The frequency and diagnostic accuracy of hand deformities in Parkinson's disease.

Hand deformities are well-known abnormalities observed in patients with Parkinson's disease (PD). We determined the frequency and diagnostic accuracy of hand deformities in PD. We studied 44 consecutive patients with PD, 44 age- and gender-matched normal controls and 22 patients with essential tremor (ET). By means of photographs taken in both hands of all participants, the degree of metacarpophalangeal (MCP) joint flexion was quantified by software and by blinded evaluations using a semiquantitative scale from the radial aspect, we grouped hands into four grades. The presence of classical striatal hand deformity (CSHD), defined as MCP joint flexion, proximal interphalangeal joint extension and distal interphalangeal joint flexion was also evaluated. Patients with PD had a higher frequency of MCP joint flexion and CSHD compared to normal controls and patients with ET. Mean MCP joint flexion was higher in both hands in patients with PD: 20.8° vs. normal controls (3.3°-3.9°) and patients with ET (2.8°-6.3°), P = 0.001. Concordance between evaluators for MCP joint flexion was fair: κ = 0.34 (P < 0.001), but poor for CSHD: κ = 0.142-0.235 (P < 0.05). A right hand MCP joint flexion of 12.5° and left hand of 10.5°, showed similar sensitivity (0.70) and specificity (between 0.75 and 0.80) than any degree of MCP joint flexion for the diagnosis of PD. CSHD had a sensitivity (0.60-0.80) and specificity (0.78-0.98) for the diagnosis of PD. Hand deformities are commonly observed in patients with PD, they may aid in the diagnosis of PD when compared to normal controls and patients with ET.