Causes of Brain Dysfunction (Part 1)

Question 1

2 types of tumours

Answer 1

• encapsulated

- infiltrating

Question 2

encapsulated tumours

Answer 2

• Grow between meninges
• “Meningiomas”
• Benign tumours -> can be removed without removing other tissues

Question 3

infiltrating tumours

Answer 3

• Grow diffusely through surrounding brain tissue
• Malignant tumours -> cannot be removed without removing other important tissues
• Ex. Metastatic tumours: grow from tumour fragments carried into the brain from another body part via the bloodstream; commonly originate from a breast cancer or lung cancer
• Glioblastoma/glioma: problem with white matter/glia; most type of malignant brain tumour in adults; aggressive – life expectancy 12-15 months post-diagnosis

Question 4

strokes (and tissues affected)

Answer 4

• Sudden-onset cerebrovascular disorders that cause brain damage
• Infarct: area of dead/dying tissue (not worth treating)
• Penumbra: dysfunctional area surrounding the infarct; tissue in that area may either recover or die (treatment is focused on this)

Question 5

2 major types of strokes

Answer 5

• resulting from cerebral hemorrhage

- resulting from cerebral ischemia

Question 6

strokes: resulting from hemmorhage

Answer 6

• More severe type of stroke
• Driven by aneurysms
• • Aneurysm: Blood pressure creates bubble of blood that may burst, damaging tissue (circle of Willis is prone to this)
• – If it does burst -> hemorrhagic stroke
• – Treatment: clipping it off (more invasive, more effective), “coiling” using tube going through artery into brain (less invasive, less effective)

Question 7

strokes: resulting from cerebral ischemia (what it is; 3 main causes)

Answer 7

• Disruption of blood supply to some area of the brain
• 3 main causes: (can occur simultaneously)
• • Thrombosis: some sort of plug (plaque, blood clot, etc.) preventing blood from flowing past it
• • Embolism: “thrombosis on wheels”; thrombosis starts moving through the body
• • Arteriosclerosis: narrowing of blood vessels (due to fat deposits, cholesterol, etc.)

Question 8

strokes: resulting from cerebral ischemia (3 properties of its brain damage)

Answer 8

• Takes a while to develop
• Damage more likely in some parts of brain (ie. Neurons in hippocampus)
• Mechanisms of ischemia-induced damage vary between brain structures

Question 9

strokes: resulting from cerebral ischemia (types of ischemia-produced damage)

Answer 9

• Contralateral neglect – damage post-ischemia leaves you with an inability to pay attention to the left side of things (ie. A picture of a cat)
• Prosopagnosia – damage to facial recognition areas

Question 10

strokes: resulting from cerebral ischemia (recovery)

Answer 10

• Time-sensitive: treatments that occur in the “sensitive period” quickly post-stroke are more likely to succeed
• • Constraint-induced movement therapy: restraining the “good” arm in order to force you to use the one affected by the stroke -> increases recovery

Question 11

open-head injuries

Answer 11

• Entry into the brain (ex. By foreign objects like bullets)
• Ex. Phineas Gage – damage to front of brain damaged pro-social tendencies

Question 12

2 types of closed-head injuries

Answer 12

• contusion

- concussion

Question 13

contusions

Answer 13

• Involve damage to the cerebral circulatory system, producing internal hemorrhaging and hematoma
• Occur when brain slams against skull
• Contrecoup injuries: the blow causes the brain to strike the inside of the skull on the other side of the head (damage to both sides -> initial is “coup”, second side is “contrecoup”)

Question 14

concussions

Answer 14

• When there is a blow to the head but no evidence of a contusion or other structural damage
• Form of Mild Traumatic Brain Injury (MTBI)
• Cases of chronic traumatic encephalopathy (CTE) suggest that there is long-term damage associated with concussion, even if it is not visible after a single episode

Question 15

CTE

Answer 15

• Brain damage associated with hitting your head (concussions not necessary to get it -> most are actually sub-concussive)
• Repeated hits to the head are especially damaging, even if none result in concussions
• In brains of people with CTE, you’ll find Tau (a protein) and Neurofibrillary Tangles (clumps of tau) -> loss of cell structure -> cell damage/death (unsure if it’s cause of cell death or effect)
• Symptoms of CTE: paranoia, jealousy, depression, headaches, aggression, mood swings, suicidality, cognitive impairments, motor deficits, etc.
• Developing techniques to identify CTE while patient is alive (ex. With ligands that bind to tau)

Question 16

apoptosis

Answer 16

programmed cell death; normally a good thing, but too much activity near penumbra causes too much apoptosis (excitotoxicity) which could kill it

Question 17

concussions vs. TBI vs. CTE

Answer 17

• concussions: a syndrome
• TBI: the event/injury
• CTE: progressive disease -> will progress whether you have future hits or not

Question 18

distinct profile of cognitive impairments post-stroke

Answer 18

• Studies have previously shown negative impact on attention, memory, language, orientation, visuospatial skills, abstract reasoning, verbal fluency, and executive function, and speed of processing
• However, more recent studies suggest problems are weighted more toward attention-executive dysfunction rather than memory/language dysfunction

Question 19

types of deficits associated with features of stroke-related damage

Answer 19

• Hemorrhagic stroke, left hemisphere involvement, and recurrence predict subsequent dementia
• Broca’s aphasia: damage to left posterior, inferior frontal gyrus (limited speech)
• Wernicke’s aphasia: damage to left posterior, superior temporal gyrus (fluent but meaningless speech)
• Focal damage leads to selective cognitive impairments
• Diffuse damage produces more uniform mental slowing and deficits; usually results from an underlying white matter disease (can be seen using DTI)

Question 20

post-stroke interventions

Answer 20

• Compensatory approaches: adapting external environment to altered cognitive abilities
• Restorative approaches: ex. Repetitive transcranial magnetic stimulation, prism glasses to reduce hemispatial neglect
• Lowering blood pressure reduces risk of cognitive decline
• Certain pharmacological agents can benefit cognitive function
• Increasing physical activity

Question 21

Taupathy

Answer 21

neurofibrillary tangles (seen in CTE, Alzheimer’s, and Parkinson’s)

Question 22

TBI

Answer 22

• Likelihood of suffering mild TBIs from collision-heavy sports is high
• Concussive (symptomatic) or subconcussive (asymptomatic) injuries are both subsets of mild TBI
• Repetitive mild TBI thought to contribute to development of CTE (correlation exists)
• The earlier in life you experience TBI, the worse the outcome; TBI is risk factor for dementia

Question 23

Junior Seau

Answer 23

• Experienced multiple concussions; displayed headaches and behavioural changes
• Post-mortem brain exam showed tau consistent with CTE and scarring from TBI