Quantitative Assessment of Hand Dysfunction in Patients with Early Parkinson's Disease and Focal Hand Dystonia

Abstract

Objective: Motor impairments related to hand function are common symptoms in patients with movement disorders, such as Parkinson's disease (PD) and focal hand dystonia (FHD). However, hand dysfunction has not been quantitatively assessed as a clinical tool for screening patient groups from healthy controls (HCs). The aim of our study was 1) to quantitatively assess hand dysfunction in patients with PD and FHD and its usefulness as a screening tool 2) to grade disease severity in PD and FHD based on hand dysfunction.

Methods: The current case-control study included HCs (n = 50) and patients with known history of PD (n = 25) or FHD (n = 16). Hand function was assessed by a precision grip task while participants lifted objects of 1.3 N and 1.7 N under dry skin conditions, followed by very wet skin conditions (VWSCs). Receiver operating characteristic and summative scoring analyses were performed.

Results: In PD, the combination of loading phase duration and lifting phase duration at quantitative cutoffs of 0.36 and 0.74 seconds identified 21/25 patients as diseased and 49/50 subjects as HCs with 1.7 N under VWSCs. In PD, 5/21 was graded as "mild" and 16/21 as "moderate cases." In FHD, slip force at a cutoff of 1.2 N identified 13/16 patients as diseased and 41/50 subjects as HC with 1.7 N under VWSCs, but disease severity could not be graded.

Conclusion: Our results demonstrate the use of precision grip task as an important clinical tool in assessment of hand dysfunction in movement disorder patients. Use of quantitative cutoffs may improve diagnostic accuracy and serve as a valuable adjunct to existing clinical assessment methods.

Keywords: Parkinson’s; focal hand dystonia; hand dysfunction; lifting phase duration; loading phase duration; precision grip; slip force.

Figure 1.

Schematic drawing of the apparatus used for precision grip lift task. The rectangular object (1) is held with the thumb and index finger. The apparatus is made up of an outer steel frame (2). An elastic band (3) is wound around the frame, and it marks the height to which the object is required to be lifted. Subjects place their hands on the touch pad (4) prior to the beginning of each trial. An infrared sensing module (5) is clamped to the frame and it records the position of the object. The object is connected to the signal conditioning box (6) through a cable. Data are collected and stored in the laboratory computer.

Figure 2.

A: ROC curve of LPD and LFD combined to improve diagnostic accuracy between HCs and patients with PD under the 1.7 N VWSC is shown. Both temporal parameters were combined to enhance the diagnostic accuracy of our analysis. B: Comparison of temporal parameters between HCs and patients with PD under 1.7 N VWSC. This explains a significant temporal latency (p < 0.001) shown by Parkinson’s patients while holding and lifting objects. ^*p < 0.001. ROC: receiver operating characteristic curve, VWSC: very wet skin condition, PD: Parkinson’s disease, HCs: healthy controls, LPD: loading phase duration, LFD: lifting phase duration. Time delay is represented in seconds.

Figure 3.

A: A single parameter, namely, SF, in the ROC curve, which improved diagnostic accuracy of HCs and patients with FHD under the 1.7 N VWSC. B: Shown is the comparison of SF between HCs and patients with FHD under the 1.7 N under VWSC. The SF applied by dystonia patients (1.1 N) was below the estimated cut-off of 1.2 N. SF is represented in N. ^*p < 0.001. SF: slip force, ROC: receiver operating characteristic curve, HCs: healthy controls, FHD: focal hand dystonia, VWSC: very wet skin condition, N: Newtons, AUC: area under curve.