Neuropathology Flashcards
Name some macroscopic changes seen in Alzheimers?
Cortical atrophy (particularly over hippocampus, amygdala - frontal & parietal lobes effected most)
Flattened cortical sulci
Enlarged ventricles
Depigmentation of locus coerlus in face of persevered substantia nigra
Outline the microscopic changes seen in Alzheimer’s
- Senile plaques
- Neurofibrillary tangles
- Hirano bodies
- Astrocytic gliosis
- Granulovascular degeneration (small vaculoses with central granules in cytoplasm of neurons - especially in the temporal lobes)
What are senile plaques made of and where are they located?
Senile plaques are made of insolube amyloid peptide deposites (Amyloid beta) peptide
They are located extracellularly and form a pleated sheet configuration
What enzymes cleave amyloid-beta precursor protein?
beta-secreatase and gamma-secretase cleave to form amyloid-beta.
Alpha-secretase prevents its formation
What two types of amyloid beta plaques exist and which are counted in neuropathological tests?
Neuritic plaques - counted in neuropathological tests
- Amyloid beta is in the form of amyloid fibrils - swollen dystrophic neurites are present within the plaque
- Eosinophillic mass appearance on haematoxylin and eosin stains
- Neuritic plaques contain a dense central core of amyloid
- Beta-pleated sheets give the neuritic plaque a green apple birefringence when Amyloid sensitive congo red stain is applied
Diffuse plaques - not counted in neuropathological tests:
- These are non-fibrillar extracellular amyloid beta and do not related to cognitive decline
- No pleated sheet appearance
What are neurofibrillary tangles made of?
Hyperphosphorylated Tau
Tau is a peptite used in the making of microtubules - microtubules help transport materials down an axon
Name some other Tauopathies apart from Alzheimer’s?
Down syndrome
Pick’s disease
Progressive supranuclear palsy
Corticobasal degeneration
Frontotemporal dementia with parkinsonism (FTDP-17)
Dementia pugilistica (punch-drunk syndrome)
Parkinson-dementia complex of Guam
Hallervorden-Spatz disease
Where is Tau located?
Intraneuronal - if there is neuronal breakdown it may appear in the extracellular space
What appearance are Tau?
Basophillic
Where does Tau initial develop?
Enterohinal cortex and CA1 field of the hippocampus before acculumating in density in other parts of the hippocampus, the medial temporal neocortex and other cortical regions (hypothalamus and thalamus).
Braak and Braak (1995) devised a staging for the degree of Tau related abnormalities
What are hirano bodies made of?
Rod-shaped eosinophillic bodies in the cytoplasm of neurons - when the neuron dies the hirano body may be in the extracellular space
What are hirano bodies made of?
Intracellular aggregates of actin and actin associated bodies
What is CAA?
Cerebral Amyloid Angiopathy:
- Affects 90% of those with Alzheimers and 30% in normal aging
- Deposition of amyloid beta plaques in the walls of blood vessels in the cerebral cortex and overlying leptomeninges
- Typically CAA causes superficial lobar bleeding that can spread into subarachnoid space.
What is the antibody for synapses and why is it relavent?
Synaptophysin is an antibody for presynaptic endings
- Neuropathological decline correlates well with declines in synapses
In Alzheimers where does neuronal loss occur in the hippocampus?
Subiculum and layers II and IV of enterohinal cortex
Neuronal loss isolates hippocampus from inputs and outputs (association cortex, hypothalamus, basal forebrain, thalamus) contributing to memory decline
Apart from Lewy Body Dementia name some other synculeopathies?
Parkinson’s
Multisystem atrophy
What antibody can be used to identify Lewy bodies?
Antibody to the protease ubiquitin
What do Lewy Bodies contain?
Alpha-synuclein - function is to accelerate reuptake of dopamine into neurons. The accelerated uptake in DLB and Parkinson’s may be toxic