To evaluate the anatomical and clinical features of behavioral variant frontotemporal dementia (bvFTD) in the setting of Progressive apraxia of speech (PAOS).

Among our prospectively recruited PAOS participants, 11 were identified as having features consistent with, or reminiscent of, bvFTD and who had completed a volumetric head MRI scan. We compared clinical and anatomical atrophy patterns of these 11 PAOS-bvFTD participants to 11 PAOS participants without bvFTD and 22 healthy controls. Statistical Parametric Mapping (SPM) was applied using BrainRenders to visualize gray matter volume across both groups compared to controls and to each other. Fisher’s Exact and Mann-Whitney U tests were applied for data analysis.

Six PAOS-bvFTD participants were women. The median age of onset of AOS, and the onset of behavioral change were 57 and 62, respectively. Of the 11 PAOS-bVFTD participants, six met bvFTD criteria at first visit, the remaining five met criteria later in time. If the 3-year rule was removed from the criteria, seven would meet bvFTD criteria at baseline and four later in time. All but one PAOS-bvFTD participant had the phonetic subtype of AOS, and seven had aphasia. Four participants died with autopsy showing Picks disease (n=2), corticobasal degeneration (n=1), and mixed 3R + 4R tauopathy (n=1). As expected, PAOS-bvFTD participants had significantly more behaviors and neuropsychiatric changes than the PAOS participants without bvFTD (p<0.01). On SPM, PAOS-bvFTD and PAOS participants had more volume loss in frontal lobe regions compared to controls. On direct comparison, the PAOS-bvFTD participants showed more prefrontal atrophy than PAOS at the time of presentation.

Patients with PAOS can develop bvFTD features, which is related to greater atrophy of the prefrontal cortex.