellular space Microglia like astrocytes, microglia digest parts of dead neurons. OligodendrogliaNumber of provideneurons the insulation compared (myelin) to to glialneurons cells? in the central nervous system. Satellite Cells provide physical support to neurons in the peripheral nervous system. Schwann Cells Provide the insulation (myelin) to neurons in the peripheral nervous system. Oligodendrocyte Macroscopic Anatomy of Head and Brain Microscopic Anatomy of Head and Brain Mechanisms of Traumatic Brain Injury Criteria for Brain Injury TBI Brain Injuries Severity depends on amount of Primary and Secondary brain injury Main cause of Secondary injury = hypoxia TBI ranges from mild to severe: Categories: Open or Closed degree of force Forces: multiple trauma Shearing and Compression neurological complications speed of assistance 6 12/19/2019 Severity of Brain Injuries Mild TBI 41 yr old Mike Hill Head injury graded on: Attacked from behind length of unconsciousness Full recovery after removal length of amnesia No infection Both caused by sudden trauma and nerve cell tearing Left hospital one week after Brain cannot maintain functioning and shuts down either: removal fully (unconsciousness) or partially (dazed) Mild TBI refers to loss of consciousness for 30 mins or less Mild TBI Concussion vs Coma Unconscious Concussion: May be defined as Amnesia Any of these brief unconsciousness. Altered consciousness Indicate Mild TBI neurological deficits Coma: May be defined as unconsciousness. MBI can result in life changing consequences Coma can result from: Glasgow Coma Scale diffuse axonal injury The Glasgow Coma Scale (GCS) is the most common AIS Scales for Brain Injury neurological scoring system used to describe the level of AIS 3: Brain contusion (open) consciousness in a person following a traumatic brain injury. brainstem injury AIS 4: Subdural hematoma, small AIS 5: Diffuse axonal injury It is based on 3 functions: AIS 6: Brain stem transection Eye opening bilateral hemispheric damage Verbal response Motor response 7 12/19/2019 Severe TBI Severe TBI Best Eye Best Verbal Best Motor TBI is a process, not an event! Response Response Response 1. No eye opening 1. No verbal 1. No motor Secondary injury can be more damaging than primary injury. 2. Eye opening to response response pain 2. Incomprehensible 2. Extension to pain Main cause of Secondary injury: hypoxia 3. Eye opening to sounds 3. Flexion to pain verbal 3. Inappropriate 4. Withdrawal from command words pain 4. Eye opening 4. Confused words 5. Localizing to pain spontaneously 5. Appropriate 6. Obeys verbal responses commands Head trauma associated with a Glasgow Coma Brain Injury: Major Mechanisms Types of Brain Injury Direct contusion from skull deformation and/or fracture Contusion from internal movements Focal brain injury: a lesion causing local damage which can be seen by the naked eye. Indirect contusion or contrecoup Reduced blood flow Tissue stress and strain Diffuse brain injury : is associated with global disruption of brain tissue usually and is invisible. Edema and Interstitial Pressure Focal injuries Diffuse Injuries Subdural hematoma (SDH) Concussion The most common mechanism :tearing of veins that bridge the subdural space. The mortality rate is greater than 30 %. The most common head injury diagnosis, involves immediate loss of Epidural hematoma (EDH) consciousness following injury. 95 % recover at the end of 1 month. It occurs as a result of trauma to the skull and the underlying meningeal vessels and may not be associated with brain injury. Contusions Diffuse axonal injury (DAI) It consists of heterogeneous areas of necrosis, pulping, infarction, hemorrhage and edema. Mechanical disruption of many axons in the cerebral hemispheres and Generally occurs at the site of impact (coup: blow) and at remote sites from the impact (contrecoup: can be more significant) subcortical white matter. Involves immediate loss of consciousness lasting Intracerebral hematomas (ICH) for days to weeks. 55% are likely to have died at the end of 1 month. Homogeneous collections of blood within the cerebral parenchyma. Most commonly caused by sudden acceleration/deceleration of the head. Other causes are penetrating wounds and blows to the head. 8 12/19/2019 Proposed In Vivo Injury Mechanisms Mechanism 1: Focal Brain Contusion A brain contusion is defined by cell death accompanied by hemorrhage (leakage of blood). The soft brain tissue is vulnerable to contusion in head trauma. The contusion often occurs at a site distant from the point of Pressure causes a change in Deformation causes extension, impact www.pathology.vcu.edu tissue volume, thereby causing shear and/ or compression of damage tissue, causing primary damage Coup - Contrecoup Injury Impact Location and Contusion 83% 7% 10% 79% 14% 7% 50% 10% 40% LifeArt: Williams & Wilkins http://www.lifeart.com Mechanism 2: Increase in ICP Mechanism 2: Increase in ICP Intracranial Contents: Important Point: The intracranial vault is a fixed volume since 80% brain tissue 10% blood bone does not expand! 10% cerebrospinal fluid An increase in the volume of any of these intracranial contents ICP greater than 20mmHg, there is a high chance of Injury. causes increased intracranial pressure: 1.The brain can swell (edema) 2.Excess blood can accumulate due to hemorrhage 3.Cerebrospinal fluid can accumulate due to blockage of outflow 9 12/19/2019 Mechanism 2: Increase in ICP Mechanism 2: Increase in ICP Important Point: There is only one way out of the intracranial vault Herniation: When the brain is squeezed through the foramen magnum, the brainstem is compressed.