Ioflupane 123I (DAT scan) SPECT identifies dopamine receptor dysfunction early in the disease course in Progressive Apraxia of Speech

Abstract

Objective

To describe ¹²³I-FP-CIT (DAT scan) SPECT findings in progressive apraxia of speech (PAOS) patients and to compare those findings to progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS).

Background

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 predictably develop Parkinsonism. DAT scan is a neuroimaging tool that assesses the integrity of presynaptic dopamine transporters in basal ganglia and is usually abnormal in PSP and CBS.

Methods

As a part of an NIH-funded grant, we performed a DAT scan on 17 PAOS patients early in the disease course. DaTQUANT software was used to quantify uptake in left and right caudate and anterior/posterior putamen, with striatum to background ratios (SBRs). The PAOS cohort was compared to 15 PSP and 8 CBS patients.

Results

Five PAOS patients (29%) showed abnormalities in at least one striatal region on DAT scan. When the five PAOS patients with abnormal DAT was compared to the PSP and CBS patients, the only difference observed was lower uptake in the posterior putamen in PSP (p=0.03). There were no differences is putamen/caudate ratio or in symmetry of uptake, across all groups. There was also no difference in MDS-UPDRS-III scores between PAOS patients with and without abnormal DAT scans (p=0.56).

Conclusions

Abnormal DAT scan is observed early in the disease course in approximately 30% of PAOS patients, with striatal abnormalities similar to those in PSP and CBS.