Greater Occipital Nerve Stimulation Boosts Associative Memory in Older Individuals: A Randomized Trial.

Transcutaneous electrical stimulation (tES) is a new approach that aims to stimulate the brain. Recently, we have developed tES approaches to enhance plasticity that modulate cortical activity via the greater occipital nerve (ON) in a "bottom-up" way. Thirty subjects between the ages of 55 and 70 years were enrolled and tested using a double-blind, sham-controlled, and randomized design. Half of the participants received active stimulation, while the other half received sham stimulation. Our results demonstrate that ON-tES can enhance memory in older individuals after one session, with effects persisting up to 28 days after stimulation. The hypothesized mechanism by which ON-tES enhances memory is activation of the locus coeruleus-noradrenaline (LC-NA) pathway. It is likely that this pathway was activated after ON-tES, as supported by observed changes in α-amylase concentrations, a biomarker for noradrenaline. There were no significant or long-lasting side effects observed during stimulation. Clinicaltrial.gov (NCT03467698).

Sacral nerve stimulation increases gastric accommodation in rats: a spinal afferent and vagal efferent pathway.

Impaired gastric accommodation (GA) has been frequently reported in various gastrointestinal diseases. No standard treatment strategy is available for treating impaired GA. We explored the possible effect of sacral nerve stimulation (SNS) on GA and discovered a spinal afferent and vagal efferent mechanism in rats. Sprague-Dawley rats (450-500 g) with a chronically implanted gastric cannula and ECG electrodes were studied in a series of sessions to study: 1) the effects of SNS with different parameters on gastric tone, compliance, and accommodation using a barostat device; two sets of parameters were tested as follows: parameter 1) 5 Hz, 500 µs, 10 s on 90 s off; 90% motor threshold and parameter 2) same as parameter 1 but 25 Hz; 2) the involvement of spinal afferent pathway via detecting c-fos immunoreactive (IR) cells in the nucleus of the solitary tract (NTS) of the brain; 3) the involvement of vagal efferent activity via the spectral analysis of heart rate variability derived from the ECG; and 4) the nitrergic mechanism, Nω-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase (NOS) inhibitor, was given before SNS at 5 Hz. Compared with sham-SNS: 1) SNS at 5 Hz inhibited gastric tone and increased gastric compliance and GA. No difference was noted between the stimulation frequencies of 5 and 25 Hz. 2) SNS increased the expression of c-fos in the NTS. 3) SNS increased cardiac vagal efferent activity and decreased the sympathovagal ratio. 4) l-NAME blocked the relaxation effect of SNS. In conclusion, SNS with certain parameters relaxes gastric fundus and improves gastric accommodation mediated via a spinal afferent and vagal efferent pathway.NEW & NOTEWORTHY Currently, there is no adequate medical therapy for impaired gastric accommodation, since medications that relax the fundus often impair antral peristalsis and thus further delay gastric emptying that is commonly seen in patients with functional dyspepsia or gastroparesis. The advantage of the potential sacral nerve stimulation therapy is that it improves gastric accommodation by enhancing vagal activity, and the enhanced vagal activity would lead to enhanced antral peristalsis rather than inhibiting it.

Soleus H-reflex modulation following transcutaneous high- and low-frequency spinal stimulation in healthy volunteers.

The main aim of this work was to investigate the difference in the excitability of the soleus H-reflex in healthy volunteers following spinal transcutaneous electrical nerve stimulation (TENS) and high-frequency alternating current (HFAC) at a frequency of 10 kHz applied at the lower thoracic spinal level (T10-T12). A double-blind, randomized, crossover, controlled clinical trial was designed. Participants received three randomized interventions (TENS, 10 kHz, and sham stimulation) during 40 min. The amplitude and latency of the soleus H-reflex were registered prior to, during, and 10 min following stimulation. Twenty-four participants completed the study. A significant inhibition of H-reflex amplitude was observed following transcutaneous spinal TENS (12.7%; 95% CI 1.5-22.2%) when compared with sham stimulation (5.5%; 95% CI 3.6-14.5%; p = 0.03). An increase in H-reflex latency was also observed following transcutaneous spinal stimulation at 10 kHz (2%; 95% CI 1.4-2.5%) as compared with sham stimulation (0.7%; 95% CI 0.07-1.3%; p < 0.01). No differences were found between TENS and 10 kHz for H-reflex modulation. Transcutaneous spinal TENS and HFAC at a frequency of 10 kHz had a modulatory effect on the soleus H-reflex when compared to sham stimulation; however, no differences were found between these two interventions.

Long-Term Outcome Following Implanted Pulse Generator Change in Patients Treated With Sacral Nerve Modulation for Fecal Incontinence.

BACKGROUND: Long-term outcome of sacral nerve modulation (SNM) patients after implanted pulse generator (IPG) change for fecal incontinence (FI) is unknown. This study reported the outcome and long-term satisfaction after a change of an exhausted IPG, questioning the need to concurrently change the electrode and looking for factors involved in the maintenance of treatment efficiency. METHODS: Patients with fecal incontinence and with a Medtronic IPG implanted in a single center (2001-2016) were prospectively followed up. Satisfaction was graded according to a patient-reported outcome measure from 0 to 10. A pre- and postreplacement FI severity score (Cleveland Clinic Fecal Incontinence Score) and Fecal Incontinence Quality of Life questionnaire were also collected. RESULTS: In 170 patients with SNM, 39 had an IPG replacement. At a median of 29 month after replacement, 32 and 7 patients reported respectively a similar and reduced satisfaction (7.6 ± 1.62 vs. 5.5 ± 0.87), p < .001. Satisfied patients were younger (65 years vs. 76 years, p < .001). Cleveland Clinic Fecal Incontinence Scores were not significantly different, but the satisfied group had a significantly better Fecal Incontinence Quality of Life score (p = .047). Only 5 patients needed an electrode change at the time of the IPG replacement or later. CONCLUSIONS: Patient satisfaction and efficiency remain high after IPG replacement. Older age has a negative impact on the outcome. Electrode replacement is rarely required and does not need to be performed routinely when an IPG is exhausted. CONFLICT OF INTEREST: Paul-Antoine Lehur has a consulting agreement with Medtronic SA. This had no impact with the results of the study. The other authors have no conflict of interests to declare.

Long-term follow up of intractable chronic short lasting unilateral neuralgiform headache disorders treated with occipital nerve stimulation.

Background Occipital nerve stimulation is a potential treatment option for medically intractable short-lasting unilateral neuralgiform headache attacks. We present long-term outcomes in 31 patients with short-lasting unilateral neuralgiform headache attacks treated with occipital nerve stimulation in an uncontrolled open-label prospective study. Methods Thirty-one patients with intractable short-lasting unilateral neuralgiform headache attacks were treated with bilateral occipital nerve stimulation from 2007 to 2015. Data on attack characteristics, quality of life, disability and adverse events were collected. Primary endpoint was change in mean daily attack frequency at final follow-up. Results At a mean follow-up of 44.9 months (range 13-89) there was a 69% improvement in attack frequency with a response rate (defined as at least a 50% improvement in daily attack frequency) of 77%. Attack severity reduced by 4.7 points on the verbal rating scale and attack duration by a mean of 64%. Improvements were seen in headache-related disability and depression. Adverse event rates were favorable, with no electrode migration or erosion reported. Conclusion Occipital nerve stimulation appears to offer a safe and efficacious treatment for refractory short-lasting unilateral neuralgiform headache attacks with significant improvements sustained in the long term. The procedure has a low adverse event rate when conducted in highly specialised units.

Comparison of Bladder Inhibitory Effects of Patterned Spinal Nerve Stimulation With Conventional Neuromodulation in the Rat.

OBJECTIVES: The present study compared the effectiveness of patterned frequency of spinal nerve stimulation (SNS) with continuous, fixed-frequency nerve stimulation in an animal model of the bladder reflex contraction (BRC). MATERIALS AND METHODS: In anesthetized female rats, wire electrodes were placed under each of the L6 spinal nerve to produce bilateral SNS. A cannula was placed into the bladder via the urethra, and the urethra was ligated to ensure an isovolumetric bladder. RESULTS: Using motor threshold intensity, continuous stimulation at fixed frequencies of 4 Hz (n = 5) and 10 Hz (n = 7) decreased the frequency of BRC of 71 ± 24% (mean, SEM) and 85 ± 18% of controls, respectively (vs. no stimulation, n = 10, p < 0.05, two-way analysis of variance [ANOVA]). Fixed-frequency stimulation at 0.01, 0.1, 1, 40, and 100 Hz, did not demonstrate a trend change on BRC. When stimulation frequency is delivered with a 4-6 pulse/burst pattern every 1-100 sec, neuromodulation has demonstrated a trend toward effectiveness, with a four-pulse 40 Hz burst stimulation per second showing the most difference, reducing the BRC frequency of 74 ± 8% of control (n = 8, p < 0.05, two-way ANOVA). However, it is not more effective than continuous neuromodulation at a fixed frequency of 4 Hz or 10 Hz at BRC inhibition. CONCLUSIONS: Burst stimulations may inhibit bladder contractions; however, they are not more effective than continuous neuromodulation. Without further knowledge regarding mechanisms and potential benefit of burst stimulation on bladder control in patients with neuropathological conditions, applications should utilize continuous fixed 10 Hz stimulation for maximal clinical outcomes.

Increased yield pressure in the anal canal during sacral nerve stimulation: a pilot study with the functional lumen imaging probe.

BACKGROUND: Sacral nerve stimulation (SNS) is a well-established treatment for fecal incontinence but its mode of action remains obscure. Anal sphincter function is usually evaluated with manometry but resistance to distension may be a more appropriate parameter than luminal pressure. The functional lumen imaging probe allows detailed description of distension properties of the anal canal. Our objective in this study was to characterize the impact of SNS on distension properties of the anal canal in patients with idiopathic fecal incontinence. METHODS: We studied 10 women (median age 64 [44-79] years) with idiopathic fecal incontinence at baseline and during SNS. The luminal geometry of the anal canal was examined with the FLIP at rest and during squeeze and the distensibility of the anal canal was investigated during filling of the bag. KEY RESULTS: All patients were successfully treated with SNS and the mean Wexner Incontinence Score was reduced from 14.9 ± 4 to 7.1 ± 4.8 (P<.001). The pressure required to open the narrowest point of the anal canal during distension (yield pressure) increased from 14.5 ± 12.2 mmHg at baseline to 20.5 ± 13.3 mmHg during SNS (P<.01). The pressure-strain elastic modulus increased non-significantly from 2.2 ± 0.5 to 2.9 ± 1.6 kPa, indicating increased stiffness of the anal canal. CONCLUSION AND INFERENCES: The yield pressure and the resistance to distension increased in response to SNS for idiopathic fecal incontinence. This will inevitably increase the resistance to flow through the anal canal, which may contribute to the benefits of sacral nerve stimulation.

Long-term outcomes of occipital nerve stimulation for chronic migraine: a cohort of 53 patients.

BACKGROUND: Chronic migraine affects up to 2 % of the general population and has a substantial impact on sufferers. Occipital nerve stimulation has been investigated as a potentially effective treatment for refractory chronic migraine. Results from randomised controlled trials and open label studies have been inconclusive with little long-term data available. METHODS: The long-term efficacy, functional outcome and safety of occipital nerve stimulation was evaluated in an uncontrolled, open-label, prospective study of 53 intractable chronic migraine patients. RESULTS: Fifty-three patients were implanted in a single centre between 2007 and 2013. Patients had a mean age of 47.75 years (range 26-70), had suffered chronic migraine for around 12 years and had failed a mean of 9 (range 4-19) preventative treatments prior to implant. Eighteen patients had other chronic headache phenotypes in addition to chronic migraine. After a median follow-up of 42.00 months (range 6-97) monthly moderate-to-severe headache days (i.e. days on which pain was more than 4 on the verbal rating score and lasted at least 4 h) reduced by 8.51 days (p < 0.001) in the whole cohort, 5.80 days (p < 0.01) in those with chronic migraine alone and 12.16 days (p < 0.001) in those with multiple phenotypes including chronic migraine. Response rate of the whole group (defined as a >30 % reduction in monthly moderate-to-severe headache days) was observed in 45.3 % of the whole cohort, 34.3 % of those with chronic migraine alone and 66.7 % in those with multiple headache types. Mean subjective patient estimate of improvement was 31.7 %. Significant reductions were also seen in outcome measures such as pain intensity (1.34 points, p < 0.001), all monthly headache days (5.66 days, p < 0.001) and pain duration (4.54 h, p < 0.001). Responders showed substantial reductions in headache-related disability, affect scores and quality of life measures. Adverse event rates were favourable with no episodes of lead migration and only one minor infection reported. CONCLUSIONS: Occipital nerve stimulation may be a safe and efficacious treatment for highly intractable chronic migraine patients even after relatively prolonged follow up of a median of over 3 years.

Safety of Sacral Nerve Stimulation in Pregnancy: A Literature Review.

OBJECTIVES: Sacral nerve stimulation (SNS) is an FDA approved intervention for a spectrum of conditions. Women of childbearing age and those who are pregnant constitute a fair number of sufferers of overactive bladder symptoms and nonobstructive urinary retention; however, hypothesized effects of SNS on the fetus, mother, and the device limit its use in such a group of patients. We present a literature review to support possible safety of SNS in pregnancy. MATERIALS AND METHODS: We reviewed a number of animal studies on effects of neuromodulation on myometrial activity and fetal abnormalities, and several case reports and series describing continued SNS as well as other related modes of neuromodulation during gestation and reported effects on the mother, fetus, and device. RESULTS: Studies on female mammals showed neurostimulation of myometrial tissue aided in embryo transfer and increased latency, evidence against inducing preterm labor, and follow-up of pregnant rats showed no effects on mothers or offspring. Reviewed cases adopted interrupted and uninterrupted courses of SNS until delivery. There were almost no pregnancy complications; infants were healthy at birth, delivered electively by Caesarean section close to term. One follow-up of 2 infants reported some health issues, though SNS was not concluded as a cause. Device replacement after delivery was occasionally performed for different reasons. CONCLUSION: No negative effects of SNS on fetus, mother or device were significantly reported in literature. Further studies expanding on data in the literature could place SNS therapy during pregnancy on the way for declaration as a safe practice.

Long-Term Pain Reduction Does Not Imply Improved Functional Outcome in Patients Treated With Combined Supraorbital and Occipital Nerve Stimulation for Chronic Migraine.

BACKGROUND: Dual supraorbital and occipital nerve stimulation (SONS and ONS) have shown promising efficacy in treating primary headaches. However, its functional outcome is not well studied. OBJECTIVE: To present functional outcome studies of combined SONS and ONS for chronic migraine using verified metrics. METHOD: Consecutive patients with both SONS and ONS assessed with Migraine Disability Assessment (MIDAS) and Beck Depression Index (BDI) both preoperatively and postoperatively were studied. Selected predictor variables included patients with ≥50% improvement of pain, disability status, number of years from diagnosis to implantation, and narcotic use. Functional outcome variables included net improvement of ranked MIDAS and BDI scores. Multivariate analysis of variance was performed to assess the correlation between the outcome and predictor variables. RESULTS: Sixteen patients (12 female; average age 52 years old) were studied. Follow-up ranged from 5 to 80 months (average 44.5; σ = 21.4 months). At most recent follow-up, eight patients had a positive response (≥50% improvement in headache), which was the only predictor of functional outcome (total MIDAS, MIDAS-B, and BDI) (p = 0.021). Of note, improvement in functional outcome was only significant during the perioperative 3-6 months period and not throughout long-term follow-up. Among the predictor variables, a strong inverse correlation was found between disability status and positive response to stimulation (r = -0.582). CONCLUSION: There is a paucity of studies in quality of life, productivity, and psychosocial aspects with peripheral nerve stimulation therapy for headache. Patients with a positive response to SONS and ONS also reported overall improvement in their functional status as reflected by MIDAS and BDI in the perioperative period. Unfortunately, this effect waned over the long-term follow-up.

Anatomical relationship between BL23 and the posterior ramus of the L2 spinal nerve.

BACKGROUND: The acupuncture point BL23 is located in the region of the posterior ramus of the second lumbar spinal nerve (L2) and has historically been used to treat conditions such as lower back pain, pollakiuria, erectile dysfunction, dysmenorrhoea, tinnitus, and vertigo. Some of these treatment effects have been hypothesised to be mediated by the sympathetic nervous system. It was recently discovered that the posterior ramus of the spinal nerve (PRSN) at L2 forms not two but three branches. OBJECTIVE: To examine the relationship between the acupuncture point BL23 and the L2 PRSN in order to consider the pathways possibly affected by BL23 acupuncture. METHODS: Acupuncture needles were inserted through the skin at BL23 to a depth of 3 cm a total of 13 times in eight donor cadavers (seven right-sided, six left-sided). Leaving the needle in place, ventral dissection was performed to determine the PRSN anatomy between the L1 and L3 spinal segments. In four cadavers, the relationship between the L2 spinal nerve and sympathetic branches was additionally evaluated. Following dissection, three-dimensional (3D) data were acquired using a photo scanner and 3D structural images were created using 3D computer graphics software. One additional (female) cadaver was studied without insertion of an acupuncture needle (due to significant scoliosis). RESULTS: The L2 PRSN was divided into medial, intermediate and lateral branches. The needle inserted at BL23 came to lie in the region of the intermediate or lateral branches in all cases. Rami communicantes were found between the L2 spinal nerve and sympathetic trunk with fibres going on to supply the superior hypogastric plexus. CONCLUSIONS: Our findings suggest that acupuncture needles inserted at BL23 come into close proximity with the intermediate or lateral branch of the L2 PRSN, which could result in stimulation of both the somatic and sympathetic nervous systems.

Concordant occipital and supraorbital neurostimulation therapy for hemiplegic migraine; initial experience; a case series.

INTRODUCTION: Hemiplegic migraine is a particularly severe form of the disease that often evolves to a debilitating chronic illness that is resistant to commonly available therapies. Peripheral neurostimulation has been found to be a beneficial therapy for some patients among several diagnostic classes of migraine, but its potential has not been specifically evaluated for hemiplegic migraine. MATERIALS AND METHODS: Four patients with hemiplegic migraine were treated with concordant, combined occipital and supraorbital neurostimulation over periods ranging 6-92 months. The clinical indicators followed included assessments of headache frequency and severity, frequency of hemiplegic episodes, functional impairment, medication usage, and patient satisfaction. RESULTS: All reported a positive therapeutic response, as their average headache frequency decreased by 92% (30 to 2.5 headache days/month); Visual Analog Score by 44% (9.5 to 5.3); frequency of hemiplegic episodes by 96% (7.5 to 0.25 hemiplegic episodes/month); headache medication usage by 96% (6 to 0.25 daily medications); and Migraine Disability Assessment score by 98% (249 to 6). All were satisfied and would recommend the therapy, and all preferred combined occipital-supraorbital neurostimulation to occipital neurostimulation alone. CONCLUSIONS: Concordant combined occipital and supraorbital neurostimulation may provide effective therapy for both the pain and motor aura in some patients with hemiplegic migraine.

Differentiation and interaction of tibial versus spinal nerve stimulation for micturition control in the rat.

AIMS: To determine time course of the bladder inhibitory response to unilateral or bilateral stimulation of the tibial nerve (TN) and spinal nerve (SN) as well as the interaction of stimulation at these two sites. METHODS: In anesthetized female rats, a wire electrode was placed under either one or both of the TN or L6 SN. A cannula was placed into the bladder via the urethra. Saline infusion induced bladder rhythmic contraction (BRC). RESULTS: Compared to SN neuromodulation, TN neuromodulation is less efficacious. The first 5-min stimulation at three times motor threshold on the SN and TN decreased the BRC frequency to 9% and 69% of controls, respectively. In contrast to SN stimulation, bilateral TN neuromodulation is not more effective than unilateral and sustained TN stimulation results in an apparent desensitization of the bladder response. If a 15-min TN stimulation was applied, BRCs were shutdown only during the first 5 min of stimulation. If a 5-min stimulation, using sufficient current to abolish BRC, is repeated, at least 20 min between stimulations was required in order for the responses to the first and second stimulations to be equivalent. Finally, stimulation of the TN combined with SN never produced a significantly greater effect than TN or SN stimulation alone. CONCLUSIONS: Based on the current experiments, it would appear that SN neuromodulation of bladder activity is preferable to TN stimulation and there is no evidence to suggest that stimulation at both sites would offer a therapeutic advantage over spinal stimulation alone.

Yin and yang surfaces: an evolutionary perspective.

A search of the Chinese medicine literature reveals several conflicting explanations of the division of the body into yin and yang surfaces. This paper attempts to clarify this basic concept and reconcile the differing descriptions of it through an exploration of material from other disciplines. A remarkable similarity exists between the surfaces on the human body that are defined by the pathways of the yin and yang meridians and those that have evolved from the ventral and the dorsal aspects of early vertebrate structure. Many of the evolutionary changes described have parallels in our embryological development and are evident in the underlying anatomy of our limbs. The degree of convergence between the two descriptions strongly supports the definition of the yin and yang surfaces as those traversed by the yin and yang meridians. It also goes a long way towards reconciling the conflicting definitions found in the literature. Finding a solution to this question of yin and yang surfaces that is based on anatomy and evolutionary theories has several advantages. It can throw light on differences in the clinical effects of points on the yin and yang meridians and enable the identification of anomalies in the pathways of the main meridian network.

Occipital nerve stimulation in the treatment of medically intractable SUNCT and SUNA.

BACKGROUND: Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) or with cranial autonomic symptoms (SUNA) are primary headaches characterized by frequent attacks of severe headaches in association with cranial autonomic features. Patients with chronic SUNCT or SUNA have unremitting symptoms that necessitate prolonged use of medical preventive treatments, many of which are prone to causing side effects. They can be medically intractable, in which case neurally destructive or cranially invasive surgical treatments can be offered, though these have hitherto yielded conflicting results. Occipital nerve stimulation (ONS) offers a nondestructive and relatively low risk surgical alternative. OBJECTIVE: To assess the efficacy and safety of ONS in chronic, medically intractable SUNCT and SUNA patients. STUDY DESIGN: Prospective open-label study. METHODS: Nine medically intractable, chronic SUNCT and SUNA patients were implanted with electrodes for bilateral occipital nerve stimulation. Data were collected prospectively for pre- and postimplantation headache characteristics, including frequency, intensity and duration of attacks. Diaries were used to assess headache improvement. RESULTS: At a median follow-up of 38 months (range 24-55 months), all but one patient reported substantial improvement. Four patients became pain-free, 3 were almost pain-free (96 - 98% improvement), and one had a marked reduction in attack frequency and severity (81% improvement). After an initial rapid improvement, the maximum benefit of ONS was attained after a lag of a few months. Device malfunction was followed by recurrence or worsening of the attacks within a few days in most patients. Adverse events included lead migration, exposure of the electrode, and pain due to muscle recruitment over the leads. One patient developed hemicrania continua one month after implantation and was successfully treated with indomethacin. CONCLUSION: ONS appears to offer an effective and safe treatment option, without significant morbidity, for medically intractable SUNCT and SUNA. Given the variable results with cranially invasive or neurally destructive surgery, ONS might be considered the surgical treatment of choice for medically intractable SUNCT and SUNA.

Dual occipital and supraorbital nerve stimulation for chronic migraine: a single-center experience, review of literature, and surgical considerations.

Occipital nerve stimulation (ONS) has been studied in a few clinical trials for the treatment of chronic migraine (CM) with failure to prove sufficient efficacy. To date, peripheral nerve stimulation for the treatment of primary headache is limited to off-label use only. The authors report their institutional experience in CM therapy with combined ONS and supraorbital nerve stimulation (SONS). Fourteen patients treated with dual ONS and SONS for CM were studied with follow-up ranging from 3 to 60 months. Seventy-one percent achieved successful stimulation as defined by a 50% or greater decrease in pain severity. The mean reduction in headache-related visual analog scale (VAS) score was 3.92 ± 2.4. Half of the patients also had resolution of migraine-associated neurological symptoms and returned to normal functional capacity. The main adverse events included lead migration (42.8%), supraorbital lead allodynia (21.4%), and infection (14.2%) with a resulting high reoperation rate (35.7%). The authors' stimulation efficacy was superior to the combined 33% positive response rates (≥ 50% pain reduction) in the published studies of ONS for CM. This is likely due to the fact that topographical paresthesia induced by combined ONS and SONS covers the area of migraine pain better than ONS alone. The authors also discuss effective surgical techniques to prevent patient morbidity.

Quantification of effectiveness of bilateral and unilateral neuromodulation in the rat bladder rhythmic contraction model.

BACKGROUND: Using the isovolumetric bladder rhythmic contraction (BRC) model in anesthetized rats, we have quantified the responsiveness to unilateral and bilateral stimulation of the L6 spinal nerve (SN) and characterized the relationship between stimulus intensity and inhibition of the bladder micturition reflex. METHODS: A wire electrode was placed under either one or both of the L6 SN roots. A cannula was placed into the bladder via the urethra and the urethra was ligated. Saline infusion induced BRC. RESULTS: At motor threshold (T mot) intensity, SN stimulation of both roots (10 Hz) for 10 min reduced bladder contraction frequency from 0.63 ± 0.04 to 0.17 ± 0.09 contractions per min (26 ± 14% of baseline control; n = 10, p < 0.05). However, the same intensity of unilateral stimulation (n = 15) or sequential stimulation of both SNs (e.g. 5 min per side alternatively for a total of 10 min or 20 min) was less efficacious. The greater sensitivity to bilateral stimulation is not dependent upon precise bilateral timing of the stimulation pulses. Bilateral stimulation also produced both acute and prolonged- inhibition on bladder contractions in a stimulation intensity dependent fashion. CONCLUSIONS: Using the bladder rhythmic contraction model, bilateral stimulation was more effective than unilateral stimulation of the SN. Clinical testing should be conducted to further compare efficacies of unilateral and bilateral stimulation. Bilateral stimulation may allow the use of lower stimulation intensities to achieve higher efficacy for neurostimulation therapies on urinary tract control.

Interest of electrostimulation of peripheral motor nerves during percutaneous thermal ablation.

PURPOSE: We present our experience of utilizing peripheral nerve electrostimulation as a complementary monitoring technique during percutaneous thermal ablation procedures; and we highlight its utility and feasibility in the prevention of iatrogenic neurologic thermal injury. METHODS: Peripheral motor nerve electrostimulation was performed in 12 patients undergoing percutaneous image-guided thermal ablations of spinal/pelvic lesions in close proximity to the spinal cord and nerve roots. Electrostimulation was used in addition to existing insulation (active warming/cooling with hydrodissection, passive insulation with CO2 insufflation) and temperature monitoring (thermocouples) techniques. Impending neurologic deficit was defined as a visual reduction of muscle response or need for a stronger electric current to evoke muscle contraction, compared with baseline. RESULTS: Significant reduction of the muscle response to electrostimulation was observed in three patients during the ablation, necessitating temporary interruption, followed by injection of warm/cool saline. This resulted in complete recovery of the muscle response in two cases, while for the third patient the response did not improve and the procedure was terminated. No patient experienced postoperative motor deficit. CONCLUSION: Peripheral motor nerve electrostimulation is a simple, easily accessible technique allowing early detection of impending neurologic injury during percutaneous image-guided thermal ablation. It complements existing monitoring techniques and provides a functional assessment along the whole length of the nerve.

Stimulation of the greater occipital nerve: anatomical considerations and clinical implications.

BACKGROUND: Stimulation of the greater occipital nerve has been employed for various intractable headache conditions for more than a decade. Still, prospective studies that correlate stimulation of the greater occipital nerve with outcome of patients with respect to alleviation of headache are sparsely found in literature. OBJECTIVE: To identify anatomical landmarks for a reproducible stimulation of the greater occipital nerve. For the clinical implication, the individual response to therapy of patients with refractory chronic cluster headache undergoing occipital nerve stimulation was correlated with the postoperative localization of the electrodes and with the distribution of the stimulation field. STUDY DESIGN: Prospective observational study, approved by the local research ethics board (09-4143). SETTING: University hospital, departments of neurosurgery and neurology, institute of anatomy and radiology. METHODS: Ten formaldehyde fixed human cadavers were dissected to identify the passage of the greater occipital nerve through the trapezius muscle. The distance to the external occipital protuberance was triangulated measuring the distance of the nerve from the nuchal midline and the protuberance. Between December 2008 and December 2011, 21 consecutive patients suffering from chronic cluster headache underwent surgery in terms of bilateral occipital nerve stimulation, with electrodes placed horizontally at the level of C1. The postoperative x-rays were compared with the acquired landmarks from the anatomical study. The distribution of the stimulation field was correlated to the individual response of each patient to the therapy and prospectively analyzed with regard to reduction of daily cluster attacks and relief of pain intensity at 3 months and at last follow-up. RESULTS: The greater occipital nerve crosses the trapezius muscle at a mean distance of 31 mm below the occipital external protuberance and 14 mm lateral to the midline as found in the anatomical subjects. The electrodes were targeted at this level in all of our patients and stimulated the greater occipital nerve in all patients. Eighteen of the patients (85.7%) reported a significant reduction of the frequency of their cluster attacks and/or declined intensity of pain during the attacks. Yet, 3 of 21 patients (14.3%) did not benefit from the stimulation despite an adequate spread of the stimulation over the occiput. The spread of the stimulation-induced paraesthesias over the occiput was not correlated to a reduction of cluster attacks, to the intensity of attacks, or to the response to treatment at all. LIMITATIONS: Single center non-randomized non-blinded study. CONCLUSIONS: From our study we conclude that a reproducible stimulation of the greater occipital nerve can be achieved by placing the electrodes parallel to the atlas, at about 30 mm distance to the external occipital protuberance. The response to the stimulation is not correlated to the field width of the paraesthesia. We, therefore, consider stimulation of the main trunk of the greater occipital nerve to be more important than a large field of stimulation on the occiput. Still, an individual response to the occipital nerve stimulation cannot be predicted even by optimal electrode placement.