Changes in interstitial pressure and cross-sectional area of the cubital tunnel and of the ulnar nerve with flexion of the elbow. An experimental study in human cadavera

The purpose of this study was to determine the relationship between the ulnar nerve and the cubital tunnel during flexion of the elbow with use of magnetic resonance imaging and measurements of intraneural and extraneural interstitial pressure. Twenty specimens from human cadavera were studied with the elbow in positions of incremental flexion. With use of magnetic resonance imaging, cross-sectional images were made at each of three anatomical regions of the cubital tunnel: the medial epicondyle, deep to the cubital tunnel aponeurosis, and deep to the flexor carpi ulnaris muscle. The cross-sectional areas of the cubital tunnel and the ulnar nerve were calculated and compared for different positions of elbow flexion. Interstitial pressures were measured with use of ultrasonographic imaging to allow a minimally invasive method of placement of the pressure catheter, both within the cubital tunnel and four centimeters proximal to it, at 10-degree increments from 0 to 130 degrees of elbow flexion. As the elbow was moved from full extension to 135 degrees of flexion, the mean cross-sectional area of the three regions of the cubital tunnel decreased by 30, 39, and 41 per cent and the mean area of the ulnar nerve decreased by 33, 50, and 34 per cent. These changes were significant in all three regions of the cubital tunnel (p < 0.05). The greatest changes occurred in the region beneath the aponeurosis of the cubital tunnel with the elbow at 135 degrees of flexion. The mean intraneural pressure within the cubital tunnel was significantly higher than the mean extraneural pressure when the elbow was flexed 90, 100, 110, and 130 degrees (p < 0.05). With the elbow flexed 130 degrees, the mean intraneural pressure was 45 per cent higher than the mean extraneural pressure (p < 0.001). Similarly, with the elbow flexed 120 degrees or more, the mean intraneural pressure four centimeters proximal to the cubital tunnel was significantly higher than the mean extraneural pressure (p < 0.01). Relative to their lowest values, intraneural pressure increased at smaller angles of flexion than did extraneural pressure, both within the cubital tunnel and proximal to it. With the numbers available, we could not detect any significant difference in intraneural pressure measured, either at the level of the cubital tunnel or four centimeters proximal to it, after release of the aponeurotic roof of the cubital tunnel.

Ultrasonography shows extensive nerve enlargements in multifocal motor neuropathy

Using ultrasonography we found multiple sites with nerve enlargement along the course of the brachial plexus, median, ulnar, and radial nerves in the majority of 21 patients with multifocal motor neuropathy. Sonography and electrophysiologic studies showed more abnormalities than expected on purely clinical grounds. Moreover, sonography revealed nerve enlargement without clinical or electrophysiologic abnormalities.

Diagnostic value of high-resolution sonography in ulnar neuropathy at the elbow

OBJECTIVE

To determine the diagnostic value of high-resolution sonography in ulnar neuropathy at the elbow (UNE).

METHODS

Sonographic ulnar nerve diameter measurement was compared at three levels around the medial epicondyle with a criterion standard including clinical and electrophysiologic characteristics in a cohort of 123 patients presenting with clinical signs of UNE. UNE or probable UNE was diagnosed in 84 patients and a different condition in 39 patient controls. Reference values were obtained in 56 healthy volunteers.

RESULTS

One hundred thirty-six affected arms were studied in 123 patients (UNE in 82, probable UNE in 9, and a different condition in 45 affected arms). Patients with UNE had a larger ulnar nerve diameter than patient controls (p < 0.0001). The sensitivity of sonography was 80%, specificity 91%, positive likelihood ratio 9, and negative likelihood ratio 0.2. The highest diagnostic yield was found in patients in whom electrodiagnostic studies showed signs of ulnar neuropathy but could not localize the lesion (17/20 cases, 86%) and in patients who had motor conduction velocity slowing across the elbow without conduction block (32/37 cases, 86%).

CONCLUSIONS

High-resolution sonography is an accurate and easily applied test for the diagnosis of UNE. The authors recommend its use in addition to electrodiagnostic studies because it improves the reliability of the diagnosis of UNE.

High-resolution sonography versus EMG in the diagnosis of carpal tunnel syndrome

BACKGROUND

Carpal tunnel syndrome (CTS) is a common entrapment neuropathy. Electrodiagnostic testing (EMG) is used to confirm the diagnosis. It is not known what the diagnostic accuracy of high-resolution sonography is in comparison to EMG.

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of both tests in CTS patients.

METHODS

A prospective cohort of 207 patients with possible CTS underwent high-resolution sonography and EMG. The diagnosis of CTS was based on clinical signs and symptoms. The cross-sectional area of the median nerve at the carpal tunnel inlet and at the distal one-third level of the forearm was assessed by an investigator, blinded to the clinical and EMG data. Normal sonographic values were obtained from 137 controls. All patients and 40 controls underwent a standardised nerve conduction study. The kappa coefficient was used to evaluate the relationship between sonography, EMG and clinical diagnosis.

RESULTS

The cross-sectional area at the distal one-third of the forearm was not significantly different between the controls and patients (p = 0.59), whereas the cross-sectional area at the carpal tunnel inlet was significantly increased in the patient group (p<0.0001). The kappa coefficient for EMG using the median-ulnar distal sensory latency difference versus clinical evaluation was 0.64 and, for sonography, this coefficient was 0.69; these were not statistically different (p = 0.37). Combining the two tests resulted in a kappa coefficient of 0.72, which was not significantly different from sonography alone (p = 0.73).

CONCLUSION

In patients with a clinical diagnosis of CTS, the accuracy of sonography is similar to that for EMG. Sonography is probably preferable because it is painless, easily accessible and preferred by the patients.

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.

Morphology and dynamics of the ulnar nerve in the cubital tunnel. Observation by ultrasonography

We examined 200 normal elbows to assess the usefulness of ultrasonography in examining the ulnar nerve in the cubital tunnel. On longitudinal images in elbow extension, the nerve changed its course at the fibrous band region 11.5 (SD 2.8) mm distal to the medial epicondyle. On axial images, the diameter of the major axis of the nerve was 3.1 (0.5) mm and that of the minor axis was 1.9 (0.4) mm in men. The respective values were 2.7 (0.4) mm and 1.8 (0.4) mm in women. Dynamic studies showed that in 53 elbows (27%), the nerve moved on to the tip of the epicondyle with the elbow flexed and in 39 elbows (20%), the nerve dislocated anteriorly. The diameters of the hypermobile nerves were significantly larger than nerves that did not displace.

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 of radial, ulnar, median, and sciatic nerves in healthy subjects and patients with hereditary motor and sensory neuropathies

This study was conducted to evaluate the capability of ultrasonography to visualize extremity nerves. Fifty healthy women and men and 10 patients suffering with hereditary motor and sensory neuropathy (HMSN) were examined. The radial nerve lateral to the humerus, ulnar nerve distal to the cubital tunnel, median nerve in the middle of the forearm and proximal to the palmar crease, sciatic nerve in the middle of the thigh and tibial and common peroneal nerves just distal to their bifurcation, were investigated, employing a 7.5-MHz electronic linear-array transducer. In healthy subjects, the median, ulnar and radial nerves could be identified in all cases, the sciatic nerve in 37 cases, the tibial and peroneal nerves in 10 cases. The median values of thicknesses were about 3 mm for arm nerves and 6 to 7 mm for the sciatic nerve. Nerve sizes did not correlate with subjects' height, weight or age. In the majority of the patients, arm and sciatic nerves were also visible. Thicknesses were normal in 34, increased in 11 and decreased in six of 51 nerves. In conclusion, ultrasonography allows reliable imaging of the major arm nerves and, occasionally, facilitates visualization of the sciatic, tibial and peroneal nerves in healthy subjects. Nerve size and structure did not differ significantly between patients with HMSN and healthy subjects.

Cubital tunnel syndrome: diagnosis by high-resolution ultrasonography

The purpose of this study was to evaluate the morphologic changes in the ulnar nerve in cubital tunnel syndrome with high-resolution ultrasonography. The mean values of the short axis (cm) x long axis (cm) at the arm, epicondyle, and forearm levels were 0.057 +/- 0.01, 0.068 +/- 0.019, and 0.062 +/- 0.01 in control group; 0.069 +/- 0.04, 0.139 +/- 0.06, and 0.066 +/- 0.023 in the symptomatic side in patients with cubital tunnel syndrome; and 0.063 +/- 0.029, 0.068 +/- 0.029, and 0.057 +/- 0.012 in the normal side in patients with cubital tunnel syndrome. No significant difference was found in the area (short axis x long axis) of the ulnar nerve at the arm, epicondyle and forearm levels between the left and right ulnar nerve in the control group and between the control group and the normal side in symptomatic patients. However, the mean value of the area of the ulnar nerve at the epicondyle level in symptomatic patients was significantly larger than that of the control group and that of the contralateral side in patients, and the P value was less than 0.001. High resolution ultrasonography can detect morphologic changes in the ulnar nerve accurately, and it could therefore be useful as a screening and even follow-up modality in patients with cubital tunnel syndrome.

Ulnar neuropathy at the elbow: Follow-up and prognostic factors determining outcome

OBJECTIVE

To determine the outcome in patients with ulnar neuropathy at the elbow (UNE) treated surgically or conservatively, and the prognostic value of clinical, sonographic, and electrophysiologic features.

METHODS

After a median follow-up of 14 months, 69 of 84 patients initially included in a prospective blinded study on the diagnostic value of sonography in UNE were re-evaluated. The patients underwent renewed systematic clinical and sonographic examination. Patients were scored as having a poor (stable or progressive symptoms) or favorable (complete remission of symptoms or improvement) outcome.

RESULTS

Of the 74 initially affected arms, 12 (16%) had a complete remission, 21 (28%) improved, 25 (34%) remained stable, and 16 (22%) had progression. Surgically treated patients (28 arms) had a more favorable outcome than those treated conservatively (p = 0.03). After surgery, the mean ulnar nerve diameter decreased from 3.2 to 2.9 mm (p = 0.03), while this was not seen after conservative treatment. Multiple logistic regression analysis showed that more outspoken nerve enlargement found during sonography at the time of the diagnosis was associated with a poor outcome (OR: 2.9, p = 0.009). Furthermore, the presence of a motor conduction block (OR: 0.2, p = 0.03) and motor velocity slowing across the elbow (OR: 0.1, p = 0.01) were associated with a favorable outcome.

CONCLUSION

More pronounced ulnar nerve thickening at the time of the diagnosis is associated with poor outcome at follow-up, especially in conservatively treated cases, while electrodiagnostic signs of demyelination on testing indicate favorable outcome.

Ultrasonographic reference sizes of the median and ulnar nerves and the cervical nerve roots in healthy Japanese adults

The objective of this study was to identify, for practical use, ultrasonographic reference values for nerve sizes at multiple sites, including entrapment and non-entrapment sites along the median and ulnar nerves and among the cervical nerve roots. We verified reliable sites and site-based differences between the reference values. In addition, we found associations between the reference nerve sizes and several physical characteristics (gender, dominant hand, age, height, weight, body mass index [BMI] and wrist circumference). Nerves were measured bilaterally at 26 sites or levels in 60 healthy Japanese adults (29 males; age, 35.4 ± 9.7 y; BMI, 22.3 ± 3.6 kg/m(2); wrist circumference, 16.0 ± 1.3 cm on the right side and 15.9 ± 1.2 cm on the left side). The mean reference nerve sizes were 5.6-9.1 mm(2) along the median nerve, 4.1-6.7 mm(2) along the ulnar nerve and 2.14-3.39 mm among the cervical nerve roots. Multifactorial regression analyses revealed that the physical characteristics most strongly associated with nerve size were age, BMI and wrist circumference at the entrapment sites (F = 7.6, p < 0.01, at the pisiform bone level of the carpal tunnel; F = 15.1, p < 0.001, at the level of Guyon's canal), as well as wrist circumference and gender at the non-entrapment sites (F = 70.6, p < 0.001, along the median nerve; F = 24.7, p < 0.001, along the ulnar nerve). Our results suggest that the factors with the greatest influence on nerve size differed between entrapment and non-entrapment sites. Site-based differences in nerve size were determined using one-way analyses of variance (p < 0.001). Intra- and inter-observer reliability was highest for the median nerve, at both the distal wrist crease and mid-humerus; at the arterial split along the ulnar nerve; and at the fifth cervical nerve root level. No systematic error was indicated by Bland-Altman analysis; the coefficients of variation were 5.5%-9.2% for intra-observer reliability and 7.1%-8.7% for inter-observer reliability.

The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound

BACKGROUND AND OBJECTIVE

Seeking paresthesia and obtaining a motor response to an electrical stimulus are the two most common methods of nerve localization for the performance of peripheral-nerve blocks. However, these two endpoints do not always correlate, and the actual sensitivity and specificity of either method remains unknown. The objective of this study is to determine the sensitivity of paresthesia and motor response to electrical nerve stimulation as tools for nerve localization when a 22-gauge insulated needle is used for the performance of axillary-nerve block.

METHODS

After IRB approval and informed consent, 103 patients were enrolled. Real-time ultrasonography was used as the reference test. After needle-to-nerve contact was confirmed by ultrasonography, the patient was requested to report the presence of paresthesia, and a nerve stimulator was used to seek a motor response, with a stimulating current of 0.5 mA or less.

RESULTS

One patient was excluded from analysis because of protocol violation. Paresthesia was found to be 38.2% sensitive and motor response was 74.5% sensitive for detection of needle-to-nerve contact.

CONCLUSION

The very different and relatively low sensitivity of either technique may explain, in part, the lack of correlation previously reported between the 2 endpoints.

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.

Diagnostic ultrasonography of the ulnar nerve in cubital tunnel syndrome

Thirty-two elbows in 31 patients diagnosed as having cubital tunnel syndrome underwent ultrasonographic examination to assess morphological changes in the ulnar nerve and its surrounding tissues. On longitudinal images, the site of constriction due to the fibrous band and proximal swelling of the nerve were observed by ultrasonography and were confirmed intraoperatively. On axial images, the lengths of the major axis [7.2 (SD 1.6) mm] and the minor axis [3.7 (0.9) mm] of the nerve at the medial epicondyle were greater than those in normal subjects. There was a correlation between the stage of ulnar nerve palsy and the diameter of the major axis. Preoperatively, ganglia were detected by ultrasonography in the cubital tunnel in three cases and an anconeus epitrochlearis muscle in two.

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.

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.

Treatment of compression neuropathy of the ulnar nerve at the elbow by epicondylectomy and neurolysis

Compression neuropathy of the ulnar nerve at the elbow is treated by neurolysis and excision of the medial humeral epicondyle without transposing the ulnar nerve anteriorly. Removal of the medial humeral epicondyle is not associated with loss of motion at the elbow or reduction in strength of finger or wrist flexion because of the multiple muscle origins, as well as the firm healing of the common flexor origin to the resected bone surface. Thirty cases were treated between 1965 and 1977. Treatment halted progression of the disease in all patients. Discomfort and pain subsided in every instance. All 12 of the grade I patients had return of normal nerve function. Four of the 12 grade II patients were left with some weakness. Four of the six grade III patients improved to grade II status. None required secondary procedures on the ulnar nerve.

Role of ulnar nerve sonography in leprosy neuropathy with electrophysiologic correlation

OBJECTIVE

The purpose of this study was to evaluate the diagnostic usefulness of ulnar nerve sonography in leprosy neuropathy with electrophysiologic correlation.

METHODS

Twenty-one consecutive patients with leprosy (12 men and 9 women; mean age +/- SD, 47.7 +/- 17.2 years) and 20 control participants (14 men and 6 women; mean age, 46.5 +/- 16.2 years) were evaluated with sonography. Leprosy diagnosis was established on the basis of clinical, bacteriologic, and histopathologic criteria. The reference standard for ulnar neuropathy in this study was clinical symptoms in patients with proven leprosy. The sonographic cross-sectional areas (CSAs) of the ulnar nerve in 3 different regions were obtained. Statistical analyses included Student t tests and receiver operating characteristic curve analysis.

RESULTS

The CSAs of the ulnar nerve were significantly larger in the leprosy group than the control group for all regions (P < .01). Sonographic abnormalities in leprosy nerves included focal thickening (90.5%), hypoechoic areas (81%), loss of the fascicular pattern (33.3%), and focal hyperechoic areas (4.7%). Receiver operating characteristic curve analysis showed that a maximum CSA cutoff value of 9.8 mm(2) was the best discriminator (sensitivity, 0.91; specificity, 0.90). Three patients with normal electrophysiologic findings had abnormal sonographic findings. Two patients had normal sonographic findings, of which 1 had abnormal electrophysiologic findings, and the other refused electrophysiologic testing.

CONCLUSIONS

Sonography and electrophysiology were complementary for identifying ulnar nerve neuropathy in patients with leprosy, with clinical symptoms as the reference standard. This reinforces the role of sonography in the investigation of leprosy ulnar neuropathy.

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.

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.

Sonoanatomy of the ulnar nerve in the cubital tunnel: a multicentre study by the GEL

The objective is to determine the normal appearance of the ulnar nerve on a posterior axial sonogram section of the elbow through the medial epicondyle and the humeroulnar joint space. Ultrasound evaluation was carried out on 400 elbows with measurement of the ulnar nerve cross-sectional area and ulnar nerve-cortex distance, as well as recording of apparent ulnar nerve division. Factors that significantly influenced the study variables were sought by statistical analysis. Mean cross-sectional area of the ulnar nerve at the elbow was 7.9 +/- 3.1 mm2 overall. Values were lower in females than in males and increased between 40 and 60 years of age. The ulnar nerve-cortex distance was 0.8 +/- 0.4 mm and varied widely across individuals. Apparent ulnar nerve division at the elbow was noted in about one-fifth of individuals, with no difference between females and males or between the right and left elbows. When present, apparent division was often bilateral and was not associated with changes in cross-sectional area or in distance from the medial epicondyle cortex. This study provides normative data on ulnar nerve sonoanatomy at the elbow and establishes that apparent ulnar nerve division at the elbow is a normal variant.

The validity of ultrasonographic assessment in cubital tunnel syndrome: the value of a cubital-to-humeral nerve area ratio (CHR) combined with morphologic features

Diagnosis of a typical idiopathic cubital tunnel syndrome (CuTS) is straight forward but the work-up of mild forms is clinically challenging. The diagnostic value of high-resolution ultrasound (HRUS) relying solely on nerve measurements is doubtful. Additional textural analysis of the nerve may possibly overcome this drawback. Thirty-eight prospectively enrolled patients with idiopathic CuTS and 23 healthy volunteers underwent standardized HRUS. A cubital-to-humeral nerve area ratio (CHR) was calculated and the texture of the most swollen nerve segment assessed. CHR was significantly different among patients and volunteers (p<0.001) but with a marked overlap. Combination of at least partial inner fascicular masking plus a CHR>1.4 showed a positive linear coherence with idiopathic CuTS at a specificity>95% and a PPV>90%. Thus, the combined textural analysis and CHR calculation seems a powerful tool for the sonographic diagnosis of idiopathic CuTS.

Ultrasonographic measurements in cubital tunnel syndrome

The cubital tunnel is the most common site of ulnar nerve entrapment. Previous ultrasound studies have demonstrated enlargement of the ulnar nerve in cubital tunnel syndrome but did not report on the cubital tunnel itself. Twenty-two individuals with cubital tunnel syndrome were evaluated with nerve conduction studies and ultrasound. The ultrasound measurement that most strongly correlated with conduction velocity was the ratio of ulnar nerve to cubital tunnel cross-sectional area with the elbow flexed. Measurement of this ratio may improve the diagnostic accuracy of ultrasound in cubital tunnel syndrome, although further investigation is needed.

Ultrasound measurement of median and ulnar nerve cross-sectional area in acromegaly

CONTEXT

Acromegalic patients may complain of sensory disturbances in their hands.

OBJECTIVE

Our objective was to examine median (MN) and ulnar nerves (UN) of acromegalic patients with ultrasound (US) and to determine whether nerve abnormalities correlate with clinical parameters and nerve conduction studies (NCS).

PATIENTS

We prospectively examined the MN and UN in 34 nondiabetic, acromegalic patients (18 females and 16 males; age range 18-79 yr) and 34 sex-, age-, and body mass index-matched controls with 17-5 MHz US.

INTERVENTION

The MN was examined at the carpal tunnel (MN-Ct) and at mid-forearm (MN-f) levels; the UN at the mid-forearm (UN-f) and distal arm (UN-a). A total of 272 nerve cross-sectional areas (CSA) were recorded from both patients and controls. In addition, 22 patients underwent NCS.

RESULTS

Nerves of acromegalic patients (MN-Ct=16.5+/-4.4 mm2; MN-f=10.5+/-2.4 mm2; UN-f=9.5+/-3.0 mm2; UN-a=13.1+/-3.7 mm2) had significantly (P<0.0001) greater CSA compared with controls (MN-Ct=7.4+/-1.7 mm2; MN-f=5.5+/-1.4 mm2; UN-f=5.3+/-1.4 mm2; UN-a=6.6+/-1.7 mm2). NCS displayed at least one abnormality in 59% of patients. Acromegalic patients, grouped according to disease activity (14 controlled, 8 partially controlled, 12 uncontrolled), had significantly (P<0.0001) greater CSA compared with controls. Nerve CSA were significantly greater in uncontrolled patients compared to controlled, both at MN-Ct and at UN-f levels (P<0.01). Abnormal NCS were observed in five of seven uncontrolled patients and four of nine controlled patients. IGF-I levels, but not GH levels, were correlated with CSA (r=0.34), whereas disease duration correlated with both nerve CSA and NCS (r=0.33 and r=0.31).

CONCLUSION

US identified a significantly increased volume of MN and UN in acromegalic patients. Peripheral nerve enlargement in acromegaly seems to be an intrinsic feature of the disease related to clinical control, disease duration, and IGF-I levels.