12 Aug 2008

A paper published online today in the Archives of Neurology suggests that a non-invasive imaging procedure detects buildup of amyloid-β—the protein that forms sticky plaques in the brains of Alzheimer’s patients—in patterns consistent with those found in brain biopsy specimens. As reported earlier this year at the Human Amyloid Imaging meeting (see ARF related conference story) and at the International Conference on Alzheimer’s Disease in Chicago, Juha Rinne of the University of Turku, Finland, and colleagues performed PET scans using the widely used amyloid tracer Pittsburgh Compound B (PIB). Previous work had shown a correlation between PIB-PET images and amyloid deposition revealed in the same individuals at autopsy (see ARF related news story and ARF news story). However, the new study is the first to compare PIB-PET scans with Aβ accumulation in brain specimens from living people—in this case, 10 patients who had frontal cortical biopsies done as a routine procedure during monitoring for normal pressure hydrocephalus (NPH), a brain condition with concomitant AD pathology in some cases.

First author Ville Leinonen and colleagues evaluated patients for cognitive impairment (using CDR, MMSE, and CERAD measures) just prior to PIB-PET imaging, which was done two to 36 months following biopsy. As a group, the six people with Aβ deposits in the biopsy (three with tau pathology as well) had significantly higher PIB uptake in the frontal, parietal, and lateral temporal cortices and in the striatum, compared with those lacking frontal Aβ deposits. All patients with normal biopsy results also came up PIB-negative. However, one case that was clearly Aβ-positive in the biopsy turned out PIB-negative by PET, suggesting that there might be forms of Aβ that escape detection by PIB. The authors also noted that follow-up work is needed to determine the clinical significance of the Aβ detected by biopsy and PIB-PET imaging, as none of the six patients with AD-like features in this study had severe dementia.—Esther Landhuis