S3 Foramen Research Articles

The primary report of percutaneous polymethyl methacrylate cementoplasty in osteolytic metastases of the pelvis and peripheral bone

目的 探讨经皮注射聚甲基异丁烯酸(PMMA)治疗骨盆区与肱骨、胫骨溶骨性转移瘤的技术与疗效.方法患者24例,S1病变9例,髋臼病变7例,坐骨病变5例,肱骨病变2例,胫骨病变1例,病灶共计26个.穿刺均在X线透视监测下进行.(1) S1穿刺途径:经骶髂关节穿刺S1椎体,穿刺途径应位于第1骶前孔的上方,当穿刺针接近S1椎体边缘时,在侧位透视观察下的穿刺针尖应位于椎管前缘.(2)髋臼穿刺途径:髋臼顶部的穿刺点位于骨盆侧面,在正侧位透视下,将穿刺针送至髋臼病变区.内侧髋臼穿刺应自坐骨结节,经坐骨升支抵达病变区.(3)坐骨病变穿刺途径:穿刺点位于坐骨结节,穿刺针直接穿刺病灶.(4)肱骨、胫骨病变穿刺途径:肱骨穿刺应避开桡神经与前臂血管走行,穿刺病灶.自胫前区直接穿刺胫骨病灶.在X 线透视监测下,应用旋进式加压注射器向病灶内推注呈牙膏状的PMMA.若PMMA抵达椎体后壁或病灶外以及病灶外的血管显影,应立即停止注射,避免PMMA外溢导致并发症发生.结果术后7 d内患者均有明显的疼痛缓解:完全缓解10例,部分缓解14例. 1例肱骨病变患者术后27 d 在起床时,用患臂支撑身体,突感注射PMMA的病变区重度疼痛,考虑可能为PMMA与骨界面之间的微骨折所致,应用石膏固定和制动患臂,对症处理2 d后疼痛逐渐完全缓解.余23例患者随访2～7个月,均未出现局部疼痛加重.2例有PMMA外溢,但无相关临床症状发生.结论经皮注射PMMA治疗骨盆区与肱骨、胫骨溶骨性转移瘤的技术与方法是安全可行的.对于四肢骨病变治疗后,有发生骨折的局部潜在可能,局部应制动或外固定。

Pulsed Radiofrequency for Radicular Pain Due to a Herniated Intervertebral Disc—An Initial Report

Pulsed radiofrequency (PRF) has been used for the treatment of radicular pain, due to a herniated intervertebral disc, but so far the data are anecdotal. This is a retrospective study on 13 consecutive patients with this type of pain, at levels L3 to S1. All patients had a diagnosis confirmed by imaging, all had neurological abnormalities, and all were scheduled for surgical intervention. All 12 patients who had a profession had stopped working. Treatment consisted of application of PRF to the dorsal root ganglion of the affected segmental nerve, or in the case of S1 to the segmental nerve at the level of the S1 foramen. One patient underwent disc surgery, and one other patient underwent a spinal fusion 1 year following PRF treatment. He had no leg pain at the time of operation. The remaining patients did not require surgical intervention. The numeric rating scale (NRS) score fell from 7.83 to 2.25 over the first 2 weeks, followed by a gradual further fall to 0.27 at the final follow-up, 15.8 (11 to 23) months after the procedure. Compared with the initial NRS score the data were significant (P < 0.01) from 4 weeks after the procedure. Neurological abnormalities resolved except in one patient, who had decreased sensibility in a small area in the L3 dermatome at the last follow-up. All professionally active patients went back to work after 0.49 months (0.1 to 1). It is concluded that PRF may potentially be a viable alternative for epidural steroid injections in the treatment of acute radicular pain, due to a herniated intervertebral disc, and that further studies, including a control group, should be carried out to establish the value of this method.

Inadvertent Intraforaminal Iliosacral Screw Placement Despite Apparent Appropriate Positioning on Intraoperative Fluoroscopy

We present the case of an intraforaminal iliosacral screw placed percutaneously with aid of C-arm using inlet, outlet, and lateral views of the pelvis. The iliosacral screw was placed above the S1 foramen on the outlet view, into the middle of S1 via the ala on the inlet view, and below the cortical shadow of the ala on the lateral view. The patient was neurologically intact postoperatively, but began to complain of severe radicular pain in the S1 distribution down to the foot within 1 week postsurgery. There was mild weakness of plantar flexion. Postoperative computed tomography scan showed that the iliosacral screw was within the S1 foramen. Because of the tangential nature of the S1 foramen, slight posterior placement of the screw into the S1 body and not into the promontory resulted in violation of the foramen despite it being above the cortical shadow on the outlet view.

Preganglionic approach to transforaminal epidural steroid injections.

Several studies have demonstrated the efficacy of transforaminal epidural steroid injections (TFESI) for the treatment of lumbosacral radicular pain. 1–4 Using standard TFESI technique, the spinal needle is positioned within the “safe triangle” (bordering the pedicle, the exiting nerve root, and the posterolateral border of the vertebral body), with the bevel below the inferior aspect of the pedicle. In a selective nerve root block, the injectate typically bathes the epidural space around the dorsal root ganglion and descends along the distal aspect of the nerve root (Fig. 1, bottom arrow). Ideally, if there is no stenosis, and the needle tip is appropriately positioned, the injectate may spread rostrally to the epidural portion of the preganglionic nerve root as well (Fig. 1, top arrow).Figure 1:: Fluoroscopic image (anteroposterior view) of transforaminal selective nerve root and epidural steroid injection of the left L4 nerve root. Bottom arrow, distal aspect of the nerve root; top arrow, epidural portion of the preganglionic nerve root.In most cases of lumbosacral radiculopathy secondary to stenosis or a herniated disc, the site of impingement usually lies at the level of the supra-adjacent intervertebral disc, which is rostral to the conventional lumbar TFESI bevel position. However, one cannot always guarantee a rostral spread of injectate to bathe the epidural/preganglionic portion of the nerve root. As an example, in treating a right S1 radiculopathy with TFESI at the exiting nerve root location (S1 foramen), the injectate failed to ascend to the L5-S1 disc level (Fig. 2, bottom arrow). In situations like this, one may wish to consider a supplementary preganglionic TFESI approach. The fluoroscopic landmarks utilized for needle positioning are similar to those used for intradiscal procedures (lateral to the superior articular process and parallel to the superior endplate of the vertebral body). The final needle position is at the inferior aspect of the supra-adjacent neural foramen, with the bevel immediately dorsal to the annulus/posterior longitudinal ligament. Injection at this position places the aliquot at the epidural preganglionic site of neural impingement, where the traversing nerve root is in closest proximity to the disc. The injectate may also descend to the intraforaminal and epidural portion of the exiting nerve root (Fig. 2, top arrow).Figure 2:: Fluoroscopic image (anteroposterior view) of epidural steroid injection of the right S1 root. Bottom arrow, L5-S1 disc level; top arrow, intraforaminal and epidural portion of the exiting nerve root.Theoretical advantages of the preganglionic TFESI technique include placing of the injectate closer to the site of neural impingement and providing a more effective washout of inflammatory disc material. Perhaps this methodology may be useful as a supplementary injection technique to the conventional TFESI, especially in patients who demonstrate poor rostral spread of injectate toward the epidural/preganglionic portion of the nerve root. A prospective, randomized, controlled trial may be needed to verify its clinical efficacy and further define its utility.

Herpes Zoster Following Sacral Nerve Stimulation for Overactive Bladder

Shingles, or herpes zoster, is a viral infection caused by reactivation of the varicella-zoster virus, which commonly causes chickenpox in childhood. This virus remains dormant in nerve ganglia. When reactivated, it leads to the development of cutaneous blisters in a dermatomal distribution based on the nerve root affected. Many factors have been theorized to prompt viral reactivation, such as an immunocompromised state (for example in the elderly), trauma and stress. There are a limited number of case reports of herpes zoster following neurosurgery where nerve root manipulation led to shingles outbreaks. To our knowledge we report the first case of herpes zoster following placement of a sacral nerve root electrode for neuromodulation of overactive bladder. CASE REPORT A 73-year-old woman with refractory symptoms of urinary frequency, urgency and urge incontinence, as well as fecal incontinence who had previously failed anticholinergic therapy underwent first stage placement of a sacral nerve root electrode while under local anesthesia and intravenous sedation. With the patient in the prone position, the third sacral foramen on the right side was identified using a foramen needle under fluoroscopic guidance. An angiographic catheter (14 gauge) was then advanced through the S3 foramen, and a permanent quad electrode was then positioned anterior to the right S3 foramen. Thus, the electrode traversed the S3 foramen and ended anterior to the sacrum, adjacent to the lumbosacral nerve plexus. Electrical stimulation confirmed proper positioning, with perceived sensations in the rectum and vagina. In addition, fluoroscopy confirmed positioning of the electrode at the S3 level. An external pulse generator was connected and the patient was instructed on use of the device. She was discharged home the same day on oral antibiotics. The patient returned approximately 1 week postoperatively complaining of significant pain in the right lower extremity. She reported significant improvement in urinary frequency, urgency and urge incontinence, as well as complete resolution of fecal incontinence. The stimulation settings of the quad electrode were changed in an attempt to reduce the lower extremity discomfort, which was thought to be related to stimulation of the second sacral nerve roots. The patient then returned on postoperative day 10 complaining of a painful rash along the right inner thigh. Physical examination revealed erythematous, fluid filled blisters along the right inner thigh and medial portion of the right knee, consistent with L2 and L3 dermatomal distributions (see figure). The sacral electrode was disconnected from any electrical stimulation, and the patient received a course of oral acyclovir and analgesics. She denied any history of herpes zoster. The outbreak resolved within several weeks. However, the patient has not undergone conversion to an internal pulse generator due to concurrent medical problems. To date, she has not undergone restimulation of the electrode.

Electrophysiological recordings during the peripheral nerve evaluation (PNE) test in complete spinal cord injury patients.

Up until now, the exact mechanism by which neuromodulation using sacral nerve stimulation works still remains unknown. Recent studies of pelvic floor contraction during peripheral nerve evaluation (PNE) have shown that several muscle responses are reflexly mediated. However, whether these reflexes originate from a segmental level within the sacral spinal cord or from supraspinal neuronal centers involving spino-bulbospinal pathways remains to be determined. Therefore, recordings of external anal sphincter reflexes during PNE in complete spinal cord injury (SCI) patients was performed. Three patients with complete SCI (two female and one male) suffering from neurogenic incontinence underwent the first stage of a stimulator implant (peripheral nerve evaluation). Stimulation was obtained through an electrode placed in the S3 foramen. Concomitantly, the latency of the response of the striated anal sphincter was measured using a concentric needle electrode placed in the striated part of the anal sphincter. Repeated measurements within an interval of 30 min were performed to confirm the reliability of the responses. In all subjects, reflex responses of early and late latencies could be recorded. The early response showed a mean latency of 41.2 ms (range 33.3-62 ms), which corresponds to a segmental reflex, similar to the pudendo-anal reflex. The late response appeared with a mean latency of 189.4 ms (range: 183.3-197.8 ms) and with high variability and fatigability, suggesting a reflex response organized at polysegmental spinal levels. Despite successful foramina lead placement, none of our complete SCI patients showed any improvement of neurogenic incontinence after 5 days of treatment by sacral nerve stimulation. The findings confirm that the anal contractions observed during peripheral nerve evaluation are reflex responses mediated by afferent pathways. Both the early and late reflex responses are of spinal origin, since they were obtained in complete SCI patients in whom all spino-bulbo spinal loops are supposed to be interrupted. The finding that neuromodulation is working in non-neurogenic patients but is less successful in complete SCI patients could give evidence that preserved spino-bulbo spinal loops contribute to the positive effects of neuromodulation. The role of an eventual spino-bulbo spinal loop acting during neuromodulation in non-neurogenic patients has to be assessed in further studies.

Modified techniques of S3 foramen localization and lead implantation in S3 neuromodulation

Introduction. We describe a reproducible and less invasive surgical approach to sacral neuromodulation (InterStim Therapy) in the treatment of voiding dysfunction. Twenty patients underwent modified lead implantation (mean operative time 45 minutes) without any difficulties or complications, with a mean follow-up of 8 months (range 1 to 14). Technical Considerations. The highlights of these modifications include (a) fluoroscopy to localize the S3 foramen; (b) paramedian incision; (c) use of a cutoff S3 finder needle and a 14-gauge Angiocath to direct permanent lead into the S3 foramen without dissection; (d) use of lateral fluoroscopy to determine the depth of the Angiocath insertion; and (e) anchoring the lead to the lumbodorsal fascia (superficial to the sacral periosteum) using a moveable lead anchor system. These modifications simplify and minimize the invasiveness of this therapy without compromising the efficacy. Conclusions. Because of the simplicity of these modifications, we are currently using an implanted lead, rather than the temporary percutaneous lead, to assess patients’ clinical response before implanting a pulse generator.

Initial Experience with Sacral Nerve Stimulation as a Treatment for Intractable Urge Incontinence

Objective: To evaluate the efficacy of sacral nerve stimulation using a permanent implantable system in the treatment of intractable urge incontinence, urgency, frequency, and nocturia.Methods: Ten women with varying degrees of urinary urge incontinence, urgency, frequency, and nocturia were implanted with an Interstim® sacral nerve stimulation device. To be eligible for the implant, subjects must have failed biofeedback and pelvic electrical stimulation therapy and at least two anti-cholinergic drugs. These women had tried at least two of tolterodine, oxybutynin, and imipramine. They then underwent a three to seven day test stimulation involving the placement of a temporary electrode into the S3 foramen, one on each side, attached to a portable external stimulation device. During this period, all subjects kept a voiding diary and noted their number of incontinent episodes, pads used, and symptoms of urgency, frequency, and nocturia. If at least a 50 Percent improvement was noted, both objectively and subjectively, the subjects were offered a permanent implant. All procedures were done in the operating room and involved the placement of a permanent electrode into the S3 foramen on one side through a small 5–7 cm vertical incision over the sacrum. The electrode body was tunneled under the skin and connected to the stimulating device implanted in the upper buttock through a second horizontal incision. Subjects have been followed for an average of 12.2 months (range 7–16 months).Results: The average age of the subjects was 55.1 years range 30–76 years). All 10 subjects experienced a marked decrease in urge incontinence, urgency, frequency, and nocturia. Eight subjects currently experience no incontinent episodes and are no longer using pads; the other two use only one pad per day. All were using at least four pads daily prior to the implant. All now describe their urgency as “appropriate”. Pre-implant urgency descriptions included “moderate”, “constant”, and “strong” in two, one, and seven subjects respectively. Frequency in all is at least two hours, and reaches four hours in five subjects. Nine of the subjects voided every hour before the implant. Eight subjects experienced three or more episodes of nocturia before the implant; three now void twice per night, while the rest get up either once or not at all. Interestingly, one subject who also suffered from fecal incontinence was cured by this therapy. Another subject with a long history of chronic constipation and an average of one bowel movement per week now moves her bowels daily. All 10 subjects reported satisfaction and responded yes to having this procedure again. There were no adverse effects reported.Conclusions: Sacral nerve stimulation is a promising new therapy for women with intractable urge incontinence and associated urgency, frequency, and nocturia. It appears to be both safe and efficacious. Long term studies with larger numbers of subjects will determine its ultimate place in the management of the overactive bladder. The potential role of sacral nerve stimulation in women with bowel dysfunction and pelvic pain also needs to be investigated.

PMMA cementoplasty in symptomatic metastatic lesions of the S1 vertebral body.

We describe a lateral transiliac direct puncture approach to the S1 vertebral body for polymethylmethacrylate (PMMA) cementoplasty of painful metastatic lesions. This approach was performed using a 15-cm-long trocar needle with 3-mm outer diameter, introduced under general anesthesia and fluoroscopic control. A lateral projection was used to center the needle just in front of the spinal canal and subjacent to the superior plate of the S1 vertebral body. Needle progression was controlled using anteroposterior and lateral fluoroscopic projections alternately with a needle course parallel to an axial plane, avoiding conflict with the S1 foramen. After needle tip placement in the center of the S1 vertebral body, diluted PMMA with a setting time of 8 min was delivered. Ipsilateral lesions of the lateral sacral compartment were filled with the same needle by stepwise withdrawal and continuous PMMA injection.

Safe placement of S1 and S2 iliosacral screws: the "vestibule" concept.

To determine the optimal starting points for placement of S1 and S2 iliosacral screws as well as the pertinent anatomy surrounding the S1 and S2 vertebral bodies. Normal subject study evaluating helical CT scans of thirty normal posterior pelvic rings. Methodist Hospital, Indianapolis, Indiana, Level I trauma center. Consenting adults for limited pelvis CT. The three-dimensional anatomy of the posterior pelvic ring pertinent to S1 and S2 iliosacral screw placement. Safety of simulated S1 iliosacral screw placement using different lateral ilium starting points. The transversely placed (horizontal) iliosacral screw was the least safe of the screws tested. The safest lateral ilium starting point for our entire population was at the posterior sacral body sagittally and at the inferior S1 foramen coronally. S2 iliosacral screws had less cross-sectional area for placement than S1 screws. Placement of the S2 screw slightly to the S1 foraminal side of the S2 vertebral body increased the safety of placement. The iliosacral screw starting point at the posterior sacral body and inferior S1 foramen was the safest when considering the entire population. Careful attention to the size and orientation of the S2 vertebral body should be taken if S2 iliosacral screws are placed.

Percutaneous sacral third nerve root neurostimulation improves symptoms and normalizes urinary HB-EGF levels and antiproliferative activity in patients with interstitial cystitis

Objectives. A highly effective treatment for interstitial cystitis (IC) remains elusive. We determined whether sacral third nerve root (S3) percutaneous neurostimulation (PNS) might be effective in relieving symptoms of IC, as well as in normalizing urinary factors that are specifically altered in IC. Methods. Six consecutive patients with symptoms and cystoscopic findings compatible with IC underwent 5 days of continuous S3 neurostimulation by way of leads placed percutaneously into the S3 foramen. Patients filled out voiding frequency diaries and pain and urgency questionnaires before PNS and at the end of PNS when the leads were removed. Urine specimens were collected at these two time points and measured for heparin-binding epidermal growth factor-like growth factor (HB-EGF) by enzyme-linked immunosorbent assay and for antiproliferative factor (APF) activity by 3H-thymidine uptake by normal human bladder urothelial cells. Results. S3 PNS significantly improved all measured parameters toward normal values. Voiding frequency decreased twofold from 23.1 ± 4.6 to 10.6 ± 4.0 voids daily during PNS ( P = 0.0001). Pelvic pain on a scale of 1 to 10 decreased from 7.0 ± 1.6 to 2.3 ± 3.2 ( P = 0.05). Urinary urgency on a scale of 1 to 10 decreased from 6.0 ± 2.2 to 1.8 ± 1.7 ( P = 0.02). Urinary HB-EGF concentration increased sevenfold from 1.5 ± 2.1 to 11.0 ± 1.7 ng/mL ( P <0.0001), and urinary APF activity decreased from −76.1% ± 31% to −4.5% ± 8.8% ( P = 0.005). Conclusions. S3 PNS significantly decreased symptoms and normalized urinary HB-EGF and APF activity in patients with IC. These results suggest that permanent S3 PNS may be beneficial in treating IC.

STUDIES OF THE LATENCY OF PELVIC FLOOR CONTRACTION DURING PERIPHERAL NERVE EVALUATION SHOW THAT THE MUSCLE RESPONSE IS REFLEXLY MEDIATED

Whether neuromodulation using an implanted sacral nerve stimulator acts by its effects on pelvic afferent or efferent nerves remains to be determined. However, it has been observed that eliciting an "anal wink" is helpful in the optimal siting of the foraminal stimulating electrode. This observation has been interpreted as indicating that a direct effect on efferent pelvic innervation is an important functional component of the technique. We studied the latency of this motor response to determine whether it is consistent with neuromodulation working via a direct efferent mechanism. We studied 9 women with urinary retention undergoing the first stage of a stimulator implant (peripheral nerve evaluation). Stimulation was applied to an electrode placed in the S3 foramen and the latency of the response of the striated anal sphincter, a contraction which gives rise to the "anal wink," was measured using a concentric needle electrode placed in the striated part of the anal sphincter. Mean latency of response was 98 milliseconds (range 52 to 140), which is approximately 10 times longer than would be expected from that resulting from direct motor nerve stimulation. Our results indicate that anal sphincter contraction observed during peripheral nerve evaluation is the result of an afferent mediated response.

Urodynamic monitoring during percutaneous sacral nerve neurostimulation in patients with neurogenic detrusor hyperreflexia.

The purpose of this study was to assess urodynamics parameter changes induced by acute sacral neurostimulation (SNS) in spinal cord injury (SCI) patients with neurogenic detrusor hyperreflexia. Fourteen SCI patients with urge incontinence owing to a hyperreflexive bladder were prospectively evaluated. Neurostimulation was performed on the root that obtained the best motor response (10 Hz, 210 microseconds) and amplitude ranges of >0 to 10 V. The urodynamics study was done in the prone position. Four cystometries were recorded before (two), during (one), and 10 minutes after stimulation (one). Maximal bladder capacity (MBC) (volume to first leakage), bladder volume at first uninhibited contraction (BV(1stC)), and maximal detrusor pressure during uninhibited contractions (P(det)max) were compared. Left S3 foramen was the most commonly used (9/14). Mean amplitude of stimulation was 4.5 V (range, 0.5-8.5 V). Statistically significant differences (Mann-Whitney U-test) were found for MBC, BV(1stC), and P(det)max with mean variations of +206.8 mL (+107%, P < 0.001), +151.5 mL (+98%, P < 0.01), and -23.4 cm H2O (-27%, P < 0.05), respectively. Patient gender and SCI level did not reveal any difference. Patients who reached a MBC of up to 400 mL (+278.2 mL, +129%, n = 10) with SNS had statistically significant improvement of BV(1stC) (+210.2 mL, +125%, P < 0.01) and P(det)max (-33.3 cm H2O, -38%, P < 0.01). Acute temporary SNS in SCI patients has a profound effect on key urodynamics parameters. These neurologically impaired patients with detrusor hyperreflexia may be appropriate candidates for implantable SNS.

Effects of short term sacral nerve stimulation on anal and rectal function in patients with anal incontinence

BACKGROUNDSome patients with faecal incontinence are not amenable to simple surgical sphincter repair, due to sphincter weakness in the absence of a structural defect.AIMSTo evaluate the efficacy and possible mode...

SACRAL ROOT NEUROMODULATION IN IDIOPATHIC NONOBSTRUCTIVE CHRONIC URINARY RETENTION

Purpose Sacral root neuromodulation is becoming a superior alternative to the standard treatment of idiopathic nonobstructive urinary retention. We report results in 20 successive patients who underwent sacral foramen implantation to restore bladder function. Materials and Methods After an initial, thorough baseline assessment 20 patients 19.43 to 55.66 years old with idiopathic nonobstructive urinary retention underwent percutaneous nerve evaluation. Response was assessed by a detailed voiding diary. Responders underwent implantation with an S3 foramen implant, and were followed 1, 3 and 6 months postoperatively, and every 6 months thereafter. Results Sacral root neuromodulation restored voiding capability in these patients. Bladders were emptied with minimal post-void residual urine, which decreased from 78.3 to 5.5 to 10.2% of the total voided volume from baseline to postoperative followup. These results were reflected in uroflowmetry and pressure-flow studies, which were almost normal after implantation. Furthermore, the urinary tract infection rate decreased significantly and associated pelvic pain improved substantially. The Beck depression inventory and SF-36 quality of life questionnaire indicated some improvement but reached significance in only 1 item. In addition, cystometrography showed no significant difference after 6 months of implantation compared with baseline values. Complications were minimal and within expectations. Conclusions Sacral root neuromodulation is an appealing, successful modality for nonobstructive urinary retention. Only patients who have a good response to percutaneous nerve evaluation are candidates for implantation. The high efficacy in patients who undergo implantation, relative simplicity of the procedure and low complication rate make this a treatment breakthrough in this difficult group.

Neuromodulation: urodynamic effects of sacral (S3) spinal nerve stimulation in patients with detrusor instability or detrusor hyperflexia

The aim of this study was to determine the urodynamic effects of sacral (S3) nerve stimulation in patients with urge incontinence due to detrusor overactivity which has been refractory to conservative treatment. A total of 24 patients with idiopathic detrusor instability and five with neurogenic hyperreflexia were studied urodynamically before and 6 months after a permanent S3 foramen electrode implant. The urodynamic studies at follow-up were done with the stimulus on. Clinically, the average voiding frequency, the number of leakage episodes and pad use per 24 h decreased significantly. Improvement in several urodynamic parameters was noted. In the idiopathic as well as in the neurogenic group, the correlation between symptomatic and urodynamic improvement was incomplete. Neuromodulation leads to improvement of several urodynamic parameters in patients with urge incontinence due to detrusor overactivity which has been refractory to conservative treatment and appears to be a valuable treatment option in these patients.

Soleus H-reflex to S1 nerve root stimulation

H-reflexes in normals were elicited by percutaneous electrical and magnetic stimulation of proximal nerve roots at the cauda equina. H-M interval to S1 nerve root stimulation at the level of the S1 foramen was 6.8±0.33 ms, with side to side difference of 0.16±0.13 ms. Compression/ischemia of the sciatic nerve in the mid-thigh abolished the H-reflex to stimulation of the tibial nerve at the popliteal fossa when the H-reflex to S1 nerve root stimulation was preserved. The length of the S1 nerve root in human cadavers was measured to be 17.5±03 cm, providing an estimated dorsal root conduction velocity of 67.3 m/s and a ventral root conduction velocity of 54 m/s. We conclude that the H-M interval to S1 root stimulation can provide reliable measures of conduction within the spinal canal including proximal afferents, anterior horn cells and ventral roots.

Magnetic stimulation of muscle evokes cerebral potentials by direct activation of nerve afferents: A study during muscle paralysis

We tested the hypothesis that magnetic stimulation of muscle evokes cerebral potentials by causing a muscle contraction that then activates muscle receptors. We measured cerebral evoked potentials accompanying magnetic stimulation of muscle in 3 patients during surgery both before and after muscle paralysis with succinylcholine, a depolarizing agent. The magnetic stimulation was at low intensity (30%) and at a 2/s rate. The administration of succinylcholine sufficient to produce muscle paralysis did not alter cerebral potentials evoked by either low-intensity magnetic stimulation of muscle (gastrocnemius/soleus) or electrical stimulation of peripheral nerve (tibial nerve). In 1 normal subject, the S1 nerve root action potentials conducting at rapid velocity (> 60 m/s) were detected at the S1 foramen with a needle electrode using electrical stimulation of the tibial nerve. However, no S1 nerve root potentials could be identified to magnetic stimulation of muscle that evoked a cerebral potential. We conclude that magnetic stimulation of muscle activates terminal afferents in the muscle to provide the afferent drive for the cerebral potentials independent of muscle contraction. The failure to detect the afferent volley in S1 nerve root to magnetic stimulation suggests that only a few afferents are activated or that the activation of afferents is temporally dispersed. © 1996 John Wiley & Sons, Inc.

Magnetic stimulation of muscle evokes cerebral potentials by direct activation of nerve afferents: a study during muscle paralysis.

We tested the hypothesis that magnetic stimulation of muscle evokes cerebral potentials by causing a muscle contraction that then activates muscle receptors. We measured cerebral evoked potentials accompanying magnetic stimulation of muscle in 3 patients during surgery both before and after muscle paralysis with succinylcholine, a depolarizing agent. The magnetic stimulation was at low intensity (30%) and at a 2/s rate. The administration of succinylcholine sufficient to produce muscle paralysis did not alter cerebral potentials evoked by either low-intensity magnetic stimulation of muscle (gastrocnemius/soleus) or electrical stimulation of peripheral nerve (tibial nerve). In 1 normal subject, the S1 nerve root action potentials conducting at rapid velocity (> 60 m/s) were detected at the S1 foramen with a needle electrode using electrical stimulation of the tibial nerve. However, no S1 nerve root potentials could be identified to magnetic stimulation of muscle that evoked a cerebral potential. We conclude that magnetic stimulation of muscle activates terminal afferents in the muscle to provide the afferent drive for the cerebral potentials independent of muscle contraction. The failure to detect the afferent volley in S1 nerve root to magnetic stimulation suggests that only a few afferents are activated or that the activation of afferents is temporally dispersed.

P135 Retest reliability in facial nerve conduction studies

The H-reflex on stimulation of the tibial nerve in the popliteal fossa is routinely used in the diagnosis of first sacral (S1) nerve-root radiculopathy. The H-reflex latency, however, is considered to lack sensitivity since a small change from the focal root pathology can be diluted in a relatively long reflex latency. We have studied the soleus H-reflex elicited by stimulation of the S1 nerve root at the S1 foramen. The normal values for the S1-foramen H-reflex have been reported in a previous study, but there are no definitive reports in patients with S1 radiculopathy. This study was undertaken to determine whether stimulating at the S1 nerve root can improve the utility of the H-reflex for detecting an S1-root lesion.A randomised paired-study design was utilised to evaluate two H-reflexes: one elicited with tibial nerve stimulation and one elicited with S1-root stimulation. Fifty-five patients with unilateral S1 radiculopathy, confirmed by clinical, electrodiagnostic and magnetic resonance imaging (MRI) evidences were studied. A high-voltage electrical stimulator was used to elicit H-reflexes bilaterally at the S1 foramen and L4/L5 spine level. Latencies were compared with previously generated normal values and similar responses from the asymptomatic leg, focussing on the interval between the peak of M- and H-waves (HMI).On the symptomatic side, 39 of the 55 patients had abnormal tibial H-reflex latencies and 54 patients had abnormal responses on S1-foramen stimulation (absent in 18; HMI prolonged >0.4 ms in 36). On the asymptomatic side, all 55 patients had normal tibial H-reflexes, and 52 had normal responses on S1-foramen stimulation. In three patients, the HMI was abnormal on S1-foramen stimulation. In 46 patients tested with L4/L5-level stimulation, H-reflex was present in 39 and absent in seven. The latency of the M-wave to S1 stimulation was normal.Abnormal S1-root H-reflexes reveal lesions at the S1 root in patients with normal tibial H-reflexes; therefore, enhancing diagnostic sensitivity. The appearance of the H-reflex to L4/L5-level stimulation in patient with absent H-reflex to S1-foramen stimulation further localises the site of S1 nerve-root lesion to the L5/S1 spine level. Thus, H-reflex to S1-root stimulation significantly increases the diagnostic sensitivity for S1 radiculopathy.In our study, the S1-root H-reflex with high-voltage electrical stimulation has shown greater sensitivity than the tibial H-reflex in evaluating S1 compressive radiculopathies. An abnormal S1-root H-reflex helps to localise the lesion to the S1 root in patients with concurrent abnormal tibial nerve H-reflex, which may increase diagnostic specificity.