Erlick A. C. Pereira

Long-term outcomes of deep brain stimulation for neuropathic pain.

BACKGROUND Deep brain stimulation (DBS) to treat neuropathic pain refractory to pharmacotherapy has reported variable outcomes and has gained United Kingdom but not USA regulatory approval. OBJECTIVE To prospectively assess long-term efficacy of DBS for chronic neuropathic pain in a single-center case series. METHODS Patient reported outcome measures were collated before and after surgery, using a visual analog score, short-form 36-question quality-of-life survey, McGill pain questionnaire, and EuroQol-5D questionnaires (EQ-5D and health state). RESULTS One hundred ninety-seven patients were referred over 12 years, of whom 85 received DBS for various etiologies: 9 amputees, 7 brachial plexus injuries, 31 after stroke, 13 with spinal pathology, 15 with head and face pain, and 10 miscellaneous. Mean age at surgery was 52 years, and mean follow-up was 19.6 months. Contralateral DBS targeted the periventricular gray area (n = 33), the ventral posterior nuclei of the thalamus (n = 15), or both targets (n = 37). Almost 70% (69.4%) of patients retained implants 6 months after surgery. Thirty-nine of 59 (66%) of those implanted gained benefit and efficacy varied by etiology, improving outcomes in 89% after amputation and 70% after stroke. In this cohort, >30% improvements sustained in visual analog score, McGill pain questionnaire, short-form 36-question quality-of-life survey, and EuroQol-5D questionnaire were observed in 15 patients with >42 months of follow-up, with several outcome measures improving from those assessed at 1 year. CONCLUSION DBS for pain has long-term efficacy for select etiologies. Clinical trials retaining patients in long-term follow-up are desirable to confirm findings from prospectively assessed case series.

Sustained reduction of hypertension by deep brain stimulation.

Deep brain stimulators were implanted in the left periaqueductal gray matter (PAG) and sensory thalamus for right sided neuropathic facial pain refractory to other treatments in a man aged 58 years. PAG stimulation 8 months later acutely reduced systolic blood pressure by 25 mm Hg during revision surgery. One year post procedure, ambulatory blood pressure monitoring demonstrated significant and sustained reduction in blood pressure with PAG stimulation. Mean systolic blood pressure decreased by 12.6mm Hg and diastolic by 11.0mm Hg, alongside reductions in variability of heart rate and pulse pressure. This neurosurgical treatment may prove beneficial for medically refractory hypertension.

Elevated gamma band power in humans receiving naloxone suggests dorsal periaqueductal and periventricular gray deep brain stimulation produced analgesia is opioid mediated.

BACKGROUND The midbrain periaqueductal and periventricular gray (PAVG) region is important for pain and autonomic modulation. We have previously described changes in blood pressure dependent upon dorsal or ventral electrode positioning with PAVG deep brain stimulation (DBS), yet controversy exists about whether DBS acts via endogenous opioid release. METHOD AND RESULTS We combined local field potential (LFP) recording from PAVG DBS electrodes in humans with naloxone and saline infusions to determine whether dorsal and ventral PAVG DBS act through opioidergic or other mechanisms. Four awake human subjects were investigated. DBS were implanted contralateral to the painful body part. Electrode contact positions were mapped using MRI and brain atlas information. Naloxone then saline were randomly administered to the blinded subjects and pain rated using a numeric pain rating scale at 30s intervals for 3 min. Two subjects received dorsal DBS electrodes and two had ventral placements. Significantly elevated gamma frequency band (30-90 Hz) power concomitant with pain exacerbation was found with naloxone versus both saline and rest in dorsal not ventral PAVG LFPs (p<0.005). Significantly elevated delta frequency band (0-4 Hz) power (p=0.001) was seen in one ventral PAVG subject with both naloxone and saline infusions. CONCLUSIONS Dorsal PAVG DBS may reduce pain by augmenting endogenous opioid release. Elevated gamma oscillations enhance awareness of worsening pain with opioid blockade. Ventral PAVG DBS may act by separate possibly autonomic mechanisms. Increased delta oscillations indicate a survival rhythm involved in the initiation of passive coping responses to homeostatic changes.

Pedunculopontine stimulation from primate to patient

Deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) is a novel neurosurgical therapy developed to address symptoms of gait freezing and postural instability in Parkinson’s disease and related disorders. Here we summarise our non-human primate investigations of relevance to our surgical targeting of the PPN and relate the primate research to initial clinical experience of PPN DBS.

Long-term motor cortex stimulation for phantom limb pain

Abstract We present the long-term course of motor cortex stimulation to relieve a case of severe burning phantom arm pain after brachial plexus injury and amputation. During 16-year follow-up the device continued to provide efficacious analgesia. However, several adjustments of stimulation parameters were required, as were multiple pulse generator changes, antibiotics for infection and one electrode revision due to lead migration. Steady increases in stimulation parameters over time were required. One of the longest follow-ups of motor cortex stimulation is described; the case illustrates challenges and pitfalls in neuromodulation for chronic pain, demonstrating strategies for maintaining analgesia and overcoming tolerance.

Simulation in Spinal Surgery and the Transition from Novice to Expert

he Nobel prize winning physicist Carl Wieman has written prolifically on the subject of how novices become experts T (1). He proposes that experts have a mental framework for organizing information that enables effortless retrieval of relevant collected facts; fast reasoning through chains of possibilities; recognition of ideas that conflict with prior knowledge and efficient integration of related ideas. They are able to notice relevant cues to next steps in a problem; recognize whether disparate events have the same underlying structure; organize evidence to find structure; identify empirical discrepancies and revise their ideas. In contrast, novices have piecemeal recollection; jump to unfounded conclusions; fail to recognize contradictions; memorize rather than integrate new ideas. They may miss obvious cues; organize examples based on surface features; dive into a task without organizing its components and fail to recognize when their ideas should be revised. This constructivist approach argues that expertise can be taught by facilitating students through problem solving in carefully selected cases, a paradigm highly relevant for teaching neurosurgery to residents by simulation.

Double insurance redux

We commend Professor Goel for his innovative combination of C1-2 transarticular and C1 lateral mass screws. We discussed his and Harms’ intraarticular methods and Magerl’s transarticular approach in our technical report that described the novel application of his ‘double insurance’ fixation to la maladie de Grisel, but was editorially limited to three references. We have also performed it in 30 patients since 2004, of which 26 have at least 1 year of clinical follow-up with similarly good outcomes in the 18 patients he reported. Most had rheumatoid arthritis, others having trauma, os odontoideum and failed posterior instrumented craniocervical fusion. Ninety-two per cent had neck pain, 23% brachalgia and 11% limb weakness. Mean age at surgery was 59 years and mean inpatient stay 7 days. After 18 months’ mean follow-up, statistically significant (p5 0.05) improvements were observed in mean visual analogue scores both for neck pain from 5.5 to 1.6 and C2 pain from 2.1 to 0.5. Ranawat grading of functional disability showed median improvement from grade II to grade I. Three patients complained of persisting C2 hypoaesthesia as found in Goel’s patients. Two cases were converted to posterior instrumented craniocervical fusion. Like Goel, we find pre-operative CT invaluable to assess lateral mass and pedicle dimensions and ensure adequate C2 pedicle height. Unlike him, we use titanium polyaxial screws and rods rather than steel screws and plates; do not operate with the head in weighted traction nor do we advise 3 months of hard collar use after surgery as we consider the spine sufficiently stabilised intra-operatively. We agree with Prof. Goel that double insurance fixation is both safe and effective, particularly for treating atlanto-axial instability with basilar invagination in the rheumatoid spine in our experience, and furthermore after retropharyngeal abscess as our article illustrates.