Striatal [123I]β-CIT SPECT and prefrontal cognitive functions in Parkinson's disease

Twenty non-demented patients with idiopathic Parkinson's disease (PD) underwent single photon emission computed tomography (SPECT) with [I-123]beta-CIT to further investigate the contribution of nigrostriatal dysfunction to cognitive and motor deficits. Compared to matched controls PD patients showed normal verbal intelligence, short-term memory and phasic alertness. There were significant (p < 0.05) deficits in tests of verbal working memory (digit ordering, reading span), strategic memory (story recall) and executive functions (card sorting), indicating a "prefrontal" cognitive deficit. Significant (p < 0.05) correlations were observed between dopamine transporter (DAT) density in the putamen and motor deficits as well as between DAT density in both striatal compartments (head of the caudate nucleus and putamen) and prefrontal functioning. Age was a major contributing factor to both cognitive status and nigrostriatal integrity as measured by [I-123]beta-CIT SPECT. These results support the view that the striatum is part of a neuronal network that is mediating prefrontal cognitive functions.