Table 1 Summary of publications evaluating the effects of LFS of STN on FOG and other axial symptoms
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 | 60Â Hz/130Â Hz | 8Â 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 8Â 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 | 60Â Hz/130Â Hz | 10Â 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 10Â 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 | 60Â Hz/130Â Hz | 6Â 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. 1Â pt. switched back to 130Â 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 | 80Â Hz/130Â Hz | 1, 5 and 15Â 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 15Â 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 15Â 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. | 60Â Hz/130Â 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 | 60Â Hz/130Â 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 | 60Â Hz/130Â 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 |