Was femoral nerve block effective for pain control of medial opening-wedge high tibial osteotomy?: A single blinded randomized controlled study

BACKGROUND AND PURPOSE

Medial compartment femoro-tibial osteoarthritis (OA) is a common disease and opening-wedge high tibial osteotomy (OWHTO) is the common surgical procedure carried out for these patients. While most researchers are focusing on the surgical techniques during operation, the aim of this study is to evaluate the pain control effect of femoral nerve block (FNB) for OWHTO patients.

METHODS

In this prospective, single-center, randomized controlled trial (RCT) study, 41 patients were operated on by OWHTO for OA during 2017 to 2018. Twenty of them (group A) accepted epidural anesthesia with FNB and 21 patients (group B) only had their single epidural anesthesia. All blocks were successful and all the 41 patients recruited were included in the analysis and there was no loss to follow-up or withdrawal. Systematic records of visual analog scores (VAS), quadriceps strength, mean number of times of patient-controlled intravenous analgesia (PCIA), using of additional opioids or nonsteroidal anti-inflammatory drugs (NSAIDs), and complications were done after hospitalization. The Student t test and Chi-Squared test was used and all P values ≤.05 were considered statistically significant.

RESULTS

VAS scores at rest (3.48 ± 1.0 vs 4.68 ± 1.1) and on movemment (4.51 ± 0.6 vs 4.97 ± 0.8) decreased more in group A than group B with significance at follow-up of 12 hours. The quadriceps strength, consumption of additional opioids or NSAID injections and mean number of times that the patients pushed the PCIA button didnot differ significantly within each group.

CONCLUSION

This RCT study shows that FNB in patients undergoing OWHTO for unicompartmental osteoarthritis of the knee could result in significant reduction in VAS scores at 12 hours postoperatively.Research registry, Researchregistry4792. Registered April 7, 2019 - Retrospectively registered, http://www.researchregistry.com.

Immunohistochemical Femoral Nerve Study Following Bisphosphonates Administration

Background and objectives: Bisphosphonates represent selective inhibitors of excess osteoblastic bone resorption that characterizes all osteopathies, targeting osteoclasts and their precursors. Their long-term administration in postmenopausal women suffering from osteoporosis has resulted in neural adverse effects. The current study focuses on the research of possible alterations in the femoral nerve, caused by bisphosphonates. We hypothesized that bisphosphonates, taken orally (per os), may produce degenerative changes to the femoral nerve, affecting lower-limb posture and walking neuronal commands. Materials and Methods: In order to support our hypothesis, femoral nerve specimens were extracted from ten female 12-month-old Wistar rats given 0.05 milligrams (mg) per kilogram (kg) of body weight (b.w.) per week alendronate per os for 13 weeks and from ten female 12-month-old Wistar rats given normal saline that were used as a control group. Specimens were studied using immunohistochemistry for selected antibodies NeuN (Neuronal Nuclear Protein), a protein located within mature, postmitotic neural nucleus, and cytosol and Sox10 (Sex-determining Region Y (SRY) - High-Motility Group (HMG) - box 10). The latter marker is fundamental for myelination of peripheral nerves. Obtained slides were examined under a light microscope. Results: Samples extracted from rats given alendronate were more Sox10 positive compared to samples of the control group, where the marker's expression was not so intense. Both groups were equally NeuN positive. Our results are in agreement with previous studies conducted under a transmission electron microscope. Conclusions: The suggested pathophysiological mechanism linked to histological alterations described above is possibly related to toxic drug effects on Schwann and neuronal cells. Our hypothesis enhances the existing scientific evidence of degenerative changes present on femoral nerve following bisphosphonates administration, indicating a possible relationship between alendronate use and neuronal function.

Electrical stimulation of the saphenous nerve in anesthetized rats: a novel therapeutic approach to treating overactive bladder

Posterior Tibial Nerve Stimulation (PTNS) is a minimally invasive yet effective therapy for treating overactive bladder (OAB) symptoms with electrical stimulations applied at 20 Hz coupled with amplitudes approximating the foot-twitch threshold (T). However, pre-clinical studies indicate that PTNS-evoked bladder reflexes require stimulation amplitudes exceeding 2T. The objective of this work was to evaluate the presence of secondary low-threshold sensory pathways in the hind-limb region that can be a potential target of activation during clinical PTNS set-up. Given the close proximity of the electrode tip and the cutaneous branches in the lower leg, we hypothesized the concomitant activation of saphenous nerve (SAFN) afferents during percutaneous PTNS. To this end, urodynamic model was established in ten anesthetized rats to investigate (1) the isolated role of SAFN trunk in modulating bladder activity and (2) characterize frequency-dependent changes in inhibitory response at low stimulation amplitudes. Our pre-clinical findings suggest that direct stimulation of SAFN can elicit robust and consistent inhibitory effects at 20 Hz. This novel inhibitory reflex may rationalize the therapeutic effects of clinical PTNS therapy and support the feasibility of enhancing the current algorithm of incontinence care.

TT-TG vs. modified lateral patellar edge for determination of tibial tubercle transfer distance in Fulkerson osteotomy procedures

BACKGROUND

Tibial tubercle-trochlear groove (TT-TG) distance is currently used at our institution to determine tibial tubercle medialization required in Fulkerson osteotomies. If the correlation between a modified lateral patellar edge (LPE) and the transfer distance was found to be stronger than its correlation with TT-TG, it would suggest that the best measurement to use is actually modified LPE.

METHODS

The electronic medical records of 32 patients who underwent Fulkerson osteotomy procedures with femoral nerve stimulation were reviewed and measured. For each patient, modified LPE was measured on quadriceps active hyperextension MRI, and TT-TG was measured on passive extension MRI. Correlation between both TT-TG and LPE and tibial tubercle transfer distance was then determined and analysed.

RESULTS

The correlation between TT-TG and actual intra-operative tibial tubercle transfer distance in Fulkerson osteotomy procedures with intra-operative femoral nerve stimulation was found to be weak at 0.436 (p<0.05). The correlation between modified LPE and actual intra-operative tibial tubercle transfer distance was found to be strong at 0.697 (p<0.001).

CONCLUSIONS

The correlation between modified LPE and actual intra-operative tibial tubercle transfer distance was stronger than the correlation between TT-TG and tibial tubercle transfer distance. This suggests that the modified LPE may actually be a better preoperative determinant than the currently-utilized TT-TG of the transfer distance required during Fulkerson osteotomy procedures.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Myelin Basic Protein Cleaves Cell Adhesion Molecule L1 and Improves Regeneration After Injury

Myelin basic protein (MBP) is a serine protease that cleaves neural cell adhesion molecule L1 and generates a transmembrane L1 fragment which facilitates L1-dependent functions in vitro, such as neurite outgrowth, neuronal cell migration and survival, myelination by Schwann cells as well as Schwann cell proliferation, migration, and process formation. Ablation and blocking of MBP or disruption of its proteolytic activity by mutation of a proteolytically active serine residue abolish L1-dependent cellular responses. In utero injection of adeno-associated virus encoding proteolytically active MBP into MBP-deficient shiverer mice normalizes differentiation, myelination, and synaptogenesis in the developing postnatal spinal cord, in contrast to proteolytically inactive MBP. Application of active MBP to the injured wild-type spinal cord and femoral nerve augments levels of a transmembrane L1 fragment, promotes remyelination, and improves functional recovery after injury. Application of MBP antibody impairs recovery. Virus-mediated expression of active MBP in the lesion site after spinal cord injury results in improved functional recovery, whereas injection of virus encoding proteolytically inactive MBP fails to do so. The present study provides evidence for a novel L1-mediated function of MBP in the developing spinal cord and in the injured adult mammalian nervous system that leads to enhanced recovery after acute trauma.

Neuroprotection by peripheral nerve electrical stimulation and remote postconditioning against acute experimental ischaemic stroke

OBJECTIVE

Local electrical stimulation (ES) was reported to protect the brain during ischaemic injury, while the protective effect of limb remote ischaemic postconditioning (RIPostC) was confirmed. The aim of this study was to explore whether remote peripheral nerve ES exerted neuroprotection and whether this procedure shared the same neuroprotective mechanism underlying RIPostC.

METHODS

Stroke in Sprague-Dawley rats was induced by distal middle cerebral artery occlusion (dMCAO). Rats were divided into five groups: dMCAO, RIPostC, ES, nerve resection (NR) + ES and RIPostC+ES. Twenty-four hours after reperfusion, rats were examined for neurobehavioural function, including forelimb fault placing test, Ludmila Belayev 12 score test, and infarct volume. The expression of Bcl-2 and cleaved-caspase-3 in ischaemic cortex was assessed by Western blot.

RESULTS

In forelimb fault placing test, as compared to the highest score in the stroke-only group, RIPostC, ES and RIPostC+ES groups showed a significantly (P < 0.01) lower score. The results were similar for the Ludmila Belayev 12 score test. The infarct volume of the treatment groups also exhibited significant (P < 0.01) reduction as compared to the stroke-only group. The volume of infarct tissue in the combination of RIPostC+ES was significantly less than RIPostC and ES alone (P < 0.05). Furthermore, NR blocked the ES's protection (P < 0.05) as compared to the ES group by using above-mentioned methods. Bcl-2 was upregulated, while cleaved-caspase-3 was downregulated in the experimental groups as compared to the control group. No difference was found among the experimental groups.

DISCUSSION

Peripheral nerve ES appears to have a neuroprotective effect in a rat dMCAO model. This effect may indicate a neural protective mechanism underlying beneficial effect of RIPostC.

Motor evoked potentials for femoral nerve protection in transpsoas lateral access surgery of the spine

Detecting potential intraoperative injuries to the femoral nerve should be the main goal of neuromonitoring of lateral lumber interbody fusion (LLIF) procedures. We propose a theory and technique to utilize motor evoked potentials (MEPs) to protect the femoral nerve (a peripheral nerve), which is at risk in LLIF procedures. MEPs have been advocated and widely used for monitoring spinal cord function during surgical correction of spinal deformity and surgery of the cervical and thoracic spine, but have had limited acceptance for use in lumbar procedures. This is due to the theoretical possibility that MEP recordings may not be sensitive in detecting an injury to a single nerve root considering there is overlapping muscle innervation of adjacent root levels. However, in LLIF procedures, the surgeon is more likely to encounter lumbar plexus elements than nerve roots. Within the substance of the psoas muscle, the L2, L3, and L4 nerve roots combine in the lumbar plexus to form the trunk of the femoral nerve. At the point where the nerve roots become the trunk of the femoral nerve, there is no longer any alternative overlapping innervation to the quadriceps muscles. Insult to the fully formed femoral nerve, which completely blocks conduction in motor axons, should theoretically abolish all MEP responses to the quadriceps muscles. On multiple occasions over the past year, our neuro-monitoring groups have observed significantly degraded amplitudes of the femoral motor and/or sensory evoked potentials limited to only the surgical side. Most of these degraded response amplitudes rapidly returned to baseline values with a surgical intervention (i.e., prompt removal of surgical retraction).

Lateral femoral cutaneous nerve palsy following shoulder surgery in the beach chair position: a report of 4 cases

Neuropathy of the lateral femoral cutaneous nerve can present as pain, decreased sensation, and/or burning or tingling on the anterolateral thigh. We present 4 cases of lateral femoral cutaneous nerve palsy following shoulder surgery in the beach chair position, all of which occurred in obese patients. This complication, to our knowledge, has never been reported in conjunction with the beach chair position. We believe that the neurapraxia was due to external compression by the patients' abdominal pannus. Full resolution of symptoms can be expected within 6 months following conservative management. A preoperative discussion regarding this complication should occur with obese patients undergoing shoulder surgery in the beach chair position.

The impact of motor axon misdirection and attrition on behavioral deficit following experimental nerve injuries

Peripheral nerve transection and neuroma-in-continuity injuries are associated with permanent functional deficits, often despite successful end-organ reinnervation. Axonal misdirection with non-specific reinnervation, frustrated regeneration and axonal attrition are believed to be among the anatomical substrates that underlie the poor functional recovery associated with these devastating injuries. Yet, functional deficits associated with axonal misdirection in experimental neuroma-in-continuity injuries have not yet been studied. We hypothesized that experimental neuroma-in-continuity injuries would result in motor axon misdirection and attrition with proportional persistent functional deficits. The femoral nerve misdirection model was exploited to assess major motor pathway misdirection and axonal attrition over a spectrum of experimental nerve injuries, with neuroma-in-continuity injuries simulated by the combination of compression and traction forces in 42 male rats. Sciatic nerve injuries were employed in an additional 42 rats, to evaluate the contribution of axonal misdirection to locomotor deficits by a ladder rung task up to 12 weeks. Retrograde motor neuron labeling techniques were utilized to determine the degree of axonal misdirection and attrition. Characteristic histological neuroma-in-continuity features were demonstrated in the neuroma-in-continuity groups and poor functional recovery was seen despite successful nerve regeneration and muscle reinnervation. Good positive and negative correlations were observed respectively between axonal misdirection (p<.0001, r(2)=.67), motor neuron counts (attrition) (p<.0001, r(2)=.69) and final functional deficits. We demonstrate prominent motor axon misdirection and attrition in neuroma-in-continuity and transection injuries of mixed motor nerves that contribute to the long-term functional deficits. Although widely accepted in theory, to our knowledge, this is the first experimental evidence to convincingly demonstrate these correlations with data inclusive of the neuroma-in-continuity spectrum. This work emphasizes the need to focus on strategies that promote both robust and accurate nerve regeneration to optimize functional recovery. It also demonstrates that clinically relevant neuroma-in-continuity injuries can now also be subjected to experimental investigation.

[Impact of saturation of the mixed capillary blood on the subjective estimation of the postoperative pain intensity]

The impact of prolonged perineural blocade of n. femoralis on a subjective estimation of the postoperative pain intensity and its connection with the mixed capillary blood saturation was investigated.

Venous graft-derived cells participate in peripheral nerve regeneration

BACKGROUND

Based on growing evidence that some adult multipotent cells necessary for tissue regeneration reside in the walls of blood vessels and the clinical success of vein wrapping for functional repair of nerve damage, we hypothesized that the repair of nerves via vein wrapping is mediated by cells migrating from the implanted venous grafts into the nerve bundle.

METHODOLOGY/PRINCIPAL FINDINGS

To test the hypothesis, severed femoral nerves of rats were grafted with venous grafts from animals of the opposite sex. Nerve regeneration was impaired when decellularized or irradiated venous grafts were used in comparison to untreated grafts, supporting the involvement of venous graft-derived cells in peripheral nerve repair. Donor cells bearing Y chromosomes integrated into the area of the host injured nerve and participated in remyelination and nerve regeneration. The regenerated nerve exhibited proper axonal myelination, and expressed neuronal and glial cell markers.

CONCLUSIONS/SIGNIFICANCE

These novel findings identify the mechanism by which vein wrapping promotes nerve regeneration.

Incidence of lateral femoral cutaneous nerve neuropraxia after anterior approach hip arthroplasty

BACKGROUND

Although injury to the lateral femoral cutaneous nerve (LFCN) is a known complication of anterior approaches to the hip and pelvis, no study has quantified its' incidence in anterior arthroplasty procedures.

QUESTIONS/PURPOSES

We therefore defined the incidence, functional impact, and natural history of LFCN neuropraxia after an anterior approach for both hip resurfacing (HR) and primary total hip arthroplasty (THA).

METHODS

We followed 132 patients who underwent an anterior hip approach (55 THA; 77 HR). We administered self-reported questionnaires for sensory deficits of LFCN, neuropathic pain score (DN4), visual analog scale, as well as SF-12, UCLA, and WOMAC scores at one year postoperatively. A subset of 60 patients (30 THA; 30 HR) was evaluated at two time intervals.

RESULTS

One hundred seven patients (81%) reported LFCN neuropraxia with a mean severity score of 2.32/10 and a mean DN4 score of 2.42/10. Hip resurfacing had a higher incidence of neuropraxia as compared with THA: 91% versus 67%, respectively. No functional limitations were reported on SF-12, WOMAC, or UCLA scores. Of the subset of 60 patients followed over an average of 12 months, 53 (88%) reported neuropraxia at the first followup interval with only three (6%) having complete resolution at second followup. Improvement in DN4 scores was observed over time: 3.6 versus 2.5, respectively.

CONCLUSIONS

Although LFCN neuropraxia was a frequent complication after anterior approach THA, it did not lead to functional limitations in our patients. A decrease in symptoms occurred over time but only a small number of patients reported complete resolution.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Complications of femoral nerve block for total knee arthroplasty

Preemptive and multimodal pain control protocols have been introduced to enhance rehabilitation after total knee arthroplasty (TKA). We determined the complication rate associated with preoperative femoral nerve block (FNB) for TKA. Among 1018 TKA operations, we performed 709 FNBs using a single-injection technique into the femoral nerve sheath and confirming position with nerve stimulation before induction. After TKA, weightbearing as tolerated was initiated using a walker or crutches on postoperative Day 1. Twelve patients (1.6%) treated with FNB sustained falls, three (0.4%) of whom underwent reoperations. Five patients had postoperative femoral neuritis, which may have been secondary to the block. One patient had new onset of atrial fibrillation after FNB, and the TKA was postponed. Femoral nerve block before TKA is not a harmless intervention. We recommend postoperative protocols be modified for patients who have FNB to account for decreased quadriceps function in the early postoperative period, which can lead to falls.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

[Effect of chronic hypotension on the adrenergic nerve plexus of the rat a. saphena and on its regeneration after femoral nerve injury]

The influence of chronic hypotension on density and fluorescence intensity (after glyoxylic acid treatment) of periarterial plexus of nerve fibers in saphenous artery wall and on reinnervation of this vessel was studied in Wistar rats. Regional hypotension in the rat hindquarters vascular system was created by partial occlusion of abdominal aorta distally to the renal arteries. Four weeks later, the segment of femoral nerve was resected in one of the limbs to denervate the saphenous artery. In the limb with intact nerve, chronic (6-7 weeks-long) hypotension resulted in 20% decrease of fluorescence intensity of nerve fibers, as compared to that one in normotensive (control) rats, however the density of the nerve plexus did not change. Partial reinnervation of the vessel occurred in 2-3 weeks after femoral nerve injury. After 2 weeks parameters of reinnervation were similar in hypotensive and normotensive rats, but after 3 weeks hypotensive rats demonstrated more complete restoration of the innervation.

[Peripheral neuropathic pain relieved by somatosensory rehabilitation]

The femoral neuralgia is a rather frequent and invalidating clinical disorder. It takes on many clinical forms because of the anatomical variations of the cutaneous branches of saphenous and femoral nerves. The neuroplasticity of the somato-sensory system has now been determined which allows for a better understanding of the techniques of somatosensory rehabilitation. The authors precisely explain the various stages necessary in the care of patients suffering from femoral neuralgia. The various strategies of somatosensory rehabilitation are mentioned. The authors also present a brief review of the pharmacological treatments of peripheral neuropathic pain. Lastly, the result of the somatosensory rehabilitation of femoral neuralgia (NNT = 1.8) is documented on the basis of a prospective study done on 59 patients.

Proximal femoral conductions in patients with lumbosacral radiculoplexus neuropathy

OBJECTIVES

Lumbosacral radiculoplexus neuropathy (DLRPN) is a rare form of neuropathy observed in diabetic and rarely non-diabetic patients. Pathophysiology and lesion location are not clearly understood. Our aim was to analyze proximal and distal femoral conductions in patients with DLRPN.

METHODS

Six patients with DLRPN, 14 patients with diabetic polyneuropathy and 25 healthy subjects were included in the study. We performed L3 monopolar root stimulation and femoral nerve trunk stimulation at the inguinal region and calculated lumbar plexus conduction time by subtracting the latency of compound muscle action potential (CMAP) of the vastus medialis evoked by femoral nerve stimulation from the latency of CMAP of vastus medialis evoked by L3 root stimulation. Additionally peak to peak amplitudes and areas of CMAPs were analyzed.

RESULTS

Electrophysiological examination showed that there was an axonal involvement in all patients with DLRPN. Prolonged lumbar plexus conduction time (in five extremities), and prolonged distal latency of the femoral nerve (in five extremities) probably due to secondary demyelination were also observed. Similar abnormalities were not observed in the diabetic polyneuropathy group.

CONCLUSIONS

DLRPN may affect different localizations on the peripheral nerves. L3 root stimulation may have an important role in the electrodiagnosis of DLRPN.

The neurocytokine, interleukin-6, corrects nerve dysfunction in experimental diabetes

Interleukin-6 (IL-6) is a member of the neuropoietic cytokine family and has a multifunctional biological role in regulating the immune response, acute phase reactions, and hematopoiesis. IL-6 is also important in neural development and has neurotrophic actions. The aim was to ascertain whether IL-6 treatment could rectify some of the adverse early changes in neurovascular function in streptozotocin-induced diabetic rats. After 4 weeks of untreated diabetes, rats were treated with IL-6 (1-10 microg/kg thrice weekly) for 4 weeks. Diabetes caused 22% and 22.5% reductions in sciatic nerve motor and saphenous nerve sensory conduction velocity, respectively, which were dose dependently corrected by treatment. Diabetic rats also showed thermal hyperalgesia and tactile allodynia, which were completely corrected by IL-6; however, IL-6 was ineffective against mechanical hyperalgesia. Sciatic nerve endoneurial perfusion was 42.2% reduced by diabetes and blood flow was returned to the nondiabetic range by 10 microg/kg IL-6 treatment. The ED(50) values for these actions ranged from 1.2 microg/kg for sensory conduction velocity to 3.2 microg/kg for sciatic nerve perfusion. Thus, IL-6 treatment improved several measures of nerve dysfunction in experimental diabetes, and these effects correlated with a recovery of nerve blood flow. The magnitude of these beneficial effects and the potential joint neurotrophic and vascular action suggests that IL-6 could be a candidate for further evaluation in clinical trials of diabetic neuropathy.

A clinical study of corticospinal and peripheral conductions to proximal lower limb muscles

OBJECTIVE

To investigate the clinical utility of the newly developed "quadriceps combined technique" (QCT), which provides a global evaluation of the central and peripheral conduction to the proximal muscles of lower limbs, in a variety of central and peripheral neurological disorders.

METHODS

Using surface recordings from the vastus medialis of the quadriceps muscle, we analyzed amplitudes and latencies of M response, patellar T reflex and motor evoked potentials (MEPs) after transcranial magnetic stimulation. We studied 180 patients with disorders impairing proximal strength of one or both lower limbs and compared them with 100 controls reported previously.

RESULTS

The best parameters to detect central motor disorders were the central motor conduction time, MEP/M amplitude, T/MEP amplitude and latency ratios, whereas peripheral motor conduction time (PMCT) was best to assess peripheral disorders. The best parameter to identify proximal peripheral disorder was PMCTprox, whereas for distal peripheral disorders M amplitude and T/MEP amplitude ratio were most discriminative.

CONCLUSIONS

We report a simple, rapidly performed and well-tolerated method that improves proximal lower limbs evaluation, helps distinguishing pathologic from physiological brisk reflexes and provides clues for etiologic diagnosis.

SIGNIFICANCE

The QCT is a sensitive and specific tool to investigate central and peripheral neurological disorders.

Complication neurologique après posture obstétricale «en tailleur» lors d'un travail sous analgésie péridurale

Obstetrical positioning is used more and more often because of the supposed or proven benefits although side effects are not well known. We therefore report the case of a patient who presented with a postpartum neurological deficit after a seven hour hip-flexed posture during labour under epidural analgesia. The parturient did not complain of pain or discomfort during labour. The neurological injury was suspected because of delayed recovery of epidural analgesia-induced motor block. Neurological examination disclosed sensory and motor abnormalities in the left femoral and sciatic nerve distribution areas. The early performed lumbar CT-scan did not show any complication and electromyographic evaluation performed on the ninth postpartum day was normal. Three months after delivery, some degree of neuropathic pain in the sciatic nerve distribution remained. The risk of neurological injury directly related to obstetrical positioning is discussed. Prolonged positioning using a posture which can induce nerve stretching should be avoided. This is especially true when the patient is receiving epidural analgesia which can mask pain or discomfort.

Postoperative femoral motor neuropathy: diagnosis and treatment without neurologic consultation or testing

OBJECTIVE

To review the diagnosis and treatment of postoperative femoral motor neuropathy without neurologic consultation or testing.

STUDY DESIGN

A retrospective review of 6 consecutive patients with postoperative femoral motor neuropathy following gynecologic surgery. Diagnosis was made on clinical evaluation: history of falling during postoperative ambulation, quadriceps weakness, straight leg raise weakness, diminished knee jerk response, and no evidence of psoas hematoma or abscess. Neurologic consultation, electromyography, nerve conduction study and radiologic imaging, such as computed tomography, were not obtained. Instead, a physical therapy consultation was obtained for a knee orthotic and rehabilitation.

RESULTS

Four postoperative femoral motor neuropathies developed following 3,014 cases of major gynecologic surgery (0.1%). Two additional cases were seen in consultation. The median age was 57 years. All patients fell while attempting ambulation on postoperative day 1. Recovery occurred at a median of 3 months (1-4). At a median follow-up of 4 years, no patient had developed additional neurologic sequelae. A history of prior postoperative femoral motor neuropathy was noted in 2 of 6 patients (33%).

CONCLUSION

This was the first study of diagnosis and treatment of postoperative femoral motor neuropathy following gynecologic surgery without neurologic consultation or testing. Because of the significant expense of neurologic consultation and testing, patients with postoperative femoral motor neuropathy can have the condition diagnosed by the gynecologist and be referred directly to physical therapy without adversely affecting outcome. This also was the first study to elicit a prior history offemoral neuropathy in 33% of patients. Thus, a prior history may be a risk factor for recurrence.

Motor neuron regeneration accuracy: balancing trophic influences between pathways and end-organs

The key to recovery of function following peripheral nerve lesions is guiding axons back to their original target end-organs. The parent femoral nerve splits into two comparable terminal pathways: one to the muscle and the other to the skin. Normally, motor neurons only innervate the pathway to the muscle, but after the parent nerve is repaired regenerating motor neurons are often misrouted to the skin. When the muscle and skin pathways remain connected to their respective targets after the parent nerve is repaired, reinnervation favors the muscle pathway. If contact with the muscle is instead prevented, reinnervation favors the pathway to the skin. Here we examine whether shortening the skin pathway can alter motor reinnervation accuracy when the muscle pathway remains connected to the muscle. We demonstrate that reducing the influence of the skin pathway results in a more rapid and extensive reinnervation of the muscle pathway. These findings suggest that the relative balance of trophic influences from the pathways and their end-organs is an important determinant of motor neuron regeneration accuracy, and that the muscle pathway by itself is not the primary regulator for regeneration accuracy of motor neurons.

The specificity of motor neurone regeneration (preferential reinnervation)

The major determinant of functional recovery after lesions in the peripheral nervous system is the accurate regeneration of axons to their original target end-organs. Unfortunately, regenerating motor axons are often misrouted to sensory target end-organs, and sensory axons formerly innervating skin are often misrouted to muscle. As such regeneration is robust, but often inaccurate, a better understanding of how regenerating axons reinnervate terminal pathways would be of fundamental interest to basic and clinical neuroscience. This review will consider the underlying cellular and molecular mechanisms that influence the accuracy of peripheral nerve regeneration, within the context of 'preferential motor reinnervation' (PMR). Much previous work with PMR has utilized the rodent femoral nerve and has shown that regenerating motor axons preferentially, albeit incompletely, reinnervate a distal terminal nerve branch to muscle (quadriceps) vs. skin (saphenous). One interpretation of this body of work has been that Schwann cell tubes have a specific identity that can be recognized by regenerating motor axons and that influences their subsequent behaviour. We disagree with that interpretation, and suggest motor and cutaneous pathways are not inherently different in terms of their ability to support regeneration of motor axons. In fact, recent experiments indicate under certain conditions motor axons will preferentially reinnervate the inappropriate terminal cutaneous pathway instead of the appropriate pathway to muscle. We suggest that it is the relative level of trophic support provided by each nerve branch that determines whether motor axons will remain in that particular branch. Within the context of the femoral nerve model, our results suggest a hierarchy of trophic support for regenerating motor axons with muscle contact being the highest, followed by the length of the terminal nerve branch and/or contact with skin.

Characterization of chronic constriction of the saphenous nerve, a model of neuropathic pain in mice showing rapid molecular and electrophysiological changes

Neuropathic pain is one of the most inextricable problems encountered in clinics, because few facts are known about its etiology. Nerve injury often leads to allodynia and hyperalgesia, which are symptoms of neuropathic pain. The aim of this study was to understand some molecular and electrophysiological mechanisms of neuropathic pain after chronic constriction of the saphenous nerve (CCS) in mice. After surgery, CCS mice displayed significant allodynia and hyperalgesia, which were sensitive to acute systemic injection of morphine (4 mg/kg), gabapentin (50 mg/kg), amitriptyline (10 mg/kg), and the cannabinoid agonist WIN 55,212-2 (5 mg/kg). These behavioral changes were accompanied after surgery by an increase of c-Fos expression and by an overexpression of mu-opioid and cannabinoid CB1 and CB2 receptors in the spinal cord and the dorsal hind paw skin. In combination with the skin-nerve preparation, this model showed a decrease in functional receptive fields downstream to the injury and the apparition of A-fiber ectopic discharges. In conclusion, CCS injury induced behavioral, molecular, and electrophysiological rearrangements that might help us in better understanding the peripheral mechanisms of neuropathic pain. This model takes advantage of the possible use in the future of genetically modified mice and of an exclusively sensory nerve for a comprehensive study of peripheral mechanisms of neuropathic pain.

Nerve conduction studies of the lateral femoral cutaneous nerve. Implications in the diagnosis of meralgia paresthetica

The diagnosis of meralgia paresthetica, while based on clinical suspicion, can be confirmed via electrophysiological testing. Previous testing of the sensory conduction of the lateral femoral cutaneous nerve placed the stimulating electrode one centimeter medial to the anterior superior iliac spine (ASIS). This position is both uncomfortable for the patient and difficult for the operator to perform. The following article suggests an alternate position for the stimulating electrode, four centimeters distal to the ASIS. Twenty subjects served as their own controls and both the old technique and the new technique were performed. Using the old technique, the response rate was 35% (7 out of 20 subjects). Using the new technique, the response rate was 90% (18 out of 20 subjects). These results indicate a significantly higher response rate when the only variable altered is the electrode placement. This simple change in technique requires no more effort, cost, or training on the part of the operator yet produces a much higher percentage of responses.

Electrophysiological evaluation of the genitofemoral nerve in patients with inguinal hernia

Groin pain in the lower abdomen but including the ilioinguinal region is frequent after inguinal hernia operations, but the integrity of the nerves in this region, including the genitofemoral nerve (GFN), has not been investigated. We studied GFN motor conduction time to the cremasteric muscle (CM), the CM electromyogram (EMG), and the CM reflex in 30 patients with unilateral inguinal hernia who underwent herniorrhaphy and in 26 similar patients who had no surgical intervention. Among the 30 patients undergoing herniorrhaphy, 14 (47%) showed motor involvement of the GFN, whereas 6 of the 26 (23%) patients not treated surgically had involvement of the GFN. These findings indicate that subclinical motor involvement of the GFN can be demonstrated by electrophysiological methods and is common after inguinal herniorrhaphy. Based on patient complaints, the herniated mass may also be responsible for motor involvement of the GFN in some patients before surgery.

[A role of central control in development and progression of diabetic polyneuropathy in teenagers]

A role of central control of peripheral nervous system was investigated in 79 teenagers with noninsulin-dependent diabetes mellitus. The patients were studied using clinical and neurophysiological methods, electroneuromyography and somatosensory evoked potentials (SSEP). The SSEP analysis revealed the disturbances of sensory pathways in the central nervous system at early stage of diabetes mellitus. A new pathogenic mechanism of progressive polyneuropathy with trophic complications is presented. At the initial stage of the disease, low conductivity is combined with a compensating acceleration of conductivity in the central structures. In diabetes course, central conductivity declines and control over peripheral system decreases resulting in the disease progression. In trophic complications, acceleration of conductivity is absent already at the early stages, suggesting a primary weak control over the peripheral nervous system.

Assessment of low-frequency fatigue with two methods of electrical stimulation

The aim of this study was to compare the use of transcutaneous vs. motor nerve stimulation in the evaluation of low-frequency fatigue. Nine female and eleven male subjects, all physically active, performed a 30-min downhill run on a motorized treadmill. Knee extensor muscle contractile characteristics were measured before, immediately after (Post), and 30 min after the fatiguing exercise (Post30) by using single twitches and 0.5-s tetani at 20 Hz (P20) and 80 Hz (P80). The P20-to-P80 ratio was calculated. Electrical stimulations were randomly applied either maximally to the femoral nerve or via large surface electrodes (ES) at an intensity sufficient to evoke 50% of maximal voluntary contraction (MVC) during a 80-Hz tetanus. Voluntary activation level was also determined during isometric MVC by the twitch-interpolation technique. Knee extensor MVC and voluntary activation level decreased at all points in time postexercise ( P < 0.001). P20 and P80 displayed significant time × gender × stimulation method interactions ( P < 0.05 and P < 0.001, respectively). Both stimulation methods detected significant torque reductions at Post and Post30. Overall, ES tended to detect a greater impairment at Post in male and a lesser one in female subjects at both Post and Post30. Interestingly, the P20-P80 ratio relative decrease did not differ between the two methods of stimulation. The low-to-high frequency ratio only demonstrated a significant time effect ( P < 0.001). It can be concluded that low-frequency fatigue due to eccentric exercise appears to be accurately assessable by ES.

High-frequency electrical stimulation of femoral nerve reduces infarct size following myocardial ischemia-reperfusion in rats

The effects of femoral nerve electrostimulation (FNES) on ischemia-reperfused myocardium were examined in the urethane- anesthetized rats to determine whether FNES may provide cardioprotection and to observe the possible mechanism. The area at risk (AR) and infarct area (IA) were determined using Evans blue and nitro-blue tetrazolium staining, respectively. Infarct size (IS) was defined as 100xIA/AR (%). The results are as follows: (1) During 30 min myocardial ischemia and subsequent 120 min reperfusion, the myocardial infarct size occupied (54.96+/-0.82)% of the area at risk. (2) FNES of high frequency (10 V, 100 Hz, 1 ms) significantly reduced myocardial infarct size to (36.94+/-1.34)% (P<0.01), indicating the cardioprotective effect FNES of high frequency on myocardial ischemia-reperfusion, while FNES of low frequency (10 V, 10 Hz, 1 ms) had no effect on myocardial infarct size. (3) Pretreatment with either naloxone (5 mg /kg, i.v), a nonselective opioid receptor antagonist, or glibenclamide (5 mg /kg, i.v), a K(ATP) channel antagonist, completely abolished the cardioprotection of FNES (100 Hz) from myocardial ischemia-reperfusion. It is suggested that FNES of high frequency can protect myocardium from ischemia-reperfusion injury. The possible mechanism is that FNES of high frequency may induce the release of opioids from the central nervous system, and the activation of opioid receptors in the heart results in an opening of myocardial K(ATP) channels which can protect myocardium.

Morbidity of harvesting of bone grafts from the iliac crest for preprosthetic augmentation procedures: A prospective study

It has been the aim of the present prospective clinical study to assess the morbidity following the harvest of bone from the anterior and posterior ilium in elective preprosthetic augmentations. Fifty consecutive healthy patients (30 female, 20 male, mean age 52.5+/-9.3 years, range 31 years to 65 years) underwent augmentations of implant sites by iliac crest bone grafts. The bone harvest was carried out in 25 cases from the anterior and in 25 cases from the posterior ilium. The superficial sensory function of the skin was determined quantitatively preoperatively, 7 and 30 days after surgery with the 'Pain and Thermal Sensitivity' Test (PATH Test). On the same occasions subjective pain on a visual analogue scale (VAS) and gait disturbances were documented. In the PATH Test, for the innervation areas of the lateral femoral cutaneous nerve (LFCN) and the superior and middle cluneal nerves (SMCN) a significant impairment of the superficial sensory function could be found after 1 week and a significant tendency towards recovery after 1 month (warm stimulus(FCNpreop) 37.9+/-3.0 degrees C, warm stimulus(LFCNday7): 38.6+/-3.2 degrees C, warm stimulus(LFCNday30): 37.9+/-2.9 degrees C, P(LFCNwarmpreop/day7)=0.023,P(LFCNwarmpreop/day30) =0.886, warm stimulus(SMCNpreop): 36.1+/-2.4 degrees C, warm stimulus(SMCNday7): 36.6+/-2.3 degrees C, warm stimulus(SMCNday30): 36.3+/-4.0 degrees C,P(SMCNwarmpreop/day7) <0.0005,P(SMCNwarmpreop/day30) =0.086). Gait disturbances were seen in seven patients after anterior and in three patients after posterior bone harvest 7 days after surgery (P(gaitdisturbanceanterior/posterior)=0.123). After 1 month none of the patients of both groups showed gait disturbances any longer. The maximum subjective pain level was found on the second postoperative day in both groups. It was significantly higher for the anterior approach (VAS(anteriorday2) 7.0+/-1.5, VAS(posteriorday2) 5.5+/-1.8,P(VASanterior/posteriorday2) =0.004). At day 7 and at day 30, the pain levels did no longer differ significantly (VAS(anteriorday7) 3.7+/-1.4, VAS(posteriorday7) 3.2+/-1.6,P(VASanterior/posteriorday7) =0.165, VAS(anteriorday30) 1.4+/-0.7, VAS(posteriorday30) 1.4+/-0.8,P(VASanterior/posteriorday30) =0.724). Because of the lower morbidity of bone harvest from the posterior ilium in the early postoperative phase compared to the anterior approach it seems that it should be preferred in elective augmentation procedures.

[Electrophysiological evaluation of peripheral nerves in ischemic lower limbs]

The study concerned electrophysiological parameters during stimulation of peroneal, tibial, sural and femoral nerves of patients with ischemia of lower limbs. The disease was clinically verified and confirmed on the basis of an ankle-brachial index (ABI). Peripheral nerves injuries caused by other reasons have been excluded from the research. For statistical evaluation of the material, groups of 86 chronic ischemic limbs (ABI < 0.91) and 57 healthy ones (ABI > 0.99) were created. All observation allowed to recognize an axonal-demyelization neuropathy, with strong axonal element. Changes concerned mainly long nerves. Coexistence of spinal roots damage was often (75.4%) noticeable. The correlation between degree of ischemia (ABI) and studied parameters has not been noticed. We described 5 cases of acute ischemia. There was no significant improvement after surgical or conservative therapy.

Somatosensory evoked potentials for the electrodiagnosis of meralgia paresthetica

The aim of this study was to evaluate the diagnostic utility of somatosensory evoked potential (SSEP) studies of the lateral femoral cutaneous nerve (LFCN) in assessing patients with meralgia paresthetica. Twenty-one consecutive patients with unilateral meralgia paresthetica, as defined clinically (sensory impairment of lateral aspect of the thigh) and electrodiagnostically (abnormal sensory nerve conduction), and 21 control subjects were studied with two SSEP methods. SSEPs were elicited by stimulation of the LFCN below the anterior superior iliac spine (ASIS stimulation) and by cutaneous stimulation of the lateral aspect of the distal third of the thigh (thigh stimulation). Abnormalities were defined by the SSEP interside latency difference, interside amplitude ratio, or an absent response. The SSEP with ASIS stimulation had a sensitivity of 5% and a specificity of 95%, whereas with thigh stimulation it had a sensitivity of 52% and a specificity of 76%. Overall, SSEP after ASIS stimulation had no diagnostic value. Recording of the SSEP after thigh stimulation is recommended in obese patients only when sensory nerve conduction cannot be determined.

Femoral, saphenous nerve palsy after tourniquet use: a case report

Persistent motor and sensory abnormalities after surgery may affect the rehabilitation process. Patients with continued weakness may be perceived as lacking motivation by health care providers. However, there may be an underlying pathophysiologic abnormality preventing patients from progressing through their rehabilitation programs. We report a case of a 20-year-old man who underwent surgical repair of multiple knee structures with the use of a pneumatic tourniquet. Several weeks after surgery, electromyographic evaluation was done because he was having difficulty in his rehabilitation because of persistent weakness. An electromyography and nerve conduction study (NCS) revealed femoral and saphenous nerve palsies. Our report is the first on tourniquet-induced saphenous nerve injury as well as on abnormal femoral NCSs caused by tourniquet use. A review of the literature indicates that tourniquet-induced nerve palsies are not a rare event. Further evaluation should be considered if patients who are having persistent weakness or sensory findings after surgery have used a tourniquet.

Cortical processing of brush-evoked allodynia

The cortical processing of allodynia (touch-evoked pain) resulting from neuralgia of the lateral cutaneous femoral nerve was investigated with a newly designed pneumatically driven brush by means of magnetoencephalography. Brushing the unaffected thigh produced subsequent activation of the contralateral primary somatosensory cortex (S1) with peak latencies of 37 and 56 ms. Brushing the affected side led to comparable activation of the contralateral S1 cortex. In addition, the magnetic fields were stronger, and the corresponding equivalent current dipoles were located more laterally, consistent with the presence of cortical reorganisation. Allodynia was also accompanied by an activation of the cingulate cortex, occurring only 92 ms. after stimulus onset, an observation suggesting an Abeta-fiber-mediated neuronal pathway involved in dynamic mechanical allodynia. This study corroborates the concept of cortical reorganisation underlying chronic pain. Furthermore, it demonstrates that a remarkable early activation of the cingulate cortex may be involved in the cortical processing of allodynia.

Treatment of meralgia paresthetica with a deep inferior epigastric perforator adiposal flap: case report

A case of a 40-year-old female with meralgia paresthetica after malignant tumor resection in the right inguinal region is reported. Traditionally, meralgia paresthetica is treated with neurotransection or neurolysis. The therapeutic strategy using neurolysis, and the use of a deep inferior epigastric perforator adiposal flap wrapping as a prophylactic procedure against reentrapment is discussed.

Effect of intrathecal clonidine on group I and group II oligosynaptic excitation in paraplegics

We investigated the possibility that a change in transmission in group II pathways contributes to the spasticity of patients with spinal lesions. Thirteen patients were tested by measuring the quadriceps stretch reflex (Ashworth scale), the threshold of the quadriceps H reflex, and the oligosynaptic facilitation of the quadriceps H reflex elicited by volleys to groups I and II afferents in the common peroneal nerve (CPN). All these tests were performed before and after intrathecal injection of clonidine (60 microg). Early group I CPN-induced excitations occurred in 13 patients, and late group II CPN-induced excitations in 12. Both facilitations were, on average, significantly greater than those reported for normal subjects, but these increases were not correlated with the clinically assessed spasticity. Clonidine caused a constant, prolonged and dramatic decrease in spasticity, but did not alter the threshold of the quadriceps H reflex. CPN-induced group I and group II non-monosynaptic excitations of quadriceps motoneurones were significantly decreased, although they did not return to normal values. These results provide a further indication that group II pathways gives rise to the heteronymous late CPN-induced excitation. The pathophysiological role of a change in transmission in group II pathways in spasticity is discussed.

Evoked potentials elicited by stimulation of the lateral and anterior femoral cutaneous nerves in meralgia paresthetica

Seventy-five consecutive patients with clinical symptoms and signs of meralgia paresthetica underwent bilateral somatosensory evoked potential (SEP) studies involving stimulation of skin areas innervated by the lateral and anterior femoral cutaneous nerves of the thighs. The most common abnormality was an absolute lateral femoral cutaneous SEP latency > 40 ms in 35 patients (47%), followed by an absent response in 14 patients (19%), an absolute latency < 40 ms but amplitude reduction > 50% compared with the contralateral response in 8 patients (11%), and an absolute latency < 40 ms but > 5 ms interside latency difference in 5 patients (7%). Anterior femoral cutaneous SEPs were of value in distinguishing meralgia paresthetica from a proximal lumbar radiculopathy in an additional 4 patients and confirming bilateral meralgia paresthetica in 10 patients.

[Prostaglandin inhibitor indomethacin inhibits afferent activities of Adelta and C units in the saphenous nerve of diabetic hyperalgesic rats]

The effects of a non-selective inhibitor of cyclo-oxygenase (COX) indomethacin, and exogenous prostaglandin E(2) (PGE(2)) on A(delta) units and C units in the saphenous nerve of diabetic hyperalgesic rats were studied. The results showed that the conduction velocity of A(delta) units and C units and their mechanical threshold in diabetic hyperalgesic rats were obviously decreased, and a small number of A(delta) units (4/24) and C units (2/18) produced increased spontaneous activities. Intraperitoneal injection of indomethacin in diabetic hyperalgesic rats significantly relieved mechanical hyperalgesia, and resulted in a decrease in spontaneous afferent activities of the A(delta) units and C units. Subcutaneous injection of exogenous PGE(2) into the diabetic hyperalgesic and control rats produced a significant decrease in mechanical threshold of the A(delta) units and C units, and elicited discharge from 3 A(delta) units (3/24) and 1 C unit (1/18) in diabetic hyperalgesic rats and from 2 A(delta) units (2/13) in control rats. The present data suggest that the synthesis and release of PGs are increased in diabetic neuropathy, PGs can sensitize and /or activate A(delta) units and C units and elicit hyperalgesia and allodynia in diabetic rats.

Contralateral genitofemoral sympathetic nerve discharge increases following ipsilateral testicular torsion

The decrease in blood flow due to the activation of sympathetic system has been suggested to play a role in contralateral testicular deterioration associated with unilateral testicular torsion. Sympathetic nerve discharges (SND) from the genitofemoral nerve were evaluated before and during unilateral testicular torsion. Under urethane anesthesia, arterial blood pressure and SND from splanchnic and right genitofemoral nerves were recorded in 12 male Sprague-Dawley rats, 8 of which were included in subsequent analyses. After control recordings of basal discharges for 2 min the left testis was twisted 720 degrees counterclockwise, and recording was resumed for an additional 30 min. Changes in nerve activity were calculated by measuring the area under the autospectrum curve, and alterations were compared. Following testicular torsion no significant changes were obtained for splanchnic SND, but the amplitude of SND from contralateral genitofemoral nerve showed an overall increase of 21.20+/-7.03% in six rats. This increase lasted about 10-15 min and activities returned to pretorsion levels. In two other rats no significant change was observed in either splanchnic or genitofemoral SND. Ipsilateral testicular torsion results in a transient increase in genitofemoral SND. A possible autonomic reflex mechanism may exist, and it may be activated by noxious stimuli from contralateral side. This reflex mechanism may initiate a series of events that lead to the injury of contralateral testis.

Altered vastii recruitment when people with patellofemoral pain syndrome complete a postural task

OBJECTIVE

To investigate the recruitment of the vastus medialis obliquus (VMO) and vastus lateralis during voluntary tasks that challenge the stability of the knee and to evaluate whether there is a change in the coordination of the postural response by the central nervous system in subjects with patellofemoral pain syndrome (PFPS).

DESIGN

Cross-sectional.

SETTING

University laboratory in Australia.

PARTICIPANTS

Thirty-seven subjects with PFPS and 37 asymptomatic sex-matched controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Recordings of electromyographic activity of the VMO, vastus lateralis, tibialis anterior, and soleus were made by using surface electrodes. Subjects rose onto their toes (rise task) or rocked back on their heels (rock task) in a visual choice-reaction time task. Electromyographic onsets were determined by using a computer algorithm and were verified visually.

RESULTS

Our results confirm that, in asymptomatic subjects, contraction of the VMO and vastus lateralis occurs as part of the feed-forward postural response associated with ankle movements in standing, and the contraction of these separate heads of the quadriceps group occurs simultaneously. However, when subjects with PFPS perform identical tasks, the electromyographic onset of the vastus lateralis occurs before that of the VMO.

CONCLUSION

These findings indicate a difference in motor control in subjects with PFPS. They also support the hypothesized relation between changes in the timing of activity of the vastii and PFPS and provide the theoretic rationale to support physiotherapy treatment commonly used in the management of PFPS.

[Clinical and neurophysiological features and outcome prognosis criteria of Guillain-Barre syndrome in children]

Clinical and electroneuromyographical (ENMG) study of 24 children with Guillain-Barre syndrome (GBS) was conducted. Using ENMG, axonal and demyelinating GBS variants differing by course and rehabilitation time were distinguished. To predict a development of bulbar and respiratory disorders and to evaluate their severity and duration, diaphragm and adductive nerves conduction was investigated. Factors influencing motor function rehabilitation rate in GBS were the following: mean distal M-response amplitude during peroneal nerve stimulation, proximal to distal amplitudes ratio, M-response amplitude for femoral nerves. Three types of ENMG parameter rehabilitation in children with GBS (linear, stepped and undular) which characterize different rates of rehabilitation process are described.

Effectiveness of femoral nerve selective block in patients with spasticity: preliminary results

OBJECTIVES

To determine if the vastus intermedius nerve can be blocked by using surface coordinates and to measure the effects of selective nerve block on quadriceps spasticity and immediate gait.

DESIGN

Case series.

SETTING

Physical medicine and rehabilitation department of a university hospital.

PARTICIPANTS

Twelve patients with hemiplegia disabled by quadriceps overactivity.

INTERVENTION

Anesthesic block of the vastus intermedius by using surface coordinates, femoral nerve stimulation before and after block, and surface electrodes recording of the amplitude of the maximum direct motor response of each head of the quadriceps.

MAIN OUTCOME MEASURES

Assessment of spasticity, voluntary knee extension velocity, speed of gait, and knee flexion when walking.

RESULTS

To be effective, the puncture point (.29 of thigh length and 2cm lateral) had to be slightly modified to 1cm laterally from a point situated at 0.2 of the thigh length. A selective block of the vastus intermedius could not be achieved, but a block of the vastus lateralis was always achieved, twice associated with a block of the vastus intermedius, resulting in decreased quadriceps spasticity, no changes in gait parameters, no decrease in voluntary knee extension velocity, and subjective improvement in gait for 3 patients.

CONCLUSION

Selective block of the vastus lateralis with or without the vastus intermedius can be achieved by using surface coordinates without any dramatic effect on knee extension velocity, and it could be useful for phenol or alcohol block or surgical neurotomy.

Meralgia paresthetica in differential diagnosis of low-back pain

OBJECTIVE

Meralgia paresthetica is a syndrome of pain or dysesthesia or both in the anterolateral thigh, caused by entrapment of the lateral femoral cutaneous nerve at the anterior superior iliac spine. The aim of this report is to emphasize that meralgia paresthetica can be confused with low-back pain.

PATIENT

A 21-year-old man was admitted to hospital because of low-back and thigh pain. He had a history of low-back pain. Physical examination and radiologic studies for low-back pain and radiculopathy showed no pathologic findings. It was suspected that the most likely cause was lateral femoral cutaneous neuropathy, caused by the wide military belt he continuously wore tightly around his waist.

INTERVENTIONS

The nerve was blocked with 10 ml of bupivacaine 0.25%, which provided immediate pain relief. A nonsteroidal anti-inflammatory drug was administered orally.

RESULTS

After 15 days of bed rest and 45 days without the belt, he was completely symptom-free.

CONCLUSIONS

It is important to be rigorous in investigating the etiology of low-back pain. Meralgia paresthetica can mimic low-back pain because of the similarity of the symptoms. It can be treated by conservative or ablative therapeutic interventions; however, conservative methods should be considered primarily.

Inflammation with no axonal damage of the rat saphenous nerve trunk induces ectopic discharge and mechanosensitivity in myelinated axons

Inflammation along a nerve trunk with no frank axonal nerve damage produced by complete Freund's adjuvant (CFA) or Carrageenan is known to induce a painful peripheral neuropathy. In the present study, we examined the electrophysiological properties of myelinated axons (spontaneous discharge and mechanical sensitivity) at the inflamed nerve site. The rat saphenous nerves were exposed at mid-thigh level and wrapped in 2 mm wide bands of haemostatic oxidized cellulose (Oxycel) that were saturated with undiluted CFA. In the control rats the Oxycel) was saturated with saline. At postoperative days (PODs) 2-5 and 6-10, fine axon bundles were teased from the nerve, and electrophysiological recordings performed. At both time points spontaneous activity at the site of the application in CFA rats (PODs 2-5=9.9+/-2.5%: PODs 6-10=6.1+/-1.4%) was significantly higher than in the control animals (PODs 2-5=2.9+/-1.1%: PODs 6-10=1.6+/-1.4%: P=0.03, P=0.02, respectively). Mechanical sensitivity at both time points was significantly higher in CFA rats (PODs 2-5=12.6+/-3.1%: PODs 6-10=10.3+/-3.1%) than in saline rats (PODs 2-5=3.4+/-2.91%: PODs 6-10=0.8+/-1.0%: P=0.03, P=0.04, respectively). This study clearly shows that perineural inflammation with no axonal nerve damage induced by CFA application around the nerve trunk elevates spontaneous activity and induces mechanosensitivity in myelinated axons.