Percutaneous nerve field stimulation (PENS) of the occipital region as a possible predictor for occipital nerve stimulation (ONS) responsiveness in refractory headache disorders? A feasibility study.

BACKGROUND: Occipital nerve stimulation (ONS) has been reported to diminish pain levels in intractable chronic headache syndromes of different origin. No reliable objective markers exist to predict ONS responsiveness. This study investigated the predictive value of occipital percutaneous nerve field stimulation (PENS) prior to ONS. METHODS: This trial included 12 patients (CCH, CM, PTH, CH) with chronic refractory headache syndromes eligible for ONS. Repetitive PENS (3 × /10 days) was performed and the headache severity/frequency monitored over four weeks before ONS implantation. Further assessment of PENS/ONS outcomes were stimulation-related complications, perception/tolerance stimulation threshold, the Migraine Disability Scale (MIDAS) and the Beck Depression Inventory (BDI). RESULTS: All PENS responders benefited from ONS. Of the seven PENS-nonresponders with VAS 6.1(±1.1), six experienced significant pain relief from ONS after three months and one patient failed the PENS/ONS trial (VAS 3.7 (±1.6)); (95% CI 3.6 to 5.7, p < 0.001). The VAS baseline was 8.4 (±0.5) and decreased significantly (50% reduction in severity/frequency) in five patients after PENS, while seven failed to improve (VAS 4.9 (±1.1); (95% CI 2.5 to 4.5, p < 0.001). BDI baseline (from 22.6 (±4.2) to 10.6 (±5.9) (95% CI 7.4 to 16.6, p < 0.001)) and MIDAS baseline (from 143.9 (±14.5) to 72.8 (±28.7) (95% CI 1.17 to 2.3, p < 0.001)) significantly declined after ONS. No PENS/ONS-related complications occurred. CONCLUSIONS: Presurgical applied occipital PENS failed to identify ONS responders sufficiently according to our study protocol, thus requiring further specific investigations to determine its predictive usefulness.

The impact of brain shift in deep brain stimulation surgery: observation and obviation.

BACKGROUND: The impact of brain shift on deep brain stimulation surgery is considerable. In DBS surgery, brain shift is mainly caused by CSF loss. CSF loss can be estimated by post-surgical intracranial air. Different approaches and techniques exist to minimize CSF loss and hence brain shift. The aim of this survey was to investigate the extent and dynamics of CSF loss during DBS surgery, analyze its impact on final electrode position, and describe a simple and inexpensive method of burr hole closure. METHODS: Sixty-six patients being treated with deep brain stimulation were retrospectively analyzed for this treatise. During surgery, CSF loss was minimized using bone wax as a burr hole closure. Intracranial air volume was calculated based on early post-surgery stereotactic 3D CT and correlated with duration of surgery and electrode deviations derived from post-surgery image fusion. RESULTS: Median early post-surgery intracranial air was 2.1 cm(3) (range 0-35.7 cm(3), SD 8.53 cm(3)). No correlation was found between duration of surgery and CSF-loss (R = 0.078, p = 0.534), indicating that CSF loss mainly occurs early during surgery. Linear regression analysis revealed no significant correlations regarding volume of intracranial air and electrode displacement in any of the three principal axes. No significant difference regarding electrode deviations between first and second side of surgery were observed. CONCLUSIONS: CSF loss mainly occurs during the early phase of DBS surgery. CSF loss during a later phase of surgery can be effectively averted by burr hole closure. Postoperative intracranial air volumes up to 35 cm(3) did not result in significant electrode displacement in our series. Comparing our results to studies previously published on this subject, burr hole closure using bone wax is highly effective.

GPi-DBS may induce a hypokinetic gait disorder with freezing of gait in patients with dystonia.

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.

Battery lifetime in pallidal deep brain stimulation for dystonia.

BACKGROUND AND PURPOSE: The aim of the study was to analyse the lifetime of Soletra implantable pulse generators (IPG) in deep brain stimulation (DBS) of the globus pallidus internus (GPi) for dystonia, depending on stimulation parameters and the total electrical energy delivered (TEED) by the IPG. METHODS: In a prospective series of 20 patients with GPi DBS for dystonia, we recorded IPG longevity and stimulation parameters over time. An evaluation of the TEED was performed using the previously suggested equation [(voltage(2) × pulse width × frequency)/impedance] × 1 s. RESULTS: During median follow-up of 57 months (range 23-79 months), 64 IPGs were replaced because of battery depletion or end of life signal. We found a mean IPG longevity of 25.1 ± 10.1 (range 16-60) months, which was inversely correlated with the TEED (r = -0.72; P < 0.001). IPG longevity was not different between bipolar and monopolar stimulation (24.9 ± 10.8 vs. 25.4 ± 9.0 months, P = 0.76). Incongruously, the mean TEED applied throughout the lifetime cycle was significantly higher in patients with bipolar compared with monopolar stimulation (584 ± 213 vs. 387 ± 121 Joule; P < 0.01). CONCLUSIONS: Battery lifetime in GPi DBS for dystonia is substantially shorter compared with that reported in DBS for Parkinson's disease, caused by a considerably higher voltage and greater pulse width and therefore a higher TEED applied during the battery lifetime cycle. The commonly used equation to calculate TEED, however, seems to be correct only for monopolar, but not bipolar stimulation.