L9- CNS Pathology

Question 1

How is the arterial blood supply to the brain structured?

Answer 1

• Vertebral arteries join to form the single basilar artery that enters the skull via foramen magnum
• 2 internal arteries- internal carotid artery and middle cerebral artery enter skull through common carotic canal
• These arteries are joined in the circle of Willis
• Arteries branch off into arterioles and perforate all parts of the brain

Question 2

What are cerebrovascular accidents?

Answer 2

• Disruption to blood supply rapidly leads to loss of consciousness and death
• Caused by hypertension, atherosclerosis leading to cerebral thrombosis from MI
• Or from embolism from MI

Question 3

What are the macroscopic changes in ischaemic stroke?

Answer 3

• MCA stenosis
• Loss of white/grey brain matter differentiation
• Loss of sulcal effacement

Question 4

What are histopathological (microscopic) changes in ischaemic stroke?

Answer 4

• Eosinophilic neurons
• Pyknosis- irreversible condensation of chromatin in nucleus of cell undergoing necrosis or apoptosis
• Coagulative necrosis
• Vascular thrombosis
• Axonal fragmentation
• Reactive astrocytes

Question 5

What is a haemorrhagic stroke (aneurysm)?

Answer 5

• Weakening of an artery wall that creates a bulge or distension of the artery
• Most aneurysms don’t show symptoms but can rupture at their most severe stage
• Leads to internal bleeding which can be fatal

Question 6

How does venous drainage of the brain occur?

Answer 6

• Cerebral veins have branches which empty deoxygenated blood into double layers of dura called sinuses
• Sinuses have no valves, natural drainage by gravity

Question 7

Where are the meningeal arteries?

Answer 7

• Run on the outer surface of the dura between the skull bone and the dura

Question 8

What can cranial trauma be caused by?

Answer 8

• Road traffic accidents
• Concussion (lack of conciousness)
• Contrusion (subdural haemorrhage due to rupture of small blood vessel)
• Lacerations (tears/cuts in cerebral tissue)
• Severe blunt trauma, gun shot wounds

Question 9

What are the types of cerebral bleeds?

Answer 9

• Extra-dural haemorrhage- between skull and dura, usually arterial
• Subdural haemorrhage- between skull and dura, usually venous
• Intracerebral haemorrhage- second cause of stroke

Question 10

What are cerebral infections?

Answer 10

• Pyogenic meningitis, viral, fungal or bacterial
• Cerebral abscess- bacteria, ear infections, pus filled cavity
• Cerebral toxoplasmosis- AIDs, toxoplasma gondii
• Herpes simplex encephalitis
• Cytomegalovirus encephalitis

Question 11

What are the neurodegenerative disorders?

Answer 11

• Alzheimer’s
• Parkinson’s
• Huntingdon’s
• Multiple Sclerosis
• Dementia

Question 12

What is dementia?

Answer 12

• Complex loss of higher brain function including loss of memory, motor control and emotional activity

Question 13

What happens in Alzheimer’s disease?

Answer 13

• Formation of amyloid plaques made from b-amyloid protein in brain tissue
• Neurofibrilliary protein tangles in neuron
• Symptom not cause of disease

Question 14

What happens in Parkinson’s disease?

Answer 14

• Age related
• Sporadic cases may be genetic or environmental
• Degeneration of dopaminergic neurons which produce melanin in the substantia nigra pars compacta

Question 15

What happens in Huntingdon’s disease?

Answer 15

• CAG expression in Huntingtin gene
• Mutant protein contains over 36 glutamate residues
• Genetically dominant
• Build up of protein and degeneration of neurons

Question 16

What are ALS and FTD?

Answer 16

ALS- motor neuron disease, neuronal loss, neuroinflammation, microgliosis
FTD- Neurofibrilliary tangles

Question 17

What happens in multiple sclerosis?

Answer 17

• Demyelinating autoimmune disease