Nuclear imaging can predict pathologic diagnosis in progressive nonfluent aphasia

Progressive nonfluent aphasia (PNFA) is a subgroup of frontotemporal dementia (FTD).1 The histopathologic substrate includes individuals with tau inclusions (including some with corticobasal degeneration2), ubiquitin inclusions, and dementia lacking distinctive histology.3 However, a substantial minority have atypically distributed Alzheimer disease (AD) pathology.4,5 While FDG-PET has indicated that the site of neural dysfunction underpinning loss of fluency in PNFA is in the left anterior insula and posterior Broca area,6 FDG-PET hypometabolism or HMPAO-SPECT hypoperfusion in posterior temporoparietal association cortex (TPA) is the hallmark of standard clinical AD.7 We tested the hypothesis that PET or SPECT findings in the TPA could predict the presence, or absence, of AD pathology in PNFA. Blinded visual rating of SPECT (n = 14) or PET (n = 5) for TPA lesions was compared to the gold standard of postmortem histopathologic diagnosis in 19 patients with PNFA (13 FTD-spectrum and 6 AD pathology; see E-Methods on the Neurology Web site at www.neurology.org). In the AD pathology group, three …