Objective: To evaluate the possible improvement of lateral and forward axial dystonia in PD patients following correction of minimal oculomotor abnormalities including version and saccades hypometria, fusional amplitude reduction of and gaze limitation through prismatic lenses.

Background:  (Several pathophysiological mechanisms have been proposed to explain the occurrence of trunk dystonia in Parkinson’s disease (PD). We have recently reported subjective and objective improvement of lateral axial dystonia in two PD patients following correction of  convergence insufficiency, one of the most common oculomotor abnormality in these patients [1].

Methods: : Five patients with PD were enrolled in the study. Exclusion criteria were: atypical parkinsonism, use of drugs known to worse dystonia, binocular vision < 20/28, advanced cataract, glaucoma, active maculopathy as well as radiological evidence of skeletal deformity or fracture. Concomitant treatments remained stable during the observation period. Patients were evaluated before and after two months (T1) of prismatic correction. The assessment included MDS-UPDRS II and III scale, orthotic examination, grading of the trunk dystonia through kinematic evaluation in the lateral and anterior axes and VAS scale.

Results: The following are the preliminary results of an open label ongoing trial (enrollment target 20 patients).. Prisms correction degrees ranged between 2 and 6. Mean lateral trunk bending was 10.36 (±2.06) degrees at baseline and 6.51 (±4.42) at T1, with a reduction of 3.65 degrees; Mean forward bending was 25.63 (±12.49) degrees at baseline and 18.03 (±15.21) at T1, with a reduction of 7.6 degrees; VAS mean score was 4 (±3.85) at baseline and 0.5 (±0.57) at T1, with a reduction of 3.5 scores. UPDRS II mean score was 15.50 (±9.03) at baseline and 13.50 (±10.9) at T1, with a reduction of 2 points. UPDRS III mean score was 46.50 at baseline, with no change at T1. The greatest improvement of trunk dystonia was observed in patients with higher prisms correction.

Conclusions: The present results might help to better interpret the pathophysiological mechanisms of trunk dystonia in PD. We hypothesize a that  the abnormal trunk posture in PD is a compensatory mechanism which improves visual acuity and maintains binocular vision.

References: [1] Santilli M, Meglio M, Varanese S, Lena F, Iezzi E, Grillea G, Modugno N. Improvement of lateral axial dystonia following prismatic correction of oculomotor control disorders in Parkinson’s disease. J Neurol. 2016 Jan 11

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MDS Abstracts - https://www.mdsabstracts.org/abstract/correction-of-minimal-oculomotor-disorders-improves-forward-and-lateral-axial-dystonia-in-pakinsons-disease/