Initial findings using high-resolution magnetic resonance imaging for visualisation of the sural nerve and surrounding anatomy in healthy volunteers at 7 Tesla.

BACKGROUND AND AIMS: Histopathological diagnosis is the gold standard in many acquired inflammatory, infiltrative and amyloid based peripheral nerve diseases and a sensory nerve biopsy of sural or superficial peroneal nerve is favoured where a biopsy is deemed necessary. The ability to determine nerve pathology by high-resolution imaging techniques resolving anatomy and imaging characteristics might improve diagnosis and obviate the need for biopsy in some. The sural nerve is anatomically variable and occasionally adjacent vessels can be sent for analysis in error. Knowing the exact position and relationships of the nerve prior to surgery could be clinically useful and thus reliably resolving nerve position has some utility. METHODS: 7T images of eight healthy volunteers' (HV) right ankle were acquired in a pilot study using a double-echo in steady-state sequence for high-resolution anatomy images. Magnetic Transfer Ratio images were acquired of the same area. Systematic scoring of the sural, tibial and deep peroneal nerve around the surgical landmark 7 cm from the lateral malleolus was performed (number of fascicles, area in voxels and mm2, diameter and location relative to nearby vessels and muscles). RESULTS: The sural and tibial nerves were visualised in the high-resolution double-echo in steady-state (DESS) image in all HV. The deep peroneal nerve was not always visualised at level of interest. The MTR values were tightly grouped except in the sural nerve where the nerve was not visualised in two HV. The sural nerve location was found to be variable (e.g., lateral or medial to, or crossing behind, or found positioned directly posterior to the saphenous vein). INTERPRETATION: High-resolution high-field images have excellent visualisation of the sural nerve and would give surgeons prior knowledge of the position before surgery. Basic imaging characteristics of the sural nerve can be acquired, but more detailed imaging characteristics are not easily evaluable in the very small sural and further developments and specific studies are required for any diagnostic utility at 7T.

Diagnostic accuracy of ultrasound and MR imaging in peroneal neuropathy: A prospective, single-center study.

INTRODUCTION/AIMS: Magnetic resonance imaging (MRI) findings in peroneal neuropathy are not well documented and the prognostic value of imaging remains uncertain. Upper limits of cross-sectional area (CSA) on ultrasound (US) have been established, but uncertainty regarding generalizability remains. We aimed to describe MRI findings of the peroneal nerve in patients and healthy controls and to compare these results to US findings and clinical characteristics. METHODS: We prospectively included patients with foot drop and electrodiagnostically confirmed peroneal neuropathy, and performed clinical follow-up, US and MRI of both peroneal nerves. We compared MRI findings to healthy controls. Two radiologists evaluated MRI features in an exploratory analysis after images were anonymized and randomized. RESULTS: Twenty-two patients and 38 healthy controls were included. Whereas significant increased MRI CSA values were documented in patients (mean CSA 20 mm2 vs. 13 mm2 in healthy controls), intra- and interobserver variability was substantial (variability of, respectively, 7 and 9 mm2 around the mean in 95% of repeated measurements). A pathological T2 hyperintense signal of the nerve was found in 52.6% of patients (50% interobserver agreement). Increased CSA measurements (MRI/US), pathological T2 hyperintensity of the nerve and muscle edema were not predictive for recovery. DISCUSSION: Imaging is recommended in all patients with peroneal neuropathy to exclude compressive intrinsic and extrinsic masses but we do not advise routine MRI for diagnosis or prediction of outcome in patients with peroneal neuropathy due to high observer variability. Further studies should aim at reducing MRI observer variability potentially by semi-automation.

High Resolution MRI Confirms Torsional Injury as Mechanism for Combined Ankle and Common Fibular (Peroneal) Nerve Injuries.

Common fibular nerve (CFN) injury due to ankle fracture is an underreported complication. The authors have proposed that torsional injury to the ankle can be translated along the interosseous membrane (IOM), producing tension on the CFN at the fibular neck. A 23-year-old woman presented to our clinic for left foot drop. Three months prior, the patient sustained a fall with left ankle inversion injury while running. She was diagnosed with a minor ankle fracture and placed in an orthopaedic boot. Unfortunately, her swelling worsened and one week later the patient was diagnosed with foot drop, which was further corroborated with EMG studies showing severe CFN injury localizing to the fibular neck. Because of the lack of recovery, she underwent decompression of the CFN. She experienced immediate symptomatic relief. High resolution imaging in this case supports our previous mechanism for indirect trauma to the ankle resulting in CFN injury. (Journal of Surgical Orthopaedic Advances 33(1):053-055, 2024).

[Superficial peroneal nerve entrapment: ultrasound-guided hydrodissection. A case report]. / Atrapamiento de nervio peroneo superficial: hidrodisección ecoguiada. A propósito de un caso.

Peripheral nerve entrapment is an underdiagnosed pathology when it is not the most common syndromes such as carpal tunnel syndrome or cubital tunnel syndrome. The symptomatic lesion of the superficial peroneal nerve (SPN) has a low incidence, being its diagnosis sometimes complex. It is based on a exhaustive physical examination and imaging tests such as ultrasound (US) or magnetic resonance imaging (RMI). Conservative treatment may sometimes not be sufficient, requiring surgical techniques in refractory cases. We present a patient diagnosed with superficial peroneal nerve entrapment by ultrasound and diagnostic nerve block that was subsequently resolved by hydrodissection technique at the level of the deep crural fascia tunnel. The results were satisfactory with a complete resolution of the clinical process since the application of this technique.

Ultrahigh-frequency ultrasound of fascicles in the common fibular, superficial fibular, and sural nerves.

INTRODUCTION/AIMS: While ultrasound assessment of cross-sectional area and echogenicity has gained popularity as a biomarker for various neuropathies, there is a scarcity of data regarding fascicle count and density in neuropathies or even healthy controls. The aim of this study was to determine whether fascicles within select lower limb nerves (common fibular, superficial fibular, and sural nerves) can be counted in healthy individuals using ultrahigh-frequency ultrasound (UHFUS). METHODS: Twenty healthy volunteers underwent sonographic examination of the common fibular, superficial fibular, and sural nerves on each lower limb using UHFUS with a 48 MHz linear transducer. Fascicle counts and density in each examined nerve were determined by a single rater. RESULTS: The mean fascicle number for each of the measured nerves included the following: common fibular nerve 9.85 (SD 2.29), superficial fibular nerve 5.35 (SD 1.59), and sural nerve 6.73 (SD 1.91). Multivariate linear regression analysis revealed a significant association between cross-sectional area and fascicle count for all three nerves. In addition, there was a significant association seen in the common fibular nerve between fascicle density and height, weight, and body mass index. Age and sex did not predict fascicle count or density (all p > .13). DISCUSSION: UHFUS enabled the identification and counting of fascicles and fascicle density in the common fibular, superficial fibular, and sural nerves. Knowledge about normal values and normal peripheral nerve architecture is needed in order to further understand and identify pathological changes that may occur within each nerve in different disease states.

Anterior Tarsal Tunnel Syndrome: Entrapment of the Articular Branch of Deep Peroneal Nerve: A Case Report.

CASE: A 28-year-old male patient who injured his ankle 2 years ago presented with unilateral ankle pain, tingling, and numbness for 1 year. Clinically, tenderness and positive Tinel sign were localized on anterior aspect of ankle. On exploration, deep peroneal nerve and mainly its articular branch were encased in fibrotic tissue. Decompression of both nerves resulted in symptomatic relief after surgery. CONCLUSION: High index of suspicion, a thorough medical history, meticulous clinical examination, complete knowledge of nerve anatomy, proper radiological studies, and careful surgical decompression are all necessary for the diagnosis and management of such atypical cases.

Pediatric Peroneal Nerve Palsy Secondary to Fibular Osteochondroma.

Peripheral nerve injuries due to mass effect from bony lesions can occur when the nerve exists in an anatomically constrained location, such as the common peroneal nerve at the fibular head which passes into the tight fascia of the lateral leg compartment. We report a case of a pediatric patient who developed a common peroneal nerve palsy secondary to an osteochondroma of the fibular head and describe the clinical evaluation, radiographic findings, and surgical approach. Rapid diagnosis and nerve decompression after the onset of symptoms restored full motor function at the 8-month postoperative mark.

Optimizing the technique for eliciting antidromic sural and superficial fibular sensory nerve action potentials.

INTRODUCTION/AIMS: Lower limb sensory nerve action potentials are an important component of nerve conduction studies. Most testing of the sural and superficial fibular nerves involves antidromic techniques above the ankle, which result in a falsely unobtainable response in 2%-6% of healthy people. Cadaver, surgical, and more recent ultrasound series suggest this may relate to the site of fascia penetration of the nerve, and it is hypothesized that a modified technique may be more likely to produce reliable responses and reduce false-negative errors. METHODS: This article evaluates a variety of recording distances for both nerves in 100 healthy controls, including varying recording electrode positions and techniques, to provide the optimal electrodiagnostic information in healthy control subjects. RESULTS: Shorter stimulation distances produce higher-amplitude responses but become confounded by increasing stimulation artifact at very short distances, with the best balance found at around 10 cm. In both sural and superficial fibular nerves, amplitude increases by approximately 10%/cm compared with the standard 14 cm distance. The Daube superficial fibular technique produced a higher amplitude than the Izzo Intermediate technique (by 22.46%, p < .001). The calculated upper limit of normal for side-to-side variation in amplitude was around 50% in the sural nerve but over 70% in the superficial fibular nerve. DISCUSSION: It is proposed that the 10 cm recording distance for both nerves is optimal, with minimal false-negatives and a higher amplitude elicited than with existing techniques.

Blind Versus Ultrasound-Guided Low-Volume Perineural Injection of Tibial and Fibular Nerves in Equine Cadaver Limbs.

Techniques for local anesthesia of the tibial (TN) and superficial and deep fibular nerves (FNs) in horses are well established. Ultrasound-guided perineural blocks can identify the nerve location, reduce the anesthetic volume needed and avoid needle misplacement. The aim of this research was to compare the success of blind perineural injection technique (BLIND) to ultrasound-guided technique (USG). Fifteen equine cadaver hindlimbs were divided into two groups. Perineural injection of the TN and FNs was performed using a mixed solution of radiopaque contrast, saline and food dye. BLIND (n = 8) used 15 mL for the TN and 10 mL for each fibular nerve. USG (n = 7) used 3 mL for the TN and 1.5 mL for each fibular nerve. The limbs were radiographed immediately after injections and sectioned transversally to evaluate the diffusion and presence of the injectate adjacent to the TN and FNs. The presence of dye immediately adjacent to the nerves was considered a successful perineural injection. No statistically significant difference was observed between groups for success. Distal diffusion of injectate following perineural injection of the TN was significantly less for USG compared to BLIND. Proximal, distal and medial diffusion of injectate following perineural injection of FNs was significantly less for USG compared to BLIND. Low-volume USG results in less diffusion but similar success compared to BLIND leaving it up to veterinarian preference when selecting a technique.

Can MR neurography of the common peroneal nerve predict a residual motor deficit in patients with foot drop?

OBJECTIVE: To determine if MR neurography of the common peroneal nerve (CPN) predicts a residual motor deficit at 12-month clinical follow-up in patients presenting with foot drop. MATERIALS AND METHODS: A retrospective search for MR neurography cases evaluating the CPN at the knee was performed. Patients were included if they had electrodiagnostic testing (EDX) within 3 months of imaging, ankle and/or forefoot dorsiflexion weakness at presentation, and at least 12-month follow-up. Two radiologists individually evaluated nerve size (enlarged/normal), nerve signal (T2 hyperintense/normal), muscle signal (T2 hyperintense/normal), muscle bulk (normal/Goutallier 1/Goutallier > 1), and nerve and muscle enhancement. Discrepancies were resolved via consensus review. Multivariable logistical regression was used to evaluate for association between each imaging finding and a residual motor deficit at 12-month follow-up. RESULTS: Twenty-three 3 T MRIs in 22 patients (1 bilateral, mean age 52 years, 16 male) met inclusion criteria. Eighteen cases demonstrated common peroneal neuropathy on EDX, and median duration of symptoms was 5 months. Six cases demonstrated a residual motor deficit at 12-month follow-up. Fourteen cases underwent CPN decompression (1 bilateral) within 1 year of presentation. Three cases demonstrated Goutallier > 1 anterior compartment muscle bulk. Multivariable logistical regression did not show a statistically significant association between any of the imaging findings and a residual motor deficit at 12-month follow-up. CONCLUSION: MR neurography did not predict a residual motor deficit at 12-month follow-up in patients presenting with foot drop, though few patients demonstrated muscle atrophy in this study.

Preoperative Imaging of Intraneural Ganglion Cysts: A Critical Systematic Analysis of the World Literature.

BACKGROUND: Advancements in imaging and an understanding of the pathomechanism for intraneural ganglion cyst formation have led to increased awareness and recognition of this lesion. However, the precise role of imaging has been advocated for but not formally evaluated. METHODS: We performed a systematic review of the world literature to study the frequency of imaging used to diagnose intraneural ganglion cysts at different sites and compared trends in identifying joint connections. RESULTS: We identified 941 cases of intraneural ganglion cysts, of which 673 had published imaging. Magnetic resonance imaging (MRI, n = 527) and ultrasonography (US, n = 123) were the most commonly reported. They occurred most frequently in the common peroneal nerve (n = 570), followed by the ulnar nerve at the elbow (n = 88), and the tibial nerve at the ankle (n = 58). A joint connection was identified in 375 cases (48%), with 62% of MRIs showing a joint connection, followed by 16% on US, and 6% on computed tomography (CT). MRI was statistically more likely to identify a joint connection than was US (P < 0.01). In the last decade, joint connections have been identified with increasing frequency using preoperative imaging, with up to 75% of cases reporting joint connections. CONCLUSIONS: Preoperative imaging plays an important role in establishing the diagnosis of intraneural ganglion cyst as well as treatment planning. Imaging has proved superior to the sole reliance of operative exposure to identify a joint connection, which is necessary to treat the underlying disease. Failure to identify cyst connections on imaging can result in an inability to truly address the underlying pathoanatomy at the time of definitive surgery, leading to a risk for clinical recurrence. Therefore, management should be guided by an intersection between new knowledge presented in the literature, clinical expertise, and surgeon experience.

Low Intensity Focused Ultrasound Increases Duration of Anti-Nociceptive Responses in Female Common Peroneal Nerve Injury Rats.

OBJECTIVE: Chronic pain affects 7%-10% of Americans, occurs more frequently and severely in females, and available treatments have been shown to have less efficacy in female patients. Preclinical models addressing sex-specific treatment differences in the treatment of chronic pain have been limited. Here we examine the sex-specific effects of low intensity focused ultrasound (liFUS) in a modified sciatic nerve injury (SNI) model. MATERIALS AND METHODS: A modified SNI performed by ligating the common peroneal nerve (CPN) was used to measure sensory, behavioral pain responses, and nerve conduction studies in female and male rats, following liFUS of the L5 dorsal root ganglion. RESULTS: Using the same dose of liFUS in females and males of the same weight, CPN latency immediately after treatment was increased for 50 min in females compared to 25 min in males (p < 0.001). Improvements in mechanical pain thresholds after liFUS lasted significantly longer in females (seven days; p < 0.05) compared to males (three days; p < 0.05). In females, there was a significant improvement in depression-like behavior as a result of liFUS (N = 5; p < 0.01); however, because males never developed depression-like behavior there was no change after liFUS treatment. CONCLUSIONS: Neuromodulation with liFUS has a greater effect in female rats on CPN latency, mechanical allodynia duration, and depression-like behavior. In order to customize neuromodulatory techniques for different patient phenotypes, it is essential to understand how they may alter sex-specific pathophysiologies.

The Risk of Iatrogenic Peroneal Nerve Injury in Lateral Meniscal Repair and Safe Zone to Minimize the Risk Based on Actual Arthroscopic Position: An MRI Study.

BACKGROUND: Lateral meniscal repair using an all-inside meniscal repair device involves a risk of iatrogenic peroneal nerve injury. To our knowledge, there have been no previous studies evaluating the risk of injury with the knee in the standard operational figure-of-4 position with joint dilatation in arthroscopic lateral meniscal repair. PURPOSE: To evaluate and compare the risk of peroneal nerve injury and establish the safe and danger zones in repairing the lateral meniscus through the anteromedial, anterolateral, or transpatellar portal in relation to the medial and lateral borders of the popliteal tendon (PT). STUDY DESIGN: Descriptive laboratory study. METHODS: Using axial magnetic resonance imaging (MRI) studies of knees in the figure-of-4 position with joint fluid dilatation at the level of the lateral meniscus, we drew direct lines to simulate a straight all-inside meniscal repair device deployed from the anteromedial, anterolateral, and transpatellar portals to the medial and lateral borders of the PT. If the line passed through or touched the peroneal nerve, a risk of iatrogenic peroneal nerve injury was noted, and measurements were made to determine the safe and danger zones for peroneal nerve injury in relation to the medial or lateral border of the PT. RESULTS: Axial MRI images of 29 adult patients were reviewed. Repairing the lateral meniscus through the anteromedial portal in relation to the lateral border of the PT and through the anterolateral portal in relation to the medial border of the PT had a 0% risk of peroneal nerve injury. The "safe zone" in relation to the medial border of the PT through the anterolateral portal was between the medial border of the PT and 9.62 ± 4.60 mm medially from the same border. CONCLUSION: It is safe to repair the body of the lateral meniscus through the anteromedial portal in the area lateral to the lateral border of the PT or through the anterolateral portal in the area medial to the medial border of the PT. CLINICAL RELEVANCE: There is a risk of iatrogenic peroneal nerve injury during lateral meniscal repair. Thus, we recommend repairing the lateral meniscal tissue through the anteromedial portal in the area lateral to the lateral border of the PT and using the anterolateral portal in the area medial to the medial border of the PT, as neither of these approaches resulted in peroneal nerve injury. Additionally, the surgeon can decrease this risk by repairing the meniscal tissue using the all-inside meniscal device in the safe zone area.

Ultrasound-guided hydrodissection of the superficial peroneal nerve for chronic neuropathic pain: a war veteran's story.

Aim: This case report presents the application of ultrasound-guided hydrodissection of the superficial peroneal nerve to treat chronic refractory neuropathic pain, rated by the patient with an average intensity of 6/10 on the numerical rating scale. Materials & methods: Under ultrasound guidance, the nerve was identified compressed by a herniation of the peroneus brevis. An in-plane hydrodissection was performed using a solution of 10 ml of ropivacaine and methylprednisolone until the epineurium was entirely separated from the surrounding tissue. Results: At the 2-month follow-up, the patient reported a decrease of pain, which he rated a 2/10 on the numerical rating scale. At this point, night-time episodes of moderate pain persisted. The procedure was repeated and at the 6-month follow-up, the patient remained pain free. Conclusion: This case report suggests that consecutive ultrasound-guided hydrodissection techniques might be a valuable option in the treatment of superficial peroneal nerve entrapment neuropathy.

Peripheral neuropathic pain is a debilitating pain condition. Management can be challenging and clinicians often rely on oral medications and surgical options. This case report presents the treatment of a case of longstanding, moderate-to-severe superficial peroneal nerve entrapment neuropathy due to a grenade explosion, with consecutive nerve hydrodissection using a solution containing an anesthetic and a corticosteroid. Immediately after the second procedure and at the 6-month follow-up the patient reported near-total relief.

Shear wave elastography of the common fibular nerve at the fibular head.

ABSTRACT: The aim of this work is to study the sonoelastographic features of the common fibular nerve in healthy adult subjects.This is an observational cross-sectional study. Shear wave elastography was used to evaluate the common fibular nerve. Crosssectional area and stiffness were measured in kilopascal (kPa) and meters/second (m/s).The study included 82 common fibular nerves in 41 healthy adult subjects. The mean cross-sectional area of the common fibular nerve at the fibular head was 8.7 mm2. Positive correlation was noted between stiffness measurements between short and long axes by both methods. The mean stiffness of the common fibular nerve in the short axis was 22.5 kPa, and in the long axis (LA) was 35.4 kPa. Positive correlation was noted between height and stiffness measured by both methods in both axes by kPa. In m/s, the mean stiffness of the common fibular in the short axis was 2.6 m/s, and while in the LA was 3.4 m/s. Height showed positive correlation with both axes for stiff measurements in m\s. Weight showed positive correlation with stiffness measurements by m/s in the LA.The results obtained in our study could be a reference point for evaluating stiffness of the common fibular nerve in research involving different pathologies.

Matched-Pair Analysis of Magnetic Resonance Images for Location of the Common Peroneal Nerve in Valgus Knees: Comparison with the Varus Knees.

This study aimed to assess the distance and angular location of the common peroneal nerve (CPN) on axial magnetic resonance imaging (MRI) in the valgus knees and compare the measurements with those obtained from the control group. We compared the location of the CPN according to the type of alignment by performing a subgroup analysis. From January 2009 to December 2019, we identified 41 knees with preoperative MRI in patients who underwent total knee arthroplasty (TKA) for valgus deformity (valgus group). We performed one-to-two matched-pair analysis to a cohort of patients who underwent MRI but were not candidates for TKA (control group), according to sex and age. The valgus group was classified according to the grading system reported by Ranawat et al, and the control group was also subdivided according to the hip-knee-ankle (HKA) angle obtained from lower extremity scanography: neutral (-3 to +3 degrees from the neutral mechanical axis), valgus (> +3 degrees), and varus alignment (< -3 degrees). Distance between the CPN and posterolateral cortex of the tibia at the knee joint (distance J) and tibial cut level (distance C) were measured. Angle of the CPN from the central anteroposterior axis of the tibia (angle α) was measured. We compared the measurements between the groups. Distance J was significantly closer in the valgus group (p < 0.001), whereas angle α was significantly smaller in the valgus group (p < 0.001). However, no significant differences were found in the subgroup analysis. Moreover, a significant correlation was found between distance J and the HKA angle (p < 0.001). The location of the CPN in the valgus knees was closer to the posterolateral cortex of the tibia at the joint level and showed a smaller angle than that in the other aligned knees. We recommend that lateral soft tissue release for valgus knees should not be performed at the joint line. The results of this study suggest that this would be less safe than a release performed at the level of the proximal tibial bone resection.