1. Chapter 10 Brain Damage and Neuroplasticity
Can the Brain Recover from Damage?
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2. Causes of Brain Damage Brain tumors Cerebrovascular disorders
Closed-head injuries
Infections of the brain
Neurotoxins
Genetic factors

3. Brain Tumors
A tumor (neoplasm) is a mass of cells that grows independently of the rest of the body – a cancer
~20% of brain tumors are meningiomas – encased in meninges
Encapsulated, growing within their own membranes
Usually benign, surgically removable

4. Brain Tumors Most brain tumors are infiltrating
Grow diffusely through surrounding tissue
Malignant, difficult to remove or destroy
About 10% of brain tumors are metastatic – they originate elsewhere, usually the lungs

5. Cerebrovascular Disorders
Stroke – a sudden-onset cerebrovascular event that causes brain damage
Cerebral hemorrhage – bleeding in the brain
Cerebral ischemia – disruption of blood supply
3rd leading cause of death in the US and most common cause of adult disability

6. Cerebrovascular Disorders
Cerebral hemorrhage – blood vessel ruptures
Aneurysm – a weakened point in a blood vessel that makes a stroke more likely. May be congenital or due to poison or infection.
Congenital – present at birth
Cerebral ischemia – disruption of blood supply
Thrombosis – plug forms
Embolism – plug forms elsewhere and moves to the brain
Arteriosclerosis – wall of blood vessels thicken, usually due to fat deposits

7. Damage due to Cerebral Ischemia
Does not develop immediately
Most damage is a consequence of excess neurotransmitter release – especially glutamate
Blood-deprived neurons become overactive and release glutamate
Glutamate overactivates its receptors, especially NMDA receptors leading to an influx of Na+ and Ca++

8. Damage due to Cerebral Ischemia
lnflux of Na+ and Ca++ triggers:
the release of still more glutamate
a sequence of internal reactions that ultimately kill the neuron
Ischemia-induced brain damage
takes time
does not occur equally in all parts of the brain
mechanisms of damage vary with the brain structure affected

10. Closed-Head Injuries
Brain injuries due to blows that do not penetrate the skull – the brain collides with the skull
Contrecoup injuries – contusions are often on the side of the brain opposite to the blow
Contusions – closed-head injuries that involve damage to the cerebral circulatory system. A hematoma, a bruise, forms.
Concussion – when there is a disturbance of consciousness following a blow to the head and no evidence of structural damage.

11. Concussions
While there is no apparent brain damage with a single concussion, multiple concussions may result in a dementia referred to as “punch-drunk syndrome”
When might this occur?
Can it be prevented?

12. Brain Infection Invasion of the brain by microorganisms
Encephalitis – the resulting inflammation
Bacterial infections
Often leads to abscesses, pockets of pus
May inflame meninges, creating meningitis
Treat with penicillin and other antibiotics
Viral infections
Some viral infections preferentially attack neural tissues

13. Brain Infections - Some Causes
Bacterial
Syphilis – may produce a syndrome of insanity and dementia known as general paresis
Syphilis bacteria are passed to the noninfected and enter a dormant stage for many years.
Viral
Rabies – high affinity for the nervous system
Mumps and herpes – typically attack tissues other than the brain
Viruses may lie dormant for years

14. Neurotoxins
May enter general circulation from the GI tract, lungs, or through the skin
Toxic psychosis – chronic insanity produced by a neurotoxin.
The Mad Hatter – may have had toxic psychosis due to mercury exposure

15. Neurotoxins
Some antipyschotic drugs produce a motor disorder caused tardive dyskinesia
Recreational drugs, such as alcohol, may cause brain damage
Neurotoxic effects of alcohol
Thiamine deficiency
Some neurotoxins are endogenous – produced by the body

16. Genetic Factors
Most neuropsychological diseases of genetic origin are associated with recessive genes. Why?
Down syndrome
0.15% of births, probability increases with advancing maternal age
Extra chromosome 21
Characteristic disfigurement, mental retardation, other health problems

17. Neuropsychological Diseases
Epilepsy
Parkinson’s disease
Huntington’s disease
Multiple sclerosis
Alzheimer’s disease

18. Neuroplastic Responses to Nervous System Damage
Degeneration - deterioration
Regeneration – regrowth of damaged neurons
Reorganization
Recovery

19. Neural Regeneration
Does not proceed successfully in mammals and other higher vertebrates - capacity for accurate axonal growth is lost in maturity
Regeneration is virtually nonexistent in the CNS of adult mammals and unlikely, but possible, in the PNS

20. Can the brain recover from brain damage?
Consider what you now know about the brain’s ability to adapt following brain damage, can it “recover”?
If so, what conditions promote recovery?