The ultrasonographic appearance of the femoral nerve and cases of iatrogenic impairment

Femoral and obturator neuropathies

The femoral and obturator nerves both arise from the L2, L3, and L4 spinal nerve roots and descend into the pelvis before emerging in the lower limbs. The femoral nerve's primary function is knee extension and hip flexion, along with some sensory innervation to the leg. The obturator nerve's primary function is thigh adduction and sensory innervation to a small area of the medial thigh. Each may be injured by a variety of potential causes, many of them iatrogenic. Here, we review the anatomy of the femoral and obturator nerves and the clinical features and potential etiologies of femoral and obturator neuropathies. Their necessary investigations, including electrodiagnostic studies and imaging, their prognosis, and potential treatments, are discussed in this chapter.

Two-dimensional ultrasound and two-dimensional shear wave elastography on femoral and saphenous neuropathy in patients with type 2 diabetes mellitus

Objective

This study aims to examine the value of two-dimensional (2D) ultrasound and two-dimensional shear wave elastography (2D-SWE) in evaluating femoral nerve (FN) and saphenous nerve (SN) neuropathy in patients with type 2 diabetes mellitus (T2DM).

Materials and methods

According to the diabetic peripheral neuropathy (DPN) diagnostic criteria, 60 patients with T2DM were enrolled and divided into 35 T2DM patients without DPN (non-DPN group) and 25 T2DM patients with DPN (DPN group). The control group consisted of another 15 healthy volunteers. The width, thickness, cross-sectional area (CSA), and perimeter of the FN and SN in the lower extremities were measured with 2D ultrasound. The average shear wave velocity (SWV) of the FN and SN was measured by 2D-SWE. Parameters of the left and right lower extremities were compared in each group, and the above parameters were compared among groups. The correlations between ultrasonographic and laboratory parameters were evaluated, and the independent influencing factors of SWV of the FN and SN were analyzed.

Results

The width, thickness, CSA, perimeter, and SWV of FN and SN in the DPN group were greater than those in the non-DPN groups and control group (P < 0.05). The width, thickness, CSA, perimeter, and SWV of the FN and SN in the non-DPN group were greater than those in the control group (P < 0.05). The CSA of FN was positively correlated with FPG, HbA1c, and TG (r = 0.34–0.69, P < 0.01). The perimeter of FN was positively correlated with FPG, HbA1c, and TG (r = 0.37–0.68, P < 0.01). The perimeter of the FN was negatively correlated with IgF-1 (r = −0.31, P < 0.05). The CSA of the SN was positively correlated with FPG and TG (r = 0.26–0.42, P < 0.05). The perimeter of the SN was positively correlated with FPG and TG (r = 0.37–0.39, P < 0.01). The SWV of FN and SN were positively correlated with FPG and TG (r = 0.35–0.57, P < 0.01; r = 0.43–0.49, P < 0.01). FPG and TG were independent influencing factors of the SWV of the FN and SN (P < 0.05).

Conclusion

2D ultrasound and 2D-SWE could be used to non-invasively, objectively, and accurately evaluate the abnormal changes of the FN and SN in patients with T2DM. It has important clinical significance for the early diagnosis of DPN and the curative effect evaluation.

Proximal Perineural Femoral Nerve Injection in Pigs Using an Ultrasound-Guided Lateral Subiliac Approach-A Cadaveric Study

Simple Summary

Desensitizing the femoral nerve improves pain control in several species undergoing pelvic limb surgeries. Despite possible advantages, this method has not yet been described in pigs, although they make an accepted surgical animal model. We developed an approach for femoral nerve blockade using ultrasound guidance in pigs which could be useful for pain control in pigs undergoing pelvic limb surgery.

Abstract

Desensitizing the femoral nerve (FN) improves pain control in several species undergoing pelvic limb surgeries. Despite its advantages, this method has not yet been described in pigs, although they make an accepted surgical animal model. Based on anatomical dissections, first performed in two pig cadavers, an ultrasound-guided access for localization and perineural infiltration of the FN trunk at the iliopsoas compartment level was specified. The FN was found running between the psoas major and medial portion of iliac muscle. Ultrasonographically, the FN appeared as a hypoechogenic round–oval structure surrounded by a hyperechogenic rim. Technical feasibility and accuracy were assessed in six additional pig cadavers by injecting 0.15 mL kg⁻¹ methylene blue dye bilaterally in direct proximity to the nerve. The needle was inserted caudoventral to the coxal tuber, traversing the ultrasound plane as it progressed towards the FN in dorsomedial direction. Staining of the nerve was evaluated by dissection. The injection was considered effective if the nerve was stained in its entire circumference over a length of 2 cm. FNs of all investigated individuals could be successfully stained. This ultrasound-guided subiliac approach allows feasible and accurate access to the FN and may be useful in producing a successful blockade in vivo.

Clinico-radiological review of peripheral entrapment neuropathies - Part 2 Lower limb

PURPOSE

This review discusses the relevant anatomy, etiopathogenesis, current notions in clinical and imaging features as well as management outline of lower limb entrapment neuropathies.

METHODS

The review is based on critical analysis of the current literature as well as our experience in dealing with entrapment neuropathies of the lower limb.

RESULTS

The complex anatomical network of nerves supplying the lower extremities are prone to entrapment by a heterogenous group of etiologies. This leads to diverse clinical manifestations making them difficult to diagnose with traditional methods such as clinical examination and electrodiagnostic studies. Moreover, some of these may mimic other common conditions such as disc pain or fibromyalgia leading to delay in diagnosis and increasing morbidity. Addition of imaging improves the diagnostic accuracy and also help in correct treatment of these entities. Magnetic resonance imaging is very useful for deeply situated nerves in pelvis and thigh while ultrasound is well validated for superficial entrapment neuropathies.

CONCLUSION

The rapidly changing concepts in these conditions accompanied by the advances in imaging has made it essential for a clinical radiologist to be well-informed with the current best practices.

Ultrasound and magnetic resonance imaging evaluation of the femoral and sciatic nerves. A study of healthy volunteers

Background and aims

The study describes the femoral (FN) and sciatic nerves (SN), explored using ultrasound (US) and magnetic resonance imaging (MRI). The aims of the study are: to establish US/MRI correlations and define reference values: for the anteroposterior (AP) and mediolateral (ML) diameters and cross-sectional area (CSA) of the two nerves respectively, in well-defined anatomical measuring sites; to analyze the intraobserver variation; to define the value with least variability; to determine differences between the right-left and male-female reference values.

Methods

A prospective study was carried out on 24 healthy volunteers (11 men and 13 women). MRI scans were performed using a 1.5T system. To visualize both nerves (FN and SN), a single 3D T2 weighted acquisition was performed, in the coronal plane, with a wide FOV. For ultrasonographic examinations, a Hitachi EUB-8500 ultrasound machine, equipped with a 13 MHz linear transducer was used. The measurements were performed at well-defined anatomical locations. The mean reference values of the AP, ML diameters and CSA were calculated for femoral and sciatic nerves, both on MRI and US. The correlations between the values determined by the two techniques were analyzed. The intra-observer variation was calculated by measuring the nerves at the same anatomical location at two separate time points.

Results

Wilcoxon matched-pairs signed rank test indicated a non-significant difference (p> 0.05) for the femoral and sciatic nerves, on both sides, except the femoral nerve ML diameter on MRI (p=0.014). The mean MRI and US reference values for the femoral nerve were calculated between the psoas and iliac muscles: FNAPMRI 4.533 ± 0.486, FNAPUS 4.800 ± 1.237, FNMLMRI 6.172 ± 1.203, FNMLUS 7.685 ± 3.338, FNCSAMRI 24.811 ± 3.394, FNCSAUS 26.285 ± 17.608. The mean MRI and US measurements for the sciatic nerve were determined under the buttock, at the level of the ischial tuberosity: SNAPMRI 5.500 ± 1.201, SNAPUS 5.975 ± 1.312, SNMLMRI 10.375 ± 2.272, SNMLUS 13.500 ± 1.661, SNCSAMRI 50.625 ± 15.373, SNCSAUS 53.631 ± 15.847. The MRI and US differences between right and left sides, both for the femoral and sciatic nerves were insignificant. In selected cases, Wilcoxon paired test indicated differences between subjects, according to their gender, both on MRI and US.

Conclusion

Reference values for the femoral and sciatic nerves at specific anatomical sites were identified. Side to side variation and gender related differences add to current knowledge on nerve size in young Caucasian population.

Entrapment Neuropathies of the Lower Extremity

Entrapment neuropathies in the lower limbs are a common neurologic problem and may present in any medical setting. Accurate identification and management of these nerve palsies can prevent pain, sensory loss, incoordination, and muscle weakness that may significantly affect a patient's functional mobility. In this article, the authors focus on the cause, signs and symptoms, diagnosis, and treatment of select entrapment neuropathies of the lower extremity, including palsies of the common peroneal, lateral femoral cutaneous, femoral, and posterior tibial nerves.

Femoral nerve excursion with knee and neck movements in supine, sitting and side-lying slump: An in vivo study using ultrasound imaging

BACKGROUND

Neurodynamic assessment and management are advocated for femoral nerve pathology. Contrary to neurodynamic techniques for other nerves, there is limited research that quantifies femoral nerve biomechanics.

OBJECTIVES

To quantify longitudinal and transverse excursion of the femoral nerve during knee and neck movements.

DESIGN

Single-group, experimental study, with within-participant comparisons.

METHODS

High-resolution ultrasound recordings of the femoral nerve were made in the proximal thigh/groin region in 30 asymptomatic participants. Scans were made during knee flexion in supine and a semi-seated position, and during neck flexion in side-lying slump (Slump _FEMORAL). Healthy participants were assessed to reveal normal nerve biomechanics, not influenced by pathology. Data were analysed with one-sample and paired t-tests. Reliability was assessed with intraclass correlation coefficients (ICC).

RESULTS

Longitudinal and transverse excursion measurements were reliable (ICC≥0.87). With knee flexion, longitudinal femoral nerve excursion was significant and larger in supine than in sitting (supine (mean (SD)): 3.6 (2.0) mm; p < 0.001; sitting: 1.1 (1.6) mm; p = 0.001; comparison: p = 0.001). There was also excursion in a medial direction (supine: 1.4 (0.3) mm; p < 0.001; sitting: 0.7 (0.6) mm; p < 0.001) and anterior direction (supine: 0.2 (0.2) mm; p < 0.001; sitting: 0.1 (0.2) mm; p = 0.06). Neck flexion in Slump _FEMORAL did not result in longitudinal (0.0 (0.3) mm; p = 0.55) or anteroposterior (0.0 (0.1) mm; p = 0.10) excursion, but resulted in medial excursion (1.1 (0.5) mm; p < 0.001).

CONCLUSION

Although the femoral nerve terminates proximal to the knee, femoral nerve excursion in the proximal thigh occurred with knee flexion; Neck flexion in Slump _FEMORAL resulted in medial excursion.

[Imaging of the lumbosacral plexus : Diagnostics and treatment planning with high-resolution procedures]

BACKGROUND

Technical advances in magnetic resonance (MR) and ultrasound-based neurography nowadays facilitate the radiological assessment of the lumbosacral plexus.

OBJECTIVE

Anatomy and imaging of the lumbosacral plexus and diagnostics of the most common pathologies.

MATERIAL AND METHODS

Description of the clinically feasible combination of magnetic resonance imaging (MRI) and ultrasound diagnostics, case-based illustration of imaging techniques and individual advantages of MRI and ultrasound-based diagnostics for various pathologies of the lumbosacral plexus and its peripheral nerves.

RESULTS

High-resolution ultrasound-based neurography (HRUS) is particularly valuable for the assessment of superficial structures of the lumbosacral plexus. Depending on the examiner's experience, anatomical variations of the sciatic nerve (e. g. relevant in piriformis syndrome) as well as more subtle variations, for example as seen in neuritis, can be sonographically depicted and assessed. The use of MRI enables the diagnostic evaluation of more deeply located nerve structures, such as the pudendal and the femoral nerves. Modern MRI techniques, such as peripheral nerve tractography allow three-dimensional depiction of the spatial relationship between nerves and local tumors or traumatic alterations. This can be beneficial for further therapy planning.

CONCLUSION

The anatomy and pathology of the lumbosacral plexus can be reliably imaged by the meaningful combination of MRI and ultrasound-based high resolution neurography.

Automatic Segmentation and Probe Guidance for Real-Time Assistance of Ultrasound-Guided Femoral Nerve Blocks

Ultrasound-guided regional anesthesia can be challenging, especially for inexperienced physicians. The goal of the proposed methods is to create a system that can assist a user in performing ultrasound-guided femoral nerve blocks. The system indicates in which direction the user should move the ultrasound probe to investigate the region of interest and to reach the target site for needle insertion. Additionally, the system provides automatic real-time segmentation of the femoral artery, the femoral nerve and the two layers fascia lata and fascia iliaca. This aids in interpretation of the 2-D ultrasound images and the surrounding anatomy in 3-D. The system was evaluated on 24 ultrasound acquisitions of both legs from six subjects. The estimated target site for needle insertion and the segmentations were compared with those of an expert anesthesiologist. Average target distance was 8.5 mm with a standard deviation of 2.5 mm. The mean absolute differences of the femoral nerve and the fascia segmentations were about 1-3 mm.

Real-Time Automatic Artery Segmentation, Reconstruction and Registration for Ultrasound-Guided Regional Anaesthesia of the Femoral Nerve

The goal is to create an assistant for ultrasound- guided femoral nerve block. By segmenting and visualizing the important structures such as the femoral artery, we hope to improve the success of these procedures. This article is the first step towards this goal and presents novel real-time methods for identifying and reconstructing the femoral artery, and registering a model of the surrounding anatomy to the ultrasound images. The femoral artery is modelled as an ellipse. The artery is first detected by a novel algorithm which initializes the artery tracking. This algorithm is completely automatic and requires no user interaction. Artery tracking is achieved with a Kalman filter. The 3D artery is reconstructed in real-time with a novel algorithm and a tracked ultrasound probe. A mesh model of the surrounding anatomy was created from a CT dataset. Registration of this model is achieved by landmark registration using the centerpoints from the artery tracking and the femoral artery centerline of the model. The artery detection method was able to automatically detect the femoral artery and initialize the tracking in all 48 ultrasound sequences. The tracking algorithm achieved an average dice similarity coefficient of 0.91, absolute distance of 0.33 mm, and Hausdorff distance 1.05 mm. The mean registration error was 2.7 mm, while the average maximum error was 12.4 mm. The average runtime was measured to be 38, 8, 46 and 0.2 milliseconds for the artery detection, tracking, reconstruction and registration methods respectively.

Morphological distinction of cervical nerve roots associated with motor function in 219 healthy volunteers: a multicenter prospective study

STUDY DESIGN

A prospective study.

OBJECTIVE

To examine the diameter (mm), transverse diameter (mm), and cross-sectional area (mm²) of the C5, C6, and C7 nerve roots using ultrasonography.

SUMMARY OF BACKGROUND DATA

Each of the cervical nerve roots affected a different motor or sensory area. Although there were several studies that performed a detailed assessment of cervical nerve root anatomy in cadavers, only a few studies on the thickness of cervical nerve roots in living specimens have been performed. We examined whether the thickness of the C5, C6, and C7 nerve roots, as well as the area supplied by each of the roots, varied.

METHODS

All 219 subjects (99 males and 120 females; mean age, 47 ± 15 yr) were healthy volunteers. The diameter and the transverse diameter were measured via ultrasonography, and the cross-sectional area was calculated for each of the C5-C7 nerve roots.

RESULTS

The following diameter measurements (right and left, respectively) were obtained: C5, 2.8 and 2.9 mm; C6, 3.6 and 3.8 mm; and C7, 3.3 and 3.4 mm. The following transverse diameter measurements were obtained (right and left, respectively): C5, 2.8 and 3.0 mm; C6, 3.7 and 3.8 mm; and C7, 3.5 and 3.4 mm. The following cross-sectional area measurements (right and left, respectively) were obtained: C5, 6.3 and 6.4 mm²; C6, 10.7 and 11.0 mm²; and C7, 8.8 and 8.8 mm². Based on the 3 measurement methods, the C5 nerve root was significantly thinner than the other 2 nerve roots (P < 0.001), and the C7 nerve root was smaller than the C6 nerve root (P = 0.001).

CONCLUSION

The C5 nerve root was significantly thinner than the C6 and C7 cervical nerve roots. The fact that the C5 nerve is thinner may render it more susceptible to damage during cervical surgery.

Ultrasound in diagnosis of retroperitoneal femoral nerve injury: a case report

We present a case of retroperitoneal femoral nerve injury after cut wounds at the lower abdomen. Electrodiagnostic tests revealed impaired function of nerve and muscles. A mass was observed at the retroperitoneal part of the femoral nerve by ultrasound, indicating that a traumatic neuroma composed of disordered fascicles was configurated after the injury. Postoperative pathology confirmed hypertrophic and hyperplastic nerve bundles of the mass. Great improvements were shown in the patient's symptoms and electrodiagnostic tests in the subsequent 3 months. This case presented a rare position of neuroma formation by ultrasound.

Ultrasound assessment of selected peripheral nerves pathologies. Part II: Entrapment neuropathies of the lower limb

Similarly to entrapment neuropathies of upper extremities, the ultrasound constitutes a valuable supplementation of diagnostic examinations performed in patients with suspicions of nerve entrapment syndromes of the lower limb. For many years, it was claimed that such pathologies were rare. This probably resulted from the lack of proper diagnostic tools (including high frequency ultrasound transducers) as well as the lack of sufficient knowledge in this area. In relation to the above, the symptoms of compression neuropathies were frequently interpreted as a manifestation of pathologies of the lumbar part of the spine or a other orthopedic disease (degenerative or overuse one). Consequently, many patients were treated ineffectively for many months and even, years which led to irreparable neurological changes and changes in the motor organ. Apart from a clinical examination, the diagnostics of entrapment neuropathies of lower limb is currently based on imaging tests (ultrasound, magnetic resonance) as well as functional assessments (electromyography). Magnetic resonance imaging is characterized by a relatively low resolution (as compared to ultrasound) which results in limited possibilities of morphological evaluation of the visualized pathology. Electromyography allows for the assessment of nerve function, but does not precisely determine the type and degree of change. This article presents examples of the most common entrapment neuropathies of the lower limb concerning the following nerves: sciatic, femoral, lateral femoral cutaneous, obturator, fibular and its branches, tibial and its branches as well as sural. The pathomorphological basis of the neuropathies as well as corresponding ultrasound images are presented in this paper. Attention has been drawn to echogenicity, degree of vascularization and bundle presentation of the trunk of a pathological peripheral nerve.

Ultrasound-guided dorsal approach for femoral nerve blockade in cats: an imaging study

This study was conducted to describe and validate a dorsal ultrasound-guided approach to block the femoral nerve (FN) in cats by means of anatomical and computed tomography (CT) studies. The anatomical study was carried out in four fresh feline cadavers to determine the anatomic landmarks to approach this nerve. Then, an ultrasonographic study of the FN was performed in another eight cadavers using a 13 MHz linear transducer. The accuracy of the neurolocation by ultrasonography (US) was determined in four cadavers by the injection of 1 ml blue ink around the FN. The staining of the nerve was evaluated in anatomical studies. The feasibility of this technique was also evaluated by CT after injecting 1 ml of an iodinated contrast medium (150 mgl/ml) around the FN in the other four cadavers. The landmarks to approach the FN were the cranial border of the iliac crest and the dorsal processes of L6 and L7. The FN was visualised as a round hypoechogenic structure surrounded by a hyperechogenic rim located within the iliopsoas muscle on transverse scans. The anatomical and CT studies confirmed the accuracy of the US location of the FN. The dorsal ultrasound-guided approach may allow feasible and accurate access to the FN in cats and it could be useful in producing successful blockade.

Imaging of neuropathies about the hip

Neuropathies about the hip may be cause of chronic pain and disability. In most cases, these conditions derive from mechanical or dynamic compression of a segment of a nerve within a narrow osteofibrous tunnel, an opening in a fibrous structure, or a passageway close to a ligament or a muscle. Although the evaluation of nerve disorders primarily relies on neurological examination and electrophysiology, diagnostic imaging is currently used as a complement to help define the site and aetiology of nerve compression and exclude other disease possibly underlying the patient' symptoms. Diagnosis of entrapment neuropathies about the hip with US and MR imaging requires an in-depth knowledge of the normal imaging anatomy and awareness of the anatomic and pathologic factors that may predispose or cause a nerve injury. Accordingly, the aim of this article is to provide a comprehensive review of hip neuropathies with an emphasis on the relevant anatomy, aetiology, clinical presentation, and their imaging appearance. The lateral femoral cutaneous neuropathy (meiralgia paresthetica), femoral neuropathy, sciatic neuropathy, obturator neuropathy, superior and inferior gluteal neuropathies and pudendal neuropathy will be discussed.

Iatrogenic femoral neuropathy: two cases and literature update

Iatrogenic femoral neuropathy is an uncommon surgical or obstetric complication that may be underreported. It results from compression, stretch, ischemia, or direct trauma of the nerve during hip arthroplasty, self-retaining retractor use in pelvicoabdominal surgery, lithotomy positioning for anesthesia or labor, and other more rare causes. Decreasing incidence of this complication after abdominal and gynecologic surgery but increase in its absolute numbers after hip arthroplasty has emerged over the last decade. We describe two illustrative cases related respectively to lithotomy positioning and self-retaining retractor use. The variability in clinical presentation of iatrogenic femoral nerve lesions, some new insights in their diverse pathophysiology, and in the diagnostic and treatment options are discussed with an update from the literature.

[Ultrasound guidance in pediatric regional anesthesia]

Ultrasound imaging is being used to guide pediatric nerve block procedures. Difficulties that arise because of the smaller anatomical structures in children can be compensated for by the greater aqueous consistency and reduced calcification. Given the shorter distance between the surface of the skin and nerves, it is advisable to use a linear array transducer working at a high frequency (7-10 MHz). Like adults, children benefit when ultrasound guidance is used in the performance of neuraxial nerve trunk blocks, particularly of the umbilical and ilioinguinal nerves, and in greater measure in spinal blocks. Ultrasound guidance enhances efficacy and also affords the important advantage of greater safety. The main disadvantages are the cost of equipment and the necessary learning curve.

Relationship between ultrasound imaging and eliciting motor response during femoral nerve stimulation

OBJECTIVE

Nerve stimulator-assisted localization of the femoral nerve is well described; however, direct ultrasound imaging of the femoral nerve branches may be challenging. The purpose of this study was to correlate the evoked motor responses obtained by femoral nerve stimulation and the topographic orientation of the femoral nerve branches during ultrasound examinations of the infrainguinal region.

METHODS

Eighty-two patients undergoing total knee replacement were enrolled in this study. A 25-mm, 5- to 10-MHz broadband linear array transducer was used to identify the femoral nerve at the inguinal crease. The medial and lateral aspects of the femoral nerve were stimulated under ultrasound imaging. Twenty cadavers were dissected to support our clinical findings.

RESULTS

A quadriceps contraction was elicited in 1.2% and 96% of the patients when stimulating the medial and lateral aspects of the femoral nerve, respectively. In contrast, a sartorius muscle contraction was elicited in 94% and 0% when stimulating the medial and lateral aspects of the femoral nerve. Our findings during anatomic dissection revealed that the femoral nerve branch to the quadriceps muscle, when compared with the branch to the sartorius muscle, originated laterally in 95% and medially in 5% of the specimens.

CONCLUSIONS

When using out-of-plane ultrasound imaging at the inguinal crease, directing the stimulating needle to the lateral half of the femoral nerve may be associated with a higher probability of encountering the motor branch to the quadriceps muscle.

Ultrasound-guided peripheral nerve blockade

Peripheral nerve blockade (PNB) for orthopedic surgery is usually performed without visual guidance, relying mainly on surface anatomic landmarks and electrical stimulation to localize nerves. Moreover, multiple trial and error attempts to place a needle can frustrate the operator, cause unwarranted pain to the patient, and waste valuable time in the operating room. Inaccurate needle placement and spread of local anesthetic account for most PNB failures, whereas "trial and error" needle manipulations for nerve localization can cause complications. The recent application of ultrasound (US) to PNB affords real-time imaging of the target nerve, needle, and surrounding vasculature, such that needle proximity to the nerve is ensured and vascular puncture avoided. This article reviews the advantages, principles, and techniques of US for the most common types of PNB.

Use of a nerve stimulator does not improve the efficacy of ultrasound-guided supraclavicular nerve blocks

OBJECTIVE

To evaluate the efficacy of nerve stimulation as an adjunct to ultrasound-guided supraclavicular nerve blocks.

DESIGN

Prospective database review.

SETTING

Tertiary-care medical center.

MEASUREMENTS

The records of 94 consecutive adult patients requiring surgery below the elbow and consenting to receive regional anesthesia were studied. The focus of this study was on supraclavicular nerve block using ultrasound guidance for nerve identification and needle localization. A nerve stimulator with a motor response lower than 0.5 mA was used for confirmation of findings. An ultrasound image was considered adequate if two trunks of the brachial plexus were visualized and if the needle was completely seen on the long axis. A successful block was defined as one that sufficed as the sole anesthetic without conversion to general anesthesia. Motor and sensory examination findings on the upper extremity were also evaluated.

RESULTS

74 patients had an adequate ultrasound image. Of the 64 patients with a positive motor response, 88% had a successful block, as compared with 90% of the 10 patients without a motor response (relative risk, 1.09; 95% confidence interval, 0.79-1.51; P = 0.52). Neither multivariate correction for baseline characteristics nor inclusion of the 20 patients with inadequate ultrasound images changed the results.

CONCLUSION

For adequately imaged ultrasound-guided supraclavicular nerve blocks, a positive motor response to nerve stimulation does not increase the success rate of the block. In addition, the high false-negative rate suggests that these blocks are usually effective, even in the absence of a motor response. Nerve stimulation as an adjunct to ultrasound guidance may have a limited role.

Ultrasonographic guidance in pediatric regional anesthesia. Part 2: techniques

The benefits of regional anesthesia are well documented. The downsides of such techniques have been a significant failure rate and a potential for serious complications. Nearly, all regional blocks were first described as essentially 'blind' techniques. The development of high-resolution portable ultrasound (US) has made the use of US for regional anesthesia possible. Improved understanding of sonographic anatomy should lessen both the failure rate and the possibility of incurring serious complications. Natural caution has dictated that only a selection of blocks used in adults has been commonly used in pediatric practice, but with the aid of US, the repertoire of blocks for infants and children may be widened. The second part of this review will concentrate on the practice of both peripheral and central blocks.

High-resolution ultrasound of the supraclavicular brachial plexus—can it improve therapeutic decisions in patients with plexus trauma?

Patients with major traumatic brachial plexus lesions benefit from early surgery, but they are seldom isolated by today's diagnostic workup. Subjects with ambiguous findings after such workups usually undergo a trial of conservative treatment and those without improvement delayed surgery. Our study focuses on this problem. Hence, the purpose of this study was to evaluate the impact of high-resolution ultrasound (HR-US) on patient recruitment for non-delayed surgery. Twelve patients after blunt shoulder trauma and standardized HR-US assessment who underwent plexus surgery were included in this prospective observational study. Thereby, a total of 168 plexus elements were evaluated. All findings were compared to electrophysiological data if available and tested statistically against the gold-standard, i.e., surgical validation. Major plexus lesions were correctly detected by HR-US in nine patients (20 plexus elements). In two patients (five plexus elements), the lesion was underestimated by HR-US in relation to the gold standard (surgical inspection). Our analysis showed a high positive (1.0) and an acceptable negative predictive value (0.92) for the grading of traumatic plexus lesions with HR-US. Based on HR-US findings alone, 9 of 11 patients with objective major lesions would have undergone early surgery. In conclusion, HR-US proved a valuable tool for the triage of patients with traumatic lesions into surgical and non-surgical candidates.

Peroneal Nerve Palsy Associated with Knee Luxation: Evaluation by Sonography—Initial Experiences

OBJECTIVE

Traumatic knee dislocation needs immediate surgical repair to restore joint function. A concomitant traction injury of the peroneal nerve is reported to exist in up to 25% of cases and is often overlooked initially. In patients with major nerve lesions, immediate surgical nerve repair might be necessary to avoid irreversible loss of neural function. In the present study, we tried to evaluate whether sonography is a valuable tool for identification of nerve pathology that warrants surgical intervention.

SUBJECTS AND METHODS

In this prospective study, both peroneal nerves in nine patients with one-sided peroneal nerve palsy after closed knee luxation and the peroneal nerves of 11 healthy volunteers were investigated with sonography. Using statistical analysis, we tried to define the comparability and significance of the findings.

RESULTS

The mean cross-sectional area of healthy peroneal nerves in the genicular region was 0.18 cm2 (SD, 0.07 cm2). Impaired nerves were significantly discerned because of their increased cross-sectional area at the level of the injury (mean cross-sectional area, 0.7 cm2; SD, 0.46 cm2; p < 0.05). Identification of caliber changes and depiction of at least one nerve stump were found to be the most specific criteria for the definition of a major neural lesion. The ability of sonography to provide additional information about surrounding soft-tissue impairment (scar tissue and hematoma formation) proved helpful.

CONCLUSION

Sonography allows radiologists to visualize neural and extraneural pathology and to define the exact level and extent of lesions. Thus, it may be a valuable adjunct in the decision of whether surgical intervention is necessary.

Neuromuscular ultrasound

High-resolution ultrasound now is capable of imaging muscle and nerve in fine detail. It is sensitive in detecting chronic myopathies and neurogenic atrophy and may be able to detect subtle changes associated with acute denervation. It is particularly well suited to the study of fasciculations and kinesiology. Recent studies show that ultrasound also is capable of imaging most peripheral nerves,including small branches, and of sensitively measuring the swelling that follows chronic compression. This noninvasive technology holds considerable promise for providing anatomic information to complement other tests of nerve and muscle function.

Image-guided HIFU neurolysis of peripheral nerves to treat spasticity and pain

Spasticity, a major complication of central nervous system disorders, signified by uncontrollable muscle contractions, is very difficult to treat effectively. We report on the use of ultrasound (US) image-guided high-intensity focused US (HIFU) to target and suppress the function of the sciatic nerve complex of rabbits in vivo, as a possible treatment of spasticity. The image-guided HIFU device included a 3.2-MHz spherically curved transducer and an intraoperative imaging probe. A focal acoustic intensity of 1480 to 1850 W/cm(2), applied using a scanning method, was effective in achieving complete conduction block in 100% of 22 nerve complexes with HIFU treatment times of 36 +/- 14 s (mean +/- SD). Gross examination showed blanching of the nerve at the HIFU treatment site and lesion volumes of 2.8 +/- 1.4 cm(3) encompassing the nerve complex. Histologic examination indicated axonal demyelination and necrosis of Schwann cells as probable mechanisms of nerve block. With accurate localization and targeting of peripheral nerves using US imaging, HIFU could become a promising tool for the suppression of spasticity.

Chapter 25 Imaging nerve and muscle with ultrasound

Over the last two decades significant advances in ultrasound have made it possible for investigators to image and interpret pathologic changes in muscle and nerve. In addition to being able to assess the pathologic changes in these structures themselves, ultrasound also provides the unique ability to identify anatomic lesions responsible for nerve or muscle injury. They can be correlated with changes in neural structures or affected muscles. Like electrodiagnostic studies, ultrasound is portable and inexpensive, but it is even less invasive, and surprisingly sensitive in detecting a variety of unusual and common causes of neuromuscular dysfunction. Given recent developments in the field, ultrasound shows promise as the technique most suitable for clinical neurophysiologists and neuromuscular clinicians in the growing field of imaging. Such involvement is required to best adopt and exploit the potential of imaging for the research and clinical evaluation of neuromuscular disorders.