2 August 2011
Schrader C, Capelle HH, Kinfe TM, Blahak C, Bäzner H, Lütjens G, Dressler D, Krauss JK
Objectives:
Stimulation-induced hypokinetic gait disorders with freezing of gait
(FOG) have been reported only recently as adverse effects
of deep brain stimulation (DBS) of the globus
pallidus internus (GPi) in patients with dystonia. The aim of this work
was
to determine the frequency and the nature of
this GPi-DBS–induced phenomenon.
Methods: We
retrospectively screened our database of patients with dystonia who
underwent DBS. Patients with focal, segmental, or
generalized dystonia of primary or tardive
origin and no gait disorder due to lower limb dystonia before DBS,
bilateral pallidal
stimulation, and a follow-up for more than 6
months were included. Reports of adverse events were analyzed, and gait
abnormalities
were scored by comparing preoperative and
postoperative video recordings using Movement Disorder Society–sponsored
revision
of the Unified Parkinson's Disease Rating Scale
(MDS-UPDRS) items 3.10 (gait) and 3.11 (FOG). To assess the role of
GPi-DBS
in gait abnormalities, DBS was paused for 24
hours. Gait and FOG were assessed 30 minutes, 2 hours, and 24 hours
after restarting
DBS. Finally, a standardized adjustment
algorithm was performed trying to eliminate the gait disorder.
Results: Of a
collective of 71 patients with dystonia, 6 presented with a new gait
disorder (8.5%; 2 men, 4 women, mean age 61.3 years
[48–69 years], 2 craniocervical, 1 DYT-1
segmental, 1 truncal, 2 tardive dystonia). GPi-DBS improved
Burke-Fahn-Marsden Dystonia
Rating Scale motor score by 54% and disability
score by 52%. MDS-UPDRS item 3.10 worsened from 0.5 (±0.8) to 2.0 (±0.9)
and
item 3.11 from 0 to 2.5 (±0.5). The gait
disorder displayed shuffling steps and difficulties with gait initiation
and turning.
Increasing voltages improved dystonia but
triggered FOG, sometimes worsening over a period of a few hours. It
vanished within
minutes after ceasing DBS. Electrode
misplacement was ruled out. In all but one patient, no optimal
configuration was found
despite extensive testing of settings
(monopolar, bipolar, pulse width 60–210 μs, frequency 60–180 Hz).
Nevertheless, a compromise
between optimal stimulation for dystonia and
eliciting FOG was achieved in each case.
Conclusions: A hypokinetic gait disorder with FOG can be a complication of GPi-DBS.
