Ultrasound versus MRI in common fibular neuropathy

Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

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.

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.

An Update on Peroneal Nerve Entrapment and Neuropathy

Peroneal neuropathy is the most common compressive neuropathy of the lower extremity. It should be included in the differential diagnosis for patients presenting with foot drop, the pain of the lower extremity, or numbness of the lower extremity. Symptoms of peroneal neuropathy may occur due to compression of the common peroneal nerve (CPN), superficial peroneal nerve (SPN), or deep peroneal nerve (DPN), each with different clinical presentations. The CPN is most commonly compressed by the bony prominence of the fibula, the SPN most commonly entrapped as it exits the lateral compartment of the leg, and the DPN as it crosses underneath the extensor retinaculum. Accurate and timely diagnosis of any peroneal neuropathy is important to avoid progression of nerve injury and permanent nerve damage. The diagnosis is often made with physical exam findings of decreased strength, altered sensation, and gait abnormalities. Motor nerve conduction studies, electromyography studies, and diagnostic nerve blocks can also assist in diagnosis and prognosis. First-line treatments include removing anything that may be causing external compression, providing stability to unstable joints, and reducing inflammation. Although many peroneal nerve entrapments will resolve with observation and activity modification, surgical treatment is often required when entrapment is refractory to these conservative management strategies. Recently, additional options including microsurgical decompression and percutaneous peripheral nerve stimulation have been reported; however, large studies reporting outcomes are lacking.

Evidence in peroneal nerve entrapment: A scoping review

BACKGROUND AND PURPOSE

Daily management of patients with foot drop due to peroneal nerve entrapment varies between a purely conservative treatment and early surgery, with no high-quality evidence to guide current practice. Electrodiagnostic (EDX) prognostic features and the value of imaging in establishing and supplementing the diagnosis have not been clearly established.

METHODS

We performed a literature search in the online databases MEDLINE, Embase, and the Cochrane Library. Of the 42 unique articles meeting the eligibility criteria, 10 discussed diagnostic performance of imaging, 11 reported EDX limits for abnormal values and/or the value of EDX in prognostication, and 26 focused on treatment outcome.

RESULTS

Studies report high sensitivity and specificity of both ultrasound (varying respectively from 47.1% to 91% and from 53% to 100%) and magnetic resonance imaging (MRI; varying respectively from 31% to 100% and from 73% to 100%). One comparative trial favoured ultrasound over MRI. Variable criteria for a conduction block (>20%-≥50) were reported. A motor conduction block and any baseline compound motor action potential response were identified as predictors of good outcome. Based predominantly on case series, the percentage of patients with good outcome ranged 0%-100% after conservative treatment and 40%-100% after neurolysis. No study compared both treatments.

CONCLUSIONS

Ultrasound and MRI have good accuracy, and introducing imaging in the standard diagnostic workup should be considered. Further research should focus on the role of EDX in prognostication. No recommendation on the optimal treatment strategy of peroneal nerve entrapment can be made, warranting future randomized controlled trials.

Techniques for Imaging Vascular Supply of Peripheral Nerves

Few studies have been developed to map the vascular structures feeding peripheral nerves, with the majority using cadaveric models and inadequate sample sizes. Preliminary evidence, while limited, indicates that the mapping of these vessels may allow or preclude certain procedures in nerve reconstruction due to the location of essential arterial inflow to the vasa nervorum. This review evaluates the evidence regarding historical, current, and emerging techniques for visualizing these vascular structures in vivo and considers their potential application in peripheral nerve vasculature.

Lower extremity entrapment neuropathies

Entrapment neuropathies are frequently encountered by rheumatologists, not only because they are common but also because of their association with certain rheumatological and systemic disorders. Recognizing entrapment neuropathy early can help avoid progressive neurological deficits, as well as facilitate appropriate treatment measures, which can effectively minimize a patient's symptoms. Entrapment neuropathies may be distinguished from other musculoskeletal causes of lower extremity pain by identifying characteristic patterns of weakness and/or sensory loss, so a focused bedside neurological examination is key for diagnosis. In this chapter, we review the most common entrapment neuropathies that occur in the lower extremities, review the relevant neuroanatomy, outline a diagnostic approach to distinguish them from other mimics, and highlight appropriate management options.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Imaging of Damaged Nerves

Nerve imaging is an important component in the assessment of patients presenting with suspected peripheral nerve pathology. Although magnetic resonance neurography and ultrasound are the most commonly utilized techniques, several promising new modalities are on the horizon. Nerve imaging is useful in localizing the nerve injury, determining the severity, providing prognostic information, helping establish the diagnosis, and helping guide surgical decision making. The focus of this article is imaging of damaged nerves, focusing on nerve injuries and entrapment neuropathies.

Indications for neuromuscular ultrasound: Expert opinion and review of the literature

Over the last two decades, dozens of applications have emerged for ultrasonography in neuromuscular disorders. We wanted to measure its impact on practice in laboratories where the technique is in frequent use. After identifying experts in neuromuscular ultrasound and electrodiagnosis, we assessed their use of ultrasonography for different indications and their expectations for its future evolution. We then identified the earliest papers to provide convincing evidence of the utility of ultrasound for particular indications and analyzed the relationship of their date of publication with expert usage. We found that experts use ultrasonography often for inflammatory, hereditary, traumatic, compressive and neoplastic neuropathies, and somewhat less often for neuronopathies and myopathies. Usage significantly correlated with the timing of key publications in the field. We review these findings and the extensive evidence supporting the value of neuromuscular ultrasound. Advancement of the field of clinical neurophysiology depends on widespread translation of these findings.