PSYCH 202 Brain Damage: Mechanisms and Impact

Severe vs Mild TBI What is TBI

An alteration in brain function, or other evidence of brain pathology, caused by an external force

Severe vs Mild TBI What proportion of TBIs are mild vs moderate-to-severe

• Mild TBI = ~95%

• Moderate-to-severe = ~5%

Severe vs Mild TBI Which demographic groups are most affected by TBI

• children

• adolescents

• young adults

• more common in males (63%) than females (37%)

Severe vs Mild TBI What is penetrating TBI

Injury whether the skull is broken and the brain is penetrated, producing focal damage

Severe vs Mild TBI What is closed TBI

A blow to the head that does not penetrate the skull; damage results from movement of the brain within the skull

Severe vs Mild TBI Which type of TBI is more common

Closed TBI

Severe vs Mild TBI What 3 behavioural measures are used to classify TBI severity

• Length of Loss of Consciousness (LOC)

• Glasgow Coma Scale (GCS)

• Length of Post-Traumatic Amnesia (PTA)

Severe vs Mild TBI What is Loss of Consciousness (LOC)

The period during which a person is unconscious or has altered consciousness following injury

Severe vs Mild TBI What does the Glasgow Coma Scale (GCS) measure

Level of consciousness based on

• eye opening

• verbal response

• motor response

Severe vs Mild TBI GCS score for mild TBI

13-15

Severe vs Mild TBI GCS score for moderate TBI

9-12

Severe vs Mild TBI GCS score for severeTBI

3-8

Severe vs Mild TBI What is post-traumatic amnesia (PTA)

A period of confusion and disorientation after TBI during which new memories cannot be formed

Severe vs Mild TBI When does PTA end

When the person becomes oriented and can form continuous memories again

Severe vs Mild TBI Why is PTA considered an important severity indicator

Longer PTA predicts greater injury severity and poorer outcomes

Severe vs Mild TBI What are the 2 major forms of damage in closed TBI

• Focal damage

• Diffuse damage

Severe vs Mild TBI What causes focal damage in TBI

Direct impact forces causing bruising and bleeding

Severe vs Mild TBI What causes diffuse damage in TBI

• acceleration

• deceleration

• rotational forces

that stretch brain tissue

Severe vs Mild TBI Why are rotational forces particularly damaging in closed TBI

They stretch and shear axons throughout the brain

Severe vs Mild TBI What secondary complications can occur after TBI

• hypoxia/anoxia

• hypotension

• swelling (oedema)

• infection

• increased intracranial pressure

• cranial nerve damage

Severe vs Mild TBI What delayed complications may occur following TBI

• post-traumatic epilepsy

• hydrocephalus

Severe TBI What is a cerebral contusion

Bruising and haemorrhage of the brain surface

Severe TBI common areas affected in a cerebral contusion

• coup lesion

• countrecoup lesion

Severe TBI What is a coup lesion

Damage directly beneath the site of impact

Severe TBI What is a contrecoup lesion

Damage on the opposite side of the brain from the impact site

Severe TBI Which brain regions are especially vulnerable to contusions

• frontal lobes

• temporal lobes

Severe TBI What behavioural consequences commonly result from frontal lobe contusions

• poor decision making

• increased risk-taking

• executive dysfunction

• emotional dusregulation

• social difficulties

Severe TBI What cognitive deficit is commonly associated with tempotal lobe damage

Memory impairment

Severe TBI What is extradural (epidural) haematoma

Rapid bleeding from damaged arteries outside the dura, usually following skull fracture

Severe TBI Why is extradural haematoma dangerous

It rapidly increases pressure and can compress the brainstem

Severe TBI Wha causes a subdural haematoma

Tearing of veins beneath the dura

Severe TBI Why are subdural haematomas often chronic

Venous bleeding occurs slowly and can accumulate over time

Severe TBI What is an intracerebral haemorrhage

Bleeding directly into brain tissue

Severe TBI What is a traumatic subarachnoid haemorrhage

Bleeding into the space between the arachnoid and pia mater

Mild TBI & Diffuse Axonal Injury What is Diffuse Axonal Injury (DAI)

Widespread damage to axons by stretching and shearing forces

Mild TBI & Diffuse Axonal Injury What is the most consistent mechanism of damage in mild and severe TBI

Diffuse Axonal Injury (DAI)

Mild TBI & Diffuse Axonal Injury What type of brain tissue is primarily affected in DAI

White matter tracts

Mild TBI & Diffuse Axonal Injury Why does DAI cause cognitive slowing

Damaged axons reduce communication efficiency between brain regions

Mild TBI & Diffuse Axonal Injury What is a concussion

A mild TBI involving disturbance of consciousness without focal brain damage

Mild TBI & Diffuse Axonal Injury What is the likely neural basis of concusison

DAI, including damage affecting brainstem pathways

Mild TBI & Diffuse Axonal Injury What is the hallmark cognitive symptom of concussion

Slowed information processing speed

Mild TBI & Diffuse Axonal Injury What other cogntiive symptoms commonly occur after concussion

• attention difficulties

• concentration problems

• memory impairment

• difficulty multitasking

Mild TBI & Diffuse Axonal Injury What emotional symptoms can occur after concussion

• depression

• anxiety

• irritability

Mild TBI & Diffuse Axonal Injury What physical symptoms are commonly associated with concussion

• headache

• dizziness

• fatigue

• visual problems

• sensitivity to light/noise

• sleep disturbance

Mild TBI & Diffuse Axonal Injury What is considered normal recovery from concussion

A few days to ~3months

Mild TBI & Diffuse Axonal Injury What are Persistent Concussive Symptoms (PCS)

Symptoms lasting beyond the typical recovery period

Mild TBI & Diffuse Axonal Injury What percentage of mTBI patients develop PCS

15%

Mild TBI & Diffuse Axonal Injury Why is PCS controversial

symptoms may arise from

• ongoing neural injury

• psychological factors

• attribution biases

• premorbid anxiety/personality factors

DTI and mBTI How is injury measured in mild TBI

Diffuse Tensor Imaging (DTI)

DTI and mBTI What does Diffusion Tensor Imaging (DTI) measure

Water diffusion within white matter (assesses integrity of brain connections)

• Can detect microstructural damage not visible on standard MRI.

• Helps identify possible disruption to neural connections following concussion.

DTI and mBTI What does Fractional Anisotropy (FA) measure

Directionality of water movement

DTI and mBTI What does high FA indicate

Better white matter integrity

DTI and mBTI What does Mean Diffusivity (MD) measure

Average diffusion in all directions

DTI and mBTI What does low MD indicate

Better white matter integrity

DTI and mBTI Major conclusion

• People with high persistent concussion symptoms often show:

  Lower FA + Higher MD

  ↓

  Reduced white matter integrity

  ↓

  Evidence of ongoing neural injury/recovery

DTI and mBTI What differences were found between the High PCS and Low PCS groups?

Participants with high persistent concussion symptoms showed:

• Lower FA

• Higher MD

compared with the low symptom group.

This indicates poorer white matter integrity in individuals experiencing more persistent symptoms.

DTI and mBTI What important conclusion comes from DTI research

Persistent post-concussive symptoms likely have a genuine neural basis (poorer white matter integrity)

DTI and mBTI Why are the High PCS vs Low PCS findings important?

• Both groups had experienced mild TBI.

• The main difference was symptom severity.

• Greater symptoms were associated with poorer white matter integrity.

• Suggests persistent symptoms have an underlying neural basis rather than being purely subjective.

Repetitive TBI & CTE Is TBI a risk factor for dementia

Yes

Repetitive TBI & CTE What factors increase dementia risk after TBI

• greater injury severity

• multiple

• TBIs

• repeated mild TBIs

Repetitive TBI & CTE What is Chronic Traumatic Encephalopathy (CTE)

A progressive neurodegenrative disease associated with repetitive mild TBI

Repetitive TBI & CTE Which groups are most commonly associated with CTE

• contact sport athletes

• military veterans

Repetitive TBI & CTE How is CTE currently diagnosed

Post-mortem examination only

Repetitive TBI & CTE What symptoms typically appear first in CTE

• Aggression

• Impulsivity

• Depression

• Mood disturbance

• Paranoia

• Suicidality

Repetitive TBI & CTE What cognitive symptoms develop later in CTE?

• Memory impairment

• Confusion

• Executive dysfunction

Repetitive TBI & CTE What is the hallmark pathological feature of CTE?

Accumulation of phosphorylated tau (p-tau).

Repetitive TBI & CTE What other neuropathological changes occur in CTE?

• Microgliosis

• Astrocytosis

• Neurodegeneration

Repetitive TBI & CTE What are subconcussive impacts?

Repeated head impacts that do not cause obvious concussion symptoms.

• They may contribute to CTE development over time.

Implications for Neuropsychological Research Which neuropsychological research aims are best addressed using focal lesions?

Understanding the relationship between specific brain regions and behaviour.

Implications for Neuropsychological Research Which research aims can use both focal and diffuse injuries?

• Understanding cognitive organisation

• Understanding disease impacts

• Understanding specific neurological disorders

Implications for Neuropsychological Research Why are focal lesions especially valuable for cognitive neuroscience?

They allow stronger inferences about whether a brain region is necessary for a cognitive function.