Abstract
Lateral trunk flexion (LTF) is a common phenomenon in patients with Parkinson's disease (PD) and has recently been associated with peripheral vestibular dysfunction. Since deviation of the subjective visual vertical (SVV) is a well-recognized feature of disorders involving vestibular processing, we analyzed SVV angles in 30 PD patients with and without LTF to assess the possible role of vestibular dysfunction in the pathogenesis of LTF in PD. Quantification of SVV was obtained using a simple bedside test. PD patients with LTF had significantly greater SVV angles as compared to PD patients without LTF (median: 4.3° [range: 0.1–17.7], n = 21, versus 0.8° [0.1–1.9], n = 9; p < 0.001). 14 of 21 patients with LTF showed pathological SVV, while all 9 patients without LTF had normal SVV. Abnormal SVV was more frequent when LTF was reversible in the supine position compared to fixed LTF. In a subgroup of PD patients with LTF, pathological SVV suggests vestibular dysbalance, which might be involved in the pathophysiological mechanisms underlying LTF.
Highlights
Lateral trunk flexion (LTF) in Parkinson’s disease (PD) is usually evident when subjects are standing or sitting and may be reversible in the supine position
10 of 14 PD patients (71%) with pathological subjective visual vertical (SVV) but none with normal SVV reported LTF to have occurred after PD symptom onset
All PD patients with mobile LTF reported lateral flexion occurring after PD symptom onset, and in all PD patients with fixed LTF, lateral flexion was reported to have occurred before PD symptom onset (Table 1)
Summary
Lateral trunk flexion (LTF) in PD is usually evident when subjects are standing or sitting and may be reversible in the supine position. The term “Pisa Syndrome” has been defined as LTF > 10∘ in the standing position, which typically subsides in the supine position (“mobile LTF”) [1]. Vitale and colleagues have provided evidence for peripheral vestibular dysbalance in PD patients with LTF applying vestibular tests including caloric testing, head-shaking test, vibration test, and fast positioning maneuvers [3]. Since vestibular dysbalance in the roll plane is associated with deviation of the subjective visual vertical (SVV) [4], we applied a simple bedside test to measure SVV in PD patients with or without LTF in an attempt to obtain further evidence for vestibular dysfunction in LTF of PD
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