Vignessh Kumar

Evolving Concepts in Posterior Subthalamic Area Deep Brain Stimulation for Treatment of Tremor: Surgical Neuroanatomy and Practical Considerations.

Background: Although thalamic deep brain stimulation (DBS) has been established as an effective therapy for refractory tremor in Parkinsons disease and essential tremor, reports investigating the efficacy of posterior subthalamic area (PSA) DBS for severe, debilitating tremors continue to emerge. However, questions regarding the optimal anatomical target, surgical approach, programming paradigms and effectiveness compared to other targets remain. Objectives: In this report, we aimed to review the current literature to assess different stereotactic techniques, anatomical considerations, adverse effects and stimulation settings in PSA DBS. Methods: A comprehensive literature review was performed searching for articles discussing tremors and PSA stimulation. We performed a quantitative analysis comparing different DBS tremor targets. Results: Tremor improvement is consistently documented in most reports with an average reduction in tremor of 79% depending on the specific tremor syndrome. Tremor benefit in patients with multiple sclerosis (MS) tremor was significantly higher than for other stimulation targets. Transient paresthesias, imbalance, dizziness and dysarthria are the most common side effects with PSA DBS. Conclusions: PSA DBS is an effective and safe treatment for tremor control and should be considered in patients with refractory tremors with associated cerebellar or dystonic features, proximal tremors and MS tremor.

The Use of Preoperative Psychological Evaluations to Predict Spinal Cord Stimulation Success: Our Experience and a Review of the Literature.

Pre‐operative psychological assessment is commonly used to assess patients for spinal cord stimulation (SCS). Though often times mandated by insurance, its value is frequently questioned.

Deep brain stimulation significantly decreases disability from low back pain in patients with advanced Parkinson's disease.

Background: Up to 60% of Parkinsons disease (PD) patients suffer from low back pain (LBP) during the course of their disease. How LBP affects daily functional status and how to manage this aspect of PD has not been adequately explored. Methods: We examined 16 patients undergoing bilateral subthalamic nucleus deep brain stimulation (STN DBS) who met the inclusion criteria for moderate disability from LBP, as classified by the Oswestry Low Back Pain Disability Index (OLBPD). Results: Thirteen of 16 patients had attempted additional treatments for LBP, including medical management, massage, chiropractic, epidural steroid injections and/or surgery, with minimal relief. Following DBS, there was a significant improvement in the OLBPD at both the 6-month and 1-year time points (p < 0.02, p < 0.005, respectively). A mean improvement of 31.7% on the OLBPD score was noted. The Visual Analogue Scale (VAS) similarly decreased significantly at 1 year (p = 0.015). There was no correlation between the OLBPD score and other measures, including the Unified Parkinsons Disease Rating Scale (UPDRS), age and other nonmotor symptoms. Conclusion: Given the prevalent yet undertreated disability associated with LBP in PD, these results are novel in that they show that STN DBS has a significant positive effect on disability associated with LBP.

Treatment of Allodynia by Occipital Nerve Stimulation in Chronic Migraine Rodent.

BACKGROUND Occipital nerve stimulation (ONS) is a therapy that benefits one-third of medically refractory chronic migraine (CM) patients. How ONS affects sensory thresholds and whether modulation of thresholds could predict which patients respond to the therapy remains unclear. OBJECTIVE To examine the effects of ONS on mechanical and thermal thresholds in a rodent CM model to better elucidate its mechanism of action. METHODS Male Sprague-Dawley rats were implanted bilaterally with electrodes to produce ONS. The CM cohort was infused with inflammatory media epidurally based on a validated model, whereas shams were not. Thresholds were evaluated with von Frey filaments and hot plate and thermode tests. RESULTS No baseline differences in sensory thresholds were found between the sham (n = 16) and CM (n = 16) groups. After headache induction, CM animals demonstrated mechanical allodynia in the occiput, periorbital region, forepaws, and hind paws (P < .05). In CM animals, ONS increased mechanical thresholds in all regions (P < .001), whereas in shams, it did not. ONS did not affect thermal thresholds in either group. CONCLUSION We show that ONS improves mechanical thresholds in a rodent CM model, but not in shams. Our finding that mechanical but not thermal thresholds are altered with ONS suggests a more significant modulation of A-α/β fibers than of C fibers. Assessing the ability of ONS to reduce mechanical thresholds during a trial period could potentially be used to predict which patients respond.

BMI as a Predictor of Spinal Cord Stimulation Success in Chronic Pain Patients.

Spinal cord stimulation (SCS) is an effective method of treating chronic pain. Obese patients are overrepresented in chronic pain cases. We examine the effect of body mass index (BMI) on SCS success.

A Prospective Study of the Intra- and Postoperative Efficacy of Intraoperative Neuromonitoring in Spinal Cord Stimulation

Background: Accurate lead placement is critical for spinal cord stimulation (SCS) efficacy. The traditional gold standard of awake placement is often technically difficult. While there is retrospective evidence supporting the use of intraoperative neurophysiological monitoring (IOM) as an alternative, a prospective assessment has not yet been performed. Objective: To prospectively evaluate pain and functionality outcomes for IOM-guided SCS, validate two IOM modalities as a means to lateralize lead placement and assess whether IOM can be useful for postoperative programming. Methods: A total of 73 patients were implanted with SCS using electromyography (EMG) and somatosensory-evoked potential collision studies (SSEP-CS) to verify lead placement. Patient pain and function were assessed through serial administration of several validated questionnaires. Stimulation parameters at 6 months were documented. Results: Statistically significant (p < 0.05) improvements were observed in the McGill Pain Questionnaire, Oswestry Disability Index, Pain Catastrophizing Scale, and Visual Analog Scale. EMG and SSEP-CS appropriately lateralized leads in 65/73 (89.0%) and 40/58 (69.0%) cases, respectively. EMG predicted active contacts in use at follow-up with 82.7% sensitivity. Conclusions: We provide prospective evidence that IOM can be used to verify SCS placement. Additionally, EMG may help to streamline device programming and thereby improve outcomes by predicting the ideal stimulation contacts in many cases.

Establishing Minimal Clinically Important Difference of Spinal Cord Stimulation Therapy in Post-Laminectomy Syndrome

BACKGROUND The concept of minimum clinically important difference (MCID) has been shown to be effective in spine surgery to differentiate between clinically insignificant and significant improvements as determined by the patient. OBJECTIVE The MCID for spinal cord stimulation (SCS) to date has not been established. We sought to determine the MCID for SCS therapy for failed laminectomy syndromes. METHODS Preoperative and 6-mo outcomes were assessed prospectively, including the Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), and McGill and Visual Analog Survey questionnaires. Patients were asked: (1) are you satisfied with SCS therapy and (2) would you have the surgery again. Four methods of calculating the MCID were utilized. RESULTS Forty-eight patients who underwent placement of an SCS between 2012 and 2014 were reviewed. The 4 calculation methods yielded a range of outcome scores (ODI 8.2-13.3, BDI 3.2-7, McGill 0.3-1.3, and Visual Analog Scale [VAS] 1.2-3.7). The maximum area under the curve was observed for the ODI, BDI, and VAS (0.73, 0.81, and 0.89, respectively), which signifies acceptable accuracy in distinguishing responders from nonresponders with the receiver operating characteristic method and suggests that VAS may be the most sensitive in determining meaningful change for the patient. CONCLUSION The MCID for SCS placement was calculated using 4 different methods. The results are similar to calculations for the MCID for many lumbar and cervical procedures done for pain. Our results suggest that an improvement of 1.2 to 3.7 points on the VAS scale and 8.2 to 13.3 points on the ODI is clinically meaningful to the patient. Further defining the MCID for SCS therapy will remain of utmost importance in order to justify the cost of the procedure.

MRI Conditionality in Patients with Spinal Cord Stimulation Devices

Background: Because of the commonality of diagnostic magnetic resonance imaging (MRI), MRI conditional technology has increased throughout the device industry. It is often difficult to be aware of MRI specifications for each device. Objectives: We provide a review of the clinical experience with MRI and spinal cord stimulation (SCS) devices and develop a general reference of current device/MRI specifications. Methods: We reviewed the available literature on the clinical experience with SCS devices and examined its specifications. Results: We developed a user-friendly table of the specific compatibility of SCS devices in the USA and the European Union, and examined the existing literature on the clinical experience with MRI and SCS devices. We share our experience with obtaining spine MRI with MRI conditional SCS leads. Conclusion: By describing SCS device specifications and reviewing the literature, we provide a guide to implanting and treating physicians on obtaining MRIs in patients who have SCS devices.

Efficacy of Alternating Conventional Stimulation and High Frequency Stimulation in Improving Spinal Cord Stimulation Outcomes: A Pilot Study: EFFICACY OF SHUFFLE STIMULATION

Spinal cord stimulation (SCS) is an established, effective method of treating chronic pain. High frequency stimulation (HFS) is an alternative SCS waveform that has been shown to alleviate pain but also necessitates more frequent recharging. The purpose of this pilot study is to evaluate efficacy of alternating conventional stimulation and HFS (termed “shuffle” stimulation) in improving SCS outcomes.

The use of focused ultrasound for the treatment of cutaneous allodynia associated with chronic migraine

Chronic migraines (CM) are the third most common disease and are refractory to medical treatment in 15% of patients. Currently, temporary relief is achieved with steroid blocks or pulsed radiofrequency ablation, which have short-term benefits. Our project aims to develop a non-invasive treatment for medically refractory chronic migraine, which does not require a permanent implant. This project investigates the safety and effectiveness of pulsed focused ultrasound (FUS) in a validated rodent headache model of cutaneous allodynia associated with chronic migraine (CM) as compared to sumatriptan and ablative lesioning. We demonstrate a significant reduction in mechanical thresholds as measured through Von Frey filaments in CM in the forepaw and periorbital region (p < 0.001). Sumatriptan and pulsed FUS both significantly improve thresholds at day 3 after treatment in the periorbital region. Ablative lesioning has no effect. This study provides initial evidence that FUS may provide an important therapeutic option for patients suffering from CM.