Neuropathology Flashcards
Gross changes in Alzheimers?
Diffuse atrophy
Flattened cortical sulci
Enlarged cerebral ventricles
Histological changes in Alzheimers?
Neuronal loss in cortex and hippocampus Synaptic loss Granulovascular degeneration Senile plaques Neurofibrillary tangles Hirano bodies
What is granulovascular degernation?
Small vacuoles with central granules in cytoplasm of neurons - particularly in temporal lobes
Structure of senile plaques
Insoluble amyloid peptide deposits
Peptide called Beta A4 peptide
Structure of amyloids
Fibrils of multimeric chains of peptides deposited extracellulaly, with beta pleated sheet confirmation
What cleaves beta A4?
Cleaved from amyloid-beta precursor protein by beta and gamma-secretases
What prevents cleavage of amyloid beta precursor protein?
Alpha secretase
Subtypes of plaques?
Neuritic plaque
Diffuse
Structure of neuritic plaque
Beta A in form of amyloid fibrils, among which are irregularly swollen dystrophic neuritis (defenerated neuronal processes)
How are neuritic plaques visualised?
Neurites visualised with silver stains.
May be seen as an eosinophilic mass on haematoxylin and eosin stains.
Core of neuritic plaques?
May contain dense central core of amyloid
Periphery of neuritic plaques?
Microglia and astrocyte processes
Diseases in which neuritic plaques are seen?
Normal ageing
Downs
What is the ‘apple green’ birefringence of stained stissue with neuritic plaques?
Amyloid sensitive stain Congo red under polaroid light leads to ‘apple green’ stain of neuritic plaques due to presence of beta-pleated sheets.
Structure of diffuse plaques?
Consist of non-fibrillar extracellular A beta.
Which plaques are not related to cognitive decline?
Diffuse
Peptides in diffuse plaques?
Same peptides as those responsible for amyloid formation in neuritic plaques but not polymerized to form fibrils and lack of beta-sheet configuration.
What are neurofibrillary tangles composed of?
Cytoskeletal elements - primarily abnormally phosphorylated tau protein.
What type of tauopathy is Alzheimers?
One of several degenerative tauopathies
What is tau?
Peptide required for microtubule assembly.
Function of microtubules?
Transport of materials down axons.
What stimulates formation of abnormal tau?
Beta A4 peptide interacts with cholinergic receptors, stimulating abnormal hyperphosphorylation of tau.
Where is hyperphosphorylated tau present?
Abnormal tau
Degenerated neurites
How can hyperphosphorylated tau be visualised?
Staining with antibody to abnormal tau
Which conditions do neurofibrillary tangles occur in?
Alzheimers Downs Dementia pugilistica (punch-drunk syndrome) Parinkson-dementia complex of Guam Hallervorden-Spatz disease Normal elderly
Location of tangles?
Mainly intraneuronal
Upon neuronal degeneration may appear extracellularly, thus losing their basophilia
How can tangles be visualised?
Faintly basophilic
Tau immunostaining and silver impregnation can be used to improve chances of light microscopic detection.
Location of tangles on early Alzheimers?
Tangles and neuropil threads are restricted to parts of the entorhinal cortex and CA1 field of hippocampus.
Location of tangles as Alzheimers develops?
Tangles and neutrophil threads accumulate in increasing density in other parts of the hippocampus and medical temporal neocortex, then in other cortical regions and in subcortical grey matter structures such as hypothalamus and thalamus.
What staging scheme is used to describe extent of tangle related abnormalities in Alzheimers?
Braak and Braak (1995)
Which stages of Braak and Braak’s staging scheme operationally define Alzheimers?
Stages V-VI
Structure of C Hirano bodies?
Rod-shaped eosinophilic bodies n cytoplasm of neurons
Intracellular aggregates of actin and actin-associated proteins
Location of Hirano bodies when neuron dies?
Extracellular space
Location of HIrano bodies normally?
Hippocampal pyramidal cells
Pathology of cerebral amyloid angiopathy?
Accumulation of A beta in walls of blood vessels, particularly arteries and arterioles in cerebral cortex overlying leptomeninges
What % of the elderly have Cerebral amyloid angiopathy?
30%
What % of patients with Alzheimers have Cerebral Amyloid Angiopathy?
90%
What important disease can Cerebral Amyloid Angiopathy?
Haemorrhagic strokes confined to superficial blood vessels.
How does Cerebral Amyloid Angiopathy lead to haemorrhagic stroke?
Rupture of amyloid laden blood vessels causes superficial lobar haemorrhages that may extend into subarachnoid space
Relation between tangles and cognitive decline
Increase in number and distribution
Link between tangles, neuritic plaque and cognitive decline?
If both are present, presence of even a few tangles in a single field in neocortex can suggest significant cognitive decline.
Best neuropathological correlate of decline?
Number of synapces
Marker for synapses?
Antibody to synaptophysin, a protein fund in presynaptic endings
Where is synaptophysin found?
Presynaptic endings
Cellular pattern of neuronal loss in hippocampal pathology?
Subiculum of hippocampal formation and layers II and IV of entorhinal cortex.
Affected cells involved in hippocampal pathology?
Connect hippocampal formation with association cortices, basal forebrain, thalamus and hypothalamus, structures crucial to memory.
Significance of neuronal loss in hippocampal pathology?
Isolates hippocampal formation from its input and output, contributing to memory disorder in Alzheimers
What is Binswanger’s Disease?
Subcortical vascular dementia/subcortical arteriosclerotic encephalopathy
Many small infarctions of what matter that spares cortical regions.
Co-exists with Alzheimers-type changes
Which type of dementia co-exists with Alzheimers?
Subcortical
Histology of Lewy bodies?
Weakly eosinphilic
Spherical
Cytoplasmic inclusions
Where are Lewy bodies in Parkinsons?
Confined to substantia nigra
Where are Lewy bodies in Lewy body Dementia?
Substantia nigra
Areas of cerebrum including temporal and frontal lobe and cingulate gyrus
Dorsal motor nucleus of vagus
Difference between lewy bodies in substantia nigra and cortex?
In cortex they are less conspicuous, eosinophilic and lack clear halo
Take up homeneous eosinophilic staining in cytoplasm along with peripheral displacement of nucleus
Correlation between number of Lewy bodies and cognitive decline?
None
What can we use to identify Lewy body?
Antibody to protease ubiquitin
Staining with alpha-synuclein antibodies
What do lewy bodies contain?
Accumulations of alpha-synuclein
What type of disease is Lewy body dementia?
Degenerative synucleopathies
What does alpha-synuclein do?
Accelerates reuptake of dopamine in neurons; this dopamine overload may be toxic
What are Lewy neuritis?
Nerve cell processes that contain aggregates of alpha-synuclein
Where are Lewy neuritis most numerous?
CA2/3 region of hippocampus
Substania nigra
Which diseases do Lewy neurites occur?
Lewy body Dementia
Idiopathic Parkinsons
Where does microvacuolation occur in Lewy Body Dementia?
Microvacuoalation of cerebral cortex, mainly in medial temporal region.
What are Tauopathies?
Diseases with tau deposits
What are synucleopathies?
Disease with alpha synuclein deposits
Name some tauopathies?
Alzheimers Picks Progressive supranuclear palsy Corticobasal degenerations Frontotemporal dementia with Parkinsonism (FTDP-17)
Name some synucleopathies?
Parkinsons
Lewy Body Dementia
Multisystem atrophy
Which types of pathology is frontotemporal dementia associated with?
Frontal lobe degeneration type
Picks type
Motor neurone disease type
Most common type of frontotemporal dementia?
Frontal lobe degeneration
Underlying pathology of Frontal lobe degeneration?
Spongiform degeneration or microvacuolation of superficial neuropil seen chiefly in layers III and V of cortex
Loss of large cortical nerve cells with minimal gliosis