Nerve Entrapment

Entrapment and compressive neuropathies are frequent clinical conditions occurring about the elbow. In most instances clinical and electromyograhic evaluation are adequate for patient management, but in some cases further evaluation with imaging techniques is required. Magnetic resonance imaging (MRI) has been shown to be useful in the evaluation of these conditions, especially to detect space occupying lesions. In this article, compressive neuropathies involving the ulnar, median, and radial nerves are discussed, with emphasis on the normal anatomy and the MRI depiction of pathologic findings.     

Neuropathies of the foot and ankle in athletes

Although neuropathies in the athlete's foot and ankle are uncommon, they are often underdiagnosed. This is primarily due to the complex interplay of factors that are required for their presentation. The most frequently encountered entrapment syndromes (in decreasing order) involve the interdigital nerves, first branch of the lateral plantar nerve, isolated medial or lateral plantar nerves, posterior tibial nerve, deep peroneal nerve, superficial peroneal nerve, sural nerve, and saphenous nerve. A thorough knowledge of peripheral nerve anatomy is essential in establishing the diagnosis. Roentgenograms may reveal bony abnormalities that are the diagnosis. Roentgenograms may reveal bony abnormalities that are commonly contributory. Electrodiagnostic tests may be normal because these dynamic syndromes often resolve at rest. In most cases, correction of underlying etiologies combined with rest, NSAIDs, and occasionally injections will allow resolution of the syndrome. Recalcitrant cases may require surgical decompression, which frequently provides satisfactory results.     

Imaging of neuropathies about the hip

Neuropathies about the hip may be cause of chronic pain and disability. In most cases, these conditions derive from mechanical or dynamic compression of a segment of a nerve within a narrow osteofibrous tunnel, an opening in a fibrous structure, or a passageway close to a ligament or a muscle. Although the evaluation of nerve disorders primarily relies on neurological examination and electrophysiology, diagnostic imaging is currently used as a complement to help define the site and aetiology of nerve compression and exclude other disease possibly underlying the patient’ symptoms. Diagnosis of entrapment neuropathies about the hip with US and MR imaging requires an in-depth knowledge of the normal imaging anatomy and awareness of the anatomic and pathologic factors that may predispose or cause a nerve injury. Accordingly, the aim of this article is to provide a comprehensive review of hip neuropathies with an emphasis on the relevant anatomy, aetiology, clinical presentation, and their imaging appearance. The lateral femoral cutaneous neuropathy (meiralgia paresthetica), femoral neuropathy, sciatic neuropathy, obturator neuropathy, superior and inferior gluteal neuropathies and pudendal neuropathy will be discussed.     

Imaging the cranial nerves: Part I: Methodology, infectious and inflammatory, traumatic and congenital lesions

Many disease processes manifest either primarily or secondarily by cranial nerve deficits. Neurologists, ENT surgeons, ophthalmologists and maxillo-facial surgeons are often confronted with patients with symptoms and signs of cranial nerve dysfunction. Seeking the cause of this dysfunction is a common indication for imaging. In recent decades we have witnessed an unprecedented improvement in imaging techniques, allowing direct visualization of increasingly small anatomic structures. The emergence of volumetric CT scanners, higher field MR scanners in clinical practice and higher resolution MR sequences has made a tremendous contribution to the development of cranial nerve imaging. The use of surface coils and parallel imaging allows sub-millimetric visualization of nerve branches and volumetric 3D imaging. Both with CT and MR, multiplanar and curved reconstructions can follow the entire course of a cranial nerve or branch, improving tremendously our diagnostic yield of neural pathology. This review article will focus on the contribution of current imaging techniques in the depiction of normal anatomy and on infectious and inflammatory, traumatic and congenital pathology affecting the cranial nerves. A detailed discussion of individual cranial nerves lesions is beyond the scope of this article.     

Imaging of entrapment and compressive neuropathies.

Although the subject of entrapment and compressive neuropathies is huge, with dedicated textbooks on the subject, this article attempts to provide an up-to-date overview of the role of imaging in the diagnosis of nerve entrapment and compression syndromes. Entrapment and compressive neuropathies are a group of distinct syndromes secondary to physical constriction or irritation affecting peripheral nerves at specific anatomical sites in the body. Most nerve entrapment and compressive syndromes derive from an injury to the neurovascular components in a narrow anatomical passage. Because of their etiological diversity, which includes pressure, angulation, stretch, and friction, the pathophysiology of individual nerve entrapment syndromes differs widely. Neuropathy can result in considerable morbidity. Although the mainstay of achieving diagnosis is with clinical acumen and electrophysiological investigations, the increasing use of modern high-resolution imaging studies is of particular value in confirming physical findings and enabling determination of the extent of injury. Knowledge and familiarity of pertinent anatomy and appropriate choice of imaging modality is important for the radiologist to allow accurate interpretation of site and etiology of nerve entrapment and compression as well as ascertaining possible alternative diagnoses.     

Bildgebende Diagnostik von Nervenkompressionssyndromen

Compression-induced neuropathy of peripheral nerves can cause severe pain of the foot and ankle. Early diagnosis is important to institute prompt treatment and to minimize potential injury. Although clinical examination combined with electrophysiological studies remain the cornerstone of the diagnostic work-up, in certain cases, imaging may provide key information with regard to the exact anatomic location of the lesion or aid in narrowing the differential diagnosis. In other patients with peripheral neuropathies of the foot and ankle, imaging may establish the etiology of the condition and provide information crucial for management and/or surgical planning. MR imaging and ultrasound provide direct visualization of the nerve and surrounding abnormalities. Bony abnormalities contributing to nerve compression are best assessed by radiographs and CT. Knowledge of the anatomy, the etiology, typical clinical findings, and imaging features of peripheral neuropathies affecting the peripheral nerves of the foot and ankle will allow for a more confident diagnosis.     

Peripheral nerve imaging: Not only cross-sectional area

Peripheral nerve imaging is recognized as a complement to clinical and neurophysiological assessment in the evaluation of peripheral nerves with the ability to impact patient management, even for small and difficult nerves. The European Society of Musculoskeletal Radiology, suggest to use ultrasound (US) for nerve evaluation due to the fact that, in sever anatomical area, magnetic resonance imaging is not able to give additional informations. US could be considered the first-choice approach for the assessment of peripheral nerves. The relative drawback of peripheral nerve US is the long learning curve and the deep anatomic competence to evaluate even small nerves. In the recent years, the role of US in peripheral nerve evaluation has been widened. In the past, nerve US was mainly used to assess nerve-cross sectional area, but now more advanced measurements and considerations are desirable and can boost the role of peripheral nerve US. Nerve echotexture evaluation was defined in 2010: The ratio between the hypoechoic and hyperechoic areas of peripheral nerves on US was called “nerve density”. For evaluation of patients who have peripheral neuropathies, the role of peripheral nerve is US wider than simple cross-sectional area evaluation. Quantitative measurements describing the internal fascicular echotexture of peripheral nerves introduce the concept of considering US as a possible quantitative imaging biomarker technique. The potential of nerve US has started to be uncovered. It seems clear that only cross-sectional area measurement is no more sufficient for a comprehensive US evaluation of peripheral nerves.     

Compressive neuropathies of the median and radial nerves at the elbow

Compressive neuropathies of the median and radial nerves in the region of the elbow are a frequent cause of pain and weakness as well as sensory complaints. The problems associated with these neuropathies can be as severe and disabling as the more commonly encountered ulnar nerve neuropathies discussed elsewhere in this issue. Regardless of the nerve that is compressed, prompt recognition of the problem and the specific site of compression are important in order to institute effective treatment and limit, if not totally eliminate, permanent sequelae. Diagnosis and treatment are presented.     

兔坐骨神经扩散张量纤维束示踪

目的:探讨DTI成像能否用于显示兔的坐骨神经.方法:三只成年家兔,运用3T磁共振扫描仪、8通道相控阵膝关节线圈和DTI成像方法扫描兔股部,后处理3D显示坐骨神经的走行.结果:运用DTI 3D纤维束成像显示了兔的坐骨神经,其路径与兔坐骨神经大体解剖部位一致.结论:DTI成像在动物周围神经的研究中有一定的应用前景.     

Nerve injuries in the throwing elbow

The unique anatomy of the elbow combined with the angular velocity and stresses placed across this hinge joint while throwing can cause a large number of pathologic changes associated with nerves. Although the ulnar nerve is the most commonly injured, neuropathies are also seen with the branches of the median and radial nerves. These neuropathies are typically responsive to rest, activity modification, ice, splinting, and anti-inflammatories. A graduated return to throwing is then needed before returning to play. When conservative measures fail, surgical decompression is warranted, but results have been less than perfect.     

Entrapment neuropathies of the shoulder and elbow in the athlete

MRI is a useful diagnostic method for evaluating nerve disease at the shoulder and elbow. MRI can depict the normal anatomy of the nerves, confirm and identify the cause of the neuropathy, identify the site of entrapment based on muscle denervation patterns, and detect unsuspected space-occupying lesions. MRI can also narrow down the differential diagnosis of nerve disease, such as in the case of suprascapular nerve syndrome versus Parsonage-Turner syndrome, or radial tunnel syndrome versus lateral epicondylitis. Large prospective studies with surgical correlation, however, are still necessary to better elucidate MRI's exact role in the assessment of entrapment neuropathies of the upper extremity.     

High-resolution MR neurography of diffuse peripheral nerve lesions

High-resolution MR imaging of peripheral nerves is becoming more common and practical with the increasing availability of 3T magnets. There are multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies. However, there is a relative paucity of literature on MRN appearance of diffuse peripheral nerve lesions. We attempted to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and imaging techniques for MRN. Using clinical and pathologically proved relevant examples, we present the MRN appearance of various types of diffuse peripheral nerve lesions, such as traumatic, inflammatory, infectious, hereditary, radiation-induced, neoplastic, and tumor variants.     

Brachial plexus and nerves about the shoulder

Ultrasound (US) and MR imaging have been shown able to detect in-depth features of brachial plexus anatomy and to localize pathological lesions in disorders where electrophysiology and physical findings are nonspecific or nonlocalizing. High-end gradient technology, phased array coils, and selection of an appropriate protocol of pulse sequences are the main requirements to evaluate the brachial plexus nerves with MR imaging and to distinguish between intrinsic and extrinsic pathological changes. A careful scanning technique based on anatomical landmarks is required to image the brachial plexus nerves with US. In traumatic injuries, MR imaging and myelographic techniques can exclude nerve lesions at the level of neural foramina and at intradural location. Outside the spinal canal, US is an excellent alternative to MR imaging to determine the presence of a lesion, to establish the site and the level of nerve involvement, as well as to confirm or exclude major nerve injuries. In addition to brachial plexus injuries, MR imaging and US can be contributory in a variety of nontraumatic brachial plexopathies of a compressive, neoplastic, and inflammatory nature. In the thoracic outlet syndrome, imaging performed in association with postural maneuvers can help diagnose dynamic compressions. MR imaging and US are also effective to recognize neuropathies about the shoulder girdle involving the suprascapular, axillary, long thoracic, and spinal accessory nerves that may mimic brachial plexopathy. In this article, the clinical entities just listed are discussed independently, providing an overview of the current status of knowledge regarding imaging assessment.     

MR imaging of the major nerves about the elbow: cadaveric study examining the effect of flexion and extension of the elbow and pronation and supination of the forearm

Magnetic resonance (MR) imaging provides useful information in the evaluation of peripheral nerves. Recent advances in MR imaging allow for detailed depiction of the soft tissue structures of the elbow joint. Three major nerves are present about the elbow. Six cadaveric elbows were imaged to depict the normal anatomy of these nerves and to determine the best plane and position of the elbow for optimal visualization of each nerve. Axial images of the elbow in full extension with the forearm in supination allow identification of all major nerves. Axial images with the elbow in full flexion allow accurate assessment of the cubital tunnel and the ulner nerve. Axial images of the elbow in full extension with the forearm in pronation are helpful for assessment of the median and radial nerves in the forearm.     

Nerve problems and compartment syndromes in the hand, wrist, and forearm.

Most sports-related peripheral neuropathies occurring from the elbow distally are compressive in nature. These result from overuse or overload principles superimposed on normal or variant anatomy. Tensile injury occurs less often and is usually associated with the extremes of the throwing motion, i.e., cocking and follow-through phases of throwing. Neurogenic syndromes are usually incomplete, indicating the absence of severe motor or sensory deficits, but typically with subjective complaints of pain or vague sensory disturbance. As a result, nerve injuries are frequently overlooked as a source of acute or, more usually, chronic symptomatology. Further, distal symptoms are not always representative of distal pathology as evidenced by the double-crush phenomenon. Therefore, a strong neurologic and musculoskeletal evaluation is necessary in diagnosing sports-induced peripheral nerve trauma. When positive, electrodiagnostic testing can assist with localization and extent of injury, although absence of NCV or EMG abnormalities is not unusual. Accurate diagnoses are essential for planning specific treatment.     

Magnetic resonance imaging in patients with diplopia. A review

Magnetic resonance imaging may be the procedure of choice for evaluating patients with diplopia; the absence of signals from cortical bone enables the brain stem and individual cranial nerves to be visualized and the imaging planes selected easily, and there is excellent contrast resolution of pathologic lesions. A clinical assessment of diplopia including the identification of associated neurologic disturbances is necessary prior to MR imaging, however, to assure that appropriate anatomic areas are studied and imaging sessions kept within acceptable time limits. The relevant physiology and anatomy critical to normal ocular motility are reviewed and the value of MR imaging for diplopia demonstrated by selected patient examples.     

Normal anatomy of the thoracic inlet as seen on transaxial MR images

The thoracic inlet can now be studied with high-resolution MR imaging. Recent advances in fold-over suppression (antialiasing software) allow for small fields of view without the usual problems of aliasing from the shoulders. This pictorial assay shows the normal anatomy that can be seen in this area on transaxial MR images. The vagus, phrenic, and recurrent laryngeal nerves can be seen as discrete entities. MR imaging can be used more often for pathologic conditions involving the lower portion of the neck and the thoracic inlet.     

MRI of the brachial plexus: A pictorial review

Magnetic resonance imaging (MRI) of the brachial plexus is the imaging modality of first choice for depicting anatomy and pathology of the brachial plexus. The anatomy of the roots, trunks, divisions and cords is very well depicted due to the inherent contrast differences between the nerves and the surrounding fat. In this pictorial review the technique and the anatomy will be discussed. The following pathology will be addressed: neurogenic tumors of the brachial plexus and sympathetic chain, superior sulcus tumors, other tumors in the vicinity of the brachial plexus, the differentiation between radiation and metastatic plexopathy, trauma, neurogenic thoracic outlet syndrome and immune-mediated neuropathies.     

Imaging the ocular motor nerves

The ocular motor nerves (OMNs) comprise the oculomotor, trochlear and the abducens nerves.According to their course, they are divided into four or five anatomic segments: intra-axial, cisternal, cavernous and intra-orbital and, for the abducens nerve, an additional interdural segment.Magnetic resonance imaging is the imaging method of choice in the evaluation of the normal and pathologic ocular motor nerves. CT still plays a limited but important role in the evaluation of the intraosseous portions at the skull base and bony foramina.We describe for each segment of these cranial nerves, the normal anatomy, the most appropriate image sequences and planes, their imaging appearance and pathologic conditions.Magnetic resonance imaging with high magnetic fields is a developing and promising technique. We describe our initial experience with a Phillips 7.0 T MRI scanner in the evaluation of the brainstem segments of the OMNs.As imaging becomes more refined, an understanding of the detailed anatomy is increasingly necessary, as the demand on radiology to diagnose smaller lesions also increases.     

MR imaging of anterior knee pain: a pictorial essay

Anterior knee pathology is a frequent cause of joint pain and limitation of function and mobility among patients presenting to an orthopaedic department. Proper recognition and treatment of pathologic conditions depend on the knowledge of normal anatomy and of the various abnormalities, which affect this area of the knee and may present with anterior knee pain. A broad array of benign and malignant processes may be manifested as anterior knee discomfort, and this common clinical entity is among the most frequent indications for MR imaging of the lower extremities. Clinical history and physical examination are also of paramount importance. The disorders can be categorized and differentiated primarily according to their location. Traumatic or non-traumatic disorders of the patella, patellar retinacula, quadriceps and patellar tendons and supra or infrapatellar fat pad can be the source of symptoms. This article includes a comprehensive pictorial essay of the characteristic MR features of common and uncommon disorders causing anterior knee pain. For accurate assessment of the aforementioned clinical problem, a radiologist should be able to identify typical MR imaging patterns that contribute in establishing the correct diagnosis and thus tailoring the appropriate therapy. Level of evidence IV.