Skin and not dorsal root stimulation reduces hypertonus in thoracic motor complete spinal cord injury: a single case report.

On demand and localized treatment for excessive muscle tone after spinal cord injury (SCI) is currently not available. Here, we examine the reduction in leg hypertonus in a person with mid-thoracic, motor complete SCI using a commercial transcutaneous electrical stimulator (TES) applied at 50 or 150 Hz to the lower back and the possible mechanisms producing this bilateral reduction in leg tone. Hypertonus of knee extensors without and during TES, with both cathode (T11-L2) and anode (L3-L5) placed over the spinal column (midline, MID) or 10 cm to the left of midline (lateral, LAT) to only active underlying skin and muscle afferents, was simultaneously measured in both legs with the pendulum test. Spinal reflexes mediated by proprioceptive (H-reflex) and cutaneomuscular reflex (CMR) afferents were examined in the right leg opposite to the applied LAT TES. Hypertonus disappeared in both legs but only during thoracolumbar TES, and even during LAT TES. The marked reduction in tone was reflected in the greater distance both lower legs first dropped to after being released from a fully extended position, increasing by 172.8% and 94.2% during MID and LAT TES, respectively, compared with without TES. Both MID and LAT (left) TES increased H-reflexes but decreased the first burst, and lengthened the onset of subsequent bursts, in the cutaneomuscular reflex of the right leg. Thoracolumbar TES is a promising method to decrease leg hypertonus in chronic, motor complete SCI without activating spinal cord structures and may work by facilitating proprioceptive inputs that activate excitatory interneurons with bilateral projections that in turn recruit recurrent inhibitory neurons.NEW & NOTEWORTHY We present proof of concept that surface stimulation of the lower back can reduce severe leg hypertonus in a participant with motor complete, thoracic spinal cord injury (SCI) but only during the applied stimulation. We propose that activation of skin and muscle afferents from thoracolumbar transcutaneous electrical stimulation (TES) may recruit excitatory spinal interneurons with bilateral projections that in turn recruit recurrent inhibitory networks to provide on demand suppression of ongoing involuntary motoneuron activity.

Suppression of Urinary Voiding "on Demand" by High-Frequency Stimulation of the S1 Sacral Nerve Root in Anesthetized Rats.

OBJECTIVES: High-frequency (kHz) stimulation of preganglionic pelvic nerve afferents can inhibit voiding in both anesthetized and conscious rats. The afferents travel via the S1 sacral nerve root, which is easier to access than the distal pelvic nerve fibers within the abdominal cavity. We therefore investigated whether voiding could be inhibited by high-frequency stimulation at S1 and how this compared to distal pelvic nerve stimulation. METHODS: Urethane-anesthetized rats were instrumented to record bladder pressure and abdominal wall electromyogram and to stimulate the distal preganglionic pelvic nerve bundle and S1 sacral root. Saline was infused continuously into the bladder to evoke repeated voiding. Stimulation was initiated within 1-2 sec of the onset of the steep rise in bladder pressure signaling an imminent void. RESULTS: In six rats, stimulation of the distal pelvic nerve bundle (1-3 kHz sinusoidal waveform 1 mA, 60 sec) supressed the occurrence of an imminent void. Voiding resumed within 70 ± 13.0 sec (mean ± SEM) of stopping stimulation. Stimulation (using the same parameters) of the S1 root at the level of the sacral foramen suppressed voiding for the entire stimulation period in three rats and deferred voiding for 35-56 sec (mean 44.0 ± 3.2 sec) in the remaining three. Stimulation at either site when the bladder was approximately half full, as estimated from previous intervoid intervals, had no effect on voiding. CONCLUSIONS: This preliminary study provides proof-of-concept for the sacral root as an accessible target for high-frequency stimulation that may be developed as an "on demand" neuromodulation paradigm to suppress unwanted urinary voids. CONFLICT OF INTEREST: The authors reported no conflict of interest.

Blood perfusion changes during sacral nerve root stimulation versus surface gluteus electrical stimulation on in seated spinal cord injury.

The objective of this article is to examine dynamic changes of ischial blood perfusion during sacral nerve root stimulation against surface functional electrical stimulation (FES). Fourteen adults with suprasacral spinal cord injury (SCI) were recruited. The gluteal maximus was activated by surface FES or stimulating sacral nerve roots by functional magnetic stimulation (FMS) or a sacral anterior root stimulator implant (SARS). Ischial skin index of hemoglobin (IHB) and oxygenation (IOX) was measured.Skin blood perfusion was significantly higher during FMS than the baseline (IHB 1.05 ± 0.21 before vs.1.08 ± 0.02 during stimulation, p = 0.03; IOX 0.18 ± 0.21 before vs. 0.46 ± 0.30, p = 0.01 during stimulation). Similarly, when using the SARS implant, we also observed blood perfusion significantly increased (IHB 1.01 ± 0.02 before vs.1.07 ± 0.02 during stimulation, p = 0.003; IOX 0.79 ± 0.81 before vs. 2.2 ± 1.21 during stimulation, p = 0.036). Among four participants who completed both the FMS and FES studies, the magnitude of increase in both parameters was significantly higher during FMS. This study demonstrates sacral nerve root stimulation confer better benefit on blood perfusion than applying traditional FES in SCI population.

Effect of electroacupuncture at Zusanli (ST 36) on dorsal root nerve signals in normal rats.

OBJECTIVE: To investigate how electroacupuncture (EA) at Zusanli (ST 36) with varying intensities of stimulation affects dorsal root nerve signals in normal rats. METHODS: Adult female Wistar rats were examined after drug-induced anesthesia and isolation of the L4 dorsal root associated with the Zusanli (ST 36) acupoint, using bipolar platinum electrodes. We applied EA at Zusanli (ST 36) with a continuous wave waveform for 1 min, and recorded action potentials in the L4 spinal cord dorsal root nerve with a frequency of 5 Hz and various current intensity levels (approximately 1-4 mA). In addition, we tested EA with a frequency of 15 Hz and current intensity of 1-4 mA. The L4 spinal cord dorsal nerve bundle action potentials were measured for 1 min of EA. To analyze the discharge frequency, we used the maximum Lyapunov exponent and Lempel-Ziv (LZ) complexity. RESULTS: At a fixed frequency, with increasing intensity of EA, dorsal root nerve filament discharge frequency revealed an initial increase, followed by a decreasing trend. A stimulation intensity of 3 mA induced a significantly greater discharge frequency, compared with stimulation intensities of 2 and 4 mA. EA stimulation evoked neuroelectric signals with chaotic characteristics. Increased intensity led to an initial increase in LZ complexity which then decreased, with a stimulation strength of 3 mA inducing the highest level of LZ complexity. CONCLUSION: EA of different intensities can induce nerve action potential encoding with different features.

Electrical Stimulation Able to Trigger Locomotor Spinal Circuits Also Induces Dorsal Horn Activity.

OBJECTIVES: Investigate whether electrical stimulation of the spinal cord adapted to trigger locomotor patterns additionally influences dorsal horn networks. MATERIALS AND METHODS: An in vitro model of isolated neonatal rat spinal cord was used to repetitively deliver electrical stimuli to lumbar dorsal roots and record from homolateral lumbar dorsal roots and ventral roots. RESULTS: Repetitive electrical lumbar dorsal root stimulation can affect both locomotor rhythms derived from ventral neuronal circuits and activity from dorsal neuronal circuits. CONCLUSION: These data suggest that neuro-electrostimulation protocols can simultaneously activate functionally distinct spinal neuronal circuits.

Effects of Combined Electrical Stimulation of the Dorsal Column and Dorsal Roots on Wide-Dynamic-Range Neuronal Activity in Nerve-Injured Rats.

OBJECTIVES: Electrical stimulation at the dorsal column (DC) and dorsal root (DR) may inhibit spinal wide-dynamic-range (WDR) neuronal activity in nerve-injured rats. The objective of this study was to determine if applying electrical conditioning stimulation (CS) at both sites provides additive or synergistic benefits. MATERIALS AND METHODS: By conducting in vivo extracellular recordings of WDR neurons in rats that had undergone L5 spinal nerve ligation, we tested whether combining 50 Hz CS at the two sites in either a concurrent (2.5 min) or alternate (5 min) pattern inhibits WDR neuronal activity better than CS at DC alone (5 min). The intensities of CS were determined by recording antidromic compound action potentials to graded stimulation at the DC and DR. We measured the current thresholds that resulted in the first detectable Aα/ß waveform (Ab0) and the peak Aα/ß waveform (Ab1) to select CS intensity at each site. The same number of electrical pulses and amount of current were delivered in different patterns to allow comparison. RESULTS: At a moderate intensity of 50% (Ab0 + Ab1), different patterns of CS all attenuated the C-component of WDR neurons in response to graded intracutaneous electrical stimuli (0.1-10 mA, 2 msec) and inhibited windup in response to repetitive noxious stimuli (0.5 Hz). However, the inhibitory effects did not differ significantly between different patterns. At the lower intensity (Ab0), no CS inhibited WDR neurons. CONCLUSIONS: These findings suggest that combined stimulation of DC and DR may not be superior to DC stimulation alone for inhibition of WDR neurons.

Comparative cost-effectiveness analysis of sacral anterior root stimulation for rehabilitation of bladder dysfunction in spinal cord injured patients.

BACKGROUND: Urinary disorders account for 10% of deaths in patients with complete spinal cord injury. Sacral anterior root stimulation (SARS) may be a valuable therapeutic option to restore complete and voluntary micturition (CVM), but questions on its cost-effectiveness remain. OBJECTIVE: To evaluate the cost-effectiveness of SARS to restore CVM in patients with complete spinal cord injury. METHODS: We conducted a nonrandomized, multicenter, parallel-group cohort study comparing SARS vs. current medical treatments with catheterization or reflex micturition. CVM was assessed at 12 months (end of follow-up) by urodynamic examination. Medical and nonmedical costs were measured in the perspective of the French national health insurance. Linear regression models were used to estimate the incremental net benefit ((Equation is included in full-text article.); λ = willingness-to-pay) adjusted for potential confounders, and P (INB >0) (i.e., probability of SARS being cost-effective vs medical treatment) for different values of λ. RESULTS: Twenty-five patients were included in each group in 2005 to 2009. At inclusion, mean age was 41 years; 45 (90%) patients were male, and 29 (59%) patients were paraplegic. At 12 months, 15 (60%) patients with SARS had a CVM vs. 3 (12%) patients with medical treatment (P < .001). The total mean cost was 42,803 €; and 8762 €, respectively (P < .001). After adjustment for CVM and voiding methods at inclusion, P (INB >0) was 74% at λ = 100,000 €. This probability was 94% in a sensitivity analysis excluding 6 patients presenting a CVM at inclusion. CONCLUSION: The effectiveness and cost of SARS are much higher than for medical treatment. Our results inform decision makers of the opportunity to reimburse SARS in this vulnerable population.

Chronic nerve root entrapment: compression and degeneration.

Electrode mounts are being developed to improve electrical stimulation and recording. Some are tight-fitting, or even re-shape the nervous structure they interact with, for a more selective, fascicular, access. If these are to be successfully used chronically with human nerve roots, we need to know more about the possible damage caused by the long-term entrapment and possible compression of the roots following electrode implantation. As there are, to date, no such data published, this paper presents a review of the relevant literature on alternative causes of nerve root compression, and a discussion of the degeneration mechanisms observed. A chronic compression below 40 mmHg would not compromise the functionality of the root as far as electrical stimulation and recording applications are concerned. Additionally, any temporary increase in pressure, due for example to post-operative swelling, should be limited to 20 mmHg below the patient's mean arterial pressure, with a maximum of 100 mmHg. Connective tissue growth may cause a slower, but sustained, pressure increase. Therefore, mounts large enough to accommodate the root initially without compressing it, or compliant, elastic, mounts, that may stretch to free a larger cross-sectional area in the weeks after implantation, are recommended.

[Transcutaneous electrical stimulation of the spinal cord: non-invasive tool for activation of locomotor circuitry in human].

A new tool for locomotor circuitry activation in the non-injured human by transcutaneous electrical spinal cord stimulation (tSCS) has been described. We show that continuous tSCS over T11-T12 vertebrae at 5-40 Hz induced involuntary locomotor-like stepping movements in subjects with their legs in a gravity-independent position. The increase of frequency of tSCS from 5 to 30 Hz augmented the amplitude of evoked stepping movements. The duration of cycle period did not depend on frequency of tSCS. During tSCS the hip, knee and ankle joints were involved in the stepping performance. It has been suggested that tSCS activates the locomotor circuitry through the dorsal roots. It appears that tSCS can be used as a non-invasive method in rehabilitation of spinal pathology.

The effects of temporary spinal cord stimulation (or spinal nerve root stimulation) on the management of early postherpetic neuralgia from one to six months of its onset.

OBJECTIVE: We examined the efficacy of temporary spinal cord stimulation involving the insertion of only a needle and quadripolar lead into the epidural space and applied using an extracorporeal stimulation generator for a few weeks of early postherpetic neuralgia from one to six months of its onset. MATERIALS AND METHODS: Temporary spinal cord stimulation was applied in 33 patients with postherpetic neuralgia and in whom epidural block was effective. Temporary spinal cord stimulation was applied over seven days, and analgesic effects was evaluated based on visual analog scale (VAS) values before and after one, three, and six months following treatment. An analgesic effect was defined as a decrease of over 50% in the VAS value compared with before treatment. RESULTS: VAS values decreased significantly from 68.1 mm (standard deviation [SD]± 15.2) before treatment to 37.5 mm (SD ± 20.4) after one month, to 38.0 mm (SD ± 18.7) after three months, and to 35.0 mm (SD ± 21.3) after six months. In 21/33 (63.6%) cases, an analgesic effect, defined as a decrease in the VAS value of greater than 50%, was observed one month after treatment, in 20/33 (60.6%) cases such an effect was observed three months after treatment, and in 21/33 (63.6%) cases the effect was still observed six months after treatment. CONCLUSIONS: Temporary spinal cord stimulation is an effective analgesic method for early postherpetic neuralgia from one to six months of its onset.

Long-term effect of MRI on sacral anterior root stimulator: the Stoke Mandeville experience.

STUDY DESIGN: Retrospective review study. OBJECTIVES: To identify whether it is safe to perform a magnetic resonance imaging (MRI) exam on patients who have a sacral anterior root stimulator (SARS). SETTING: Adult patients with spinal cord injury and implanted SARS attending the National Spinal Injuries Centre who have had MRI scans. METHODS: Retrospective review between 1989 and 2010. The effect of the MRI scans on the function of the SARS (Finetech-Brindley, UK) was assessed up to 6 months following MRI at 0.2 and 1.5 T. RESULTS: A total of 18 patients with SARS implants had MRI scans at 0.2 and 1.5 T of the cervical, thoracic and lumbar spine, head, shoulder and pelvis. MRI examinations were abandoned on two occasions in one patient due to radiofrequency interference. One patient's stimulator ceased to function 5 months following MRI; both of these patients showing complications had their MRI examinations at 0.2 T. There were no adverse effects at 1.5 T. In one patient the SARS was removed within 6 months after MRI due to an unrelated medical condition. A total of 17 patients showed no symptoms that required terminating the examination. In all the 11 patients with a complete and functioning implant before MRI at 1.5 T, the SARS was functioning appropriately, and no change in bladder function was reported up to 6 months following MRI. CONCLUSION: It is safe to perform an MRI scan on patients with SARS providing the examination is conducted in a 1.5 T system.

Case report: successful epiradicular peripheral nerve stimulation of the C2 dorsal root ganglion for postherpetic neuralgia.

BACKGROUND: Postherpetic neuralgia (PHN) is the most common complication following an acute varicella zoster virus infection. PHN often results in a chronic severe pain condition refractory to conservative pain management treatments. Peripheral nerve stimulation over the affected spinal nerve root may be an effective treatment option for patients with intractable PHN. OBJECTIVE: To describe a successful case of peripheral nerve stimulation of the second cervical dorsal root ganglion for the treatment of intractable PHN. CASE REPORT: An 80-year-old man with a 15-month history of severe PHN was referred to our clinic for pain management. His pain was localized to the left side in the distribution of the C2 dermatome. The patient's pain was unresponsive to comprehensive conventional treatments for PHN including physical therapy, membrane stabilizing medications, opioids, anti-inflammatories, cervical epidural steroid injections, cervical facet joint injections, and dorsal root ganglion blockade with pulsed radiofrequency. After failing to respond to conservative and interventional therapies, a peripheral nerve stimulator trial was conducted for a period of seven days. The lead was placed within the epidural space over the atlanto-axial joint under fluoroscopy to stimulate the left C2 nerve root. This trial resulted in a significant decrease of the patient's pain, and discontinuation of all pain medications. CONCLUSION: We describe a case of successful electrode placement at the C2 spinal level for the treatment of refractory PHN.

Percutaneous cephalocaudal implantation of epidural stimulation electrodes over sacral nerve roots--a technical note on the importance of the lateral approach.

OBJECTIVE: Idiopathic overactive bladder, urgency-frequency syndromes, interstitial cystitis, pudendal neuralgia, vulvodynia, prostadynia, and coccygodynia have been effectively treated with sacral nerve root modulation. This is most commonly performed with placement of electrodes via a transforaminal approach, predominately to the S3 foramen. This approach is limited by a high lead migration rate and the limitations of stimulating a single nerve root. Beginning in the 1990s, some centers began pursuing retrograde percutaneous placement from the lumbar spine, but adoption of this technique was limited by the technical difficulty of the approach. METHODS AND MATERIALS: We developed a lateral approach to the epidural space for these procedures, which has improved the learning curve and facilitated the application of the retrograde technique. In this technical note, we describe the "laterograde" approach. RESULTS: A focused description of the technique is presented in this technical report. The epidural space is accessed from lateral to medial with the bevel facing up to keep the approach to the "shingled" lumbar laminae shallow. CONCLUSION: The "laterograde" modification of cephalocaudal approach appears to be technically less difficult method for accomplishing sacral nerve root stimulator electrode placement over multiple roots.

Ultrasound-guided caudad epidural access for the lumbosacral neurostimulation: case report and technical note.

OBJECTIVES: This is a case report and description of a new ultrasound-guided caudad epidural needle placement for percutaneous stimulation of the lumbosacral roots. MATERIALS AND METHODS: Case report. RESULTS: Using ultrasonography pertinent spinal and neuroaxial anatomy was visualized. In-plane approach with continuous monitoring of the needle advancement was utilized. The needle was seamlessly placed in the epidural space on the first attempt. CONCLUSIONS: Spinal sonography is a promising imaging method to facilitate percutaneous caudad epidural access.

Association between stimulation parameters and loss of efficacy of selective sacral nerve root stimulation.

OBJECTIVES: This study sought to determine the association between stimulation parameters at the time of implantation and loss of efficacy on long-term follow-up. MATERIAL AND METHODS: Between 2002 and 2007, 143 patients underwent selective sacral nerve root stimulation at our center as a treatment for voiding dysfunction. Nine patients were explanted because of loss of efficacy. The patients' charts were retrospectively reviewed and compared with those of a well-matched group of 12 positive responders. A t-test was used to determine the differences in voiding parameters and stimulation parameters between both groups (at p < 0.05). RESULTS: The baseline amplitude levels in the loss of efficacy group were significantly higher than those of the control group (2.08 ± 0.35 V vs. 1.27 ± 0.25 V) (p= 0.008). The impedance levels were significantly higher in the loss of efficacy group than the control (1032.4 ± 181 Ω vs. 590 ± 44.6 Ω) (p= 0.025). CONCLUSION: High stimulation parameters at the time of implantation were associated with loss of efficacy at the long-term follow-up.

Sacral nerve stimulation for fecal incontinence.

OBJECTIVE: to analyze short-term outcomes and complications for our first fifty patients with fecal incontinence undergoing sacral root stimulation. PATIENTS: fifty patients with fecal incontinence receiving sacral neuromodulation in 4 hospitals are reviewed. Discussed variables include: age, sex, incontinence duration, incontinence cause, prior surgery for incontinence, Wexner scale score, anorectal manometry parameters, and endoanal ultrasonographic findings. Following the procedure Wexner scale score, anorectal manometry parameters, and associated complications are reviewed. RESULTS: mean age of patients is 59.9 years, with females predominating. Most common causes of incontinence include obstetric procedures, idiopathic origin, and prior anal surgery. Mean follow-up is 17.02 months. Follow-up revealed a statistically significant reduction in Wexner scale score and increase in voluntary anal pressure. Technique-derived minor complications included: 2 surgical wound infections that led to stimulator withdrawal; 2 patients with pain who were managed conservatively; 1 case of externalization in a gluteal stimulator; and 1 broken tetrapolar electrode. CONCLUSIONS: sacral nerve stimulation is a simple technique that improves Wexner scores in a statistically significant manner with a low complications rate.