Objective: To evaluate FOG in patients with PD treated with STN-DBS and to compare sensitivity of different assessments of FOG in this specific group of patients.

Background: Freezing of gait (FOG) is a brief sudden episode of inability to perform an effective step commonly seen in advanced Parkinson’s disease (PD) with variable response to treatment with levodopa and subthalamic deep brain stimulation (STN-DBS). The FOG limits mobility of patients, increases risk of falling and deteriorate quality of life. Detection of FOG is therefore very important for proper evaluation of treatment effects and to prevent falls.

Methods: We investigated 32 PD patients (5 F, 27 M, average age of 59.9±(SD)6.5 years) on dopaminergic medication and STN-DBS therapy lasting for 4.9±3.3 years. Each patient was tested in OFF medication state with two conditions: (i) STN-DBS bilaterally switched ON (UPDRS-III: 23.8±10.3) and (ii) STN DBS bilaterally switched OFF (UPDRS-III: 45.3±14.4). All patients completed Freezing of Gait Questionnaire (FOGQ) as a screening tool. They underwent a set of clinical examination focused on detection of FOG: Timed Up and Go test (TUG), 10m Speed walk test (10mSWT), Short step test (SST) and Ziegler test).

Results: Twenty seven patients reported at least one FOG episode per month and all patients referred some gait impairment according to FOGQ (10.5±5.5 points). Ten patients were unable to pass the entire testing in the DBS OFF condition. From the objective examination methods, the Ziegler test appeared as the most sensitive, detecting FOG in 21/32 patients in the DBS ON condition (mean score 8.3±SD 9.7) and in 19/23 patients in DBS OFF (13.0±11.7). The TUG test revealed FOG in 10/32 patients in the DBS ON condition and in 13/24 in DBS OFF. SST demonstrated FOG in 8 and 10mSWT in 2 patients. Compared with the FOGQ results, the FOG was observed in 3 patients with negative screening, but we fail to confirm FOG in 1 patient with positive screening.

Conclusions: Nearly 84 % of our patients with advanced-stage of Parkinson’s disease on DBS therapy referred FOG, however we objectively confirmed FOG in 91 % of all the patients. Out of used clinical tests for FOG assessment, the Ziegler test seems to be the most sensitive investigation tool.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/assessment-of-freezing-of-gait-in-parkinsons-disease-patients-treated-with-stn-dbs/