MR Imaging of Entrapment Neuropathies of the Lower Extremity

High-resolution Ultrasound of the Foot and Ankle

High-resolution ultrasound (US) can be used to assess soft tissue abnormalities in the foot and ankle. Compared to MRI, it has lower cost, is widely available, allows portability and dynamic assessment. US is an excellent method to evaluate foot and ankle tendon injuries, ligament tears, plantar fascia, peripheral nerves, and the different causes of metatarsalgia.

Rare entrapment neuropathies of the lower extremity: A narrative review

Lower limb entrapment neuropathies comprise a wide range of disorders, including less common conditions like tarsal tunnel syndrome, Morton neuroma, obturator nerve entrapment syndrome, superior gluteal nerve entrapment, and cluneal nerve entrapment syndrome. Despite being less prevalent, these syndromes are equally significant, presenting with symptoms such as pain, dysesthesia, muscular weakness, and distinct physical signs. Accurate diagnosis of these less common disorders is crucial for successful therapy and patient recovery, as they can sometimes be mistaken for lumbar plexopathies, radiculopathies, or musculotendinous diseases. This narrative review highlights the significance of identifying and diagnosing these particular neuropathies through a comprehensive assessment of the patient's medical history, detailed physical examination, and the use of electrodiagnostic and/or ultrasound investigations. When the diagnosis is uncertain, advanced imaging techniques like magnetic resonance neurography or magnetic resonance imaging are necessary to confirm the diagnosis. A positive diagnosis ensures prompt and targeted treatments, preventing further nerve impairments and muscle wasting. This article explores the epidemiology, anatomy, pathophysiology, etiology, clinical presentation, and electrodiagnostic interpretation of lower limb entrapment neuropathies, highlighting the importance of precise diagnosis in achieving favorable patient outcomes.

[Superficial peroneal nerve entrapment: ultrasound-guided hydrodissection. A case report]

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.

Feasibility of a promising pulsed electrostimulator for rapid motor recovery of foot drop

Purpose

Foot drop still occurs in clinical practice, including in our case. Treatments for foot drop vary based on its etiology and severity of symptoms. Hence, in intractable foot drop cases, an invasive surgical intervention is needed. Here, we introduce a special noninvasive technique to treat our patient's foot drop. In this approach, we applied STIMPOD NMS460 neuromuscular stimulator device (STIMPOD NMS460), which is a low-frequency (10 Hz or less) transcutaneous electrical nerve stimulation (TENS) device with a pulsed radiofrequency (PRF) component. We are eager to know how effective the device is in treating foot drop, and we compared it with two kinds of surgical interventions.

Materials and methods

The device settings are 5 Hz in frequency and 30mA in current amplitude. The device was applied on her left side at the L4 and L5 regions and at the fibular head. Each therapy session consists of individual 15-min treatments on these two body areas, and it only takes a total of 30 minutes. We recorded the change in ankle dorsiflexion degrees and muscle strength of our patient.

Results and Conclusions

To our surprise, our patient's actual treatment status through STIMPOD NMS460 showed more effective recovery and no specific side effects than surgical interventions in similar conditions. Besides, after a three-month intervention, her affected ankle dorsiflexion recovered to almost her usual status. The reason why this device has such an effect may be that it has the benefits of TENS and PRF. Besides, some studies have revealed the nerve-repair effect of TENS and PRF. In conclusion, we believe that this device is fairly promising and may be qualified to be used in other patients with foot drop.

Fibular (peroneal) neuropathy

Fibular neuropathy has variable presenting features depending on the site of the lesion. Anatomical features make it susceptible to injury from extrinsic factors, particularly the superficial location of the nerve at the head of the fibula. There are many mechanisms of compression or other traumatic injury of the fibular nerve, as well as entrapment and intrinsic nerve lesions. Intraneural ganglion cysts are increasingly recognized when the mechanism of neuropathy is not clear from the medical history. Electrodiagnostic testing can contribute to the localization as well as the characterization of the pathologic process affecting the nerve. When the mechanism of injury is unclear from the analysis of the presentation, imaging with MRI and ultrasound may identify nerve lesions that warrant surgical intervention. The differential diagnosis of foot drop includes fibular neuropathy and other neurologic conditions, which can be distinguished through clinical and electrodiagnostic assessment. Rehabilitation measures, including ankle splinting, are important to improve function and safety when foot drop is present. Fibular neuropathy is less frequently painful than many other nerve lesions, but when it is painful, neuropathic medication may be required. Failure to spontaneously recover or the detection of a mass lesion may require surgical management.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Diagnostic Approach to Lower Limb Entrapment Neuropathies: A Narrative Literature Review

Entrapment neuropathies of the lower limb are a misunderstood and underdiagnosed group of disorders, characterized by pain and dysesthesia, muscular weakness, and specific provoking movements on physical examination. The most frequent of these syndromes encountered in clinical practice are fibular nerve entrapment, proximal tibial neuropathy, sural nerve neuropathy, deep gluteal syndrome or sciatic nerve entrapment, and lateral femoral cutaneous nerve entrapment, also known as meralgia paresthetica. These are commonly mistaken for lumbar plexopathies, radiculopathies, and musculotendinous diseases, which appear even more frequently and have overlapping clinical presentations. A comprehensive anamnesis, physical examination, and electrodiagnostic studies should help clarify the diagnosis. If the diagnosis is still unclear or a secondary cause of entrapment is suspected, magnetic resonance neurography, MRI, or ultrasonography should be conducted to clarify the etiology, rule out other diseases, and confirm the diagnosis. The aim of this narrative review was to help clinicians gain familiarity with this disease, with an increase in diagnostic confidence, leading to early diagnosis of nerve damage and prevention of muscle atrophy. We reviewed the epidemiology, anatomy, pathophysiology, etiology, clinical presentation, and EDX technique and interpretation of the entrapment neuropathies of the lower limb, using articles published from 1970 to 2022 included in the Pubmed, MEDLINE, Cochrane Library, Google Scholar, EMBASE, Web of Science, and Scopus databases.

Nerve entrapment syndromes of the lower limb: a pictorial review

Peripheral nerves of the lower limb may become entrapped at various points during their anatomical course. While clinical assessment and nerve conduction studies are the mainstay of diagnosis, there are multiple imaging options, specifically ultrasound and magnetic resonance imaging (MRI), which offer important information about the potential cause and location of nerve entrapment that can help guide management. This article overviews the anatomical course of various lower limb nerves, including the sciatic nerve, tibial nerve, medial plantar nerve, lateral plantar nerve, digital nerves, common peroneal nerve, deep peroneal nerve, superficial peroneal nerve, sural nerve, obturator nerve, lateral femoral cutaneous nerve and femoral nerve. The common locations and causes of entrapments for each of the nerves are explained. Common ultrasound and MRI findings of nerve entrapments, direct and indirect, are described, and various examples of the more commonly observed cases of lower limb nerve entrapments are provided.Critical relevance statement This article describes the common sites of lower limb nerve entrapments and their imaging features. It equips radiologists with the knowledge needed to approach the assessment of entrapment neuropathies, which are a critically important cause of pain and functional impairment.Key points• Ultrasound and MRI are commonly used to investigate nerve entrapment syndromes.• Ultrasound findings include nerve hypo-echogenicity, calibre changes and the sonographic Tinel's sign.• MRI findings include increased nerve T2 signal, muscle atrophy and denervation oedema.• Imaging can reveal causative lesions, including scarring, masses and anatomical variants.

Magnetic resonance neurography techniques in the pediatric population

The use of magnetic resonance imaging (MRI) in the evaluation of the central extracranial nervous system, namely the brachial and lumbosacral plexuses, is well established and has been performed for many years. Only recently after numerous advances in MRI, has image quality been sufficient to properly visualize small structures, such as nerves in the extremities. Despite the advances, peripheral MR Neurography remains a complex and difficult examination to perform, especially in the pediatric patient population, in which the risk for motion artifact and compliance is always of concern. Thus, technical aspects of the MR imaging protocol must be flexible but robust, to balance image quality with scan time, in a patient population of varying sizes. An additional important step for reliably performing a successful MR Neurography examination is the non-technical pre-imaging preparation, which includes patient/family education and open communication with referring teams. This paper will discuss in detail the individual technical and non-technical/operational aspects of peripheral MR Neurography, to help guide in building a successful program in the pediatric population.

High-resolution Ultrasound of the Foot and Ankle

High-resolution ultrasound (US) can be used to assess soft tissue abnormalities in the foot and ankle. Compared to MRI, it has lower cost, is widely available, allows portability and dynamic assessment. US is an excellent method to evaluate foot and ankle tendon injuries, ligament tears, plantar fascia, peripheral nerves, and the different causes of metatarsalgia.

Neuropathy Score Reporting and Data System (NS-RADS): A Practical Review of MRI-Based Peripheral Neuropathy Assessment

The Neuropathy Score Reporting and Data System (NS-RADS) is a newly developed MR imaging-based classification that standardizes reporting and multidisciplinary communication for MR imaging diagnosis and follow-up of peripheral neuropathies. NS-RADS classification has shown to be accurate and reliable across different centers, readers' experience levels, and degrees of peripheral neuropathies, which include nerve injury, entrapment, neoplasm, diffuse neuropathy, post-interventional status, and temporal changes in muscle denervation. This article brings a practical review of NS-RADS classification, representative MR cases, and a step-by-step tutorial on how to approach this staging system. Readers can gain knowledge and apply it in their practice, aiming to standardize the communications between specialties and improve patient management.

Imaging of Anatomical Variants of the Lower Limb Nerves: Clinical and Preoperative Relevance

Anatomical variants of peripheral nerves of the lower limb are relatively frequent and vulnerable to injury if not considered by the surgeon. Surgical procedures or percutaneous injections are often performed without knowing the anatomical situation. In a patient with normal anatomy, these procedures are mostly performed smoothly without major nerve complications. But in the case of anatomical variants, surgery may be challenging as "new" anatomical prerequisites complicate the procedure. In this context, high-resolution ultrasonography as the first-line imaging modality to depict peripheral nerves, has become a helpful adjunct in the preoperative setting. It is crucial, on the one hand, to gain knowledge of anatomical nerve variants and, on the other hand, to depict the anatomical situation preoperatively, to minimize the risk of surgical trauma to a nerve and make surgeries safer.

Imaging of the Peripheral Nerves of the Lower Extremity

Continued advancements in magnetic resonance (MR) neurography and ultrasound have made both indispensable tools for the workup of peripheral neuropathy. Ultrasound provides high spatial resolution of superficial nerves, and techniques such as "sonopalpation" and dynamic maneuvers can improve accuracy. Superior soft tissue contrast, ability to evaluate both superficial and deep nerves with similar high resolution, and reliable characterization of denervation are strengths of MR neurography. Nevertheless, familiarity with normal anatomy, anatomic variants, and common sites of nerve entrapment is essential for radiologists to use both MR neurography and ultrasound effectively.

The value of magnetic resonance neurography in evaluation of sciatic neuropathy

Background

Sciatic neuropathy is one of the most common neuropathies of the lower extremities. One of the most common presentations of sciatic neuropathy is foot drop and may also be associated with several other clinical (sensory and/or motor) presentations. In recent years, magnetic resonance imaging (MRI) has established itself as an important tool for the study of peripheral nerves, especially after the development of protocols including sequences optimized for this purpose, referred to as magnetic resonance neurography (MRN), being used as noninvasive means of diagnosing peripheral nerve disease. Such high-resolution imaging protocols aimed to image the nerves at hip, thigh, knee, leg, ankle, and foot and can demonstrate traumatic or iatrogenic injury, tumor-like lesions, or entrapment of the nerves, causing a potential loss of motor and sensory function in the affected area. This study aimed to be familiar with MRI and MRN findings in patients with sciatic neuropathy.

Results

In this prospective study, thirty patients presented with clinical manifestations and/or electrophysiological studies having sciatic neuropathy and underwent MRI and MRN at a university Hospital from March 2021 to March 2022. In view of clinical presentation, muscle weakness (66.67%), numbness and tingling (60%), and sensory manifestation (60%) were the most prevalent presenting manifestation followed by back pain (43.33%), foot drop (33.33%), and urinary and bowel incontinence (23.33%). MRN and MRI results showed a strong correlation with the presenting symptoms of participants, in the form of increased sciatic nerve caliber in 23.33%, muscular atrophy in 13.33%, nerve root impingement in 26.67%, and lumbar spondylosis in 36.67%. MR neurography sequences gave additional findings to the conventional MRI in the form of increased nerve signal intensity in 53.33%, perineural edema in 50% of cases, neural structure disruption in 26.67%, muscular impend denervation in 16.67%, bone marrow edema in 30.33%, pseudo-meningocele in 13.33%, and nerve root avulsion in 3.33% with no correlated findings in MRI.

Conclusions

MRN is an additional accurate tool in the study of different sciatic nerve diseases and can also give detailed knowledge of the nerve anatomy, adding value to electrophysiological studies and conventional MRI.

An update on imaging of tarsal tunnel syndrome

Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the tibial nerve (TN) within the tarsal tunnel (TT) at the level of the tibio-talar and/or talo-calcaneal joints. Making a diagnosis of TTS can be challenging, especially when symptoms overlap with other conditions and electrophysiological studies lack specificity. Imaging, in particular MRI, can help identify causative factors in individuals with suspected TTS and help aid surgical management. In this article, we review the anatomy of the TT, the diagnosis of TTS, aetiological factors implicated in TTS and imaging findings, with an emphasis on MRI.

Dorsalis pedis artery thrombosis in an elite rugby player: an unusual cause of pedal claudication in a high-risk ankle

Vascular thrombosis in young elite athletes is uncommon, usually affecting calf veins and arteries beyond the knee joint. Arterial thrombosis, especially in the dorsalis pedis artery, is very rare without premature atherosclerosis or trauma. Its clinical presentation with progressive claudication of insidious onset is nonspecific and overlaps with the symptoms of deep peroneal nerve compression as a part of anterior ankle impingement, a more common entity in athletes. Ultrasound can evaluate pedal claudication in athletes differentiating vascular and neural causes expediting diagnosis, management and, in turn, return to play. Furthermore, imaging-Doppler ultrasound and MR angiography in particular-plays a vital role in the evaluation of potential aetiology and evolution (i.e., collateral development and recanalization) of the occluded vessel. We present a case of dorsalis pedis artery thrombosis with both MRI and ultrasound findings in a professional rugby player who had no systemic comorbidity, but numerous previous surgical interventions around the ankle joint in both the remote and recent past, putting the adjacent DPA at increased risk for developing thrombosis. In this high-risk ankle, the dorsalis pedis thrombosis may be iatrogenic or due to sports-related, arterial wall injury with superimposed thrombosis.

Magnetic Resonance Imaging Findings in Patients with Tarsal Tunnel Syndrome

Tarsal tunnel syndrome (TTS) is a common entrapment syndrome whose diagnosis can be difficult. We compared preoperative magnetic resonance imaging (MRI) and operative findings in 23 consecutive TTS patients (28 sides) whose mean age was 74.5 years. The 1.5T MRI sequence was 3D T2* fat suppression. We compared the MRI findings with surgical records and intraoperative videos to evaluate them. MRI- and surgical findings revealed that a ganglion was involved on one side (3.6%), and the other 27 sides were diagnosed with idiopathic TTS. MRI visualized the nerve compression point on 23 sides (82.1%) but failed to reveal details required for surgical planning. During surgery of the other five sides (17.9%), three involved varices, and on one side each, there was connective tissue entrapment or nerve compression due to small vascular branch strangulation. MRI studies were useful for nerve compression due to a mass lesion or idiopathic factors. Although MRI revealed the compression site, it failed to identify the specific involvement of varices and small vessel branches and the presence of connective tissue entrapment.

Imaging of Entrapment Neuropathies in the Ankle

Entrapment neuropathies of the ankle and foot pose a major diagnostic challenge and thus remain underdiagnosed. Recent advancements in imaging modalities, including magnetic resonance neurography (MRN), have resulted in considerable improvement in the anatomical localization and identification of pathologies leading to nerve entrapment. MRN supplements clinical examination and electrophysiologic studies in the diagnosis of neuropathies, aids in assessing disease severity, and helps formulate management strategies. A comprehensive understanding of the anatomy and imaging features of the ankle is essential to diagnose and manage entrapment neuropathies accurately. Advancements in imaging and their appropriate utilization will ultimately lead to better diagnoses and improved patient outcomes.

An Anatomic Study of the Lateral Dorsal Cutaneous Nerve Using 3-Tesla MRI: A Comparison to Cadaveric Data With Surgical Applications

BACKGROUND

The lateral dorsal cutaneous nerve (LDCN) and the anastomotic branch of the sural nerve (AB) are cutaneous sensory nerves at risk of iatrogenic injury during lateral foot surgery. This study is the first to use a large cohort of high-resolution magnetic resonance images (MRIs) of the ankle to better describe the course of these nerves in vivo in order to aid surgeons intraoperatively. Our study intends to build on the "high and inside" approach to the proximal 5MT by accounting for variations in course of the LDCN and AB.

METHODS

One hundred twenty-five 3-tesla (T) MRI studies of the ankle were analyzed. Three reviewers measured the distance from the LDCN and AB to landmarks including the most proximal aspect of the fifth metatarsal tuberosity (5MT) and the peroneus brevis tendon (PBT).

RESULTS

Mean vertical distance from the LDCN to the 5MT was 0.8 ± 0.2 cm. Presence of an AB was visualized in 59 of 125 studies (47.2%) and was found 2.2 ± 0.5 cm dorsal to the 5MT. The AB was found to become superior to PBT at a horizontal distance 1.9 ± 0.5 cm proximal to the 5MT. The LDCN was found superior to the PBT at its insertion onto the 5MT in approximately 10% (n = 12) of our studies. During these instances, the LDCN was located an average of 0.3 cm dorsal to the PBT.

CONCLUSION

Our proposed "safe zone" for the approach to the proximal 5MT remains superior to the LDCN and inferior to the AB and avoids crossing directly over either nerve in >95% of analyzed MRI studies. This incision begins 1.5 cm dorsal to the most proximal aspect of the 5MT and extends no more than 1 cm posteriorly. Careful dissection and identification of the LDCN and possible AB is necessary prior to further extension of incision.

LEVEL OF EVIDENCE

Level IV, case series.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

A problem-based approach in musculoskeletal ultrasonography: heel pain in adults

Musculoskeletal ultrasonography (US) has unique advantages, such as excellent spatial resolution for superficial structures, the capability for dynamic imaging, and the ability for direct correlation and provocation of symptoms. For these reasons, US is increasingly used to evaluate problems in small joints, such as the foot and ankle. However, it is almost impossible to evaluate every anatomic structure within a limited time. Therefore, US examinations can be faster and more efficient if radiologists know where to look and image patients with typical symptoms. In this review, common etiologies of heel pain are discussed in a problem-based manner. Knowing the common pain sources and being familiar with their US findings will help radiologists to perform accurate and effective US examinations.

Ultrasound-guided injections in pelvic entrapment neuropathies

Pelvic entrapment neuropathies represent a group of chronic pain syndromes that significantly impede the quality of life. Peripheral nerve entrapment occurs at specific anatomic locations. There are several causes of pelvic entrapment neuropathies, such as intrinsic nerve abnormality or inflammation with scarring of surrounding tissues, and surgical interventions in the abdomen, pelvis and the lower limbs. Entrapment neuropathies in the pelvic region are not widely recognized, and still tend to be underdiagnosed due to numerous differential diagnoses with overlapping symptoms. However, it is important that entrapment neuropathies are correctly diagnosed, as they can be successfully treated. The lateral femoral cutaneous nerve, ischiadic nerve, genitofemoral nerve, pudendal nerve, ilioinguinal nerve and obturator nerve are the nerves most frequently causing entrapment neuropathies in the pelvic region. Understanding the anatomy as well as nerve motor and sensory functions is essential in recognizing and locating nerve entrapment. The cornerstone of the diagnostic work-up is careful physical examination. Different imaging modalities play an important role in the diagnostic process. Ultrasound is a key modality in the diagnostic work-up of pelvic entraptment neuropathies, and its use has become increasingly widespread in therapeutic procedures. In the article, the authors describe the background of pelvic entrapment neuropathies with special focus on ultrasound-guided injections.

Clinics in diagnostic imaging (205). Baxter's neuropathy

A 48-year-old woman presented with chronic right heel pain and paraesthesia over the foot. Magnetic resonance imaging of the right foot demonstrated isolated atrophy of the abductor digiti minimi. A diagnosis of Baxter's neuropathy was made and the patient was managed successfully via surgical release. We describe the clinical and radiological features of Baxter's neuropathy and, with brief examples, outline other causes of chronic heel pain.

An MRI study of the tibial nerve in the ankle canal and its branches: a method of multiplanar reformation with 3D-FIESTA-C sequences

Background

The visualization of the tibial nerve and its branches in the ankle canal is helpful for the diagnosis of local lesions and compression, and it is also useful for clinical observation and surgical planning. The aim of this study was to investigate the feasibility of three-dimensional dual-excitation balanced steady-state free precession sequence (3D-FIESTA-C) multiplanar reformation (MPR) display of the tibial nerve and its branches in the ankle canal.

Methods

The subjects were 20 healthy volunteers (40 ankles), aged 22–50 years, with no history of ankle joint disease. The 3D-FIESTA-C sequence was used in the 3.0 T magnetic resonance equipment for imaging. During scanning, each foot was at an angle of 90° to the tibia. The tibial nerve of the ankle canal and its branches were displayed and measured at the same level through MPR.

Results

Most of the tibial nerve bifurcation points were located in the ankle canal (57.5%), few bifurcation points (42.5%) were located at the proximal end of the ankle canal, and none of them were found away from the distal end. The bifurcation between the medial plantar nerve and the lateral plantar nerve was on the line between the tip of the medial malleolus and the calcaneus, and it’s angle ranged between 6° and 35°. In MPR images, the display rates of both the medial calcaneal nerve and the subcalcaneal nerve were 100%, and the starting point of the subcalcaneal nerve was always at the distal end of the starting point of the medial calcaneal nerve. In 55% of cases, there were more than two medial calcaneal nerve innervations.

Conclusion

The 3D-FIESTA-C MPR can display the morphological features and positions of the tibial nerve and its branches and the bifurcation point’s projection position can be marked on the body surface. This method not only benefited the imaging diagnosis of the tibial nerve and branch-related lesions in the ankle canal, but it also provided a good imaging basis to plan a clinical operation of the ankle canal and avoid surgical injury.

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.

MRI appearance of jogger's foot

OBJECTIVE

To characterize the MRI findings present in patients with clinically proven or suspected jogger's foot.

MATERIALS AND METHODS

Ten years of medical charts in patients clinically suspected of having jogger's foot and who had MRI studies completed were identified utilizing a computer database search. Six study cases were identified. The MRI examinations of the study cases and an age- and gender-matched control group were reviewed in a blinded fashion by two musculoskeletal radiologists. Size and signal intensity of the medial plantar nerve were measured and characterized. The medial foot musculature was assessed for acute or chronic denervation changes.

RESULTS

The medial plantar nerve was found to have moderately increased T2 signal compared with normal skeletal muscle in 3/6 study group cases and markedly increased T2 signal in the remaining 3/6 cases. In all control cases, the nerve was reported to have T2 signal equal or minimally higher than normal skeletal muscle. The mean total size of the medial plantar nerve was significantly larger in the study group when compared with that in the control group at all measured locations (p < 0.04).

CONCLUSIONS

Abnormal thickness and T2 hyperintensity of the medial plantar nerve centered at the master knot of Henry are characteristic MRI findings in patients with jogger's foot when compared with control subjects. Muscular denervation changes may also be seen, most commonly in the flexor hallucis brevis muscle.

Recurrent position and innervation pattern of recurrent peroneal nerve: A cadaveric study

BACKGROUND

The recurrent peroneal nerve (RPN) branches from the common peroneal nerve or the deep peroneal nerve and it innervates to the lower patellar region. It has recently been reported that damage to the RPN causes pain in the lower patellar region; therefore, this study examined the recurrent position and the innervation pattern of the RPN.

METHODS

Cases of knee deformity or atrophy were excluded, and 50 legs (25 males and 25 females) of 34 cadavers (15 males and 19 females) were examined to assess the recurrent position and the innervation pattern of the RPN.

RESULTS

The recurrent position of the RPN was 27.9 ± 3.6 mm from the tip of the fibula. The RPN innervated to the patellar tendon in five of the 50 legs (10%), to the infrapatellar fat pad in 13 legs (26%), and to both the patellar tendon and the infrapatellar fat pad in 20 legs (40%), and to neither the patellar tendon nor the infrapatellar fat pad in 12 legs (24%). No significant sex differences were observed in the recurrent position and the innervation pattern of the RPN.

CONCLUSIONS

In all cases, the recurrent position of the RPN was almost fixed from the tip of the fibula. The RPN frequently innervated to the patellar tendon or the infrapatellar fat pad (76%) in both males and females. These findings would be useful in knee surgery to preserve the RPN or for the diagnosis of pain in the lower patellar region.

Treatment of "plantar fasciitis"/Plantar Heel Pain Syndrome with botulinum toxin - A novel injection paradigm pilot study

Randomized controlled trials over the last two decades, although promising with favorable results, have shown varied efficacy in treatment of "plantar fasciitis" with botulinum toxin injection¹. One reason may be due to conflating the variabilities of plantar heel conditions solely as plantar fasciitis. Plantar Heel Pain Syndrome can be of one or more etiologies and symptoms which refutes the mistaken tendency to categorize all plantar heel pain singularly as either plantar fasciitis or fasciosis. Recognizing that there is likely an interplay of inflammatory, degenerative, and neuropathic etiologic conditions of this often-difficult malady to treat, a novel injection paradigm of botulinum toxin is explored in the treatment of 4 distinct presentations of Plantar Heel Pain Syndrome with encouraging results. Botulinum toxin injection into two intrinsic foot muscles; Abductor Hallucis and Quadratus Plantae at their origins with electrical stimulation is presented as novel method to treat four distinct etiologies of Plantar Heel Pain Syndrome. This method of botulinum toxin injection resulted in significant prolonged improvement of patient function and pain reduction in four variations of Plantar Heel Pain Syndrome. A precise injection paradigm facilitated with direct intrinsic muscle stimulation of the Abductor Hallucis and Quadratus Plantae at their origins may prove to be effective in reducing the disabilities of Plantar Heel Pain Syndrome and its associated pain.

Decompression and Neurolysis of the Lateral Femoral Cutaneous Nerve in the Surgical Treatment of Meralgia Paresthetica and the Results

Meralgia paresthetica (MP), also known as Bernhardt–Roth syndrome, is a peripheral neuropathy of the primary sensory lateral femoral cutaneous nerve (LFCN). Its diagnosis is challenging, because it can mimic other clinical conditions particularly associated with upper lumbar spine or pelvis. Patients present with pain and paresthesia over the anterolateral thigh. Diagnosis is usually based on clinical examination and is supported by sensory nerve conduction (SNC) studies. The initial treatment is always conservative. In limited number of patients who are refractory to conservative managements, surgical treatment via decompression/neurolysis or neurectomy is concerned. There is still no consensus on which surgical technique is the best and the first choice. We retrospectively analyzed the surgical outcomes of 12 nonobese patients who underwent decompression/neurolysis between the years 2013 and 2018. Bilateral SNC studies were performed in all cases which supported the diagnosis. We applied conservative treatments for 3 months in addition to the treatments previously applied in other centers. Surgery was recommended for the patients who were refractory to these treatments. Preoperative and postoperative pain levels during follow-up visits were evaluated with visual analogue scale (VAS). A retrospective analysis was performed on preoperative and postoperative 6th month VAS scores. The mean preoperative VAS value was 8.75 ± 0.62 and the postoperative VAS value at the sixth month was 1.17 ± 0.72. A significant reduction in the pain was shown (p < 0.05). Our surgical results showed that decompression/neurolysis of the LFCN should be concerned as the primary surgical approach to avoid negative outcomes of resection surgeries.

Magnetic resonance imaging of the ankle and foot

This article reviews the magnetic resonance imaging (MRI) findings of the normal anatomy and various pathologic conditions of the ankle and foot commonly encountered in clinical practice. The spectrum of entities discussed includes osseous and osteochondral injuries, ligamentous injuries, common traumatic and degenerative tendon pathology, abnormalities of transverse tarsal joint (Chopart) and tarsometatarsal joint (Lisfranc) complexes, pathological conditions affecting capsuloligamentous structures of the great toe and lesser toes, as well as pedal infection, with a focus on diabetic osteomyelitis and neuropathic osteoarthropathy.

A Case of Intermittent Exercise-Induced Foot Drop in a Recreational Runner

Foot drop is a reduction in ankle dorsiflexion during the swing phase of gait. We report a case of a 51-year-old recreational runner and cyclist who presented with intermittent left foot drop initially triggered by running distances in excess of 10 km. The patient was investigated with magnetic resonance imaging (MRI) of the spine and leg, nerve conduction studies, electromyography, and compartment pressure testing, which were all normal. Surgical release of fascia, which was restricting the common peroneal (fibular) nerve, failed to resolve her symptoms. Subsequent brain MRI revealed demyelination. This case describes the unusual case of a recreational runner presenting with exercise-induced foot drop secondary to multiple sclerosis (MS). Motor fatigability is a common feature of MS, and this case highlights the need to remain cognizant of central and peripheral causes of exertional lower limb pathology, particularly in the absence of pain.

Ultrasound Imaging of Cutaneous Innervations of the Lower Extremity

Ultrasound (US) is commonly used to evaluate the cutaneous innervation of the lower extremity, owing to the following advantages: (1) US is a high-resolution soft tissue imaging modality; (2) it is feasible in patients who are deemed unsuitable to undergo magnetic resonance imaging; and (3) it enables dynamic and real-time imaging. The evaluation of cutaneous nerves requires accurate knowledge of the anatomy as well as technical details. We present a review of the US anatomy of the cutaneous nerves in the lower extremity in addition to a description of a few pathologic conditions.

Update in the evaluation of peripheral nerves by MRI, from morphological to functional neurography

Imaging studies of peripheral nerves have increased considerably in the last ten years. In addition to the classical and still valid study by ultrasound, new neurographic techniques developed from conventional morphological sequences (including 3D isotropic studies with fat suppression) are making it possible to assess different peripheral nerves and plexuses, including small sensory and/or motor branches, with great precision. Diffusion-weighted sequences and diffusion tensor imaging have opened a new horizon in neurographic studies. This new approach provides morphological and functional information about the internal structure and pathophysiology of the peripheral nerves and diseases that involve them. This update reviews the different MR neurography techniques available for the study of the peripheral nerves, with special emphasis on new sequences based on diffusion.

MR Neurography: Current Several Issues for Novice Radiologists

말초신경병증의 진단을 위해 MR neurography의 사용이 점차 증가하고 있다. 고대조도와 고해상도로 말초신경을 직접 영상화한 MR 영상을 MR neurography라고 하고, 지방억제 T2 강조영상과 확산강조영상이 흔히 사용되는 시퀀스이다. 작은 직경, 복잡한 해부학적 구조를 가진 말초신경을 합리적 시간 안에 영상화하기 위해서 최신의 isotropic 3차원 기법, 다양한 고속영상기법, post-processing 영상 기법 등이 사용된다. 이런 발전들로 인해 MR neurography가 유용하게 사용되지만 항상 적절한 MR neurography 영상을 얻을 수 있는 것은 아니다. 적절한 MR neurography 영상을 얻기 위해 영상의학과 의사가 고려해야 할 다음의 몇가지 쟁점들이 있다. 이에는 적절한 표준 프로토콜의 선책, 지방억제 기법의 선택, 해상도와 field of view와 slice thickness 간의 상호 관계의 이해, 적절한 post-processing 영상 기법의 적용, 2차원 영상획득 기법과 3차원 영상획득 기법의 장단점, 근위부 말초신경과 말단부 말초신경의 T2 대조도의 차이, 말초신경에 인접한 정맥이 MR neurography에 미치는 영향, 확산강조영상에서 기하학적 왜곡의 발생과 적절한 b value의 선택 등이다. 이런 쟁점들을 잘 이해하는 것이 경험이 적은 영상의학과 의사가 적절한 MR neurography 영상을 얻고, 말초신경병증을 정확히 평가하는 데 많은 도움이 될 것이다.

Ultrasound Imaging of Disorders of Small Nerves of the Extremities: Less Recognized Locations

Ultrasound is a well-proven imaging modality for showing peripheral nerve disorders and guiding perineural injections. The aim of this review is to focus on small peripheral nerve abnormalities, which are usually not recognized by sonologists. In fact, most of these small nerves have a tiny diameter (<2 mm), and their anatomy is less familiar. We describe the most common causes of small peripheral nerve disorders, providing an accurate description of their anatomic locations and relationships with adjacent structures; we also focus on technical hints that may help in their evaluation.

The peroneus longus muscle and tendon: a review of its anatomy and pathology

This article will review the anatomy and common pathologies affecting the peroneus longus muscle and tendon. The anatomy of the peroneus longus is complex and its long course can result in symptomatology referable to the lower leg, ankle, hindfoot, and plantar foot. Proximally, the peroneus longus muscle lies within the lateral compartment of the lower leg with its distal myotendinous junction arising just above the level of the ankle. The distal peroneus longus tendon has a long course and makes two sharp turns at the lateral ankle and hindfoot before inserting at the medial plantar foot. A spectrum of pathology can occur in these regions. At the lower leg, peroneus longus muscle injuries (e.g., denervation) along with retromalleolar tendon instability/subluxation will be discussed. More distally, along the lateral calcaneus and cuboid tunnel, peroneus longus tendinosis and tears, tenosynovitis, and painful os peroneum syndrome (POPS) will be covered. Pathology of the peroneus longus will be illustrated using clinical case examples along its entire length; these will help the radiologist understand and interpret common peroneus longus disorders.

Intra-neural ganglion cyst of the lateral dorsal cutaneous nerve: an uncommon cause of lateral ankle pain

INTRODUCTION

An intra-neural ganglion cyst of the lateral dorsal cutaneous branch of the sural nerve is rare, with only a few cases reported in the literature.

MATERIALS AND METHODS

We carried out a retrospective investigation of patients with an intraneural ganglion cyst of the lateral dorsal cutaneous nerve.

RESULTS

We present a case series of four patients with intra-neural ganglion cysts of the lateral dorsal cutaneous nerve, the distal continuation of the sural nerve at the lateral aspect of the foot.

CONCLUSION

Intra-neural ganglion cysts of the lateral dorsal cutaneous nerve are rare. They represent a relatively uncommon source of lateral ankle pain, which can easily be diagnosed with ultrasound (US) and magnetic resonance imaging and managed effectively with US-guided aspiration or surgical excision.

Partial anterior tunnel syndrome: a retrospective analysis of ultrasound findings in four surgically proven cases

We present the cases of four patients (two men and two women, mean age of 48.5 years) with surgically confirmed partial anterior tarsal syndrome, diagnosed by ultrasound. All patients reported pain in the dorsal aspect of the forefoot radiating to the first intermetatarsal space. Ultrasound showed compression of the medial branch of the deep fibular nerve by the extensor hallucis brevis tendon at the level of the Lisfranc joint, associated with a hypoechoic neuroma. The ultrasound allowed a correct diagnosis to be obtained, which was not evident from clinical examination or by standard radiographs (four patients) or MRI (three patients). Surgery confirmed the sonographic findings, and all patients showed complete recovery.

Pharmacological Attenuation of Electrical Effects in a Model of Compression Neuropathy

BACKGROUND

Peripheral nerve compression and entrapment can be debilitating. Using a validated animal model of peripheral nerve compression, we examined the utility of 2 drugs approved for other uses in humans, 4-aminopyridine (4-AP) and erythropoietin (EPO), as treatments for surgically induced ischemia and as adjuvants to surgical decompression.

METHODS

Peripheral nerve compression was induced in wild-type mice by placing an inert silicone sleeve around the sciatic nerve. Decompression surgery was performed at 6 weeks with mice receiving 4-AP, EPO, or saline solution either during and after compression or only after decompression. A nerve conduction study and morphometric analyses were performed to compare the extent of the injury and the efficacy of the therapies, and the findings were subjected to statistical analysis.

RESULTS

During peripheral nerve compression, there was a progressive decline in nerve conduction velocity compared with that in sham-treatment animals, in which nerve conduction velocity remained normal (∼55 m/s). Mice treated with 4-AP or EPO during the compression phase had significantly smaller declines in nerve conduction velocity and increased plateau nerve conduction velocities compared with untreated controls (animals that received saline solution). Histomorphometric analyses of newly decompressed nerves (i.e., nerves that underwent decompression on the day that the mouse was sacrificed) revealed that both treated groups had significantly greater proportions of large (>5-µm) axons than the untreated controls. Following surgical decompression, all animals recovered to a normal baseline nerve conduction velocity by day 15; however, treatment significantly accelerated improvement (in both the 4-AP and the EPO group), even when it was only started after decompression. Histomorphometric analyses at 7 and 15 days following surgical decompression revealed significantly increased myelin thickness and significantly greater proportions of large axons among the treated animals.

CONCLUSIONS

Both the 4-AP and the EPO-treated group demonstrated improvements in tissue architectural and electrodiagnostic measurements, both during and after peripheral nerve compression, compared with untreated mice.

CLINICAL RELEVANCE

Peripheral nerve decompression is one of the most commonly performed procedures in orthopaedic surgery. We believe that there is reason for some optimism about the translation of our findings to the clinical setting. Our findings in this murine model suggest that 4-AP and EPO may lessen the effects of nerve entrapment and that the use of these agents after decompression may speed and perhaps otherwise optimize recovery after surgery.

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.

Exercise-induced leg pain in athletes: diagnostic, assessment, and management strategies

The purpose of this review is to describe and critically evaluate current knowledge regarding diagnosis, assessment, and management of chronic overload leg injuries which are often non-specific and misleadingly referred to as 'shin splints'. We aimed to review clinical entities that come under the umbrella term 'Exercise-induced leg pain' (EILP) based on current literature and systematically searched the literature. Specifically, systematic reviews were included. Our analyses demonstrated that current knowledge on EILP is based on a low level of evidence. EILP has to be subdivided into those with pain from bone stress injuries, pain of osteo-fascial origin, pain of muscular origin, pain due to nerve compression and pain due to a temporary vascular compromise. The history is most important. Questions include the onset of symptoms, whether worse with activity, at rest or at night? What exacerbates it and what relieves it? Is the sleep disturbed? Investigations merely confirm the clinical diagnosis and/or differential diagnosis; they should not be solely relied upon. The mainstay of diagnosing bone stress injury is MRI scan. Treatment is based on unloading strategies. A standard for confirming chronic exertional compartment syndrome (CECS) is the dynamic intra-compartmental pressure study performed with specific exercises that provoke the symptoms. Surgery provides the best outcome. Medial tibial stress syndrome (MTSS) presents a challenge in both diagnosis and treatment especially where there is a substantial overlap of symptoms with deep posterior CECS. Conservative therapy should initially aim to correct functional, gait, and biomechanical overload factors. Surgery should be considered in recalcitrant cases. MRI and MR angiography are the primary investigative tools for functional popliteal artery entrapment syndrome and when confirmed, surgery provides the most satisfactory outcome. Nerve compression is induced by various factors, e.g., localized fascial entrapment, unstable proximal tibiofibular joint (intrinsic) or secondary by external compromise of the nerve, e.g., tight hosiery (extrinsic). Conservative is the treatment of choice. The localized fasciotomy is reserved for recalcitrant cases.

Unusual variant of distal biceps femoris muscle associated with common peroneal entrapment neuropathy: A cadaveric case report

RATIONALE

The anatomical variant of the distal biceps femoris muscle with regard to common peroneal nerve entrapment neuropathy (CPNe) was suggested through magnetic resonance images (MRI) study.

PATIENT CONCERNS

An unusual variant of distal biceps femoris muscle was observed in 78 years old male cadaver.

DIAGNOSES

The short head of biceps femoris muscle (SHBFM) was extended more distal and posteriorly.

INTERVENTION

The popliteal area was dissected at knee joint level in a cadaveric limb.

OUTCOMES

Common peroeal nerve (CPN) was situated within tunnel formed between the lateral head of the gastrocnemius muscle (LGCM) and the SHBFM. Also, the length of tunnel was 4.4 cm.

LESSONS

The case illustrated here, to the best of our knowledge, is the first one with cadaveric findings of variant of distal biceps femoris muscle associated with CPNe. The tunnel formed between the more posterior or distal extension of the SHBFM and the LGCM could be possible entrapment area of CPN, clinically.