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Table 1 Summary of publications evaluating the effects of LFS of STN on FOG and other axial symptoms

From: Effect of low versus high frequency stimulation on freezing of gait and other axial symptoms in Parkinson patients with bilateral STN DBS: a mini-review

Ref# Author, year Number of patients Study design Med On/Off FOG at HFS LFS/HFS value Follow up duration TEED adjustment Outcomes
[4] Moreau et al., 2008 13 Randomized double blinded Off Yes 60 Hz/130 Hz 8 months Yes Acutely, significantly better in all aspects of SWS, including FOG at LFS. F/U: 85% pts. had maintenance of clinical benefit on gait 8 months after on LFS. 10 pts. on ventral, 3 pts. on dorsal contacts. 2 pts. switched back to HFS due to worsening tremor.
[11] Brozova et al., 2009 12 Non-randomized non-blinded On Yes (7/12 pts) 60 Hz/HFS (unknown exact Hz for HFS) 8–12 weeks in 9 pts. (3 pts. unable to stay on LFS due to worsening of tremor, gait, and rigidity) Not mentioned
but voltage increased in 7 pts
F/U: overall, improvements in speech, falling and walking in UPDRS-II and speech and gait in UPDRS-III subscores but worsening of postural stability and gait in 2 pts.
[6] Xie et al., 2012 2 Non-randomized non-blinded Both Yes 60 Hz/130 Hz 10 months No Acutely: improvements in UPDRS-III score, FOG and speech at LFS at medication Off and On state. F/U: the beneficial effects lasted for 10 months of the study period.
[10] Ramdhani et al., 2015 5 Non-randomized non-blinded On Yes (4/5) 60 Hz/130–185 Hz 2–6 months Not mentioned F/U: at HFS 4/5 had FOG while at LFS only 2/5 pts. had FOG, with reduced severity and axial symptoms, along with amelioration of segmental symptoms and levodopa induced dyskinesia. All pts. had ventral contacts and 3 pts. had simultaneous dorsal contacts.
[7] Xie et al., 2015 7 Randomized double blinded On Yes 60 Hz/130 Hz 6 weeks No Acutely: compared with HFS, LFS improved swallowing function, FOG, and axial and overall parkinsonism. The axial score and UPDRS-III score also improved at LFS compared to DBS Off. The axial score was worse at HFS. F/U: benefits persisted over the 6-week study period. 1 pt. switched back to 130 Hz due to worsening tremor.
[16] Ricchi et al., 2012 11 Non-randomized
blinded and non-blinded portions
On No FOG on exam, some had FOG in history 80 Hz/130 Hz 1, 5 and 15 months Yes Acutely: improvement on SWS test after acutely switching to LFS, with no deterioration of segmental symptoms. F/U: gait improvement no longer detectable by the SWS test 1, 5, and 15 months later. 3 pts. switched back to HFS because of unsatisfactory control of motor symptoms (tremor in 2). 8 pts. maintained at LFS for up to 15 months, with 5 showing a clinical global improvement on the scale. All on dorsal except 1 on ventral contacts.
[13] Sidiropoulos et al., 2013 45 Non-randomized non-blinded On Not specified, but axial impairment with no satisfactory benefit from HFS 60–80 Hz/130–185 Hz
(6 on 60 Hz, 39 on 80 Hz)
111.5 days,
(the median, up to 4 years)
No F/U: overall, no improvement with LFS on any of the measures in UPDRS III motor, axial, gait, and speech subscores, and self-reported number of falls.
[9] Khoo et al., 2014 14 Randomized
double blinded
On No FOG at medication ON assessment, but most had FOG at medication OFF by history. 60 Hz/130 Hz No long term follow up Yes Acutely: mean UPDRS III score, axial motor subscore and akinesia subscores were improved for LFS. Also, less time and fewer steps to complete the 10-m walk and a tendency of improving the balance. No difference between HFS and LFS in tremor or rigidity. Optimal contacts for LFS were more ventrally distributed.
[14] Stegemoller et al., 2013 17 Randomized double blinded Off Not specified 60 Hz/≥130 Hz No long term follow up No Acutely: HFS significantly reduced tremor in tremor dominant (TD) pts., but no acute differences between LFS and HFS on gait, balance, and verbal fluency in both TD and non-TD pts.
[15] Vallabhajosula et al., 2015 19 Randomized, blinded and non-blinded portions Off Not specified Phase 1: Off stim, optimal with HFS (≥100 Hz), LFS (60 Hz) without TEED maintained
Phase 2 (10/19 pts): Off stim, very LFS (30 Hz) with highest tolerable voltage, LFS (60 Hz) with highest tolerable voltage, HFS at baseline voltage
No long term follow up No Acutely: UPDRS-III score, step length and velocity during gait initiation and gait speed improved during LFS and HFS when compared to the DBS Off condition. No significant differences between LFS and HFS conditions. Using LFS at higher voltages showed no improvement over HFS condition.
[12] Phibbs et al. 2014 20 Randomized double blinded Off Yes (7/19 pts) per history but hard to replicate on exam 60 Hz/130 Hz No long term follow up No Acutely: no significant difference was found in primary outcome of stride length with the change in frequency or the secondary measures (time on SWS test, data on gait from GaitRite). Improved FOG at LFS in the pt. with FOG at HFS, per description.
[5] Moreau et al., 2011 11 Randomized double blinded Off Yes 60 Hz/130 Hz No long term follow up Yes Acutely: improvement in aerodynamic speech parameters during LFS accompanied by significant clinical benefit of more intelligible speech compared to HFS and DBS Off states
  1. Notes: LFS low frequency stimulation, HFS high frequency stimulation, FOG freezing of gait, Med medications, TEED total electrical energy delivered, SWS stand walk sit test, Pts patients, Ref# reference number, F/U follow up.