Role of magnetic resonance imaging in entrapment and compressive neuropathy—what, where, and how to see the peripheral nerves on the musculoskeletal magnetic resonance image: part 2. Upper extremity

The diagnosis of nerve entrapment and compressive neuropathy has been traditionally based on the clinical and electrodiagnostic examinations. As a result of improvements in the magnetic resonance (MR) imaging modality, it plays not only a fundamental role in the detection of space-occupying lesions, but also a compensatory role in clinically and electrodiagnostically inconclusive cases. Although ultrasound has undergone further development in the past decades and shows high resolution capabilities, it has inherent limitations due to its operator dependency. We review the course of normal peripheral nerves, as well as various clinical demonstrations and pathological features of compressed and entrapped nerves in the upper extremities on MR imaging, according to the nerves involved. The common sites of nerve entrapment of the upper extremity are as follows: the brachial plexus of the thoracic outlet; axillary nerve of the quadrilateral space; radial nerve of the radial tunnel; ulnar nerve of the cubital tunnel and Guyon’s canal; median nerve of the pronator syndrome, anterior interosseous nerve syndrome, and carpal tunnel syndrome. Although MR imaging can depict the peripheral nerves in the extremities effectively, radiologists should be familiar with nerve pathways, common sites of nerve compression, and common space-occupying lesions resulting in nerve compression in MR imaging.     

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.     

Entrapment neuropathies I: upper limb (carpal tunnel excluded)

Several entrapment neuropathies of the upper extremity can cause hypoechoic swelling and nerve compression as seen at ultrasound. The ulnar nerve can be compressed at the cubital tunnel of the elbow and Guyon's canal at the wrist. The deep branch of the radial nerve can be compressed at the supinator muscle at the elbow, and the superficial radial nerve may be compressed at the dorsal wrist (Wartenberg's syndrome). In addition to compression at the carpal tunnel, the median nerve may be compressed at the elbow, related to a supracondylar process or by the pronator teres. Knowledge of these key anatomical sites of potential nerve compression is essential for accurate diagnosis of entrapment neuropathies.     

Refining the sensory and motor ratunculus of the rat upper extremity using fMRI and direct nerve stimulation.

It is well understood that the different regions of the body have cortical representations in proportion to the degree of innervation. Our current understanding of the rat upper extremity has been enhanced using functional MRI (fMRI), but these studies are often limited to the rat forepaw. The purpose of this study is to describe a new technique that allows us to refine the sensory and motor representations in the cerebral cortex by surgically implanting electrodes on the major nerves of the rat upper extremity and providing direct electrical nerve stimulation while acquiring fMRI images. This technique was used to stimulate the ulnar, median, radial, and musculocutaneous nerves in the rat upper extremity using four different stimulation sequences that varied in frequency (5 Hz vs. 10 Hz) and current (0.5 mA vs. 1.0 mA). A distinct pattern of cortical activation was found for each nerve. The higher stimulation current resulted in a dramatic increase in the level of cortical activation. The higher stimulation frequency resulted in both increases and attenuation of cortical activation in different regions of the brain, depending on which nerve was stimulated.     

Nerve sheath ganglion of the tibial nerve presenting as a Baker’s cyst: a case report

Nerve sheath ganglion is a relatively rare clinical entity commonly found in the peroneal nerve in the lower limb or the ulnar nerve in the upper extremity. It is rarely found in the tibial nerve. The occurrence of a nerve sheath ganglion in a patient’s tibial nerve has been identified. The initial presentation of the tumor mass has been very similar to that of a Baker’s cyst, namely a soft undulating popliteal mass. Yet, the case also presented symptoms and signs of tibial nerve compressive neuropathy. We present here a rare case of nerve sheath ganglion of the tibial nerve. Clinical courses of the patient were reviewed, and relevant issues were discussed with a thorough literature review.     

Clinical, electrophysiological and MRI correlations in carpal tunnel syndrome]

Even though diagnosis of carpal tunnel syndrome is mainly based on clinical findings, other examinations are often useful for confirmation and management. The most useful of these examinations is EMG. However, EMG may be inconclusive and MRI may then be helpful. The indications for MRI in patients with carpal tunnel syndrome will be reviewed. METHOD: 20 patients with a total of 33 clinically suspected cases of carpal tunnel syndrome (CTS) underwent EMG and MRI evaluation. Clinical and EMG findings identified three groups of patients based on degree of deficit: mild, moderate, and severe. The following structures were evaluated at MRI: median nerve, retinaculum, retrotendinous fat, flexor tendons, thenar space, and muscles and bones of the wrist. Surgery was performed for 19 wrists. RESULTS: Only retinacular bowing and increased T2W signal intensity within the median nerve were significantly related to the diagnosis of CTS (sensitivity of 70% and 57% respectively). Retinacular bowing indicates increased "pressure" within the compartment (mechanical compression of the nerve) and increased T2W signal of the median nerve indicates nerve suffering. These findings correlated well with more severe cases based on clinical and EMG findings. CONCLUSION: In cases where there is discordance between clinical and EMG findings, MRI is helpful to identify patients who would benefit from surgical intervention.     

Sonographic evaluation of uncommonly assessed upper extremity peripheral nerves: anatomy,technique, and clinical syndromes

Skeletal Radiology - Targeted ultrasound of the median, ulnar, and radial nerves is a well-established technique for suspected upper extremity peripheral neuropathy. However, sonographic imaging of...     

Distal arterial flow in patients undergoing upper extremity dialysis shunting: a prospective study using doppler sonography

OBJECTIVE: The objective of this study was to document changes in the distal circulation after creation of a proximal upper extremity dialysis shunt and to correlate these findings with the patient's clinical condition. SUBJECTS AND METHODS: We prospectively examined 18 patients scheduled for upper extremity shunt creation. We used color and spectral Doppler sonography to examine flow in the radial and ulnar arteries, noting flow direction and peak systolic velocity. After the shunt procedure, we repeated the measurements and correlated them statistically with hand symptomatology. RESULTS: Six (33%) of 18 patients were symptomatic. The mean peak systolic velocities in the radial and ulnar arteries were 52 and 61 cm/sec, respectively, before surgery, and decreased to 12 cm/sec after surgery in the radial artery and 44 cm/sec in the ulnar artery. The mean percentage of decrease in peak systolic velocity was 77% in the radial artery and 28% in the ulnar artery. Eight patients showed reversed flow. No statistical correlation was found between change in peak systolic velocity values before and after surgery and the presence of hand symptoms. Similarly, no correlation was found between flow reversal and symptoms. The most consistent factor associated with symptoms was diabetes; all symptomatic patients were diabetic, but only 54% of the diabetic patients were symptomatic. CONCLUSION: The difference in the peak systolic velocities in the radial and ulnar arteries after shunt construction does not correlate with symptoms. The hand can tolerate a significant decrease in the peak systolic velocity and even flow reversal without symptomatology.     

Nerve conduction studies of upper extremities in tennis players

Objectives: The influence of regular and intense practice of an asymmetric sport such as tennis on nerves in the elbow region was examined.

Methods: The study included 21 male elite tennis players with a mean (SD) age of 27.5 (1.7) years and 21 male non-active controls aged 26.4 (1.9) years. Anthropometric measurements (height, weight, limb length, and perimeters of arm and forearm) were determined for each subject, and range of motion assessment and radiographic examination carried out. Standard nerve conduction techniques using constant measured distances were applied to evaluate the median, ulnar, and radial nerves in the dominant and non-dominant limb of each individual.

Results: The sensory and motor conduction velocities of the radial nerve and the sensory conduction velocity of the ulnar nerve were significantly delayed in the dominant arms of tennis players compared with their non-dominant arms and normal subjects. There were no statistical differences in the latencies, conduction velocities, or amplitudes of the median motor and sensory nerves between controls and tennis players in either the dominant or non-dominant arms. However, the range of motion of the upper extremity was significantly increased in tennis players when compared with control subjects. Tennis players were taller and heavier than control subjects and their dominant upper limb lengths were longer, and arm and forearm circumferences greater, than those of the control subjects.

Conclusions: Many of the asymptomatic tennis players with abnormal nerve conduction tests in the present study may have presymptomatic or asymptomatic neuropathy similar to subclinical entrapment nerve neuropathy.

     

Cubital tunnel syndrome

The tremendous forces generated by the upper extremity during throwing places the athlete at risk for developingvalgus tension injuries to the medial aspect of the elbow. Cubital tunnel syndrome, or ulnar neuritis, represents one component of a spectrum of medial elbow pathology that can affect the throwing athlete. This article reviews the pertinent anatomy, pathophysiology, clinical presentation, and surgical treatment for this condition. When nonoperative management fails, anterior submuscular transposition of the ulnar nerve deep to the flexor muscle group provides adequate protection from the trauma that occurs during athletic activity.     

Magnetic resonance microscopy imaging of posterior interosseous nerve palsy

Posterior interosseous nerve palsy, also called deep radial nerve syndrome, is a neuropathy caused by radial nerve entrapment or compression at the level of the supinator muscle. Although imaging studies are not necessary for diagnosing this syndrome because of its characteristic clinical manifestations, the causes of palsy, which include mass lesions, or precise anatomical findings can sometimes be demonstrated by imaging. Magnetic resonance (MR) findings of posterior interosseous nerve palsy have been described as involving atrophy of related muscles caused by denervation, a common secondary change of this nerve disorder. We present a case in which the swollen posterior interosseous nerve itself could be directly depicted by MR imaging using a 4.7-cm microscopy coil in a patient with neuropathy.     

Peripheral nerves of the extremities: imaging with US

High-resolution real-time ultrasonography (US) was used to evaluate peripheral nerves of the extremities in healthy subjects and in 11 patients with a mass developed from a peripheral nerve. The normal median and ulnar nerves in the upper extremity and the normal sciatic and external popliteal nerves in the lower extremity were seen, all having an echogenic fibrillar echotexture. Pathologic findings included nine cases of benign tumor (four schwannomas, three neurofibromas, two traumatic neuromas), one of neurilemmitis, and one of tuberculoid leprosy. All lesions were hypoechoic. Three of the four schwannomas had well-defined contours, and two were associated with a typical distal sound enhancement. Neurofibromas and traumatic neuromas were less sharply delineated. Inflammatory conditions were characterized by a hypoechoic, thickened nerve. US was effective in imaging nerve masses in the extremities, and large normal nerves can now be demonstrated with high-resolution US.     

Neurolymphomatosis on F-18 FDG PET/CT and MRI Findings: A Case Report

Neurolymphomatosis is a rare manifestation of malignant lymphoma. A 74-year-old man, in complete remission from diffuse large B cell lymphoma, presented with a loss of pain and temperature sensation in the left hemiface and left upper extremity, and motor weakness in the left upper and both lower extremities. Cerebrospinal fluid analysis and brain magnetic resonance imaging (MRI) findings were negative. Combined fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) revealed multiple linear hypermetabolic lesions along the mandibular branch of the left trigeminal nerve, left brachial plexus, right axillary nerve, right suprarenal plexus, right adrenal gland, right femoral nerve, and both sciatic nerves, which corresponded to the patient’s complex neurologic symptoms. C-spine and pelvic MRI revealed diffuse thickening with enhancement in the left brachial plexus and in the proximal portion of the left sciatic nerve, but negative findings for other sites identified by FDG-PET/CT. These findings suggest that FDG-PET/CT can detect peripheral nerve infiltration by malignant lymphoma earlier than MRI. Thus, if a patient with a history of lymphoma presents with neurologic symptoms, FDG-PET/CT should be performed to evaluate neurolymphomatosis.     

Ultrasound anatomy of the brachial plexus nerves in the neurovascular bundle at the axilla in patients undergoing upper-extremity block anesthesia

Purpose

Familiarity with the localization of the nerves in the neurovascular bundle that constitutes the axillary segment of the brachial plexus (BP) is important when applying ultrasound (US)-guided block anesthesia. Therefore in this study we aimed to delineate the anatomy of the median, radial, and ulnar nerves of the BP at the axilla with US and electrical stimulation.

Materials and methods

The study included 60 patients who were scheduled to undergo upper-arm surgery with axillary block anesthesia. Prior to anesthesia, ulnar, radial, and median nerves were localized with US using a 12-h quadrant identification system that placed the axillary artery (AA) in the middle. The nerves were then functionally tested using a neurostimulator.

Results

The radial nerve was mainly located in the 4–6 o’clock arc (posterior and posteromedial to AA) in 50 (83 %) of patients. Ulnar nerve was mainly at the 12–3 o’clock arc (anteromedial to AA) in 51 (85 %) of patients. Ulnar nerve showed a second peak at 9–10 o’clock quadrant (anterolateral to AA) in 11 % (7) of patients. Median nerve location was most common in the 12 and 9 o’clock arc (anterior and anterolateral to AA) in 53 (88 %) of the patients.

Conclusions

Ultrasound is a useful tool for depicting BP anatomy in the axillary fossa prior to block anesthesia. Median, ulnar, and radial nerves form a highly consistent triangular pattern around the axillary artery that is easily recognizable with US.     

MRI诊断肘管综合征的影像与临床应用研究

目的:探讨MRI对肘管综合征的影像及临床应用价值.方法:对18例肘管综合征患者和20例健康成年人行肘部3.0T MR横轴面、冠状面及矢状面扫描,扫描序列包括SE T1 WI、脂肪抑制SE T2 WI和脂肪抑制SE PDWI.对比分析患者组和对照组中肘部尺神经的信号及形态特点.结果:患者组和对照组中尺神经的横截面积分别为(0.17±0.08)和(0.07±0.01)cm2,两组间差异有统计学意义(P＜0.001);两组中尺神经/肌肉信号强度比分别为2.82±1.41和1.56±0.38,两组间差异有统计学意义(P=0.002).18例肘管综合征患者中有13例行肘管内尺神经减压术,5例行保守治疗.结论:MRI可显示肘管综合征患者肘部尺神经的变化,是一种能较好地评估肘管综合征的检查方法.     

Epithelioid hemangioendothelioma mimicking a nerve sheath tumor clinically and on MR imaging

Epithelioid hemangioendothelioma is a tumor of the soft tissues arising from the vascular endothelium. It is considered an intermediate grade malignancy. A 42-year-old female patient presented with pain and tingling down her right arm and a mass at the right medial upper extremity. MRI revealed an oblong mass along the course of the neurovascular bundle. Given the clinical and MR findings, a nerve sheath tumor was suspected. At surgery, the mass was adherent to both the brachial artery medially and the median nerve posteriorly. Pathology revealed epithelioid hemangioendothelioma. The imaging characteristics of epithelioid hemangioendothelioma on ultrasound, CT, and MRI are reviewed. Epithelioid hemangioendothelioma can mimic a nerve sheath tumor clinically and radiologically and should be considered in the differential diagnosis of tumors involving or adjacent to a neurovascular bundle.     

MRI safety update 2008: part 2, screening patients for MRI

OBJECTIVE: This article is the second part of a two-part series on MRI safety. In this article, part 2, the topic of screening patients for MRI procedures is addressed. CONCLUSION: To prevent incidents and accidents associated with MRI, it is necessary to regularly revisit the safety topics that directly impact patient management especially with respect to the subjects that are "new," those that should be reassessed because of recent changes, topics that deserve emphasis because of controversy or confusion, and information that should be considered in light of new findings.     

In-office MR imaging

The development of new metal alloys, along with more innovative magnet technology, has permitted the construction of smaller magnets for magnetic resonance (MR) systems, which, in turn, has allowed development of MR imaging systems designed to be physically smaller than conventional whole-body MR imaging systems. These specialized devices are commonly referred to as "niche," "dedicated," or "extremity" MR imaging systems. Performing MR imaging procedures with this type of system offers distinct advantages that include reduced overall costs, more convenient installation and siting, and greater patient comfort and safety. Importantly, these critical features permit extremity MR imaging systems to be readily utilized in an "in-office" setting. This article will provide an overview of the technical aspects and clinical applications for extremity MR imaging systems, present patient management issues, and discuss the economic and practical considerations of the use of extremity MR imaging systems in an in-office environment.     

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.     

Spontaneous craniospinal hypotension

Spontaneous cerebrospinal fluid (CSF) leak has been called "spontaneous intracranial hypotension," emphasizing the intracranial symptoms and imaging findings. We present a patient with spontaneous CSF leak whose initial spinal magnetic resonance imaging (MRI) findings were thought to represent epidural tumor or infection. Subsequent MRI examinations showed an improvement of both intracranial and spinal CSF hypotension findings coinciding with clinical symptom resolution. We propose the term "spontaneous craniospinal hypotension" to better emphasize this syndrome's unifying intracranial and spinal pathophysiology and imaging findings.