Single photon emission computed tomography striatal asymmetry index may predict dopaminergic responsiveness in Parkinson disease.

Objectives: Parkinson disease (PD) is a neurodegenerative disorder, characterized by the excellent response to l-dopa and by asymmetry of neurological signs. The aim of the present study is to investigate a possible relationship between responsiveness to l-dopa in patients with PD and asymmetry detected by single photon emission computed tomography (SPECT) with [I]FP-CIT (DaTSCAN).

Methods: We performed a retrospective study in 20 patients with PD never previously exposed to l-dopa, who had undergone (1) a short-term l-dopa test with l-dopa/carbidopa 250/25 mg to quantify dopaminergic responsiveness, and (2) a SPECT with DaTSCAN to assess the degree of nigrostriatal neuronal degeneration. We estimated the magnitude and the duration of the response to l-dopa test as well as the striatal asymmetry index (SAI) detected by SPECT with DaTSCAN.

Results: At l-dopa short-term test, most patients showed at least a mild response to the drug, and only 3 patients presented no response. Overall, the Unified Parkinson's Disease Rating Scale-Motor Examination section score at baseline was 24.9 ± 8.2, and that at peak was 21.2 ± 8 with a magnitude of the response scoring 16 ± 13.9%; the duration was 254 ± 91.2 minutes. The caudate and putamen uptakes of DaTSCAN were lower contralaterally to the most affected side. A significant positive correlation between the SAI and the magnitude of the response to l-dopa was found (r = 0.64, P = 0.002). Linear regression model provided an increase of 0.76 units of magnitude of l-dopa response every SAI unit.

Conclusions: Asymmetry resulted positively related to the magnitude of the response to l-dopa short-term test and may be usefully used to predict dopaminergic responsiveness in patients with PD.