Neuromodulation involves altering neuronal circuitry and subsequent physiological changes with the aim to ameliorate neurological symptoms. Over the years several techniques have been used to obtain neuromodulatory effects for treatment of conditions including Parkinson disease, essential tremor, dystonia or seizures. We provide brief description of the various therapeutics that have been used and mechanisms involved in pathophysiology of these disorders as well as the therapeutic mechanisms of the treatment modalities.

Neuromodulation therapies, including deep brain stimulation (DBS) and pump therapies, are currently the standard of care for PD patients with advanced disease and motor complications that are difficult to control with medical management alone. The quest for alternate lesser invasive approaches led to the development of several novel therapies like intrajejunal levodopa infusions (IJLI), continuous subcutaneous apomorphine infusions (CSAI) and Magnetic Resonance guided Focused Ultrasound (MRgFUS) in recent years. To achieve good outcomes with any of these therapeutic modalities, careful patient selection, multidisciplinary evaluation and technical expertise are equally important. In this review, we will provide an overview of the neuromodulation strategies currently available for PD, emphasizing on patient selection and choosing among the various strategies.

The clinical application of DBS has become manifold and there has been a tremendous growth in DBS technology in the last few decades making it safer and user friendly. The earlier concept of its delayed application in motor fluctuations of Parkinson's disease has been replaced by Class-I evidence of EARLY-STIM trial in 2013, leading to its FDA approval to be used in early-stage despite criticism. Various studies have provided evidence of beneficial effects of bilateral STN-DBS on both motor as well as nonmotor symptoms and different new targets such as the pedunculopontine nucleus, posterior subthalamic area or caudal zona incerta, centromedian-parafascicular complex, and substantia nigra pars reticulata have now become a new area of interest in addition to the subthalamic nucleus and globus pallidus internus for the alleviation of both motor and nonmotor symptoms of Parkinson's disease. New data has confirmed that the DBS is clinically as effective and safe in elderly patients as it is in younger ones. Technological advances like current steering, directional leads, and closed-loop DBS are directed towards reducing the stimulation-induced adverse effects and preservation of the battery life for a longer period. Results of the long-term efficacy of DBS on Parkinson's disease are now available. These have shown that as the motor benefit continues, the clinical progression of Parkinson's disease also continues. We plan to discuss all these in this paper.

Deep brain stimulation (DBS) is the most commonly used surgical treatment for drug-refractory movement disorders such as tremor and dystonia. Appropriate patient selection along with target selection is important to ensure optimal outcome without complications. This review summarizes the recent literature regarding the mechanism of action, indications, outcome, and complications of DBS in tremor and dystonia. A comparison with other modalities of surgical interventions is discussed along with a note of the recent advances in technology. Future research needs to be directed to understand the underlying etiopathogenesis of the disease and the way in which DBS modulates the intracranial abnormal networks.

Facial spasms are of various types. Hemifacial spasm (HFS) is characterized by unilateral tonic-clonic contractions of facial muscles, following a specific pattern of disease progression. It has well-delineated clinical, radiological and electrophysiological features. We have conducted an extensive review of existing literature on the subject, as regards etiopathogenesis, clinical features, investigations and management options for facial spasms. Primary Hemifacial spasm (HFS) may be treated using pharmacotherapy, botulinum toxin injections or microvascular decompression surgery. Microvascular decompression has the potential to reverse the pathological changes of the disease and has proved to be the most successful of all treatment options. Other facial spasms are exceedingly difficult to treat and may need neuromodulation as an option. The following article attempts to review the clinical features and therapeutic approaches to managing patients with facial spasms.

Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) is a well-established technology that has been developed during the last decade and is currently used in the treatment of a diverse range of neurodegenerative brain disorders and neuropsychiatric diseases. This innovative noninvasive technology uses nonionizing ultrasound waves to heat and thus ablate brain tissue in selected targets. In comparison with other lesioning and surgical techniques, MRgHIFU has the following advantages: noninvasive, an immediate clinical outcome with no risk of long-standing ionizing radiation injury, no need for general anesthesia, and no device implantation.

Pediatric movement disorders are heterogeneous and complex disorders with various aetiologies. These are broadly classified as hypo and hyperkinetic disorders. Genetic causes of basal ganglia dysfunction or direct injuries to the basal ganglia mark the genesis of these abnormal movements. The management of pediatric movement disorders is multidisciplinary with pharmacotherapy as the first line of management along with physical therapy. Patients resistant to medications are candidates for invasive neuromodulation which is an upcoming treatment modality in pediatric movement disorders. Deep brain stimulation of basal ganglia and thalamic nuclei are associated with promising symptomatic benefit with reduction in disability and improvement in quality of life of these children. In this article, we have reviewed the management of pediatric movement disorders with emphasis on neuromodulation i.e., deep brain stimulation.

Spinal cord stimulation (SCS) is a neuromodulation surgical technique that allows the treatment of various causes of chronic pain. SCS is effective in the treatment of chronic low back pain, neuropathic pain, chronic regional pain syndrome, and failed back surgery syndrome, among others. The mechanisms underlying the efficacy are still under investigation and different mechanisms are likely responsible for the effects of different waveforms used in the therapy. Successful application of SCS to individual patients depends on patient selection and meticulous surgical technique. Important factors in patient selection depend on preoperative imaging, maximizing noninvasive therapy, and neuropsychological evaluation. Percutaneous and open techniques exist for placing both paddle-shaped epidural leads as well as typical cylindrical leads. Benefits and risks exist for both techniques and the exact technique that is optimal depends on surgeon experience and surgeon and patient preference. Complications are rare and can be minimized and managed with appropriate preoperative mitigation.

Background: Spinal cord stimulation (SCS) has emerged as state-of-the-art evidence-based treatment for chronic intractable pain related to spinal and peripheral nerve disorders. Traditionally delivered as steady-state, paraesthesia-producing electrical stimulation, newer technology has augmented the SCS option and outcome in the last decade. Objective: To present an overview of the traditional and newer SCS waveforms. Materials and Methods: We present a short literature review of SCS waveforms in reference to newer waveforms and describing paraesthesia-free, high frequency, and burst stimulation methods as well as advances in waveform paradigms and programming modalities. Pertinent literature was reviewed, especially in the context of evolution in the waveforms of SCS and stimulation parameters. Results: Conventional tonic SCS remains one of the most utilized and clinically validated SCS waveforms. Newer waveforms such as burst stimulation, high-frequency stimulation, and the sub-perception SCS have emerged in the last decades with favorable results with no or minimal paraesthesia, including in cases otherwise intractable to conventional tonic SCS. The recent evolution and experience of closed-loop SCS is promising and appealing. The experience and validation of the newer SCS waveforms, however, remain limited but optimistic. Conclusions: Advances in SCS device technology and waveforms have improved patient outcomes, leading to its increased utilization of SCS for chronic pain. These improvements and the development of closed-loop SCS have been increasingly promising development and foster a clinical translation of improved pain relief as the years of research and clinical study beyond conventional SCS waveform come to fruition.

Background: Chronic, focal, neuropathic pain is difficult to treat. Local nerve blocks are either ineffective or do not last. Regular neuromodulation modalities like spinal cord stimulation (SCS) or pain pump are invasive and affect a larger area. Objectives: To discuss the indications, technique, nuances, programming, and outcomes of peripheral neuromodulation Methods: The article reviews published literature and the author's own experience of over 500 cases of peripheral neuromodulation. Results and Conclusion: Peripheral neuromodulation using peripheral nerve field stimulation (PNFS) is an effective, minimally invasive, targeted method of treatment. It is a relatively new modality in the field of neuromodulation but is used more often.

Headaches are an increasing cause of disability in the world. Intractable headache syndromes affect all age groups but predominantly the middle-aged, working population. Occipital neuralgia is a frequent comorbidity with intractable migraine headaches. Occipital nerve stimulation at the level of nuchal ridge is a reasonable option for these refractory patients. Ultrasound guidance of occipital nerve stimulation can optimize depth placement of leads. Revision surgeries of occipital nerve stimulation are usually performed using surgical leads. Cluster headaches and trigeminal autonomic cephalagias (TACs) are refractory headache conditions that are mediated by sphenopalatine ganglion. Sphenopalatine ganglion stimulation with infrazygomatic approach and fluoroscopic guidance of percutaneous leads can help alleviate pain from cluster headaches and TACs. Innovation in neurostimulation technologies have brought new optimism to these refractory conditions. Efficient and optimal delivery of neurostimulation for intractable headache syndromes requires a multidisciplinary team-based approach for long term compliance and efficacy.

Deep brain stimulation (DBS) and Motor Cortex stimulation (MCS) have been used for control of chronic pain. Chronic pain of any origin is complex and difficult to treat. Stimulation of various areas in brain-like sensory thalamus, medial nuclei of thalamus including centro-lateral nucleus of thalamus (CL), periaqueductal gray, periventricular gray, nucleus accumbence and motor cortex provides partial relief in properly selected patients. This article reviews the pain pathways, theories of pain, targets for DBS and rationale of DBS and MCS. It also discusses the patient selection, technical details of each target.

Spasticity is a major cause of disability following upper motor neuron (UMN) injury. The diagnosis and treatment of spasticity has been a focus of clinicians and researchers alike. In recent years, there have been significant advances both in strategies for spasticity assessment and in the development of novel treatments. Currently, several well-established spasticity management techniques fall into the major categories of physiotherapy, pharmacotherapy, and surgical management. The majority of recent developments in all of these broad categories have focused more on methods of neuromodulation instead of simple symptomatic treatment, attempting to address the underlying cause of spasticity more directly. The following narrative review briefly discusses the causes and clinical assessment of spasticity and also details the wide variety of current and developing treatment approaches for this often-debilitating condition.

The choice of neuromodulation techniques has greatly increased over the past two decades. While vagal nerve stimulation (VNS) has become established, newer variations of VNS have been introduced. Following the SANTE's trial, deep brain stimulation (DBS) is now approved for clinical use. In addition, responsive neurostimulation (RNS) has provided exciting new opportunities for treatment of drug-resistant epilepsy. While neuromodulation mostly offers only a ‘palliative’ measure, it still provides a significant reduction of frequency and intensity of epilepsy. We provide an overview of all the techniques of neuromodulation which are available, along with long-term outcomes. Further research is required to delineate the exact mechanism of action, the indications and the stimulation parameters to extract the maximum clinical benefit from these techniques.

Epilepsy surgery currently offers the best treatment for patients with drug-refractory epilepsy (DRE). Resective surgery, in the presence of a well-localized epileptogenic focus, remains the best modality towards achieving seizure freedom. However, localization of the focus may not be possible in all the cases of DRE, despite comprehensive epilepsy workup. Neuromodulation techniques such as vagal nerve stimulation (VNS), deep brain stimulation (DBS) and responsive neurostimulation (RNS) may be a good alternative in these cases. This article intends to provide an overview of VNS in the management of DRE, including indications, comprehensive preoperative workup, exemplified by case illustrations and outcomes by reviewing the evidence available in the literature.

Deep brain stimulation (DBS) has been used in the treatment of motor diseases with remarkable safety and efficacy, which abet the interest of its application in the management of other neurologic and psychiatric disorders such as epilepsy. Experimental data demonstrated that electric current could modulate distinct brain circuits and decrease the neuronal hypersynchronization seen in epileptic activity. The ability to carefully choose the most suitable anatomical target as well as to define the most reasonable stimulation parameters is highly dependable on the comprehension of the underlying mechanisms of action, which remain unclear. This review aimed to explore the relevant clinical data regarding the use of DBS in the treatment of refractory epilepsy.

There is a considerable number of patients with epilepsy that have drug resistant epilepsy (DRE). An additional option for these patients is resective surgery of ictal onset zones. However, a significant portion of DRE patients have unidentified or unresectable ictal zones. For these patients, RNS is a potential treatment option. The RNS system is a closed loop system that delivers stimulation in response to ECoG changes at seizure foci. It is programmed with an algorithm capable of detecting specific patterns of epileptogenic activity and triggers focal stimulation to interrupt seizures. The long term monitoring potential of the RNS system allows for a better understanding of the circadian rhythms behind epilepsy.

Background: Depression, Obsessive-compulsive Disorder (OCD), and addiction are the leading disabling psychiatric conditions with huge health care and psychosocial burden besides increased morbidity and mortality. Deep brain stimulation (DBS) for depression, OCD, and addiction is increasingly explored and is quite challenging. We present a brief review of the pertinent literature of DBS for depression, OCD, and addiction and present the status and challenges. Objective: The aim of this study was to review the current status and challenges with the DBS for Depression, Obsessive-compulsive Disorder (OCD), and addiction. Method: The pertinent brief literature was reviewed in reference to the DBS for Depression, Obsessive-compulsive Disorder (OCD), and addiction. Results: To date, OCD is the only psychiatric condition approved for DBS therapy (under humanitarian device exemption). Although the initial encouraging results of DBS in depression were encouraging but the two larger multicenter clinical trials failed to meet the primary objective. Further evaluation and studies are ongoing. Similarly, the initial results of DBS for addiction are encouraging; however, the experience is limited. Conclusion: DBS for depression, OCD, and addiction seem challenging but promising. Further refinement of the target and evaluation in a larger and controlled setting is needed, specifically for depression and addiction.

Alzheimer's disease (AD) and other forms of dementia can have a large impact on patients, their families, and for the society as a whole. Current medical treatments have not shown enough potential in treating or altering the course of the disease. Deep brain stimulation (DBS) has shown great neuromodulatory potential in Parkinson's disease, and there is a growing body of evidence for justifying its use in cognitive disorders. At the same time there is mounting interest at less invasive and alternative modes of neuromodulation for the treatment of AD. This manuscript is a brief review of the infrastructure of memory, the current understanding of the pathophysiology of AD, and the body of preclinical and clinical evidence for noninvasive and invasive neuromodulation modalities for the treatment of cognitive disorders and AD in particular.

Use of spinal cord stimulation (SCS) has expanded beyond pain control. There are increasing indications in which SCS is being used. The understanding of central and peripheral neural pathways and their controlling influences on peripheral organs is better understood now. The concept of stimulating the spinal cord and modulating central pathways with SCS is already established. Different studies have shown the benefit with SCS on visceral pain control, improving quality of live in severe peripheral vascular disease and even assist in controlling the vago-sympathetic balance. We will discuss the art of implantation. Patient selection and stimulation with respect to current clinical data.

Epidemiological studies show a steady rise in the prevalence of obstructive sleep apnea (OSA). Untreated OSA is responsible for numerous chronic health conditions, motor vehicle, and workplace-related accidents leading to substantial economic burden both to the individual and society. Multiple causes for OSA and a wide range of consequences has made its diagnosis and treatment difficult. Obstructive sleep apnea may be caused by anatomical variation, increased collapsibility of the upper airway, low sleep arousal threshold, and exaggerated response to desaturation. Lifestyle changes, anatomical corrective surgeries, and oral appliances have been used but patient compliance is poor as it interferes in the daily routine. Neuromodulation is a promising functional modifying option that addresses the cause of obstructive sleep apnea at multiple levels.

Control of the lower urinary tract is a complex, multilevel process that involves the peripheral and central nervous systems. Patients with spinal cord diseases or injuries present with multiple bladder and bowel problems. The commonest are urinary, urgency, frequency, urge incontinence, retention and/or fecal incontinence. Though the first reports of neurostimulation to empty bladder came in 1970s’, it was only in 1988 that Schmidt and Tanagho restarted discussion and application of neuromodulation and electrical stimulation of sacral nerve in urology. In April, 1999 - FDA approved the InterStim System for treatment of symptoms of urgency-frequency and urinary retention. In October 2000, Medtronic Commercial Release for SNS-Bowel was approved. In October 2002, the Tined lead was launched and N’Vision programmer was launched in the official market in Europe. SNM is now considered the third line of management in refractory cases of OAB, chronic NOUR, frequency and urgency. Role in neuropathic bladder is still being assessed. SNM includes a thorough preoperative assessment, PNE (Percutaneous Nerve Evaluation) without any muscle relaxation and finally installation of a permanent IPG after assessing reponse. We have an experience of over 20 patients in last 11 years. These include patients of refractory OAB, chronic NOUR and Cauda Equina Syndrome. We do a two-staged procedure in view of the high cost and abide by the AUA, EAU and ICS guidelines. Our long term results for neuropathic OAB are awaited.

Altering the enormous complex connectivity and output of the central nervous system is one of the most fascinating development in medical technologies. It harbors the ability to treat and modulate different neurological disorders and diseases such as Parkinson's disease, Alzheimer's disease and even help with drug delivery to treat unreachable areas of brain via opening of the blood brain barrier. Evolution of neuromodulation techniques has been significant in last few years. They have become less invasive and more focused. Newer neuromodulation techniques consist of invasive, minimally invasive and non-invasive technologies. The decision to use one of these technologies depends on the indication and the targeted area within the central or peripheral nervous system. In the last decade technological advances and the urge to minimize the surgical and the long term complications of hardware implantation, have pushed the neurosurgical community to increase the use of non-invasive neuromodulation technics. In this article, we will discuss the different emerging technologies in neuromodulation and the increasing role of non-invasive neuromodulation.

Background: Deep brain stimulation (DBS) is currently the preferred surgical treatment for various movement disorders. Pallidotomy is an effective procedure for patients with dystonia and Parkinson's disease and was the surgical treatment of choice before the advent of DBS. However, it can be the preferred modality in immunocompromised patients and those patients who cannot afford DBS due to financial constraints. Hypophonia, dysarthria and dysphagia are the most significant complications of bilateral pallidotomy. Objective: The aim of this study was to present the surgical technique and nuances involved in bilateral simultaneous pallidotomy in a patient with generalized dystonia. Procedure: A 30-year male with primary generalized dystonia presented to us with preoperative Burke–Fahn–Marsden (BFM) Dystonia Rating Scale of 24. After acquiring preoperative volumetric 3T MRI and stereotactic CT, bilateral pallidotomy was done under general anesthesia. There were no procedure related complications. Results: At two months of follow-up, his BFM dystonia score improved from 24 to 4.5. Conclusion: Appropriately acquired volumetric MRI, meticulous planning and meticulously performed surgical procedure can help in achieving good outcome and minimize the complications.

Background: Vagal nerve stimulation (VNS) is a form of neuromodulation for patients with drug-refractory epilepsy (DRE), in whom extensive preoperative evaluation fails to localize the epileptogenic zone. VNS is often compared to Corpus callosotomy (CC) in terms of both indications and efficacy. However, VNS represents a less invasive and less morbid procedure compared to CC and is the preferred procedure in majority of patients with DRE. Objective: The aim of this study was to present the surgical technique and nuances involved in the implantation of vagal nerve stimulator. Procedure: A 16-year-old boy suffering from DRE, with bilateral seizure onset on evaluation, for 12 years, underwent left vagal nerve stimulator placement. The VNS device has a lead and a pulse generator, the lead has coils to be wrapped around the vagus nerve and the pulse generator is placed in a subcutaneous pocket in the infraclavicular region (demonstrated in the video). Results: The patient is relieved of the disabling drop attacks along with improved cognitive functions at 1 year follow up. Conclusions: In carefully selected patients, VNS is a safe and effective procedure to alleviate seizures, in cases otherwise morbidly affected due to drug refractory epilepsy.

Background: Deep brain stimulation (DBS) is an effective surgical technique used to ameliorate the motor symptoms associated with Parkinson's disease. One of the key elements that determine successful patient outcomes is the accurate positioning of the DBS electrode during surgery. Objective: To describe a robotic DBS (R-DBS) procedure using “awake” technique. Methods and Materials: This procedure was performed using a frame-based approach with the NeuroMate surgical robot and intraoperative image verification of DBS electrode placement using the O-arm mobile x-ray system. The procedure was performed “Awake” using microelectrode recording (MER), stimulation, and macro-electrode testing. Results: The accurate placement of DBS electrodes was confirmed with intraoperative image verification. This patient had good therapeutic response intraoperatively. No immediate postoperative complications related to DBS electrode placement were identified. Conclusions: R-DBS is a technique that can be used for the highly accurate placement of electrodes necessary for DBS.

Background: Bilateral anterior cingulotomy (BAC) constitutes the most commonly performed procedure for treatment of refractory OCD. Evolution of stereotactic procedures has rekindled the interest in the effective management of refractory psychiatric disorders, especially OCD with utmost safety and excellent outcomes. Objective: The aim of this study was to demonstrate the technique of performing BAC under robotic guidance using radiofrequency ablation with an operative video. Procedure: A 23-year-old gentleman diagnosed with symptoms of OCD for a duration of 8 years and was refractory to conventional therapy. The trajectories for BAC were planned on the robotic platform (ROSA, Zimmer-Biomet, Warsaw, Indiana, USA). The target point was selected on the anterior cingulate, approximately 2 cms posterior to the anterior most point of the frontal horn, 2-3 mm above the corpus callosum and 7 mm lateral to the midline. Pre coronal (1 cm anterior and 3 cms lateral to midline) holes of 2.5 mm diameter were made using pneumatic handheld drill. Radiofrequency (RF) thermocoagulation of the anterior cingulum was performed using an RF probe of 2.2 mm diameter and 4 mm uninsulated tip under robotic guidance after confirming the position with intraoperative O-arm imaging bilaterally. Results: The surgery was uneventful and the patient had a significant improvement following surgery, with the Yale Brown Obsessive Compulsive Scale of 18 at 1 year follow-up compared to the preoperative score of 36. Conclusion: Robotic-guided BAC is a safe and effective technique for the treatment of drug-refractory OCD. Intraoperative O arm CT augments the precision of the lesions created.

Background and Introduction: Spinal cord stimulation (SCS) is well established treatment. In a prospective randomised controlled trial, novel 10-kHz High-frequency Therapy (HF10 Therapy) was superior to traditional low-frequency SCS for the treatment of chronic back and leg pain. Objective: To demonstrate the percutaneous SCS implant technique and discuss the operative nuances. Surgical Technique/Procedure: During the stage 1 procedure (permanent trial), two percutaneous electrodes were placed in the midline posterior epidural space spanning T8-T10 segments straddling the T9-10 disc space. The electrodes were anchored to the fascia, tunnelled into the supragluteal incision and connected to the extensions, which were tunnelled out for the external trial. Results and Conclusions: The patient reported 90% pain reduction at follow-up. Thoracic HF10 SCS is effective modality in managing chronic neuropathic pain