Frontotemporal decreases in rCBF correlate with degree of dysnomia in primary progressive aphasia

Primary progressive aphasia (PPA) is an uncommon degenerative dementia characterized by gradual impairment of language function with initial sparing of the memory domain. Using semiquantitative 99mTc-hexamethyl propyleneamine oxime (HMPAO) brain SPECT as a measure of regional cerebral blood flow (rCBF), we investigated the relationship between reduced 99mTc-HMPAO uptake and the severity of dysnomia in PPA.

Seven right-handed patients with PPA had their dysnomia assessed by the Boston Naming Test (BNT), a subtest of the Boston Diagnostic Aphasia Examination. Neuroimaging studies, including 99mTc-HMPAO brain SPECT, CT, and MRI, were performed. Correlational analysis between reduced rCBF and BNT was performed.

Brain SPECT showed a reduction in 99mTc-HMPAO uptake involving the frontal and temporal lobes in all 7 patients. CT and MRI showed mild to moderate cerebral atrophy in 4 patients. Low scores on the BNT correlated with low frontotemporal 99mTc-HMPAO (Spearman r = 0.97, P = 0.004) in the 5 patients with left-hemisphere involvement.

Decreased rCBF to the frontotemporal region characterized the cerebral abnormalities associated with PPA. The finding of focal rCBF abnormalities in the right hemisphere of 2 right-handed women corroborates that PPA symptoms may arise from a "non-left-dominant"-hemisphere degenerative process. Our results support the usefulness of rCBF SPECT imaging as a diagnostic aid in PPA.