Compression of the peripheral branches of the sciatic nerve by lipoma

The authors report two female patients with chronic sensitive and motor findings in lower limbs caused by compression of distal branches of sciatic nerve by lipoma. Similar eases were not described on literature. Nerve conduction studies allowed to localize the exact site of compression. At surgery, lipomas compressing the deep peroneal nerve (case 1) and the posterior tibial nerve (case 2) were observed. Histologic studies of tumors confirmed the diagnoses.

HIGH VOLTAGE PULSED CURRENT STIMULATION OF THE SCIATIC NERVE IN RATS: ANALYSIS BY THE SFI

Objective: To analyze the efficiency of high voltage pulsed current (HVPC) with early application in three different sites, in the regeneration of the sciatic nerve in rats submitted to crush injury, the sciatic functional index (SFI) was used to assess the functional recovery. Methods: After crushing of the nerve, 57 animals were submitted to cathodal HVPC at frequency of 50Hz and voltage of 100V, 20 minutes per day, 5 days per week. The rats were divided into five groups: control group; ganglion group; ganglion + muscle group; muscle group; and sham group. The SFI was determined weekly for seven weeks, from the preoperative period to the 6th postoperative week. Results: Compared with the control group, the results showed a significantly better performance of group 2 for the first 3 weeks; group 3 showed significantly better performance in the third week; and group 4 showed a significantly negative performance during the 481 and 6th weeks. Conclusion: Early application of HVPC had a positive effect in the treatment of the spinal cord region and the sciatic nerve root ganglion with a dispersive electrode on the contralateral lumbar region or on the gastrocnemius. However, HVPC had a negative effect in the treatment with an active electrode on the gastrocnemius and a dispersive electrode on the contralateral thigh. Level of evidence II, Prospective comparative study.

Sciatic nerve regeneration in rats by a nerve conduit engineering with a membrane derived from natural latex

PURPOSE: To evaluate the capacity of natural latex membrane to accelerate and improve the regeneration quality of the of rat sciatic nerves. METHODS: Forty male adult Wistar rats were used, anesthetized and operated to cut the sciatic nerve and receive an autograft or a conduit made with a membrane derived from natural latex (Hevea brasiliensis). Four or eight weeks after surgery, to investigate motor nerve recovery, we analyzed the neurological function by walking pattern (footprints analysis and computerized treadmill), electrophysiological evaluation and histological analysis of regenerated nerve (autologous nerve graft or tissue cables between the nerve stumps), and anterior tibial and gastrocnemius muscles. RESULTS: All functional and morphological analysis showed that the rats transplanted with latex conduit had a better neurological recovery than those operated with autologous nerve: quality of footprints, performance on treadmill (p<0.01), electrophysiological response (p<0.05), and quality of histological aspects on neural regeneration. CONCLUSION: The data reported showed behavioral and functional recovery in rats implanted with latex conduit for sciatic nerve repair, supporting a complete morphological and physiological regeneration of the nerve.

Percutaneous sciatic nerve block with tramadol induces analgesia and motor blockade in two animal pain models

Local anesthetic efficacy of tramadol has been reported following intradermal application. Our aim was to investigate the effect of perineural tramadol as the sole analgesic in two pain models. Male Wistar rats (280-380 g; N = 5/group) were used in these experiments. A neurostimulation-guided sciatic nerve block was performed and 2% lidocaine or tramadol (1.25 and 5 mg) was perineurally injected in two different animal pain models. In the flinching behavior test, the number of flinches was evaluated and in the plantar incision model, mechanical and heat thresholds were measured. Motor effects of lidocaine and tramadol were quantified and a motor block score elaborated. Tramadol, 1.25 mg, completely blocked the first and reduced the second phase of the flinching behavior test. In the plantar incision model, tramadol (1.25 mg) increased both paw withdrawal latency in response to radiant heat (8.3 +/- 1.1, 12.7 +/- 1.8, 8.4 +/- 0.8, and 11.1 +/- 3.3 s) and mechanical threshold in response to von Frey filaments (459 +/- 82.8, 447.5 +/- 91.7, 320.1 +/- 120, 126.43 +/- 92.8 mN) at 5, 15, 30, and 60 min, respectively. Sham block or contralateral sciatic nerve block did not differ from perineural saline injection throughout the study in either model. The effect of tramadol was not antagonized by intraperitoneal naloxone. High dose tramadol (5 mg) blocked motor function as well as 2% lidocaine. In conclusion, tramadol blocks nociception and motor function in vivo similar to local anesthetics.

Iatrogenic sciatic nerve injury in eighteen dogs and nine cats (1997-2006)

OBJECTIVE: To report clinical features associated with iatrogenic peripheral nerve injury in dogs and cats admitted (1997-2006) to a referral teaching hospital. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=18), 9 cats. METHODS: Patients had acute signs of monoparesis attributable to sciatic nerve dysfunction that developed after treatment. Neurologic examination and electrodiagnostic testing were performed. Surgical therapy was used for nerve entrapment and delayed reconstructive surgery used in other cases. RESULTS: Of 27 nerve injuries, 25 resulted from surgery (18 with treatment of pelvic injuries). Iliosacral luxation repair resulted in tibial (4 cats) and peroneal (3 dogs) nerve dysfunction. Other causes were intramedullary pinning of femoral fractures (3), other orthopedic surgery (cemented hip prosthesis [2] and tibial plateau-leveling osteotomy [1]), and perineal herniorrhaphy [1]. Nerve injury occurred after intramuscular injection (1 cat, 1 dog). Immediate surgical treatment was removal of intramedullary nails, extruded cement, or entrapping suture. Delayed nerve transplantation was performed in 2 dogs. Within 1 year, 13 patients recovered completely, clinical improvement occurred in 7, and there was no improvement in 7. Five of the 7 dogs that did not recover had acetabular or ilium fracture. CONCLUSION: Iatrogenic sciatic nerve injury occurred most commonly during treatment of pelvic orthopedic diseases and had a poor prognosis. Clinical variation in sciatic nerve dysfunction in dogs and cats can be explained by species anatomic differences. CLINICAL RELEVANCE: Iatrogenic sciatic nerve injury leads to severely debilitating locomotor dysfunction with an uncertain prognosis for full-functional recovery.

Sciatic nerve enlargement in the Klippel-Trenaunay-Weber syndrome

The case of a 35-year-old woman with Klippel-Trenaunay-Weber syndrome (KTWS) showing clinical symptoms of a peroneal nerve lesion is presented. An immense nerve enlargement along most of the sciatic, peroneal and tibial nerve was found to be due to a lipoma arising from the epi- and perineurium. Treatment consisted of extensive microsurgical neurolysis and excision of the tumor resulting in decompression of the affected nerves. Although rare, a perineural lipoma should be kept in mind in patients with KTWS showing neurological abnormalities.

Use of a perineural coiled catheter at the sciatic nerve in dogs after tibial plateau levelling osteotomy – preliminary observations

The analgesic effects of peripheral nerve blocks can be prolonged with the placement of perineural catheters allowing repeated injections of local anaesthetics in humans. The objectives of this study were to evaluate the clinical suitability of a perineural coiled catheter (PCC) at the sciatic nerve and to evaluate pain during the early post-operative period in dogs after tibial plateau levelling osteotomy. Pre-operatively, a combined block of the sciatic and the femoral nerves was performed under sonographic guidance (ropivacaine 0.5%; 0.3 mL kg−1 per nerve). Thereafter, a PCC was placed near the sciatic nerve. Carprofen (4 mg kg−1 intravenously) was administered at the end of anaesthesia. After surgery, all dogs were randomly assigned to receive four injections of ropivacaine (group R; 0.25%, 0.3 mL kg−1) or NaCl 0.9% (group C; 0.3 mL kg−1) every 6 h through the PCC. Pain was assessed by use of a visual analogue scale (VAS) and a multi-dimensional pain score (4Avet) before surgery (T-1), for 390 min (T0, T30, T60, T120, T180, T240, T300, T360 and T390) as well as 1 day after surgery (Day 1). Methadone (0.1 mg kg−1) was administered each time the VAS was ≥40 mm or the 4Avet was ≥5. At T390 dogs received buprenorphine (0.02 mg kg−1). Data were compared using Mann–Whitney rank sum tests and repeated measures analysis of variance. Regardless of group allocation, 55% of dogs required methadone. VAS was significantly lower at T390 (P = 0.003), and at Day 1 (P = 0.002) and so was 4Avet at Day 1 (P = 0.012) in group R than in group C. Bleeding occurred in one dog at PCC placement and PCC dislodged six times of 47 PCCs placed. Minor complications occurred with PCC but allowed four repeated administrations of ropivacaine or saline over 24 h in 91.5% of the cases.

The visual response of retinal ganglion cells is not altered by optic nerve transection in transgenic mice overexpressing Bcl-2

Attempts to rescue retinal ganglion cells from retrograde degeneration have had limited success, and the residual function of surviving neurons is not known. Recently, it has been found that axotomized retinal ganglion cells die by apoptotic mechanisms. We have used adult transgenic mice overexpressing the Bcl-2 protein, a powerful inhibitor of apoptosis, as a model for preventing injury-induced cell death in vivo. Several months after axotomy, the majority of retinal ganglion cells survived and exhibited normal visual responses. In control wild-type mice, the vast majority of axotomized retinal ganglion cells degenerated, and the physiological responses were abolished. These results suggest that strategies aimed at increasing Bcl-2 expression, or mimicking its function, might effectively counteract trauma-induced cell death in the central nervous system. Neuronal survival is a necessary condition in the challenge for promoting regeneration and eventually restoring neuronal function.

Ultrasound Mapping of Nerve Stimulator Response during Sciatic Nerve Blockade and Relation to Postoperative Pain Scores

1.1 Background and Purpose: Ultrasound guided sciatic nerve blockade has rapid onset but at 24 hours pain is greater than nerve stimulator techniques. Injection of the nerve branches or trunk and sub-sheath blockade increase success and reduce onset times but risk injury. This study mapped needle coordinates for sciatic nerve blockade with nerve stimulation and its relation to postoperative pain scores. 1.2 Method: Angle and distance of the needle tip and infusion catheter from the popliteal sciatic nerve at which stimulated plantar flexion occurred were measured. Pain scores at postanesthesia unit discharge and 24 hours were recorded. 1.3 Results: 81% of opioid naïve patients reported immediate analgesia and 20.8% at 24 hours. In opioid tolerant patients 56.8% reported immediate analgesia and 9.1% at 24 hours. Plantar flexion was observed with the needle in the posterior medial quadrant near the sciatic nerve. Opioid tolerant patients reported adequate analgesia when the needle was located more medially and proximally to the sciatic nerve. 1.4 Conclusion: Stimulated plantar flexion is isolated to a narrow angular range in the posterior medial quadrant adjacent to the sciatic nerve. Opioid tolerant patients report adequate analgesia if the needle and catheter are more medial and proximal to the nerve surface.

Comparison of Analgesic Outcomes Following Sciatic Nerve Blockade Performed by Resident Trainees and Nurse Anesthetists

Background and objectives: Peripheral nerve blockade requires regional anesthesia skills that are taught in several formats and assessing technical proficiency has shifted from fulfillment of quotas to comprehensive procedural evaluation. Complete analgesia is the clinical endpoint validating successful nerve blockade but patient, technical and procedural factors influence this result. The purpose of this study was to determine if physician trainee or nurse anesthetist administered sciatic nerve blockade influence postoperative pain scores and opioid analgesic requirements and if patient factors, technique and repetition influence this outcome. Method: Sciatic nerve blockade by nerve stimulation and ultrasound based techniques were performed by senior anesthesiology resident trainees and nurse anesthetists under the supervision of regional anesthesia faculty. Preoperative patient characteristics including obesity, trauma, chronic pain, opioid use and preoperative pain scores were recorded and compared to the post-procedure pain scores and opioid analgesic requirements upon discharge from the post-anesthesia care unit and 24 hours following sciatic nerve blockade. Results: 93 patients received sciatic nerve blockade from 22 nurse anesthetists and 21 residents during 36 months. A significant relation between training background and improved pain scores was not demonstrated but transition from nerve stimulation to ultrasound guided techniques lowered immediate opioid usage in all groups. Patients with pre-existing chronic opioid use had higher postoperative pain scores and opioid dosages following nerve block. Conclusion: Patient analgesia should be an integral measure of proficiency in regional anesthesia techniques and evaluating this procedure outcome for all practitioners throughout their training and beyond graduation will longitudinally assess technical expertise.

Differences in analgesia in opioid naïve and tolerant patients with sciatic nerve blockade following elective foot and ankle surgery

1.1 Introduction and Purpose: Adequate postoperative analgesia in the opioid tolerant with chronic non-malignant pain is challenging. Multimodal pain relief regimens include regional anesthesia but opioid tolerant patients report increased postoperative pain and opioid consumption. This study compared analgesia in opioid naïve and tolerant patients receiving postoperative sciatic nerve blockade for foot and ankle surgery. 1.2 Method: Preoperative pain scores, trauma, maintenance and intraoperative opioid doses and following postoperative sciatic nerve blockade, patient self-reported pain scores and opioid consumption at discharge from the post-anesthesia unit and 24 hours were recorded. 1.3 Results: 191 patients enrolled. 40.3% were opioid tolerant and 33% had lower extremity trauma. Preoperative, immediate and delayed postoperative pain scores and intraoperative, immediate and 24 hour postoperative consumption of opioids were increased in opioid tolerant patients. Trauma and continuous infusion in opioid naïve and tolerant groups did not result in differences in 24 hour opioid consumption. 1.4 Limitations: Small subgroups and use of the pain score limited the accuracy of results. 1.5 Conclusion: Opioid tolerant patients require greater analgesic doses following sciatic nerve blockade for foot and ankle surgery. 24 hour opioid consumption for opioid naïve and tolerant patients is neither influenced by lower extremity injury nor continuous infusion.

Patient Variability in Sciatic Nerve Branch Point Distance Using Ultrasound Guided Localization

Background and Objectives: Improved ultrasound and needle technology make popliteal sciatic nerve blockade a popular anesthetic technique and imaging to localize the branch point of the common peroneal and posterior tibial components is important because successful blockade techniques vary with respect to injection of the common trunk proximally or separate injections distally. Nerve stimulation, ultrasound, cadaveric and magnetic resonance studies demonstrate variability in distance and discordance between imaging and anatomic examination of the branch point. The popliteal crease and imprecise, inaccessible landmarks render measurement of the branch point variable and inaccurate. The purpose of this study was to use the tibial tuberosity, a fixed bony reference, to measure the distance of the branch point. Method: During popliteal sciatic nerve blockade in the supine position the branch point was identified by ultrasound and the block needle was inserted. The vertical distance from the tibial tuberosity prominence and needle insertion point was measured. Results: In 92 patients the branch point is a mean distance of 12.91 cm proximal to the tibial tuberosity and more proximal in male (13.74 cm) than female patients (12.08 cm). Body height is related to the branch point distance and is more proximal in taller patients. Separation into two nerve branches during local anesthetic injection supports notions of more proximal neural anatomic division. Limitations: Imaging of the sciatic nerve division may not equal its true anatomic separation. Conclusion: Refinements in identification and resolution of the anatomic division of the nerve branch point will determine if more accurate localization is of any clinical significance for successful nerve blockade.

Postoperative Analgesia Following Sciatic Nerve Blockade Administered by Nurse Anesthetists Supervised by Regional Anesthesia Faculty in an Academic Hospital

Introduction: Assessment of expertise in regional anesthesia techniques is traditionally based upon quota fulfillment of procedures during training. Validation of practitioner proficiency in performing procedures in surgical specialties has moved from simple measurement of technical skills to evaluation of global patient outcomes. Complete absence of pain as a result of nerve blockade is the most important clinical endpoint but patient, technical and procedural factors influence results. The purpose of this study was to measure the postoperative pain scores and associated analgesic medication requirements for patients administered sciatic nerve blockade by nurse anesthetists and determine patient or procedural factors that influenced this outcome. Methods: Either nerve stimulator or ultrasound guided sciatic nerve blockade was administered by nurse anesthetists under the supervision of regional anesthesia faculty. Patient demographic data that was collected included gender, body mass index, surgical procedure, and pre-existing chronic pain with associated opioid use. Patient self-reported pain scores and opioid analgesic dosages in the preoperative, intraoperative, immediate postoperative and 24 hour post procedure intervals were recorded. Results: 22 nurse anesthetists administered sciatic nerve blockade to 48 patients during a 36 month interval. Transition from a nerve stimulator to ultrasound guided sciatic nerve block technique resulted in lower mean pain scores. Patients reporting chronic opioid use were observed to have elevated perioperative opioid analgesic requirements and pain scores compared to opioid naïve patients. Conclusion: Effective analgesia is a prime measure for assessing expertise in regional anesthesia and continuous evaluation of this outcome in everyday practice is proposed.