Diagnostic Imaging in Parkinson's and Alzheimer's Flashcards
Role of microglia in the amyloid cascade?
[unknown trigger] -> increased amyloid production -> oligomers -> plaques -> activate microglia -> neurotoxicity -> neuronal damage -> neurofibrillary tangles (NFTs)
NB: neuronal death itself catalyses microglial activation (vicious cycle)
Effect of clearing amyloid in AD pts?
No effect
Microglia relationship w/ amyloid plaque?
MIcroglia surround b-amyloid plaques (clearing it?)
Briefly describe the mechanism of PET imaging
PET ligand with radioisotope binds to target
Radiation (positrons) detected by scanner
Radiation detected from tissue and tracer in blood
Arterial line used to take blood sample to subtract radioactivity in blood
What does 11C-PIB PET measure?
Amyloid
Describe amyloid’s presence in cerebellum
Cerebellum has no amyloid in AD and in control
Therefore we can use it as a reference for 11C-PIB PET (instead of using arterial line)
Amyloid’s presence in AD and its progression?
Significant amyloid throught the cortex (90% of AD)
Starts in basal forebrain and then spreads (1st deposition 10-15 yrs before symptoms)
Experimental observation of amyloid and glucose metabolism in AD?
Longitudinal study over 20 months:
AD has no change in amyloid over time (but reduced glucose metabolism)
Amyloid’s presence in mild cognitive impairment (MCI)?
60% of MCI has high amyloid (50% of amyloid +ve MCI will develop AD within 2 years)
[but if it converts to AD, no change in amyloid after 2 yrs]
Amyloid’s presence in Lewy Body Dementia (DLB)?
Amyloid throughout
80% DLB has high amyloid (Amyloid not specific in AD diagnosis)
Amyloid’s presence in Parkinson’s Disease Dementia (PDD)?
Amyloid throughout
20% of PDD has high amyloid
Amyloid’s presence in cognitively normal people?
By 75 yrs, 20% of cog. normal ppl will have amyloid deposition
What does PK11195 measure?
Measures activated microglia (binds to TSPO)
NB: increased microglial activation is associated w/ a decreased MMSE
Microglial activation in AD?
Significant microglial activation throughout cortex
[some areas overlap w/ amyloid deposition, some don’t]
Microglial activation in MCI?
60% of amyloid +ve MCI have increased microglial activation
30% of amyloid -ve MCI have increased microglial activation (can happen without amyloid)