PAOS is a neurodegenerative syndrome in which patients present with apraxia of speech, a motor speech disorder affecting programming, and planning of speech. Patients with PAOS inevitably develop Parkinsonism with death occurring approximately 5-years after Parkinsonism is clinically detected. DaTscan is a neuroimaging tool that assesses the integrity of dopamine receptors in basal ganglia and is abnormal in PD.

As a part of an NIH-funded grant, we performed DaTscan on 17 PAOS patients. DaTQuant software was used to quantify uptake in left and right caudate and anterior/posterior putamen, with uptake normalized to occipital lobe and converted into age-corrected Z-scores. The PAOS cohort was compared to 17 PD patients who underwent DaTscan as part of their clinical evaluation.

Eight PAOS patients (47%) were male with mean age at onset of 68 years (SD=±9) and disease duration of 3 years (±2.5).  Of the PD patients, 9 (53%) were male with age at onset of 60 years (±11) and disease duration of 3 years (±2). PD showed lower uptake than PAOS in left and right anterior (p=0.003 and p<0.001) and posterior (p<0.001 for both) putamen. No differences were observed for left and right caudate (p=0.06 for both), with both groups showing normal median Z-scores in caudate.  Five PAOS patients (29%) and all PD patients (100%) showed abnormalities in at least one region on DaTscan. When the five abnormal PAOS patients were compared to PD, lower uptake in PD was only observed in left and right posterior putamen (p=0.03 and p=0.01). 

Abnormal DaTscan is observed early in the disease course in approximately 30% of patients with PAOS, with abnormalities observed in the putamen, similar to PD.