Striatal asymmetry index and its correlation with the Hoehn & Yahr stage in Parkinson's disease

Striatal asymmetry is a common feature in Parkinson's disease (PD), which changes with the progression of the disease. However, the correlation between the striatal asymmetry and severity of PD remains unclear. The present study aimed to investigate the characteristics of asymmetry in PD, and analyze the correlation between the striatal asymmetry index (SAI) and disease severity.

This retrospective study enrolled 63 patients with idiopathic PD. The severity of PD was classified according to the Hoehn & Yahr (H&Y) staging system. The SAI in the subregions of the striatum was measured using ¹¹C-N-2-carbomethoxy-3-(4-fluorophenyl)-tropane (¹¹C-CFT) positron emission tomography (PET).

There was a significant difference in the SAI of the posterior putamen among the three groups (H&Y stage I, H&Y stage II, and H&Y stage III-IV; p = 0.001). However, there was no difference in the SAI of the anterior putamen (p = 0.340) or SAI of the caudate nucleus (p = 0.342) among the three groups. The SAI of the posterior putamen in patients with PD was significantly higher than that in patients with multiple system atrophy or progressive supranuclear palsy (p = 0.008).

The SAI of the posterior putamen is associated with the severity of PD, and may be correlated to the loss of dopamine cells in the pars compacta of the ventrolateral substantia nigra projecting to the posterior putamen. The SAI may be a potential indicator for evaluating the severity of PD, and distinguishing PD from other degenerative diseases.