Nerve Ultrasonography as an Additive Tool to Clinical Examination and Electrodiagnostics in Sporadic Mononeuritis - Imaging is the Key

Neuropathy in ARSACS is demyelinating but without typical nerve enlargement in nerve ultrasound

BACKGROUND

To specify peripheral nerve affection in autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) by correlating high-resolution nerve ultrasound and nerve conduction studies.

METHODS

We assessed a cohort of 11 ARSACS patients with standardized nerve conduction studies and high-resolution ultrasound of peripheral nerves and compared nerve ultrasound findings to a healthy control group matched for age, sex, size and weight.

RESULTS

Mean age of patients was 39.0 (± 14.1) years and disease duration at assessment 30.6 (± 12.5) years. All patients presented with a spasticity, ataxia and peripheral neuropathy. Neuropathy appeared to be primarily demyelinating in 9/11 cases and was not classifiable in 2/11 cases due to not evocable potentials. Nerve ultrasound revealed a normal ultrasound pattern sum score (UPSS) in each ARSACS patient and no significant nerve enlargement compared to the control group.

CONCLUSIONS

Peripheral neuropathy in ARSACS showed primarily demyelinating rather than axonal characteristics and presented without nerve enlargement. As demyelinating neuropathies do commonly present enlarged nerves we recommend further genetic testing of the SACS gene in patients who present with this combination of demyelinating neuropathy without nerve enlargement. ARSACS cases that initially presented only with neuropathy without spasticity or ataxia and therefore were misdiagnosed as Charcot-Marie-Tooth disease are supporting this suggestion.

Neuromuscular Ultrasound in Polyneuropathies

Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging technique for assessing the peripheral nervous system. It can accurately depict changes in the nerves and muscles of individuals with neuromuscular conditions, and it is therefore a robust diagnostic tool for the assessment of individuals with polyneuropathies. This review will outline the typical ultrasonographic changes found in a wide variety of polyneuropathies. In general, demyelinating conditions result in greater nerve enlargement than axonal conditions, and acquired conditions result in more patchy nerve enlargement compared to diffuse nerve enlargement in hereditary conditions. This review is data-driven, but more nuanced anecdotal findings are also described. The overall goal of this paper is to provide clinicians with an accessible review of the ultrasonographic approaches and findings in a wide variety of polyneuropathies.

[Ultrasound of nerves of the lower extremities]

The ability to visualize the nerves of the lower extremities differs from that of the upper extremities in sonography because the soft tissue cover is significantly larger in some cases. Landmarks are also defined for the lower extremities, which enable precise visualization of the nerves. Nerves and muscles are to be understood as a functional unit. In addition to the clarification of nerve compression syndromes, polyneuropathies and nerve tumors, sonography is also used to visualize muscle atrophy.

[Ultrasound examination of nerves of the upper extremities]

The ultrasound examination of peripheral nerves has been further developed in recent years and is recognized as an independent discipline by the German Society of Ultrasound in Medicine (DEGUM). A systematic ultrasound examination of the musculoskeletal system is not limited to the joints, muscles and bones but should also include the examination of nerves and blood vessels. Therefore, in the practice of ultrasound examination every rheumatologist should have at least a basic knowledge of the ultrasound examination of the peripheral nerves. In this article the authors present a landmark-based concept in which the three large nerves of the upper extremities can be completely visualized from proximal to distal and evaluated.

Update: Muskel- und Nervensonografie

Die Sonografie von Nerven und Muskeln hat sich zu einem essenziellen Baustein der Diagnostik von Erkrankungen des peripheren Nervensystems und der Muskulatur entwickelt. Häufig gelingt eine umfassende Aufklärung einer Läsion erst durch die Kombination aus Kenntnissen über eine elektrophysiologisch nachgewiesene gestörte Funktion des Nervs und über sonografisch festgestellte morphologische Veränderungen des Nervs und des angrenzenden Gewebes.

Ultrasonography Findings in the Proximal Sciatic Nerve and Deep Gluteal Muscles in 29 Dogs With Suspected Sciatic Neuritis

The present study aimed to describe the ultrasonography technique and analyze the ultrasonographic findings of the proximal sciatic nerve and deep gluteal muscles in dogs with suspected sciatic neuritis. The records of 29 dogs that underwent musculoskeletal ultrasound of the sciatic nerve and deep gluteal muscles were retrospectively evaluated. Both right and left sides were evaluated. Abnormal findings were unilateral in 28/29 (97%) of the dogs. The muscles examined included the piriformis muscle, gemelli muscles, internal obturator muscle, and medial gluteal muscle. Data included signalment, purpose of the dog, orthopedic examination findings, lameness examination findings, other diagnostic imaging findings, and ultrasonography findings. Irregular margins of the sciatic nerve were recorded in 76% of the dogs. The diameter of the sciatic nerve on the affected limb was significantly larger than the nerve on the contralateral, unaffected side (p < 0.00001). The mean ± standard deviation (SD) of the sciatic nerve inner diameter between the unaffected and affected limbs was 15 ± 14.66%. The mean ± SD in sciatic nerve outer diameter was 12 ± 7.71%. Abnormal ultrasonographic findings in at least one of the examined muscles were found in 28/29 (97%) of the dogs and included changes in echogenicity in 28/29 (97%) of the dogs, loss of detail in muscle fiber pattern in 5/29 (17%) of the dogs, and impingement between the sciatic nerve and piriformis muscle in 6/29 (21%) of the dogs. The most common underlying diagnosis was lumbosacral stenosis in 9/29 (31%) of the dogs. The most common sport was agility for 21/29 (71%) of the dogs. Repetitive jumping may predispose to both lumbosacral disease, through dynamic compression, and changes within the piriformis muscle, due to overuse of the muscle leading to irritation to sciatic nerve. Ultrasonography is considered a safe and non-invasive diagnostic method to evaluate the sciatic nerve and deep gluteal muscles of dogs, and provides additional guidance for diagnostics and rehabilitation planning. This is the first study documenting ultrasonography findings in a case series of the sciatic nerve and deep gluteal muscles and their pathology in dogs.

High-Resolution Nerve Ultrasound Abnormalities in POEMS Syndrome-A Comparative Study

Background: High-resolution nerve ultrasound (HRUS) has been proven to be a valuable tool in the diagnosis of immune-mediated neuropathies, such as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes) is an important differential diagnosis of CIDP. Until now, there have been no studies that could identify specific HRUS abnormalities in POEMS syndrome patients. Thus, the aim of this study was to assess possible changes and compare findings with CIDP patients. Methods: We retrospectively analyzed HRUS findings in three POEMS syndrome and ten CIDP patients by evaluating cross-sectional nerve area (CSA), echogenicity and additionally calculating ultrasound pattern scores (UPSA, UPSB, UPSC and UPSS) and homogeneity scores (HS). Results: CIDP patients showed greater CSA enlargement and higher UPSS (median 14 vs. 11), UPSA (median 11.5 vs. 8) and HS (median 5 vs. 3) compared with POEMS syndrome patients. However, every POEMS syndrome patient illustrated enlarged nerves exceeding reference values, which were not restricted to entrapment sites. In CIDP and POEMS syndrome, heterogeneous enlargement patterns could be identified, such as inhomogeneous, homogeneous and regional nerve enlargement. HRUS in CIDP patients visualized both increased and decreased echointensity, while POEMS syndrome patients pictured hypoechoic nerves with hyperechoic intraneural connective tissue. Discussion: This is the first study to demonstrate HRUS abnormalities in POEMS syndrome outside of common entrapment sites. Although nerve enlargement was more prominent in CIDP, POEMS syndrome patients revealed distinct echogenicity patterns, which might aid in its differentiation from CIDP. Future studies should consider HRUS and its possible role in determining diagnosis, prognosis and treatment response in POEMS syndrome.

Nerve Ultrasound as Helpful Tool in Polyneuropathies

Background: Polyneuropathies (PNP) are a broad field of diseases affecting millions of people. While the symptoms presented are mostly similar, underlying causes are abundant. Thus, early identification of treatable causes is often difficult. Besides clinical data and basic laboratory findings, nerve conduction studies are crucial for etiological classification, yet limited. Besides Magnetic Resonance Imaging (MRI), high-resolution nerve ultrasound (HRUS) has become a noninvasive, fast, economic and available tool to help distinguish different types of nerve alterations in neuropathies. Methods: We aim to describe typical ultrasound findings in PNP and patterns of morphological changes in hereditary, immune-mediated, diabetic, metabolic and neurodegenerative PNP. Literature research was performed in PubMed using the terms ‘nerve ultrasound’, neuromuscular ultrasound, high-resolution nerve ultrasound, peripheral nerves, nerve enlargement, demyelinating, hereditary, polyneuropathies, hypertrophy’. Results: Plenty of studies over the past 20 years investigated the value of nerve ultrasound in different neuropathies. Next to nerve enlargement, patterns of nerve enlargement, echointensity, vascularization and elastography have been evaluated for diagnostic terms. Furthermore, different scores have been developed to distinguish different etiologies of PNP. Conclusions: Where morphological alterations of the nerves reflect underlying pathologies, early nerve ultrasound might enable a timely start of available treatment and also facilitate follow up of therapy success.

Peripheral Nerve Imaging Aids in the Diagnosis of Immune-Mediated Neuropathies-A Case Series

Background: Diagnosis of immune-mediated neuropathies and their differentiation from amyotrophic lateral sclerosis (ALS) can be challenging, especially at early disease stages. Accurate diagnosis is, however, important due to the different prognosis and available treatment options. We present one patient with a left-sided dorsal flexor paresis and initial suspicion of ALS and another with multifocal sensory deficits. In both, peripheral nerve imaging was the key for diagnosis. Methods: We performed high-resolution nerve ultrasound (HRUS) and 7T or 3T magnetic resonance neurography (MRN). Results: In both patients, HRUS revealed mild to severe, segmental or inhomogeneous, nerve enlargement at multiple sites, as well as an area increase of isolated fascicles. MRN depicted T2 hyperintense nerves with additional contrast-enhancement. Discussion: Peripheral nerve imaging was compatible with the respective diagnosis of an immune-mediated neuropathy, i.e., multifocal motor neuropathy (MMN) in patient 1 and multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) in patient 2. Peripheral nerve imaging, especially HRUS, should play an important role in the diagnostic work-up for immune-mediated neuropathies and their differentiation from ALS.

High-Resolution Nerve Ultrasound to Assess Nerve Echogenicity, Fascicular Count, and Cross-Sectional Area Using Semiautomated Analysis

BACKGROUND AND PURPOSE

Little is known about echogenicity and fascicular structure observed in high-resolution nerve ultrasound (HRUS) in both healthy subjects and patients with peripheral nerve disease. The aim of this study was to evaluate the reliability of echogenicity, fascicle count, and fascicle size analysis, to create standard values and compare these parameters to patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Median, ulnar, radial, tibial, and fibular nerve of 79 healthy subjects and patients were scanned by one examiner using HRUS. Image analysis regarding echogenicity, fascicle count, and fascicle cross-sectional area (CSA) was performed by two independent raters semiautomatically using ImageJ. Pearson correlation coefficient r reflected interrater reliability (IR), and intraclass correlation coefficient (ICC) determined intrarater reliability (IAR). Results of healthy subjects were compared to 20 patients with CIDP by analysis of variance.

RESULTS

IR was very good for echogenicity (r = .9) and good for fascicle count and size of the largest fascicle (r = .64/.56). IAR was very good for all three parameters (ICC = .9/.83/.74). Healthy subjects had a wide range of values. CIDP patients were in range of healthy subjects. Clinically progressive CIDP patients (defined as an increase in Overall Disability Sum Score by ≥1 point) had a lower fraction of black than healthy controls and stable CIDP patients (P < .001).

CONCLUSION

Semiautomated evaluation of echogenicity, fascicle count, and fascicle CSA is reliable. Cutoff values to differentiate between healthy persons and CIDP do not exist. Echogenicity is useful for detecting clinically progressive CIDP patients and should be used in clinical context or intraindividual course.

Role of high-resolution ultrasound in detection and monitoring of peripheral nerve tumor burden in neurofibromatosis in children

PURPOSE

Peripheral nerve sheath tumors are hallmark findings in neurofibromatosis types 1 and 2. With increasing size, they typically lead to neurological symptoms, and NF1 patients have a lifetime risk of 8-13% for developing malignant peripheral nerve sheath tumors. Medical imaging is therefore highly needed for early detection and exact localization of symptomatic or potentially malignant tumors. This review will give an overview of the ultrasound characteristics of peripheral nerve sheath tumors and findings in patients with neurofibromatosis types 1 and 2.

METHODS

A systematic search of electronic databases, reference lists, and unpublished literature was conducted including the keywords "schwannoma," "neurofibroma," "neurofibromatosis," "benign and malignant peripheral nerve sheath tumor."

RESULTS

The high-resolution allows a clear analysis of tumor echotexture, definition of margins, and the relation to the parent nerve. The use of color duplex/Doppler and contrast agent adds valuable information for the differentiation of benign and malignant tumors.

CONCLUSION

High-resolution ultrasound is a well-established, non-invasive, and easily repeatable first-line tool in diagnostic procedures of soft tissue tumors.