A comparison of intertendinous and classical approaches to popliteal nerve block using magnetic resonance imaging simulation

The classical approach to sciatic nerve block in the popliteal fossa (popliteal block) often requires multiple attempts to localize the sciatic nerve. Recently, it has been suggested that an intertendinous approach to popliteal block may result in a more consistent localization of the sciatic nerve. In the current study, we compared anatomical landmarks for the intertendinous and classical approaches to popliteal block with respect to the accuracy in localizing the sciatic nerve using magnetic resonance imaging simulation. Two anesthesiologists experienced in popliteal block drew landmarks for the intertendinous and classical approaches on 10 volunteers; a 1.5 Tesla superconducting magnet was used to obtain simultaneous, 10-mm thick, fast-spin echo proton density transverse axial sequences of the lower extremities. Using these acquired images, the two approaches were simulated off-line using previously identified landmarks. The spatial relationships of the simulated needle paths to the nerves and vessels in the popliteal fossa, as well as other relevant structures, were measured and compared. Simulation of the intertendinous approach to popliteal block resulted in needle-to-sciatic nerve contact in 14 legs (70%) versus 5 legs (25%) when the classical approach was used (P < 0.05). We conclude that the intertendinous approach might result in a more consistent localization of the sciatic nerve and may decrease the risk of sciatic vessel puncture. IMPLICATIONS: A simulation of popliteal block using magnetic resonance imaging in volunteers suggests that using tendons of the hamstring muscles as the anatomical landmarks yields a more consistent localization of the sciatic nerve.     

Neurilemoma in the ankle as a cause of plantar foot pain: A report of one case

One case of posterior tibial nerve neurilemoma with chronic plantar foot pain is described. At the initial examination, the case was overlooked as plantar fasciitis; it was treated for long periods prior to operation. Neurilemomas in the foot and ankle can easily be overlooked and misdiagnosed as tarsal tunnel syndrome or plantar fasciitis because of the similarity of symptoms to those of other frequently encountered foot disorders, absence of palpable mass and the rarity. Magnetic resonance imaging is the imaging modality of choice for differential diagnosis. In this case, surgical excision of the tumours resulted in immediate and complete relief of chronic plantar foot and calf pain. Despite the rarity of the disease, surgeons should consider neurilemoma as a cause of persistent chronic plantar foot and calf pain.     

A posterior tibial nerve neurilemoma unrecognized for 10 years: case report

OBJECTIVE AND IMPORTANCE: Neoplasms of peripheral nerves can be obscured, especially during the early phase. The author reports a patient with a posterior tibial nerve neurilemoma (schwannoma). For a decade, the tumor was misdiagnosed as nonspecific S1 radiculopathy and psychogenic chronic pain syndrome. The patient's presentation and initial management are unique. CLINICAL PRESENTATION: A 40-year-old woman reported severe left foot and calf pain, numbness, and weakness. The symptoms were evident during three pregnancies, and they gradually progressed. The neuropathic pain was protracted, despite implantation of a dorsal column stimulator and administration of a wide variety of medications and therapies. The symptoms were unresponsive to both inpatient and outpatient treatments, which resulted in a misdiagnosis of psychogenic pain for more than a decade. Diagnostic scans obtained by computed tomography, ultrasonography, and nuclear scintigraphy confirmed a popliteal fossa mass. INTERVENTION: A high, large posterior tibial nerve neurilemoma was found intraoperatively, positioned just below the sciatic nerve bifurcation with extensive degenerative features and hemorrhages. Surgical resection provided immediate recovery. CONCLUSION: Peripheral nerve tumors are rarely acknowledged clinical entities. Chronic unexplained foot and calf pain and a positive Tinel's sign should raise suspicion of posterior tibial nerve neurilemoma. Even in patients who have had such tumors for a decade, surgical resection remains the treatment of choice.     

Extraspinal bone and soft-tissue tumors as a cause of sciatica. Clinical diagnosis and recommendations: analysis of 32 cases.

STUDY DESIGN: Between 1982 and 1997, the authors treated 32 patients with sciatica who subsequently were found to have a tumor along the extraspinal course of the sciatic nerve. SUMMARY OF BACKGROUND DATA: Extraspinal compression of the sciatic nerve by a tumor is a rare cause of sciatica. Signs and symptoms overlap those of the more common causes of sciatica (i.e., herniated disc and spinal stenosis). OBJECTIVE: To characterize the unique clinical presentation of these patients and to formulate guidelines that may lead to early diagnosis. METHODS: All pertinent clinical data and studies were reviewed retrospectively, and standard demographic data were collected for analysis. RESULTS: These patients typically sought treatment for an insidious onset of sciatic pain that was constant, progressive, and unresponsive to change in position or bed rest. The mean time to final diagnosis was 11.9 months (median, 6 months). Seventeen patients were able to locate their pain to a specific point along the extraspinal course of the sciatic pain, and a mass was noted in 13 patients. Eighteen of these tumors were in the pelvis, 10 in the thigh, and 4 in the popliteal fossa and calf. CONCLUSIONS: A high index of clinical suspicion is the key to early diagnosis of bone or soft-tissue tumors as a cause of sciatica; special attention should be given to pain pattern, physical examination of the entire course of the sciatic nerve, and selection of proper imaging studies. Routine anteroposterior plain radiography of the pelvis as part of the initial imaging screening process is recommended.     

Ultrasound Observation of the Sciatic Nerve and its Branches at the Popliteal Fossa: Always Visible, Never Seen

BACKGROUND: In studying patients with sciatic nerve (SN) varices the author found that the sciatic nerve and its major divisions, the tibial and peroneal nerves, could be readily identified on ultrasound imaging of the popliteal fossa. The sciatic nerve lies in the space between the popliteal vein and the small saphenous vein. OBJECTIVES: To confirm that the sciatic nerve can be identified on ultrasonography in patients with venous disease as well as in normal subjects. METHOD: Thirty unselected patients (60 limbs) attending for outpatient consultations were investigated by duplex ultrasound examination of the popliteal fossa. In 10 subjects varicose veins were present, in 20 no varices were visible on clinical examination. RESULTS: The sciatic nerve and its branches where visible and easily recognised in all cases. The sciatic nerve and the small saphenous vein lay in close proximity in cases with of small saphenous vein incompetence. CONCLUSIONS: Ultrasound identification of the sciatic nerve in the popliteal fossa allows assessment of its relationship with the adjacent veins. This technique may be useful in identifying the location of the nerve prior to surgical intervention for varices in the popliteal fossa as well as for endo-luminal occlusion procedures given the close proximity of the vein to the nerve. Sciatic nerve varices, tumours, extrinsic dislocation and nerve lesions may also be detected.     

Ultrasound imaging for popliteal sciatic nerve block

BACKGROUND AND OBJECTIVES: Ultrasound is a novel method of nerve localization but its use for lower extremity blocks appears limited with only reports for femoral 3-in-1 blocks. We report a case series of popliteal sciatic nerve blocks using ultrasound guidance to illustrate the clinical usefulness of this technology. CASE REPORT: The sciatic nerve was localized in the popliteal fossa by ultrasound imaging in 10 patients using a 4- to 7-MHz probe and the Philips ATL HDI 5000 unit. Ultrasound imaging showed the sciatic nerve anatomy, the point at which it divides, and the spatial relationship between the peroneal and tibial nerves distally. Needle contact with the nerve(s) was further confirmed with nerve stimulation. Circumferential local anesthetic spread within the fascial sheath after injection appears to correlate with rapid onset and completeness of sciatic nerve block. CONCLUSIONS: Our preliminary experience suggests that ultrasound localization of the sciatic nerve in the popliteal fossa is a simple and reliable procedure. It helps guide block needle placement and assess local anesthetic spread pattern at the time of injection.     

Ultrasound-guided sciatic nerve block in the popliteal fossa for the postoperative pain control after Achilles' tendon repair

To assess the usefulness of ultrasound-guided sciatic nerve block in the popliteal fossa in the postoperative pain management after Achilles' tendon repair, we compared 15 patients managed by general anesthesia and sciatic nerve block (Group B) with 17 patients managed by general anesthesia alone (Group G). The time required for the nerve block was about 20 minutes on the average, and the success rate was 100%. No significant complication associated with the nerve block was observed. Fentanyl dosing for the postoperative analgesia was significantly smaller in the Group B. Although the postoperative analgesic requirement was comparable, the time to the first postoperative analgesic administration was significantly longer in the Group B. This retrospective study suggests that ultrasound-guided sciatic nerve block in the popliteal fossa provides safe and effective postoperative pain relief after Achilles' tendon repair.     

Intermittent claudication associated with persistent sciatic artery: Report of two cases

Two elderly women complaining of intermittent claudication complicated with persistent sciatic artery are herein reported. A direct femoral arteriogram showed hypoplasty of the superficial femoral artery and an unnatural anatomical relationship between the distal superficial femoral artery and the proximal popliteal artery, thus suggesting the presence of persistent sciatic artery. The diagnosis of persistent sciatic artery was finally made based on the aortography findings including the iliac arterial system and computed tomography (CT) scan. Magnetic resonance imaging (MRI) was helpful to demonstrate the entire image of this anomaly in cases with non-thrombolized sciatic artery. These diagnostic methods were useful in designing the optimal surgical strategy. The first case with a gluteal pulsating mass underwent exclusion of the persistent sciatic artery including the aneurysm through a retroperitoneal approach with a combination of femorotibial bypass, while the second case with thrombosed persistent sciatic artery only underwent femoropopliteal bypass. To recognize such a rare lesion, awareness of the differential diagnosis is important, and to provide appropriate treatment, an accurate whole image including adequate angiography, a CT scan, and magnetic resonance imaging is necessary.     

Popliteal Venous Aneurysms: Report of an Unusual Presentation and Literature Review

Aneurysms of the popliteal vein represent a rare clinical finding. Most patients with popliteal venous aneurysms present with pulmonary emboli. We describe a case report of a 69-year-old female who presented with popliteal fossa pain. A popliteal venous aneurysm was detected following extensive diagnostic work-up that included magnetic resonance imaging (MRI), venous duplex, and venography. At operation, the aneurysm was found to be compressing the tibial nerve. Tangential aneurysmectomy and lateral venorrhaphy was performed. A PTFE sleeve was placed around the site of venous repair to prevent recurrence of the aneurysm and to keep the tibial nerve free of the repair site. The postoperative course was uneventful, and duplex studies at 18 months after the procedure remain normal. The etiology of popliteal venous aneurysms is discussed here, and presentation, diagnostic work-up, and treatment options are reviewed. We demonstrate that pain in the popliteal fossa should be considered a presenting symptom for venous aneurysms.     

The use of magnetic resonance imaging to evaluate the accuracy of a handheld ultrasound machine in localizing the sciatic nerve in the popliteal fossa

BACKGROUND AND OBJECTIVE: Ultrasound has become an increasingly popular modality in facilitating the performance of peripheral nerve blocks. There is a paucity of data describing techniques of ultrasound-guided sciatic nerve blocks. By using magnetic resonance imaging (MRI) as a gold standard, the objective of this study was to describe the ability of a handheld ultrasound machine to accurately locate the sciatic nerve. METHODS: Ten patients were prospectively enrolled and placed in the prone position. By using a 4- to 7-MHz ultrasound transducer, the sciatic nerve was visualized in short axis between 5 to 10 cm above the popliteal crease. The distance from the skin to the nerve was measured by ultrasound, and a MRI lucent marker was placed at this site. This process was repeated in one additional location. The patient was then placed supine in the MRI scanner and short-axis T1-weighted images were obtained. On the MRI image, we recreated the 2 lines extending down from the markers using the distances previously measured by ultrasound. The point of intersection of these 2 lines represents the ultrasound-determined location of the sciatic nerve, which was then compared with the midpoint of the nerve complex on MRI. RESULTS: The sciatic nerve was easily visualized by ultrasound in all 10 patients. MRI showed the division of the sciatic nerve in 9 out of 10 patients. Ultrasound was able to confirm this division in 7 patients. The mean distance between the MRI and ultrasound midpoint location of the sciatic nerve was 2.9 +/- 1.3 mm. CONCLUSIONS: The data presented here suggest that the specific ultrasound machine evaluated in this study can accurately localize the sciatic nerve in the popliteal fossa.     

Cervicothoracic vagal neurilemoma: Report of a case

We report herein the rare case of a 45-year-old man with a cervicomediastinal neurilemoma of the vagus nerve. The tumor was 160×40×35 mm in size and extended from the angle of the right mandible to the aortic arch. Despite this being the largest such tumor ever reported, the patient presented without any symptoms. Thus, although vagal neurilemoma is uncommon, it should nevertheless be included in the differential diagnosis of any asymptomatic mass along the vagus nerve. In the evaluation of such masses, magnetic resonance imaging can provide useful information regarding not only the location, but also the nature of the lesion.     

Sciatica in a patient with unusual peripheral nerve sheath tumors

BACKGROUND: Other causes such as peripheral schwannomas can mimic lumbar disk disease. CASE DESCRIPTION: We present an unusual case of multiple nerve sheath tumors in a patient with left radicular leg pain accompanied by a Tinel sign. Initial lumbar MR imaging revealed a mass in the right lumbar plexus, side opposite the patient's symptoms. Magnetic resonance neurography subsequently revealed a compressive mass of the sciatic nerve proximal to the popliteal fossa, histologically identified as a schwannoma. CONCLUSION: This case emphasizes the importance of continued investigation when the radiographic findings do not correlate with the patient's history in the presence of localizing signs on physical examination.     

Sciatic nerve block in the popliteal fossa: description of a new medial approach

PURPOSE: Sciatic nerve blocks through lateral approaches in the popliteal fossa have been proposed. We describe a new medial approach to the sciatic nerve at this level. METHODS: After an anatomical study on six cadavers, we performed sciatic nerve blocks on 20 patients. A 100-mm insulated needle and a nerve stimulator were used; 20 mL of lidocaine 1.5% with epinephrine were injected. RESULTS: Patients lied in the supine position, the thigh flexed, abducted and rotated externally (30 degrees in all directions). The leg was flexed at 130 degrees . In this position, above the adductor tubercle, a depression known as Jobert's fossa is palpated. Through this groove, a medial approach to the sciatic nerve at the level of the popliteal fossa is possible. The mean distance between the adductor tubercle and the puncture site is 6.18 cm (range 4-8 cm) and the mean distance between the skin and the sciatic nerve is 6.62 cm (range 4-9 cm). Mean time to perform the block was 100 sec (range 55-165 sec). Complete motor blockade was obtained after a mean time of 30 min (range 5-60 min) inside the common peroneal nerve area and 43 min (range 15-75 min) inside the tibial nerve area. Motor block was complete in 17 patients and sensory block in 18 patients. No vessel puncture was observed. CONCLUSION: We describe a new medial approach to the sciatic nerve in the popliteal fossa. More studies will be required to demonstrate the technique is effective and safe.     

Anatomical location of the bifurcation of the sciatic nerve in the posterior thigh in infants and children: a formula derived from MRI imaging for nerve localization

BACKGROUND AND OBJECTIVES: Sciatic nerve block is performed at the popliteal fossa for various surgical procedures in infants and children. The aim of this study is to review magnetic resonance imaging scans in children of various ages to assess the location of the division of the nerve in the posterior thigh. METHODS: After Institutional Review Board approval was obtained, measurements of the bifurcation of the sciatic nerve in the posterior thigh were recorded from magnetic resonance images that were previously obtained in children of various ages. Data were recorded in a database and parametric and nonparametric statistical analysis was performed. RESULTS: Measurements were recorded from 59 patient images. Using a linear regression model, we were able to arrive at a formula for determining the point of bifurcation of the sciatic nerve at the posterior thigh. The mathematical formula derived from the linear regression equation was: CONCLUSIONS: We speculate that this knowledge will assist practitioners who use nerve stimulation techniques for sciatic nerve blocks in children of all ages.     

Sciatic nerve varices.

OBJECTIVE(S): To describe patients presenting with sciatic nerve varices (SNV), presenting pitfalls in diagnosis and management. DESIGN: Case series. METHODS: Patients were investigated using duplex ultrasonography pre-operatively in three cases. Treatment was undertaken both by surgery and by foam sclerotherapy. RESULTS: Clinically, SNV appeared just below the popliteal skin crease, lateral to the small saphenous vein (SSV). In two cases SNV occurred alone, in two further cases SNV occurred in conjunction with varices from other sources. Symptoms of 'sciatic' pain were present in all. Foam sclerotherapy (1% Polidocanol) was undertaken in one case with a varix. Complete obliteration of the vein and resolution of all symptoms was achieved at the 1-month follow-up examination. Surgical management was used in the other cases. CONCLUSION: The sciatic nerve vein follows the fibular saphenous nerve (lying superficial to the fascia in the leg). This nerve arises from the common peroneal nerve (in the popliteal fossa), and is a major branch of the sciatic nerve. Varices of the associated vein appear to be the result of a dysplasia. This condition may be more common than is currently recognised.     

Diagnosis and treatment of piriformis syndrome

Piriformis syndrome remains a controversial diagnosis, despite its having first been described over 60 years ago. The controversy stems from several factors: variable and sometimes unclear cause, similarity to other more easily recognizable causes of sciatica, lack of consistent objective diagnostic findings, and relative rarity. Nevertheless, it is reasonable to infer that sciatic pain may be caused by compression anywhere along its length, from the spinal root level to the popliteal fossa, as is peripheral nerve entrapment elsewhere in the body. Pathologic changes at the greater sciatic notch may well be the source of sciatic pain and should be considered by the clinician. The diagnosis of piriformis syndrome remains one of exclusion, however, and in patients who present with sciatica, more common causes such as lumbar disease should be investigated and ruled out first. After excluding the most common causes of sciatica, physicians can use the criteria described here to investigate the possibility of piriformis syndrome. If properly diagnosed, it can often be treated effectively with either surgical or nonsurgical means.     

Ultrasound-guided popliteal block demonstrates an atypical motor response to nerve stimulation in 2 patients with diabetes mellitus

BACKGROUND AND OBJECTIVES: Nerve stimulation is a useful technique to identify peripheral nerves before blockade. We report 2 cases of the failure of nerve stimulation to accurately localize the sciatic nerve in patients with diabetes mellitus undergoing outpatient foot procedures. We also introduce a novel approach to performing a popliteal fossa block using ultrasound guidance. CASE REPORT: Ultrasound-guided popliteal fossa blocks were performed in 2 patients with diabetes mellitus. Both patients failed to develop an appropriate motor response or paresthesia to nerve stimulation. The needle positions were confirmed by ultrasound guidance and injections of local anesthesia were made uneventfully. Appropriate surgical anesthesia was established and the procedures were performed uneventfully. CONCLUSION: Ultrasound facilitated the accurate localization of the sciatic nerve in 2 patients with diabetes mellitus. Neither patient had a paresthesia or muscle twitch below 2.4 mA. There is theoretical concern that patients with underlying neuropathy, such as patients with diabetes mellitus, may have an altered response to either motor or sensory stimulation.     

Long term results of vein valve transplants placed in the popliteal vein for intractable post-phlebitic venous ulcers and pre-ulcer skin changes

Most patients with chronic venous ulceration or severe pre-ulcer damaged skin have incompetent popliteal valves and a high ambulant venous pressure (AVP). Competency can be restored by a vein valve transplant taken from the arm and placed in the popliteal fossa, with subjective and objective improvement. In this study 23 patients with post-phlebitic syndromes received 25 vein valve grafts as part of management. Seventeen patients had large recurrent ulcers after unsuccessful venous surgery: 6 patients had extensive pre-ulcer skin damage. Fifteen of 17 patients healed their ulcers, and all 6 patients with skin damage showed rapid improvement with relief of symptoms. Falls in the AVP, ranging from 10 to 40 mmHg occurred in 19 patients. All vein valve transplants were patent, after 18 months, but 5 grafted valves have evidence of venous reflux. These results suggest a functioning valve replacement in the popliteal fossa may lower the AVP sufficiently to heal intractable venous ulcers or severely damaged skin. Vein valve transplants function well long term, and the falls in the AVP are usually maintained. The popliteal fossa may be the ideal site since a component popliteal valve has been shown to limit adverse post-phlebitic changes.     

The effect of obesity on the anatomical relationship of the popliteal artery and tibial nerve in the proximal and distal popliteal fossa: relevance to popliteal sciatic nerve block and a traceback technique using the popliteal artery

Study ObjectiveTo determine the effect of body mass index (BMI) on the relationship of the popliteal artery to the sciatic and tibial nerves in the popliteal fossa.DesignProspective, observational study.SettingUniversity medical center.SubjectsOne hundred patients scheduled for magnetic resonance imaging scans of the knee.MeasurementsBMI was recorded and magnetic resonance imaging scans were assessed at 3 different measurement points along the femur for the distance and angle between the popliteal artery and tibial nerve, or sciatic nerve if the sciatic nerve had not bifurcated at the measurement point.Main ResultsAt the distal femur, the tibial nerve was a mean of 2.9 mm from the popliteal artery. The nerve was consistently posterior to the artery; however, it was variably located medial or lateral to the artery. At the 5- and 8-cm measurement points, the nerve was 10.0 and 16.1 mm (SD, 4.1 and 5.2 mm), and 31° and 44° (SD, 15° and 16°) lateral to the popliteal artery, respectively. Zero degree was defined as directly posterior to the artery. Increasing BMI was correlated with increasing distance between the nerve and the artery at the 5- and 8-cm measurement points (r= 0.36 P> |t| .000 and .45 P> |t| .002).ConclusionsAt 5 cm proximal to the distal femoral condyles, the popliteal artery is a reliable sonographic landmark to locate the tibial nerve due to the close proximity and consistent location of the nerve 1 cm posterolateral to the artery, with only a moderate effect of BMI.     

Ultrasound guidance for difficult lateral popliteal catheter insertion in a patient with peripheral vascular disease

OBJECTIVE: Interest in ultrasound-guided nerve block is increasing, but clinical utility still is being determined. We report a case in which ultrasound imaging aided nerve localization during popliteal block. CASE REPORT: We report a case in which failure of nerve stimulation to locate the sciatic nerve at the popliteal fossa in a patient with underlying neuropathy was overcome by ultrasound guidance, which allowed quick and easy catheter placement. After failure of the stimulation technique, ultrasound permitted us to observe advancement of the needle, placement of the catheter, and spread of local anesthetic around the nerve. CONCLUSION: Ultrasound guidance can facilitate lateral popliteal catheter insertion in patients in whom electrolocation has failed.