Cubital tunnel syndrome: diagnosis by high-resolution ultrasonography

Sonographic appearances of the normal ulnar nerve in the cubital tunnel

PURPOSE

To investigate the sonographic characteristics of the normal ulnar nerve in the cubital tunnel, as well as any differences related to age, sex, and dominant arm.

METHOD

Two hundred twelve elbows in healthy volunteers were evaluated sonographically. The cross-sectional area (CSA) of the ulnar nerve within the cubital tunnel was measured with the elbow in extension and in flexion. The presence and number of fascicles was determined. The displacement of the ulnar nerve out of the cubital tunnel in full elbow flexion was also investigated.

RESULTS

The mean +/- SD CSA of the ulnar nerve was 6.6 +/- 1.7 mm(2) (6.7 +/- 1.8 mm(2) in men and 6.5 +/- 1.7 mm(2) in women). The mean CSA of the ulnar nerve was highest for subjects aged 50-59 years, and lowest for subjects aged 30-39 years. Forty-two of 212 (19.8%) ulnar nerves had 2 fascicles, and 5 (2.4%) had 3 fascicles. The remaining 165 (77.8%) nerves had 1 fascicle. During elbow flexion, 49 of 212 (23.1%) ulnar nerves showed subluxation, and 18 (8.5%) were dislocated.

CONCLUSION

There were differences in the CSA of the ulnar nerve between some age groups, but there was no variation with sex or handedness. Sonography can evaluate the morphologic changes of the nerve during flexion of the elbow.

Ultrasonographic measurements of the ulnar nerve at the elbow: role of confounders

OBJECTIVE

The purpose of this study was to identify factors confounding high-resolution ultrasonographic measurements of the ulnar nerve to test their influence when discriminating between limbs affected and unaffected by ulnar nerve entrapment (UNE) at the elbow.

METHODS

High-resolution ultrasonographic measurements of ulnar nerve dimensions at the elbow were compared between 2 groups of subjects: symptomatic and asymptomatic for UNE. Rank analysis of covariance regression tests were performed to determine whether significant differences existed between the 2 groups. The changing coefficient method (using rank analysis of covariance tests) was used to test for potential confounding effects of age, weight, height, body mass index, sex, limb sidedness, limb handedness, and nerve mobility. These tests were repeated for each measurement while controlling for the identified confounders. Exact 2-tailed Wilcoxon signed rank tests were performed to test for significant differences between measurements of the diameter of the ulnar nerve with the elbow in full extension and full flexion.

RESULTS

Age, weight, body mass index, sex, and elbow position were shown to have confounding influences on high-resolution ultrasonographic measurements of the ulnar nerve. No confounding effect was apparent for limb sidedness or dominance. Cross-sectional area and long-axis diameter measurements demonstrated significant differences between nerves with and without UNE after controlling for confounders.

CONCLUSIONS

Two cross-sectional measurements (area and maximum cross-sectional diameter) of the ulnar nerve, made at the level of the medial epicondyle, were found to be robust discriminators between nerves with and without UNE. In the absence of normative reference values of the ulnar nerve, the contralateral limb may be used as the comparative control.

The clinical applications of peripheral nerve imaging in the upper extremity

Use of different imaging modalities in the diagnosis of peripheral nerve pathology has been growing steadily. This review attempts to summarize their use, particularly with regard to ultrasound and magnetic resonance imaging, and their practical applications in the clinical setting.

Ultrasonographic Findings of the Normal Ulnar Nerve in Adults

OBJECTIVE

To provide a detailed description of the ultrasonographic findings along the entire length of the normative ulnar nerve.

DESIGN

Volunteers were recruited to undergo ultrasonography of both upper extremities. Age, sex, height, weight, body mass index, arm length, and hand length were recorded, and cross-sectional measurements of the ulnar nerve were obtained at 7 predetermined sites.

SETTING

The diagnostic neurology laboratory of a referral medical center.

PARTICIPANTS

Thirty volunteers (60 arms) were recruited. Volunteers were screened by history and physical examination, and those with evidence of peripheral nervous system disease were excluded.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The average cross-sectional area (CSA) of the ulnar nerve at 7 predetermined sites along the entire course of the nerve.

RESULTS

The following average ulnar nerve CSAs were obtained: distal wrist crease, 5.9 mm2; arterial split, 6.3 mm2; 2 cm distal to tip of the medial epicondyle, 6.4 mm2; tip of the medial epicondyle, 6.5 mm2; 2cm proximal to tip of the medial epicondyle, 6.7 mm2; mid-humerus, 6.1 mm2; and axilla, 6.2 mm2. There was no statistical difference in nerve size when dominant and nondominant arms were compared, but women did have smaller nerves than men. Of all the variables measured, nerve size correlated most closely with weight, with a correlation coefficient of .59.

CONCLUSIONS

The ulnar nerve was easily visualized and measured along its entire course, and the CSA of the nerve was consistent at multiple sites. The reference values obtained in this study will facilitate the analysis of abnormal nerve conditions, and the information on side-to-side variation and sex-specific differences should be particularly helpful.

Ultrasound in the diagnosis of ulnar neuropathy at the cubital tunnel

PURPOSE

Ulnar neuropathy at the cubital tunnel (UCT) is diagnosed on the basis of history, physical examination, and nerve conduction studies (NCSs); however, the wide spectrum of findings often makes the diagnosis difficult. The purpose of this study was to document the ultrasonographic differences in ulnar nerve size between patients with UCT and control subjects, and to correlate those differences with clinical examination findings and NCS abnormalities, thereby testing the validity of ultrasound (US) as an additional adjunct diagnostic modality for UCT.

METHODS

Fifteen elbows in 14 patients with symptoms, clinical examination, and NCS findings consistent with UCT had US of the ulnar nerve. Patients were excluded if they had a history of polyneuropathy, acute trauma involving the upper extremity, previous trauma in the region of the elbow (including previous surgery), or brachial plexus injury. The control group consisted of 60 elbows from 30 normal volunteers that also had US. Maximal cross-sectional areas (CSAs) were measured and compared for the 2 groups and a correlation analysis was performed between nerve size and NCS findings.

RESULTS

The average CSA of the ulnar nerve was 0.065 cm(2) in the control group, whereas in the UCT group it was 0.19 cm(2), indicating a significant statistical difference in ulnar nerve size between the 2 groups. The Pearson correlation coefficient between motor nerve conduction velocity of the ulnar nerve and the CSA was 0.80.

CONCLUSIONS

High-resolution US is a noninvasive, safe, and reliable modality for imaging the ulnar nerve at the elbow and it may provide a valuable adjunct to NCS in the diagnosis of UCT.

Ultrasound of the shoulder and elbow

Ultrasound examination of the shoulder and elbow requires careful technique, appreciation of normal anatomy, and appropriate high-end equipment. Ultrasound provides detailed diagnostic information. Its accuracy is comparable to that of MRI in the assessment of the rotator cuff. Ultrasound is cheaper than MRI and is preferred by patients.

Distance measure error induced by displacement of the ulnar nerve when the elbow is flexed

OBJECTIVES

To determine the presence of ulnar nerve displacement at the elbow when it is flexed and to determine its effect on distance measurements using the conventional measurement method for nerve conduction studies (NCSs).

DESIGN

Comparing the ultrasonography-assisted distance measurement method with the conventional measurement method.

SETTING

An electrodiagnostic laboratory at a university hospital.

PARTICIPANTS

Seventy-eight elbows of 39 healthy volunteers.

INTERVENTIONS

We used high-resolution ultrasonography in real time. Based on sonographic searching, we marked 3 points on the skin through the course of the displaced ulnar nerve when the elbow is flexed: (1) point A, 7 cm above the elbow (from the midpoint between the medial epicondyle tip and olecranon in the postcondylar groove [point M]); (2) point B, 3 cm below the elbow; and (3) point C, the point closest to the medial epicondyle tip.

MAIN OUTCOME MEASURES

Distance measurements between points A, B, and C were taken. These values were compared with measurements obtained through conventional measurement methods.

RESULTS

Ulnar nerve displacement occurred in 24.3% (19/78) of the elbows; approximately 20.5% (16/78) were subluxation, and 3.8% (3/78) were dislocation. In the ulnar nerve displacement group, the distance between points A and C was 5.84+/-0.33 cm (range, 5.10-6.30 cm), and the distance between points B and C in the flexed position was 3.35+/-0.19 cm (range, 3.10-3.70 cm). When the conventional distance measurement was used, the ulnar nerve conduction velocity across the elbow was overestimated by approximately 5.33+/-2.29 m/s in the ulnar nerve displacement group.

CONCLUSIONS

This distance measurement error may be responsible for the decreased sensitivity found in NCSs that test for ulnar neuropathy at the elbow. If the NCS results are normal in patients who have clear symptoms of ulnar neuropathy, the possibility of ulnar nerve displacement at the elbow should be considered, and further investigation with ultrasonography would be beneficial.

Sonography of the normal ulnar nerve at Guyon's canal and of the common peroneal nerve dorsal to the fibular head

PURPOSE

This study was conducted to evaluate the ability of sonography to visualize the ulnar nerve at Guyon's canal and the common peroneal nerve dorsal to the fibular head and to test for correlations between nerve measurements and subject characteristics.

METHODS

We used a 5-12-MHz linear-array transducer in sonographic evaluation of 15 healthy adult volunteers. We evaluated the correlations between nerve diameters and surface areas and subject body mass index and height. We also tested for differences between nerve measurements in women and men and between nerve measurements from the left and right sides of the body.

RESULTS

Both nerves were visualized in all subjects. Subject height correlated significantly with the anteroposterior diameter of the right ulnar nerve. Body mass index correlated significantly with the surface area of both ulnar nerves, with the anteroposterior diameter of both ulnar nerves, with the transverse diameter of the left ulnar nerve, and with the transverse diameter of the right common peroneal nerve. There was a statistically significant difference in anteroposterior diameter of the left ulnar and left common peroneal nerves between women and men. There were no significant differences between left- and right-side measurements for the combined data from the entire group of subjects.

CONCLUSIONS

A 5-12-MHz linear-array transducer readily allows for visualization of the ulnar nerve at Guyon's canal and the common peroneal nerve dorsal to the fibular head.

Neuromuscular ultrasound

High-resolution ultrasound now is capable of imaging muscle and nerve in fine detail. It is sensitive in detecting chronic myopathies and neurogenic atrophy and may be able to detect subtle changes associated with acute denervation. It is particularly well suited to the study of fasciculations and kinesiology. Recent studies show that ultrasound also is capable of imaging most peripheral nerves,including small branches, and of sensitively measuring the swelling that follows chronic compression. This noninvasive technology holds considerable promise for providing anatomic information to complement other tests of nerve and muscle function.

Standard reference values for musculoskeletal ultrasonography

OBJECTIVES

To determine standard reference values for musculoskeletal ultrasonography in healthy adults.

METHODS

Ultrasonography was performed on 204 shoulders, elbows, hands, hips, knees, and feet of 102 healthy volunteers (mean age 38.4 years; range 20-60; 54 women) with a linear probe (10-5 MHz; Esaote Technos MP). Diameters of tendons, bursae, cartilage, erosions, hypoechoic rims around tendons and at joints were measured with regard to established standard scans. Mean, minimum, and maximum values, as well as two standard deviations (2 SD) were determined. Mean values +/-2 SD were defined as standard reference values.

RESULTS

Hypoechoic rims were normally present in joints and tendon sheaths owing to physiological synovial fluid and/or cartilage. Similarly, fluid was found in the subdeltoid bursa in 173/204 (85%), at the long biceps tendon in 56 (27%), in the suprapatellar recess in 158 (77%), in the popliteal bursae in 32 (16%), and in the retrocalcaneal bursa in 49 (24%). Erosions of >1 mm were seen at the humeral head in 47 (23%). Values for important intervals were determined. The correlation between two investigators was 0.96 (0.78-0.99). The reliability of follow up investigations was 0.83 (0.52-0.99).

CONCLUSIONS

Fluid in bursae as well as hypoechoic rims within joints and around tendons are common findings in healthy people. This study defines standard reference values for musculoskeletal ultrasonography to prevent misinterpretation of normal fluid as an anatomical abnormality.

The ultrasonographic and electrodiagnostic findings of ulnar neuropathy at the elbow11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To evaluate and compare the morphologic changes of the ulnar nerve at the elbow, using ultrasonography, between patients with cubital tunnel syndrome and retrocondylar compression syndrome determined with electrodiagnosis.

DESIGN

Prospective study using electrodiagnosis and ultrasonography.

SETTING

An outpatient rehabilitation clinic in a tertiary university hospital in South Korea.

PARTICIPANTS

Thirteen patients (8 men, 5 women; mean age, 48.2y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

In the electrodiagnostic study, we used the inching technique to localize the ulnar nerve lesion at the elbow. In the ultrasonography study, we measured the length of the swollen ulnar nerve and the ratio of the nerve diameter between the proximal end of the medial epicondyle to the elbow joint level and the tip of medial epicondyle to the elbow joint level.

RESULTS

The mean length of the swollen ulnar nerve segment in retrocondylar compression syndrome (2.58+/-0.58cm) was significantly longer than that of cubital tunnel syndrome (1.64+/-0.31cm). The mean ratio of the nerve diameter between the proximal end of medial epicondyle and the elbow joint level was significantly larger in retrocondylar compression syndrome (1.52+/-0.25) than that of cubital tunnel syndrome (1.06+/-0.06).

CONCLUSIONS

Ultrasonography detected the morphologic changes and the extent of the ulnar nerve lesion at the elbow, and it can become a screening and follow-up imaging modality in patients with ulnar neuropathy at the elbow.

High-resolution sonography of the peripheral nervous system - a review of the literature

High-resolution sonography is capable of depicting peripheral nerves and the brachial plexus. In this study we review the literature on this subject. Normal peripheral nerves have a characteristic echotexture. Most nerves are readily visualized, although this is not always the case with the nerves of the lower extremity. The main pathological changes that can be demonstrated are nerve enlargement and increased hypoechogenicity. In order to demonstrate nerve enlargement, measurements should be performed and compared with a set of reference values. Several neuropathies have been studied by means of ultrasonography. However, many studies concern case reports and show methodological shortcomings. The best studied peripheral neuropathy is the carpal tunnel syndrome in which ultrasonography seems to have an additional value when combined with nerve conduction studies. Nerve enlargement has also been demonstrated in radial neuropathy at the humerus and in ulnar neuropathy at the elbow. The role of sonography in various hereditary and inflammatory neuropathies is uncertain although diffuse nerve thickening could be demonstrated. Further systematic studies are needed to determine the role of sonography in the diagnostic process of the various neuropathies. It would be important to study the subcategories of patients in whom electrodiagnostic studies are normal or show equivocal findings.

Nerves in a pinch: imaging of nerve compression syndromes

Nerve compression is a common entity that can result in considerable disability. Early diagnosis is important to institute prompt treatment and to minimize potential injury. Although the appropriate diagnosis is often determined by clinical examination, the diagnosis may be more difficult when the presentation is atypical, or when anatomic and technical limitations intervene. In these instances, imaging can have an important role in helping to define the site and etiology of nerve compression or in establishing an alternative diagnosis. MR imaging and ultrasound provide direct visualization of the nerve and surrounding abnormalities. For both modalities, the use of high-resolution techniques is important. Bony abnormalities contributing to nerve compression are best assessed by radiographs or CT. For the radiologist, knowledge of the anatomy of the fibro-osseous tunnels, familiarity with the causes of nerve compression, and an understanding of specialized imaging techniques are important for successful diagnosis of nerve compression.

Ultrasound of nerve and muscle

Over the last two decades, ultrasound has developed into a useful technology for the evaluation of diseases of nerve and muscle. Since it is currently not used at by the majority of clinicians involved in diagnosis or care of patients with neuromuscular disorders, this review briefly describes the technical aspects of ultrasound and its physical principles. It relates normal muscle anatomy and movement to ultrasound images in the axial and sagittal planes and follows with a discussion of ultrasound findings in chronic muscle disease. These include evident atrophy and the loss of the hypoechoic architecture of normal muscle tissue. It highlights evolving uses of the technique to measure other pathologic changes in disease including altered muscle dynamics. With high-resolution instruments nerve imaging has now become standard, and the relationships of median nerve anatomy and observations of static and dynamic images from ultrasound are reviewed. Changes seen in carpal tunnel syndrome include significant increases in the cross-sectional area of the nerve just proximal to the site of compression, loss of hyperechoic intensities within nerve, and reduced mobility. Preliminary use of the technique for the study of other nerves is reviewed as well. Ultrasound is an ideal tool for the clinical and research investigation of normal and diseased nerve and muscle complementary to existing diagnostic techniques. As the technology continues to evolve, it will likely assume a more significant role in these areas as those most able to exploit its potential, clinical neurophysiologists and neuromuscular clinicians, incorporate its use at the bedside.

Occupational and Sport Related Traumatic Neuropathy

BACKGROUND

Sport and occupation related traumatic nerve injury is a common problem in the United States. While the physical requirements of each pursuit place participants at risk for injury to certain peripheral nervous system structures, the vast numbers of professional and recreational pursuits limits the ability to become familiar with nerve injuries specific to each. A more pragmatic approach is to apply knowledge of mechanisms of injury, physiology of nerve injury, regional anatomy, and at-risk peripheral nervous system structures to the routine neurologic history and physical assessment to arrive at a localizing and etiologic diagnosis.

REVIEW SUMMARY

The authors discuss potential mechanisms of nerve injury, the role of electrodiagnostic testing, regional peripheral nervous system anatomic considerations and lesion localization.

CONCLUSIONS

Despite the wide variety of professionally and recreationally induced peripheral nerve injuries, application of anatomic, physiologic and mechanistic considerations allow the neurologist to make an etiologic and localizing diagnosis.

Chapter 25 Imaging nerve and muscle with ultrasound

Over the last two decades significant advances in ultrasound have made it possible for investigators to image and interpret pathologic changes in muscle and nerve. In addition to being able to assess the pathologic changes in these structures themselves, ultrasound also provides the unique ability to identify anatomic lesions responsible for nerve or muscle injury. They can be correlated with changes in neural structures or affected muscles. Like electrodiagnostic studies, ultrasound is portable and inexpensive, but it is even less invasive, and surprisingly sensitive in detecting a variety of unusual and common causes of neuromuscular dysfunction. Given recent developments in the field, ultrasound shows promise as the technique most suitable for clinical neurophysiologists and neuromuscular clinicians in the growing field of imaging. Such involvement is required to best adopt and exploit the potential of imaging for the research and clinical evaluation of neuromuscular disorders.

Peripheral nerve lesions: role of high-resolution US

The peripheral nerve is demonstrated as a reticular pattern in a transverse section at high-resolution ultrasonography (US). Its echogenicity is between that of tendon and muscle. High-resolution US applied to lesions of peripheral nerves yields impressive results in that the nerve is highly differentiated from surrounding soft tissue. In cases of trauma, high-resolution US can easily differentiate between a rupture of the nerve bundle and fibroblast infiltration that results in traumatic neuroma. In cases of inflammation or compressive syndrome, high-resolution US can easily demonstrate lesion location and cause. In the evaluation of abnormal masses, high-resolution US cannot clearly differentiate neurofibromas from schwannomas but it can clarify the relationship between tumor and neural trunk and help the clinician plan treatment strategies. The authors discuss the success that can be achieved with the application of high-resolution US in the evaluation of peripheral nerve lesions.

Subluxation of the ulnar nerve in the elbow region--ultrasonographic evaluation

Chronic ulnar nerve subluxation out of its sulcus in the elbow region may be a rare reason for undefined chronic disorders in the medial elbow aspect. We present two cases, a 38-year-old male patient complaining of a recurrent painful disorder including paresthesia of the 4th and 5th fingers and a 12-year-old boy presenting with a palpable band in the medial elbow region without pain. Ultrasonography was performed using a high frequency linear probe in the longitudinal and horizontal planes including dynamic examination. In both patients, the ulnar nerve was completely identified, both in the transverse and longitudinal planes. The sonomorphology and echogeneity of the nerve were the same as in the contralateral limb. Ulnar nerve subluxation was diagnosed in elbow joint flexion, in both cases. It is possible through dynamic ultrasonographic examination to diagnose and document ulnar nerve subluxation for further (surgical) treatment.

Ultrasonography of peripheral nerves in the normal adult horse

A study of the ultrasonographic appearance and size of the sciatic, tibial, peroneal, suprascapular, radial, median, and ulnar nerves and a comparison with the anatomic size and location of these nerves in the normal adult horse is reported. Cadavers and live horses were studied. Landmarks for localization and techniques for nerve identification are described. The depth and diameter of each nerve at various locations and the success rate in imaging each nerve are reported. Statistically significant correlations were found between anatomically and ultrasonographically measured nerve depths and diameters. The success rate in identifying nerves was 70% in the live horses and 49% in cadavers, with the deep peroneal nerve being the easiest to identify. Some applications of this technique in horses are discussed.

The ultrasonographic appearance of the femoral nerve and cases of iatrogenic impairment

OBJECTIVE

To assess the feasibility of ultrasonography of femoral nerves in a cadaveric specimen, healthy volunteers, and patients.

METHODS

In 1 unembalmed cadaveric specimen (female, 90 years) and 20 healthy volunteers (9 male and 11 female, 18-50 years; n = 40 scans), the topographic features, cross-sectional shapes (oval or triangular), and cross-sectional areas of the femoral nerves were evaluated by ultrasonography (5- to 12-MHz broadband linear array). In a subsequent study, 7 consecutive patients with postoperative findings assigned to the femoral nerve were evaluated and assessed by a neurologist.

RESULTS

The mean +/- SD anteroposterior and mediolateral diameters of the femoral nerves in the volunteers were 3.1 +/- 0.8 and 9.8 +/- 2.1 mm, respectively, at an average cross-sectional area of 21.7 +/- 5.2 mm2. The cross-sectional shape was oval in 67.5% superior to the inguinal ligament and in 95% inferior to the ligament. The infrainguinal femoral nerve showed variable distances to the femoral artery. In the subsequent patient study, 5 patients had swelling of the femoral nerve in the affected side. In 1 patient, the nerve had a blurred echo structure due to a hematoma. In 1 patient, major damage of the femoral nerve was ruled out clearly.

CONCLUSIONS

Ultrasonography allows the depiction and assessment of the femoral nerve from about 10 cm superior to 5 cm inferior to the inguinal ligament. In this region, ultrasonography is helpful in detection of impairments and, therefore, in decisions about planning and even acceleration of further treatment.

Ultrasonography of the accessory nerve: normal and pathologic findings in cadavers and patients with iatrogenic accessory nerve palsy

OBJECTIVE

To determine feasibility of ultrasonography in detecting the normal accessory nerve as well as pathologic changes in cases of accessory nerve palsy.

METHODS

Four patients with accessory nerve palsy were investigated by ultrasonography. Three cases of accessory nerve palsy after lymph node biopsy and neck dissection were primarily diagnosed on the basis of ultrasonography using a 5- to 12-MHz linear transducer. In addition, we performed ultrasonography in 3 cadaveric specimens to show the feasibility of detecting the accessory nerve.

RESULT

Nerve transection (n = 2), scar tissue (n = 1), and atrophy of the trapezius muscle (n = 4) were confirmed by electroneurographic testing and surgical nerve inspection. In 1 case in which a patient had a whiplash injury with accessory nerve palsy, ultrasonography showed atrophy of the trapezius muscle with a normal nerve appearance.

CONCLUSIONS

Ultrasonography allows visualization of the normal accessory nerve as well as changes after accessory nerve palsy.

Ultrasound in sports medicine

Musculoskeletal sonography has been shown to be effective for many applications related to sports medicine. Some advantages of sonography over MR imaging include portability, accessibility, high resolution, and relative lower cost. More importantly, dynamic imaging under sonography visualization allows diagnoses that cannot be made with routine MR imaging. Additionally, direct imaging correlation with patient symptoms provides important information to the referring clinicians. The disadvantages of sonography include operator dependence and long learning curve. This can be minimized, however, with proper training and standardized technique. Musculoskeletal sonography has proved itself as one of several imaging methods invaluable to the diagnosis of sport medicine-related abnormalities.

Ultrasound of the elbow

This article describes the use of ultrasound (US) in the evaluation of the elbow. US is able to visualize several abnormalities affecting tendons, muscles, ligaments and bursae around the elbow joint as well as to delineate the nature of soft-tissue swelling, such as a space-occupying lesion or synovial enlargement. Occult fractures, osteophytes and intra-articular loose bodies can be depicted with this technique as well. At the cubital tunnel, US allows accurate imaging of the ulnar nerve and to document changes that occur in compressive syndromes. Over other imaging modalities, US offers several key advantages, including cost effectiveness, availability and ability to perform a dynamic examination of tendon movement and joint motion. With continued experience, it is likely that the use of US will increase further with regards to evaluation of soft-tissue abnormalities of the elbow.

Ulnar nerve dislocation and snapping triceps syndrome: diagnosis with dynamic sonography--report of three cases

Initial experience with the use of dynamic sonography of the elbow for diagnosing ulnar nerve dislocation and snapping triceps syndrome is reported. Cases of three consecutive patients who underwent sonographic evaluation of the elbow and subsequent open elbow surgery for symptomatic ulnar nerve dislocation were reviewed. Dynamic sonography of the elbow was used to aid in the accurate diagnosis of and differentiation between ulnar nerve dislocation and snapping of the medial triceps muscle.

Examination of postoperative peripheral nerve lesions with high-resolution sonography

OBJECTIVE

Peripheral nerve lesions after surgery are common and are related either to direct compromise of the nerve by the surgical procedure (iatrogenic lesions) or to postoperative events such as scar formation. Despite a high sensitivity, electrodiagnosis may not reveal the exact location and cause of a nerve lesion. We hypothesized that high-resolution sonography could be helpful in diagnosing postoperative peripheral nerve lesions by direct visualization of the nerve and surrounding tissues.

SUBJECTS AND METHODS

Eighteen patients with postoperative peripheral nerve lesions that were confirmed with clinical examination and electrodiagnosis were examined on sonography. Eight patients had lesions caused by direct nerve surgery, and 10 patients had undergone a previous orthopedic operation or open biopsy. Sonographic diagnoses were correlated with neurologic examinations and surgical findings.

RESULTS

Reliable visualization of injured nerves on sonography was feasible in all patients. Axonal swelling of a nerve was diagnosed in three patients, direct compromise of a nerve by surrounding scar tissue or surgical implants was diagnosed in 10 patients, a neuroma was diagnosed in three, and insufficient surgical repair, in two. Sonographic findings were confirmed during surgery in all except one patient.

CONCLUSION

In contrast to electrophysiologic tests, high-resolution sonography can show the exact location, extent, and type of a postoperative peripheral nerve lesion and the concurrent disease of surrounding tissues. Because the latter can often be the causative agent for the development of a lesion or the lack of improvement with conservative treatment, sonography yields important information that may not be obtained with other diagnostic modalities.

Radial nerve palsy associated with humeral shaft fracture: evaluation with US--initial experience

PURPOSE

To determine the feasibility of using ultrasonography (US) for evaluation of a radial nerve injury associated with humeral shaft fracture.

MATERIALS AND METHODS

In a prospective study, 11 consecutive patients with sensorimotor radial deficiency after distal humeral fracture were evaluated with conventional radiography, US, electroneurography, and electromyography. Surgical repair of the fracture and nerve inspection were performed in five patients. The remaining six patients were successfully treated conservatively. The US appearance of the radial nerve was studied in 10 healthy volunteers and in the noninjured arm of the 11 patients for comparison.

RESULTS

In five patients, US findings of a severely damaged radial nerve were confirmed at surgical nerve inspection. In one patient, the nerve was entrapped between fragments. One patient had a complete nerve dissection, one had a lacerated nerve from a loose compression plate, and one had a nerve riding on the edge of a bone fragment. In the fifth patient who underwent surgical inspection, the nerve was buried in the callus. In the six patients treated conservatively, US showed continuity of the nerve.

CONCLUSION

US may be useful for accurate evaluation of the radial nerve in patients with nerve palsy associated with humeral shaft fracture.

US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs

The diagnosis of nerve entrapment at osteofibrous tunnels relies primarily on clinical and electrodiagnostic findings. Recently, the refinement of high-frequency broadband transducers with a range of 5-15 MHz, sophisticated focusing in the near field, and sensitive color and power Doppler technology have improved the ability to evaluate peripheral nerve entrapment in osteofibrous tunnels with ultrasonography (US). In the upper limb, osteofibrous tunnels amenable to US examination include the carpal tunnel for the median nerve and the cubital and Guyon tunnels for the ulnar nerve. In the lower limb, these tunnels include the fibular neck for the common peroneal nerve, the tarsal tunnel for the posterior tibial nerve, and the intermetatarsal spaces for the interdigital nerves. High-resolution US allows direct imaging of the involved nerves, as well as documentation of changes in nerve shape and echotexture that occur in compressive syndromes. A spectrum of extrinsic causes of entrapment, such as tenosynovitis, ganglia, soft-tissue tumors, bone and joint abnormalities, and anomalous muscles, can also be diagnosed with US. With continued experience, it is likely that this technique will be increasingly used to evaluate nerve entrapment syndromes.

Ultrasonography of peripheral nerves

With recent improvements in ultrasound (US) imaging equipment and refinements in scanning technique, an increasing number of peripheral nerves and related pathologic conditions can be identified. US imaging can support clinical and electrophysiologic testing for detection of nerve abnormalities caused by trauma, tumors, and a variety of nonneoplastic conditions, including entrapment neuropathies. This article addresses the normal US appearance of peripheral nerves and discusses the potential role of US nerve imaging in specific clinical settings. A series of US images of diverse pathologic processes involving peripheral nerves is presented.