Download - Introduction: Traumatic Brain Injury
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Introduction: Traumatic Brain Injury
Chris Rorden– Overview of course– Motivation and Significance of Topic– Basic terms and anatomy
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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.
Regeneration
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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
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.
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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).
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TBI
TBI classification remains vague.Mild injuries much more common.
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Classification
GCS: Glasgow Coma ScalePTA: Post traumatic AmnesiaLOC: Loss of consciousnessMild 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
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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.
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TBI and age
TBI most common in young and old.Classic ‘Bathtub’ function. Children run into things, do not attend wellAdolescents drive cars and are often addled
by testosterone.Older individuals often fall.
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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.
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Ambiguous Coordinates
Human brain rotated relative to spine
Ambiguous dimenstions– Dorsal/ventral– Rostral/caudal
Unambiguous dimensions– Head/Foot– Superior/Inferior– Anterior/Posterior
R C
R CR
C
V
D
V
D
V D
Rat
Human
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Anatomy – Common Terms
Posterior <> Anterior
Po
ster
ior
<>
A
nte
rio
rIn
feri
or
<>
S
up
eri
or
lateral < medial > lateral
Radiological convention: Left on right side Neurological convention: Left on left side
sagittalcoronal
axial
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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.
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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
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Recognizing the cortical lobes
Cortical lobes: Frontal, Parietal, Occipital Temporal, Insula.N.B. Cerebellum and subcortical gray matter.
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The major sulci
Postcentral easy to find: becomes intraparietal. Precentral easy to find- attached to superior frontal. Between these is the Central (Rolandic).
Interhemispheric fissure
Sylvian (lateral) fissure
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Major sulci
You can usually find the central suclus’ motor hand area (omega shape on axial slice)
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Gyri and sulci
Naming of most gyri (ridges) and sulci (valleys) follows simple pattern of position (superior, middle, inferior) and lobe name.