Man who had PIB, diagnosed with DLB and CAA
The Alzheimer Research Forum summary of the recent news about the woman with Alzheimer's followed for eight years referred to this news from 2007 of a man diagnosed with DLB during life and both DLB and CAA (cerebral amyloid angiopathy) upon autopsy. The man had a PET-PIB scan three months before he died. The scan showed a high level of PIB binding, which means that there are amyloid plaques. However, this man did not have enough Alzheimer's pathology in the brain upon post-mortem exam to diagnose him with "definite AD." The findings only supported the diagnosis of "possible AD."
The explanation for amyloid in this man's brain was CAA (cerebral amyloid angiopathy). Of the brain donation cases I've been involved with, one person in our local support group was diagnosed clinically with CBD but then with AD and CAA upon brain autopsy. Another case that I know about was a man who was diagnosed clinically with DLB and, upon brain autopsy, with cortical Lewy body disease and CAA. So, CAA hasn't shown up a lot in my small sample but it's not an unknown.
Here's a link to the summary of this 2007 news on ARF about the man with DLB:http://www.alzforum.org/new/detail.asp?id=1553
I've also copied the (short) summary below.
The research paper is available at no charge on the Archives of Neurology website. See:http://archneur.ama-assn.org/cgi/content/full/64/3/431
It Is Official: Autopsy Verifies Human PIB-Amyloid Connection
Alzheimer Research Forum
23 March 2007. Researchers have published the first postmortem confirmation of amyloid pathology corresponding to a positive PET scan using the amyloid tracer Pittsburg Compound B (PIB). In the March issue of Archives of Neurology, Brian Bacskai and colleagues from the Massachusetts General Hospital in Charlestown report on the autopsy of a 76-year-old man who died 3 months after PET-PIB imaging. Regional PIB binding detected in living tissue correlated with biochemical measures of AÃ after death. Interestingly, the patient, whose clinical diagnosis of dementia with Lewy bodies was confirmed by the exam, had only moderate levels of amyloid plaques, but severe cerebral amyloid angiopathy (CAA). The results suggest that in vivo PIB binding accurately reports the presence of amyloid, but may not differentiate between deposits in blood vessels or in brain parenchyma.
PET scanning with the amyloid binding dye PIB shows great promise as a biomarker to both diagnose AD and to monitor the effects of AÃ-reducing therapies (see ARF related news story). Despite extensive indirect experimental evidence, the tracer had never been directly proven to label amyloid-Ã in living brain. The new results provide an important confirmation of the presence of AÃ in this patient, but highlight the potential for error if positive PIB signals are presumed to indicate either current or impending AD. Despite a high level of PIB binding, the autopsy findings only support a classification of possible AD, by the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) criteria.
âOur report substantiates the view that PiB uptake is a sensitive method to detect AÃ in the brain, but points out the fact that clinical conditions other than probable or definite AD may harbor PiB-detectable amyloid depositsâthus broadening the range of clinically defined syndromes in which a PiB scan may be positive,â the authors write. It may be best, they say, ânot to equate amyloid deposition to clinical diagnosis from the outset but to think of PiB retention more fundamentally as a method to detect and quantify brain Ã-amyloidosis.â In this regard, the technique will serve as a diagnostic aid, but will be of âgreat valueâ in evaluating therapies aimed at reducing AÃ, they conclude.
Because a large proportion of the PIB signal in this patient appears to originate from CAA, it will be important to study additional patients to determine if this is a common result, or an unusual state.
âThis article provides strong validation that PiB retention is very likely reflective of AÃ that is deposited as amyloid,â writes David Holtzman of Washington University in St. Louis, Missouri, in an accompanying commentary.
However, Holtzman writes, âBecause the pattern of cortical PiB retention in this individual was very similar to that described in other cases of AD, these findings suggest that PiB imaging with current PET scanning technology cannot definitively distinguish whether amyloid deposition is present in blood vessels (as CAA), brain parenchyma (as amyloid plaques) or both.â Further studies will be necessary to determine the predictive power of PIB binding, both in PIB-positive bona fide AD patients and in PIB-negative controls.âPat McCaffrey.
Bacskai BJ, Frosch MP, Freeman SH, Raymond SB, Augustinack JC, Johnson KA, Irizarry MC, Klunk WE, Mathis CA, Dekosky ST, Greenberg SM, Hyman BT, Growdon JH. Molecular imaging with Pittsburgh compound B confirmed at autopsy: a case report. Arch Neurol. 2007 Mar;64(3):431-4.
Holtzman DM. Pittsburgh compound B retention and verification of amyloid deposition. Arch Neurol. 2007 Mar;64(3):315-6.