TY  - JOUR
AU  - Snijders, A.H.
AU  - Weerdesteijn, V.G.M.
AU  - Hagen, Y.J.
AU  - Duysens, J.E.J.
AU  - Giladi, N.
AU  - Bloem, B.R.
PY  - 2010
UR  - https://hdl.handle.net/2066/87218
AB  - Freezing of gait (FOG) is a common and disabling feature of Parkinson's disease (PD). Detailed pathophysiological studies are hampered by the fact that FOG episodes are difficult to elicit in a gait laboratory. We evaluated whether the need to avoid sudden obstacles on a treadmill can provoke FOG. We included 21 PD patients (15 with self-reported off-period FOG). Patients were tested in the off-state. FOG during overground walking was assessed using a standardized gait trajectory and axial 360 degrees turns. Subsequently, patients walked on a motorized treadmill with suddenly appearing obstacles that necessitated compensatory stepping. Performance was videotaped, and presence of FOG was scored visually by two independent raters. Thirteen patients showed FOG during overground walking. During treadmill walking, obstacle avoidance was associated with 13 unequivocal FOG episodes in eight patients, whereas only one patient froze during undisturbed treadmill walking (Wilcoxon z = -2.0, P = 0.046). FOG episodes elicited by obstacle avoidance were brief (typically <1 s). Almost all episodes were provoked when subjects had a longer available response time. In conclusion, suddenly appearing obstacles on a treadmill can elicit FOG in a controlled laboratory setting. However, the moving treadmill and the obstacle both act as cues, which apparently help to immediately overcome the provoked FOG episode. This may limit the ecological validity of this new approach.
TI  - Obstacle avoidance to elicit freezing of gait during treadmill walking.
EP  - 63
SN  - 0885-3185
IS  - iss. 1
SP  - 57
JF  - Movement Disorders
VL  - vol. 25
DO  - http://dx.doi.org/10.1002/mds.22894
ER  - 
TY  - JOUR
AU  - Delval, A.
AU  - Snijders, A.H.
AU  - Weerdesteijn, V.G.M.
AU  - Duysens, J.E.J.
AU  - Defebvre, L.
AU  - Giladi, N.
AU  - Bloem, B.R.
PY  - 2010
UR  - https://hdl.handle.net/2066/87214
AB  - Freezing of gait (FOG) is a clinically defined phenomenon of Parkinson's disease (PD). Recent evidence suggests that subtle FOG episodes can be elicited in a gait laboratory using suddenly appearing obstacles during treadmill walking. We evaluated which quantitative gait parameters identify such subtle FOG episodes. We included 10 PD patients with FOG, 10 PD patients without FOG, and 10 controls. Subjects walked on a motorized treadmill while avoiding unexpectedly appearing obstacles. Treadmill walking was videotaped, and FOG episodes were identified by two independent experts. Gait was also analyzed using detailed kinematics. Knee joint signals were processed using time-frequency analysis with combinations of sliding fast Fourier transform and wavelets transform. Twenty FOG episodes occurred during treadmill walking in 5 patients (all with clinically certified FOG), predominantly in relation to obstacle avoidance. FOG was brief when it occurred just before or after obstacle crossing and was characterized by short, rapid steps. Frequency analysis showed a typical qualitative pattern: before the FOG episode an increase in dominant frequency in the 0 to 3 Hz band (festination), followed by decreased power in 0 to 3 Hz band and an increased power in the 3 to 8 Hz band during the FOG episode. This pattern led to an increased FOG index as a qualitative measure. These approaches detected even very brief FOG with acceptable sensitivity (75-83%) and specificity (>95%). We conclude that time-frequency analysis is an appropriate approach to detect brief and subtle FOG episodes. Future work will need to decide whether this approach can support or even replace expert clinical opinion.
TI  - Objective detection of subtle freezing of gait episodes in Parkinson's disease.
EP  - 1693
SN  - 0885-3185
IS  - iss. 11
SP  - 1684
JF  - Movement Disorders
VL  - vol. 25
DO  - http://dx.doi.org/10.1002/mds.23159
ER  -