An Overview of Spinal Neuromodulation Techniques: Clinical Applications and Current Trends

Nirmala Subramanian; Umesh Srikantha; Ravi Gopal Varma

doi:10.21182/jmisst.2025.02355

J Minim Invasive Spine Surg Tech > Volume 11(Suppl 1); 2026 > Article

Subramanian, Srikantha, and Varma: An Overview of Spinal Neuromodulation Techniques: Clinical Applications and Current Trends

Review Article

Journal of Minimally Invasive Spine Surgery and Technique 2026; 11(Suppl 1): S120-S131.

Published online: January 30, 2026

DOI: https://doi.org/10.21182/jmisst.2025.02355

An Overview of Spinal Neuromodulation Techniques: Clinical Applications and Current Trends

Nirmala Subramanian

, Umesh Srikantha

, Ravi Gopal Varma

Department of Neurosurgery, Aster CMI hospital, Bengaluru, India

Corresponding Author: Umesh Srikantha Department of Neurosurgery, Aster CMI Hospital, Bengaluru-74, Karnataka, India Email: umeshsrikantha@gmail.com

Received May 17, 2025 Revised July 26, 2025 Accepted July 26, 2025

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Neuromodulation is a distinctive technology that modifies neural activity by delivering electrical impulses or pharmaceutical agents directly to specific regions of the brain or spinal cord. Spinal neuromodulation refers to therapeutic interventions designed to alter the activity of the spinal cord and nerve roots in order to relieve pain and other neurological symptoms. This approach primarily utilizes devices such as spinal cord stimulation systems, intrathecal drug delivery systems, and other advanced neuromodulatory technologies. Spinal neuromodulation devices function either by electrically stimulating nerves to produce natural biological responses or by administering precise, targeted doses of pharmaceutical agents directly to the site of action. These treatments have proven transformative for many patients, offering the potential for fewer side effects, greater patient comfort, and overall improvements in quality of life. The primary modalities discussed in this article include spinal cord stimulation, sacral neuromodulation, and intrathecal baclofen therapy. Spinal cord stimulation has long been a preferred treatment for chronic low back pain, chronic pain after spinal surgery, complex regional pain syndrome, and painful diabetic peripheral neuropathy. Recent technological advances have expanded its use to additional spinal disorders, and ongoing research is exploring its potential for promoting neurological recovery in individuals with paraplegia. Sacral neuromodulation is an interventional technique used to modulate sacral reflex arcs for the management of neurogenic bladder and neurogenic bowel dysfunction. Intrathecal baclofen therapy is a minimally invasive treatment indicated for severe poststroke spasticity and other forms of spasticity. This article reviews the clinical benefits of these therapies, as well as considerations related to safety, cost-effectiveness, and the quality of supporting evidence.

Key Words: Neuromodulation, Spinal cord stimulation, Sacral nerve stimulation, Chronic neuropathic pain, Neurogenic bladder, Intrathecal baclofen therapy

INTRODUCTION

Neuromodulation techniques, involving application of electrical stimulation or targeted drug delivery to the nervous system, have emerged as treatment options for a range of chronic neurological conditions [1]. Spinal neuromodulation techniques are established to treat diseases like chronic pain syndromes, disorders of bladder and bowel function and severe spasticity. These techniques aim to modulate pain signals, improve motor function or address spinal neurological conditions [2]. There are a wide range of spinal neuromodulatory techniques which can be classified into invasive and noninvasive methods [2]. The noninvasive techniques include transcutaneous spinal stimulation, transcranial magnetic stimulation, transcranial direct current stimulation [3]. Magnetic resonance imaging guided focused ultrasound; high-intensity focused ultrasound are newer noninvasive modalities [4].

Invasive neuromodulation techniques involve surgically implanting devices in the spinal cord or brain or implanting devices for drug delivery. Various techniques available include spinal cord stimulation (SCS), motor cortex stimulation, deep brain stimulation, dorsal root ganglion (DRG) stimulation, intrathecal baclofen therapy (ITB), and sacral neuromodulation (SNM) [4].

SCS is a commonly used implantable neuromodulation. In SCS, an electrical stimulus is applied to epidural space to provide pain relief or improve motor function in paraplegics [5]. It is a well-established technique used to reduce intensity, frequency and duration of pain [6].

Melzack and Wall proposed the gate control theory for pain and forms the basis for SCS to treat pain [6,7]. The gate control theory highlights the presence of pain pathways in dorsal columns and thus its use in SCS [7]. Though it was primarily used for treatment of pain secondary to traumatic myelopathy, SCS is nowadays also used in chronic pain after spinal surgery, complex regional pain syndrome (CRPS), critical ischemic limb pain, and intractable angina [8].

SNM was approved by U.S. Food and Drug Administration in late 1990s for nonobstructive urinary retention and over reactive bladder [9]. This therapy is used as a last resort when most of the conservative approaches like clean intermittent catheterization, behavioral modification and intradetrusor botulinum toxin injections, have failed [9,10]. SNM involves stimulating specific sacral nerves to modulate sacral reflex arcs.

Spasticity is a motor disorder where there is stiffness of muscles. Oral baclofen therapy can act as a muscle relaxant and antispastic medication. In oral route, small portion of baclofen reach central nervous system by crossing the blood-brain barrier. ITB is used when oral route fails or causes adverse reactions. Here the device delivers the muscle relaxant baclofen directly into the cerebrospinal fluid (CSF), offering a treatment for severe spasticity [11]. While these therapies are utilized in clinical practice, their efficacy and safety profiles, particularly for chronic pain refractory to conventional management, neurogenic bladder (NB) and spasticity remain subjects of ongoing investigations and debate.

Continued refinement is ongoing across spinal neuromodulation with increased focus on understanding the underlying physiological and neurochemical mechanisms of action of these therapies. Modulating stimulation parameters considering the role of spinal and supraspinal mechanisms and understanding psychosocial factors involved are important in determining effectiveness of spinal neuromodulation.

This paper summarizes key findings regarding the applications and outcomes of 3 more commonly done spinal neuromodulatory techniques: SCS, SNM, and ITB.

SPINAL CORD STIMULATION

SCS involves electrical stimulus delivered to the dorsal columns of the spinal cord using electrodes placed in the epidural space. As per the gate control theory of pain by Melzack and Wall [7], SCS was believed to cause direct inhibition of pain transmission. Shealy et al. [12] introduced the therapy for chronic pain syndromes. SCS also causes the initiation of orthodromic and antidromic action potentials, leading to supraspinal and segmental effects [8]. The most important advantage of this technique is the preservation of posterior column as against ablative methods.

National Institute for Clinical Excellence (NICE) has published guidance for SCS in 2008. It has recommended that SCS can be used for severe, prolonged pain responsive to a trial of stimulation in failed back surgery syndrome, chronic regional pain syndrome and neuropathic pain. A multidisciplinary pain management team has to be formed before providing SCS as treatment when indicated.

1. NICE Guidelines for Patient Selection for SCS

Those likely to respond: (1) neuropathic pain in leg or arm following lumbar or cervical spine surgery (failed back surgery syndrome/failed neck surgery syndrome [FBSS/FNSS]), (2) CRPS, (3) neuropathic pain secondary to nerve damage, (4) pain associated with peripheral vascular disease, (5) refractory angina pectoris, (6) brachial plexopathy.

Those who may respond: (1) amputation pain, (2) axial pain following spinal surgery, (3) Intercostal neuralgia, such as post-thoracotomy or postherpetic neuralgia, (4) pain associated with spinal cord damage.

Poor responders: (1) central pain of non-spinal cord origin, (2) spinal cord injury with clinically complete loss of posterior column function, (3) perineal or anorectal pain.

Nonresponders: (1) complete spinal cord transection, (2) nonischemic nociceptive pain, (3) nerve root avulsion

2. Procedure

The procedure is carried out in 2 stages. A trial period is typically conducted before permanent implantation, during which the electrode is placed onto the epidural space either through percutaneous (Figure 1) or minimally invasive (tubular retractor-assisted) method (Figure 2). Conventional/open laminectomy can also be used to place the electrodes on the posterior dural surface (Figure 3). The electrode is then connected to an external nerve stimulator [8]. The trial period can vary from 5–7 days, depending on subjective feeling of improvement in symptoms [13]. Trial period helps in analyzing feasibility of treatment and suitability for permanent implantation [13]. If the results of trial period are satisfactory (good pain relief with minimal and tolerable adverse sensations), the patient is considered for permanent implantation, during which the electrode is connected to an implantable pulse generator (Internal battery) placed subcutaneously in anterior abdominal wall [14].

Stimulation is then carried out using the implantable pulse generator which connects to the external handheld programmer in a wireless manner. Conventional SCS involves fixed-output, open-loop sensation-based stimulation that relies on patient’s report of paresthesia or is based on anatomical location of the electrodes [15]. However, some newer stimulation paradigms like burst and high frequency SCA may not activate or inhibit dorsal columns at clinically relevant parameters, suggesting mechanisms of action other than traditional gate control [14,15]. Other newer paradigms also include adaptive stimulation (auto adjustment of stimulation parameters based on posture; i.e. supine or standing), differential target multiplex, and closed-loop stimulation.

3. Current Trends and Developments

Recent advances in SCS are focused on post implantation programming to achieve adequate symptomatic relief. The advent of wireless devices has made trial phase shorter and postimplantation programming easier [14].

Recent developments also include evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS). The EVOKE study, a multicenter, participant-blinded, investigator-blinded. In this study a comparison was made between conventional fixed-output open-loop SCS (OL-SCS) to ECAP-controlled CL-SCS. Three hundred and twenty-eight patients were screened, 134 were enrolled, 113 underwent implantation (59 in CL-SCS, 54 in OL-SCS). They were followed up for 36 months concluded that CL-SCS causes sustained and durable pain relief [15].

The field has also advanced in using different wave forms to achieve analgesia [16]. These include traditional paresthesia-based SCA (<100 Hz), paresthesia-free high frequency SCS (5–10 kHz), burst SCS and sub perception SCS (1–5 kHz) [17]. The Senza study compared conventional low frequency stimulation to high frequency stimulation, proving that the latter was better [18]. SUN-BURST study has proven that burst stimulation for limb and back pain is more efficacious as compared to tonic stimulation [19].

SCS is by far the most common mode of treatment for chronic low back pain. The mechanism of motor activity by SCS is unclear. However, it is believed that there is recruitment of large and medium diameter proprioceptive and cutaneous afferents within the posterior roots of the dorsal column [20]. The sensory afferents convey excitatory post synaptic potentials to the spinal motoneurons via mono- and polysynaptic pathways and hence improve spinal circuits to cause locomotion [21]. Paz et al. [22] have recorded electrophysiology for all patients preoperative and postoperative. Harkema et al. [23,24] have shown patients walking with harness by 6 months.

4. Outcomes After SCS

A detailed description of the reviewed articles is given in Tables 1 and 2.

A 20-year literature review by Cameron [25], concluded that SCS had a positive, symptomatic, long-term effect for refractory angina pain, severe ischemic limb pain in peripheral vascular disease, peripheral neuropathic pain and chronic low back pain. It also stated that SCS was generally a safe and effective treatment for various chronic neuropathic conditions. SCS as compared to conventional therapies results in lesser complication rates and shorter hospital stay. Hence it is more cost effective [26].

Studies have compared SCS to conventional medical management for chronic pain [25].

Costantini et al. [27], showed that SCS is superior to conventional management at all time points for leg pain (>50% reduction), function, and health-related quality of life (QoL). There was a significant improvement in disability score. Chincholkar et al. [13] suggested that the “trial period” should be made a common practice to assess suitability of SCS for permanent implantation. The study concluded that short-term trial period can predict long-term outcomes suggesting that patient selection and education about chronic pain management are key to good long-term outcomes. Odonkor et al. [26] evaluated the cost-effectiveness and healthcare resource utilization of SCS. SCS was associated with favourable outcomes and found to be more cost effective than conventional therapy for chronic low back pain. Compared to conventional therapy, SCS resulted in shorter hospital stays and lower healthcare costs at 90 days. SCS was also associated with significant improvement in health-related QoL, health status, and quality-adjusted life years [20]. North et al. [14] described SCS studied various potential complications, including lead migration, infection, epidural haemorrhage, seroma, hematoma, CSF leakage, hardware malfunction, pain over the implant site. They concluded that SCS is a relatively safe and cost-effective procedure.

SACRAL NEUROMODULATION

SNM, also known as sacral nerve stimulation denotes electrical stimulation applied on specific sacral nerves (Figure 4). It helps in adjusting sacral reflex arc to achieve maximum response [28]. It is a minimally invasive and potentially reversible procedure. SNM is a treatment option for NB and neurogenic bowel dysfunction (NBD). NB is described as abnormal bladder and/or urethral function resulting from neurological disease or injury, with varying clinical manifestations depending on the location of the nerve damage. Treatment options for NB are varied, including pharmacological and behavioral therapy, intravesical injection of botulinum toxin, and surgery (SNM) [28].

1. Indications

1) Overactive bladder where there is (1) increased frequency-more often than normal, (2) urgency—sudden need to pass urine with or without urine leakage, and (3) nocturia-getting up from sleep to void urine more than twice in the night.

2) Nonobstructive chronic urinary retention (inability to void urine or dysfunctional voiding in women.

3) Fecal incontinence: Prior to electrode placement evaluation has to be done for bladder capacity in the form of urodynamic study and post void residual urine [28,29].

2. Procedure

It is a 2 staged procedure: trial phase and permanent implantation. In the trial phase, electrode is inserted percutaneously into the S3 (or sometimes S4) foramen under image guidance. The electrode is connected to an external stimulator. Response to proper placement include plantar flexion of ipsilateral toes, contraction of levator ani muscles, pulling sensation in the rectum or vibratory sensations in the vagina, labia, scrotum or penis (Figure 3). During trial phase, patient wears the temporary stimulator for 1–2 weeks. In trial period, periodic change in pulse width, frequency and stimulation intensity is done and the responses noted. If there is 50% or greater improvement in symptoms, then the lead is connected to an implantable pulse generator placed subcutaneously in upper part of the buttock. If no response, then the implant is removed [28,29].

3. Current Trends and Developments

Recent advances in SNM states early implantation in spinal cord injury can cause marked improvement in bladder compliance, bladder volume and low bladder filling pressures [30,31]. Previously implantable pulse generators were termed as Inter-Stim (Medtronic Sofamor-Danek, USA) and lasted for 5 years. The newer bladder pacemakers have an expectancy of 10–15 years [32]. There is a significant improvement in commercially available hardware. One of it being Bion (Bionic Neuron), an injectable microstimulator powered by radiofrequency stimulator and measuring 2.8 × 0.3 cm. It can be injected by a 12-gauge needle into the target [33].

4. Outcomes After SNM

Lai fung li et al quotes that SNM has expanding indications. Apart from bladder control, it may also be used for treatment of bowel incontinence and chronic pelvic pain [33]. Sun and Song [34] evaluated efficacy and safety of SNM for NB and NBD. It involved a systematic literature search using PubMed and Web of Science upto August 2024.It has been quoted as the largest, most update, evidence-based analysis comparing changes before and after SNM in NB and NBD. They concluded that there was a significant reduction in daily clean intermittent catheterization after SNM. The daily voiding frequency normalized after SNM treatment. Maximum urinary flow rate, detrusor pressure during storage phase and maximum bladder capacity improved following SNM [34].

Wei et al. [35] conducted a meta-analysis specifically focused on effectiveness and safety of SNM for NB. Eleven literatures were included for data analysis. It was found that patients showed improvement to varying degrees in single urine volume, bladder capacity, urinary incontinence, urination frequency, and clean catheterization after receiving SNM. The study concluded that electrical SNM is effective and relatively safe modality for NB treatment [35]. Redshaw et al. [36] formulated research protocol to increase options of bladder management after spinal cord injury. The results showed SNM had fewer urinary tract infections and hospital admissions. Siddiqui and Aboseif [37] stated that in idiopathic overactive bladder, SNM achieves sustained therapeutic success with greater reduction in leaks per day. Martin et al. [38] showed that there is an 86% improvement in fecal incontinence after SNM implantation.

INTRATHECAL BACLOFEN THERAPY

“Intrathecal drug delivery” systems are used to deliver small doses of drug directly into the spinal subarachnoid space in order to circumvent the blood-brain barrier and achieve better results with smaller drug doses and minimal side effects. The commonly used intrathecal drugs are baclofen for relief form refractory spasticity and Morphine and Ziconotide for relief from chronic pain. The subsequent section discusses about Intrathecal Balcofen therapy.

Baclofen is a gamma-aminobutyric acid (GABA) analog that acts on GABA-B receptor to enhance presynaptic inhibition [39]. Direct infusion of baclofen into the CSF concentrates the drug regionally thus achieving therapeutic effect. By attaching this to a pump infusion rate can be monitored and titrated to constant levels [40].

ITB therapy involves continuous infusion of baclofen into intrathecal space via an implantable pump in severe spasticity. It is described as a minimally invasive technique. Spasticity is defined as a velocity-exaggerated increase in tonic stretch reflexes with amplified segmental reflex responses resulting from hyperactivity of stretch reflex [41]. This causes functional disability in the form of painful spasms, sleep disturbances and reducing mobility [41]. Severe spasticity can hinder even simple activities and rehabilitation programs. Mild spasticity can be managed with oral drugs and physiotherapy [42]. Intrathecal baclofen has been the treatment of choice for severe spasticity in recent years.

1. Indications

(1) Intractable spasticity uncontrolled by drug therapy

(2) Intolerable side effects to oral baclofen

(3) Severe post stroke spasticity-who have not reached their goal with other interventions

(4) Spasticity in spinal cord injury, cerebral palsy and movement disorders

(5) As an adjunct in chronic pain

2. Procedure

Intrathecal baclofen pump insertion is done in 2 phases—trial phase and permanent implantation. Trial phase is done to screen for responders to intrathecal baclofen. Ashworth score is checked prior to procedure. Lumbar puncture is done at L3–4 level and a bolus dose (50 μg in an adult) of baclofen is injected into the CSF. The response is then checked at 1st hour after injection, 6 hours, 12 hours, and 24 hours until approximately a 4- to 8-hour response is observed. If there is an unsatisfactory or no response, the dosage of intrathecal baclofen is titrated upwards to 75 μg on day 2 and 100 μg on day 3. If there is no response even to 100 μg intrathecally, then further dose increase should not be carried on. The spasticity should reduce by a 2- or more-point decrease in Ashworth scale scores after bolus dose, only then, pump implantation is indicated [11,43].

In the second phase intrathecal baclofen pump is implanted. The system constitutes an intrathecal catheter that delivers baclofen and a pump that stores the drug to be released periodically. Lumbar puncture is done using Tuohy needle and the intrathecal catheter is passed to desired space and confirmed using intraoperative imaging. The catheter is then tunneled subcutaneously to the anterior abdominal wall and connected to the pump filled with injectable baclofen [11]. The pump can be either programmable or nonprogrammable. Using an external programmer, the dose, rate and timing can be adjusted. The pump has to be refilled through subcutaneous injection every 2–3 months. The pump has to be replaced every 5–7 years.

Post insertion programming: The main aim in programming is to reduce spasms and hence improve QoL. Initially a simple continuous cycle (same amount of drug administered every hour) is programmed, gradually it is changed to more complex cycles, depending on the relief of symptoms. Settings can vary between day, night and also depending on the activities performed [44].

3. Outcomes After ITB Therapy

A detailed description on literature has been explained in Table 3.

Creamer et al. [45] reported the SISTERS trial (Spasticity in Stroke-Randomised study [41]). It was a multicenter, randomized, controlled, open-label phase IV study evaluating the efficacy and safety of ITB versus conventional management. Both groups received physiotherapy. Results from SISTERS trial showed significant effect of ITB over conventional therapy. It also concluded that continuous infusion of baclofen via ITB is noted to provide prolonged and stable control of muscle tone. Beyond spasticity reduction, ITB therapy has been associated with improvements in pain and QoL in post stroke patients. The trial reported improvement in QoL [45]. Natale et al. [46] analyzed 112 consecutive patients with progressive severe spasticity. All of them underwent ITB. The study concluded stating that ITB is a good treatment option for severe spasticity. Penn [47] had evaluated intrathecal drugs- morphine and baclofen. The study concluded that baclofen was a better drug for spasticity. Boviatsis et al. [48] evaluated the use of intrathecal baclofen in multiple sclerosis and spinal cord injury. Evaluation was done based on symptoms like severe spasms, hygiene and QoL. Study also evaluated neurological symptoms with neurophysiological and urological assessments. They stated that evaluation of functional improvement should wait for at least 9 months. Barthel index score (BIS) was used for functional improvement. They concluded that BIS improved in both the diseases, post intrathecal baclofen pump [48]. Avellino and Loeser [49] found that while ITB significantly reduced spasticity, its effect on QoL and functionality was less. Müller et al. [50] used electromyographic findings to show improvement of intrathecal baclofen pump to show improvement post insertion of pump. Delhaas et al. [51] reported expected complications as wound complications, catheter problems, CSF leakage. But its effect on QoL and functionality is less apparent. Baclofen is reported to have good outcome scores [51]. Schiess et al. [52] conducted a longitudinal study involving 1,743 patients with an average follow-up duration of 44.6 months with a mean implant duration of 72 months. Ninety-nine percent of pumps were explanted due to battery depletion and replaced the same day. It showed that the patients and care givers were willing for the use of intrathecal baclofen and continuing the therapy [52]. Creedon et al. [53] performed a meta-analysis in which various studies were reviewed and evaluated. They concluded that use of intrathecal baclofen was extremely effective and safe in patients with severe spasticity.

DRG STIMULATION

DRG stimulation is an emerging neuromodulation technique used primarily in the management of neuropathic pain [54]. It is designed to provide targeted pain relief by stimulating the dorsal root ganglia, which are key relay stations for sensory information entering the spinal cord. By applying electrical stimulation to the ganglia, it can modulate the transmission of pain signals to the central nervous system, potentially providing relief to patients who do not respond to conventional therapies.

1. Indications [55]

(1) CRPSs types I and II

(2) Causalgia

(3) Postsurgical or traumatic neuropathic pain

(4) Focal pain syndromes not well-managed by SCS

DRG stimulation involves inserting a lead electrode through a minimally invasive procedure. It is then connected to an implantable pulse generator [54]. The ACCURATE trial is the landmark randomized control trial showing DRG stimulation superiority over traditional SCS for CRPS and causalgia [56,57]. Overall, DRG stimulation represents promising advancement in pain management, offering hope for improved QoL for individuals suffering from chronic pain conditions.

CONCLUSION

Spinal neuromodulation techniques represent significant therapeutic options within their respective fields, with ongoing research refining understanding and application [58]. Spinal neuromodulation techniques like SCS, ITB, and SNM are utilized for a wide range of chronic neurological conditions like pain, spasticity and bowel/bladder dysfunction.

SCS is a generally effective and safe treatment for various chronic neuropathic pain conditions, including FBSS and CRPS, often demonstrating superiority over conventional medical management. SCS is cost effective with lesser complication rates.

SNM is effective in improving bowel/bladder dysfunction. ITB is supported as a valuable therapy for severe spasticity showing significant reduction in spasticity with associated improvements in QoL. Current trends involve rigorous evaluation of different stimulation parameters and novel technologies like closed-loop systems.

NOTES

Conflicts of Interest

The authors have nothing to disclose.

Funding/Support

This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Figure 1.

Percutaneous technique for epidural placement of a single-channel electrode. A Touhy needle is advanced into the desired epidural space (A), with its position confirmed using C-arm fluoroscopic guidance (B). (C) The percutaneous electrode is then inserted through the needle into the epidural space, and its placement is verified with image guidance. (D) The electrode is subsequently connected to an external stimulator for trial stimulation. (E) Stimulation parameters can be adjusted using a handheld programmer.

Figure 2.

Minimally invasive (tubular retractor-assisted) technique for epidural placement of a paddle electrode. (A) A paramedian incision is made approximately 2 levels below the intended site of epidural entry, and an 18-mm tubular retractor is angled superiorly to facilitate passage of the paddle electrode into the epidural space. A silicone sheath may be used to create a tract in the epidural space (B), and accurate midline placement of the electrode is confirmed with 2-dimensional fluoroscopy (C).

Figure 3.

Conventional (open) technique for epidural placement of a paddle electrode. (A) A midline incision is made to allow standard exposure, followed by laminectomy to enable direct placement of the electrode under visualization. Electrode position is confirmed with 2-dimensional fluoroscopy (B), after which the electrode is connected to an external stimulator for trial stimulation (C).

Figure 4.

Intraoperative steps for sacral nerve stimulation. The needle entry point is selected approximately 2 cm lateral to the midline from a point either 9 cm superior to the tip of the coccyx (A) or about 3 cm superior to the inferior margin of the sacroiliac joint (B). In both approaches, 2-dimensional fluoroscopy is used to verify the entry point. The needle is directed into the S3 foramen (C), and once correctly positioned, the electrode is advanced beyond the foramen under fluoroscopic guidance (E). (D) It is then connected to an external stimulator for trial stimulation.

Table 1.

Explains about the indications and key findings in the reviewed articles on spinal cord stimulation

Source	Study type/topic	Patient population/indication	Key findings (efficacy/outcomes)
Cameron [25] (2004)	Literature review (safety/efficacy of SCS	Pain of trunk and limbs.	68 Articles met efficacy criteria (367 patients). Success rates varied by indication e.g., CRPS I/II 84% (of 224 patients), ischemic limb pain 77% (of 629), FBSS/low back and leg pain 62% (of 747).
		Grouped by diagnosis: back/leg, CRPS I/II, ischemic limb, angina, FBSS, peripheral neuropathy, SCI, postherpetic neuralgia, stump/phantom limb	69% of 344 patients reposted a reduction in narcotic consumption.
			Prospective noncontrolled studies reported beneficial
Chincholkar et al. [13] (2011)	Prospective analysis of SCS trial period	Chronic pain, majority suffered from FBSS, smaller contribution from CRPS, vascular disease, post amputation/testicular pain and erythromelalgia	Of 40 patients recruited, 82.5% had successful trials and 7 (17.5%) failed trials.
Chincholkar et al. [13] (2011)	Prospective analysis of SCS trial period		Three out of 4 patients with surgical electrodes proceeded to the final stage implant
Costantini et al. [27] (2010)	SCS for the treatment of chronic pain in patients with lumbar canal stenosis	Patients with chronic pain in lumbar spinal stenosis	Opioid use decreased significantly (from 49% to 20% of patients).
Costantini et al. [27] (2010)		Patients with chronic pain in lumbar spinal stenosis	Decreases also observed for steroids, NSAIDs, antidepressants and antiepileptics.
Head et al. [17] (2018)	Systematic review of SCS waveforms for chronic low back and leg pain	Patient populations affected by FBSS, chronic neuropathic, axial or lower limb pain, or CRPS.	Review compared on focusing waveforms
Head et al. [17] (2018)		Excluded conditions like chronic limb ischemia, angina, diabetic, peripheral neuropathy and other chronic pain	Review compared on focusing waveforms
OUP-accepted manuscript [26] (2019)	Systematic review (cost effectiveness and resource utilization of SCS vs. conventional therapies	Patients with chronic low back and leg pain. Review included 31,439 SCS patients and 299,182 conventional therapy patients, FBSS is also mentioned	SCS is associated with favourable outcomes in 8 of 11 studies reviewed significant improvement in health-related quality of life, health status and quality-adjusted years.
OUP-accepted manuscript [26] (2019)			There was a 15% change in drug and adjuvant therapy utilization with SCS.

SCS, spinal cord stimulation; CRPS, chronic regional pain syndrome; FBSS, failed back surgery syndrome; SCI, spinal cord injury; NSAID, nonsteroidal anti-inflammatory drug.

Table 2.

Detailed description on safety, complications, cost-effectiveness of SCS therapy

Source	Safety/complications	Cost effectiveness/resource utilization	Notes/limitations
Cameron [25] (2004)	51 Articles met safety criteria (2,972 patients)	Primarily focused on efficacy and safety, cost effectiveness or resource utilization	Review of literature published after January 1981.
	Complications were categorised including lead migration, epidural haemorrhage, seroma, hematoma, paralysis, CSF leakage, over or understimulation, intermittent stimulation, pain over implant site, allergic reaction, skin erosion, lead breakage, hardware malfunction, loose connection, biological reaction to IPG and battery failure		It included prospective randomized, prospective nonrandomized, controlled prospective noncontrolled and retrospective studies.
			Search also included MEDLINE and Journal of Neuromodulation
Chincholkar et al. [13] (2011)	1 Patient with surgical electrodes had the lead removed due to inadequate pain relief	Not focused on cost effectiveness or resource utilization	Study recruited 40 patients between 2004 and 2007.
			A complete data set was available for 36 patients; 4 failed to return diaries.
			Patient indicated daily usage of stimulator in hours/day
Costantini et al. [27] (2010)	Complications are not detailed in the provided excerpts	Medtronic Europe funding and statistical supports	Limited details on study size or methodology provided in the excerpts
Head et al. [17] (2018)	North et al 2005 reported 7.8% of overall adverse event rate (n=51), including 1 receiver site infection and 3 hardware revisions due to migration or malposition	Not focused on cost effective ness or resource utilization	Systematic review conducted according to PRISMA guidelines, included RCTs classified as level 1 and Level 2 evidence.
Head et al. [17] (2018)	Kumar et al. (2008) study reported a 45% overall adverse event rate (n=42) with electrode migration at 14%	Not focused on cost effective ness or resource utilization	Risk of bias was assessed using Cochrane tool, and studies were deemed to have either low risk of bias or some concerns
OUP-accepted manuscript [26] (2019)	SCS was associated with higher complications rates as compared to conventional treatment.	SCS was found to be more cost effective than CT for chronic low back pain in 8 of 11 studies. SCS resulted in shorter hospital stays and lower health care costs at 90 days	The review included studies published from January 2008 through October 2018.The majority of studies reviewed were of fair quality, with level 3 or 4 evidence.
	Date from reviewed studies show 2,074 complications in 16,060 patients.		Recommendations for SCS as a cost-effective modality as compared to conventional management
	A complication rate of 19%/year for SCS has been reported

SCS, spinal cord stimulation; CSF, cerebrospinal fluid; IPG, implantable pulse generator; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-analyse; RCT, randomized controlled trial; CT, conventional therapy.

Table 3.

Describes the study type, patient demographics, spasticity scale, complications, and outcomes after intrathecal baclofen therapy

Study type	Patient population/demographics	Spasticity etiologies	Spasticity scale/baseline/follow-up	Complications type/reported rate	Outcomes
Intrathecal. product surveillance registry [53] (2020)	1,743 (evaluated for spasticity)	Multiple sclerosis 33%	Ashworth scale/3.8/1.6	Battery replacement highest in first year postimplant (113 total, cumulative rate 0.117).	Significant improvement in spasticity post baclofen implantation
	7,975 Pump patients in registry 24	Spinal cord injury 17%		Device dislocation, device occlusion, implant site infection, intracranial hypotension (16%)
	Adult: mean 46 yr; pediatric: mean 10 yr	Cerebral Palsy 13%		Unexpected event — fecal impaction in 2
	46% Females, 34% males	Brain injury 8%, stroke 5%		No long-term morbidity or mortality
Avellino and Loeser [49] (2000)	Adult patients (n=61)	Specific breakdown not in excerpts	Ashworth scale/3.8/1.6	Total complication rate - 36%	Statistically significant decrease in spasticity
	Age 38.6 yr		Penn Spasm Frequency Scale 2.5/0.8	Catheter related complications—links, breaks, dislodgement—27 events in 13 patients	In TBI and CP the reduction was less but stabilized in 9 mo
	44% Females			Drug related complications—7 events in 7 patients
	56% Males			Other complications like wound infections were also seen
Boviatsis et al. [48] (2005)	Total of 22 patients	15 Multiple sclerosis	Penn Spasm scale for MS/3.3/1.5	Not studied	Significant reduction spasm frequency in both MS and Spinal cord injury
	Average age - 44.7 yr	7 Spinal cord injury	Penn spasm scale for Spinal cord injury/3.7/1.3
	10 Females, 12 males
Creedon et al. [53] (1997)	Meta-analysis of 27 studies	MS, SCI, stroke, TBI, Hereditary Spastic paraparesis, syringomyelia, unspecified trauma	Penn spasm frequency Scale /3.2/0.6	Over dose, sepsis, meningitis, and respiratory infection were seen in 9 of 18 subjects in one study	Significantly reduced spasticity in most cases.
	N=490 subjects				And the scores significantly low in each follow-up (1.3.6 m)
	Average age - 36 yr
Delhaas et al. [51] (2008)	115 Patients	Not explicitly mentioned	Ashworth scale 3.3/2	Wound complications (22%)	Mean follow-up for 12months
				CSF leakage (25%)	Significant lower spasticity rates except clonus
				Catheter related problems (36%)
				Other complications (17%)
Natale et al. [46] (2012)	112 Consecutive patients	Spinal cord injury, amyotrophic lateral sclerosis, transverse myelitis, syringomyelia, rigid spine syndrome, quadriparesis	Ashworth scale/4.5/1.2	Drug induced complications (6.3%)	Dramatic reduction in spasticity at last follow-up (mean 55-mo reduction in spasm score at last follow-up mean 55 mo)
Natale et al. [46] (2012)	Average age - 43.2 yr		Penn spasm frequency Scale/3.2/0.8	Catheter related problems (8.9%)

TBI, traumatic brain injury; CP, cerebral palsy; MS, multiple sclerosis; SCI, spinal cord injury.

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