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Introduction: Traumatic Brain Injury

Introduction: Traumatic Brain Injury. Chris Rorden Overview of course Motivation and Significance of Topic Basic terms and anatomy. Brain function. Brain functions are both distributed and modular. Modular: focal injury can lead to specific impairment.

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Introduction: Traumatic Brain Injury

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  1. Introduction: Traumatic Brain Injury • Chris Rorden • Overview of course • Motivation and Significance of Topic • Basic terms and anatomy

  2. Brain function • Brain functions are both distributed and modular. • Modular: focal injury can lead to specific impairment. • E.G. Lanugage deficits typically seen after left but not right hemisphere injury. • Distributed: large network involved • Damage to any nodes or white matter tracts lead to eye movement deficits. • Knock on effects: damage to one node degrades performance upstream. • Damage to V1 effectively disables V2. • Disconnection syndromes: • Damage to white matter sufficient to disable intact cortex.

  3. Regeneration • Peripheral nervous system can exhibit profound rehabilitation. • In general, CNS neurons do not regenerate, though glial cells often do. • Neurons can exhibit dendritic sprouting. • Changes in neurotransmitters and blood flow also play a role. Rivers and Head ~1908

  4. Plasticity • The brain is often able to compensate in response to small injuries. • Most rehabilitation aims to leverage this. • Plasticity effects are age related, typically younger individuals show better effects. • Plasticity also changes with time. Injury and recovery often exhibits a characteristic time course. • Plasticity is typically a good thing, but not always.

  5. Types of Injury • Focal versus Diffuse. • Focal refers to discrete spatial extent, for example TBI due to mechanical force (vulnerable regions) or stroke due to blockage (ischemic). • Diffuse refers to widespread injury to many regions. For example TBI due shearing of white matter or stroke due to bleeding (hemorrhagic).

  6. TBI • TBI classification remains vague. • Mild injuries much more common.

  7. Classification • GCS: Glasgow Coma Scale • PTA: Post traumatic Amnesia • LOC: Loss of consciousness • Mild TBI Terms • Complicated mTBI: injury visible in brain scan • Postconcussion injury: long term deficits • Concussion: mTBI ~ brain clearly injured, typically full functional recovery. Permanent injury debated

  8. Immediate and long term effects of TBI • Contusion (bruising) results in increased cranial pressure. Brain can herniate. Life or death situation. • TBI also associated with latent effects. Often symptoms get worse with time. • Epilepsy (recurrent seizures) can begin months after injury.

  9. TBI and age • TBI most common in young and old. • Classic ‘Bathtub’ function. • Children run into things, do not attend well • Adolescents drive cars and are often addled by testosterone. • Older individuals often fall.

  10. Reporting findings • How do we describe anatomy to others? • We could use anatomical names, but often hard to identify. • We could use Brodmann’s Areas, but this requires histology – not suitable for invivo research. • Both show large between-subject variability. • Requires anatomical coordinate system.

  11. C R C R R C Ambiguous Coordinates D • Human brain rotated relative to spine • Ambiguous dimenstions • Dorsal/ventral • Rostral/caudal • Unambiguous dimensions • Head/Foot • Superior/Inferior • Anterior/Posterior Rat V D Human D V V

  12. Anatomy – Common Terms coronal sagittal lateral < medial > lateral Posterior <> Anterior • Radiological convention: Left on right side • Neurological convention: Left on left side Inferior <> Superior Posterior <> Anterior axial

  13. Brain Coordinates • On Earth: North, South, East and West. • 0˚N/S explicitly defined by spheres rotation (equator). • 0˚E/W arbitrary (Greenwich by convention). • For brain: Left/Right, Sup./Inf., Ant./Post. • Origin of L/R explicitly defined (brain symmetry) • Origin of S/I and A/P arbitrary.

  14. Coordinates - Talairach • Anterior Commissure (AC) is the origin for neuroscience. • We measure distance from AC • 57x-67x0 means ‘right posterior middle’. • Three values: left-right, posterior-anterior, ventral-dorsal

  15. Recognizing the cortical lobes • Cortical lobes: Frontal, Parietal, Occipital Temporal, Insula. • N.B. Cerebellum and subcortical gray matter.

  16. The major sulci • Postcentral easy to find: becomes intraparietal. Precentral easy to find- attached to superior frontal. Between these is theCentral (Rolandic). Sylvian (lateral) fissure Interhemispheric fissure

  17. Major sulci • You can usually find the central suclus’ motor hand area (omega shape on axial slice)

  18. Gyri and sulci • Naming of most gyri (ridges) and sulci (valleys) follows simple pattern of position (superior, middle, inferior) and lobe name.

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