山中 義崇

Rigidity, a cardinal symptom of Parkinson's disease (PD), remains challenging to assess objectively. A torque-angle instrument was developed to quantify muscle tone, providing two parameters: bias difference and elastic coefficient. This study aimed to investigate the association of the instrument-measured rigidity with clinical assessments and brain function. In 30 patients with PD, the muscle tone in both arms was evaluated. Ten with wearing-off phenomenon were assessed twice, off and on condition. Twentynine patients underwent brain perfusion single-photon emission computed tomography (SPECT), and expression of PD-related covariance pattern (PDRP) was computed. Bias difference and elastic coefficient showed positive correlations with physician-rated rigidity (P < 0.002). Bias difference decreased after dopaminergic medication (P = 0.022) and was associated with lower body mass index (P = 0.012). Elastic coefficient positively correlated with the Unified PD Rating Scale Part III and PDRP scores (P < 0.044). Furthermore, the higher bias difference correlated with decreased sensory-motor cortex and increased substantia nigra perfusion (P < 0.001). The Torque-angle instrument is a viable tool for quantifying rigidity in PD. The bias difference reflects treatment responsiveness and is associated with the function in the sensory-motor cortex and substantia nigra. The elastic coefficient is indicative of overall Parkinsonism severity.

Multiple system atrophy with predominant parkinsonism (MSA-P) can hardly be distinguished from Parkinson’s disease (PD) clinically in the early stages. This study investigated whether a standardized T1-weighted/T2-weighted ratio (sT1w/T2w ratio) can effectively detect degenerative changes in the middle cerebellar peduncle (MCP) associated with MSA-P and PD and evaluated its potential to distinguish between these two diseases. We included 35 patients with MSA-P, 32 patients with PD, and 17 controls. T1w and T2w scans were acquired using a 1.5-T MR system. The MCP sT1w/T2w ratio was analyzed via SPM12 using a region-of-interest approach in a normalized space. The diagnostic performance of the MCP sT1w/T2w ratio was compared between the MSA-P, PD, and controls. Patients with MSA-P had significantly lower MCP sT1w/T2w ratios than patients with PD and controls. Furthermore, MCP sT1w/T2w ratios were lower in patients with PD than in the controls. The MCP sT1w/T2w ratio showed excellent or good accuracy for differentiating MSA-P or PD from the control (area under the curve (AUC) = 0.919 and 0.814, respectively) and substantial power for differentiating MSA-P from PD (AUC = 0.724). Therefore, the MCP sT1w/T2w ratio is sensitive in detecting degenerative changes in the MCP associated with MSA-P and PD and is useful in distinguishing MSA-P from PD.