Ulnar neuropathy is the second most common cause of entrapment neuropathy after carpal tunnel syndrome [
Between August 2010 and January 2012, twenty-nine elbows of 25 patients with a diagnosis of UNE were prospectively studied at Imam Reza Hospital, a university-affiliated teaching hospital. The study was approved by the local medical ethical committee of the Tabriz University of Medical Sciences. Informed consent was obtained from each subject in patient and control groups prior to the study. Inclusion criteria were the age of 15–65 years and presence of clinical findings and electrophysiological confirmation of UNE. The symptoms (numbness and paresthesia of the fourth and fifth digits of the hand, weakness or clumsiness of the hand muscles innervated by the ulnar nerve, and medial elbow pain) and signs (sensory loss in the area of the ulnar nerve and weakness of the ulnar innervated muscles) constituted the clinical diagnosis of UNE. Moreover, electrodiagnostic criteria for UNE were based on those proposed by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) (see below). Patients were excluded if any of they had history of polyneuropathy, acute trauma, previous trauma in the region of the elbow (including previous surgery), or symptoms of UNE more than one year.
Thirty-five elbows of 23 healthy age-group-matched controls with no signs or symptoms of UNE or had systemic diseases associated with polyneuropathy were recruited for both ultrasonography and MRI studied.
Electrophysiological studies included needle electromyography (EMG), and nerve conduction studies of the median and ulnar nerves were performed in all patients. The studies were performed with Nicolet Viking IV electrodiagnostic system and TOENINNIES NeuroScreen Plus equipment. Ulnar sensory and motor nerve conduction studies were performed with the elbow flexed at 90°. To evaluate the motor conduction velocity (MCV) of the ulnar nerve, surface recording electrodes were located over the motor point of the abductor digiti minimi (ADM) and first dorsal interosseous (FDI) muscles. Surface stimulation was performed at the wrist, 4 cm distal to the medial epicondyle (below elbow) and 10 cm above this level (above elbow). The sensory conduction studies were done antidromically, stimulating at the wrist and recording from digit 4 or 5 for the ulnar nerve. The severity of UNE was defined as mild, moderate, and severe based on the following criteria [ Mild involvement, presence of one of the following: reduced motor conduction velocity (MCV) > 10 m/s across the elbow (segment below-above elbow), compared with the more distal segment (wrist-below elbow), from the muscle I dorsal interosseus (IDI) or Abductor Digiti Minimi (ADM), plus increased F-wave (compared with the unaffected side or normative value); reduced amplitude of sensory nerve action potentials (SNAPs) at IV and/or V finger (compared with the unaffected side or normative value). Moderate involvement, presence of one of the following: point 1 plus 2 of the previous grade; motor conduction block from IDI or ADM at the elbow; reduced amplitude of proximal compound muscle action potential (CMAP) across the elbow from IDI or ADM > 20 but <50% and/or abnormal EMG of ulnar hand muscles (acute and chronic denervation potentials) and/or SNAPs absence. Severe involvement, presence of one of the following: complete motor conduction block alone across the elbow from IDI or ADM plus other abnormalities (point 3 of previous grade); reduced amplitude of proximal CMAP across the elbow from IDI or ADM > 50%; severe axonal involvement of ulnar nerve with SNAPs abnormalities and abnormal EMG of ulnar hand muscles (acute and chronic denervation potentials).
In all the patients and controls, the ulnar nerve at the elbow was examined by the same radiologist blinded to the study using high-resolution ultrasonography (Medison multifrequency 7–14 MHz). The examinee sat and faced the operator with the examined upper limb and elbow flexed to 90°. Using automatic manual tracing method within the echogenic rim, four measurements including at the level of medial epicondyle cross-sectional area (CSA)-epi, 4 cm proximal to the medial epicondyle (CSA-prox), 4 cm distal to the epicondyle (CSA-dist), and the maximum cross-sectional area (CSA-max) of the ulnar nerve found between these points were performed in axial planes.
Axial, coronal, and sagittal T1-weighted and fat suppressed T2-weighted sequences in 3 mm slice thickness through the elbow joint were obtained from all patients and controls using a same 1.5 T magnetic resonance imager (Siemens, USA). The field of view was 10 cm centered at the medial epicondyle. A single observer who was blinded to the clinical, neurophysiologic, and ultrasonographic findings analyzed the MRI findings based on the signal intensity of the ulnar nerve, nerve compression, and nerve swelling. Increased signal intensity was qualitatively determined. The caliber of the ulnar nerve was pictured over its 10 cm field of view and any apparent (or qualitative) swelling or compression was quantitated using computerized measurements. The caliber of the ulnar nerve was deemed to be abnormal if there was greater than 20% increase (defined as nerve swelling) or decrease (defined as nerve compression) in cross-sectional diameter in relation to proximal and distal segments [
Data were presented as mean ± standard deviation or as median (interquartile range). All statistical analyses were performed with Statistical Package of Social Science (SPSS Inc., Chicago, IL) for Windows version 16. Chi-square or Fisher's exact tests were used to study the qualitative data,
Twenty-nine elbows with UNE were studied. Table
Baseline characteristics and CSA of the ulnar nerve at the elbow in the patients and controls.
Variable | Patients | Controls |
|
---|---|---|---|
Age (years) |
|
|
0.62 |
Gender (male : female) | 16 : 9 | 15 : 8 | 0.85 |
Number of patients/examined elbows | 25/29 | 23/35 | — |
Side affected: |
NA | ||
Right | 10 (40%) | — | |
Left | 11 (44%) | — | |
Bilateral | 4 (16%) | — | |
UNE severity: |
NA | ||
Mild | 13 (44.8%) | — | |
Moderate | 8 (27.6%) | — | |
Severe | 8 (27.6%) | — | |
CSA-prox (mm2) | 6 (5–7) | 4 (4-5) | <0.001 |
CSA-epi (mm2) | 7 (5–12) | 4 (3–5) | <0.001 |
CSA-dist (mm2) | 5 (4–7) | 4 (3–5) | <0.001 |
CSA-max (mm2) | 9 (6.6–13.5) | 5 (4–6) | <0.001 |
UNE: ulnar neuropathy at the elbow; CSA: cross-sectional area; prox: proximal; epi: epicondyle; dist: distal; max: maximum; NA: not available.
CSA of the ulnar nerve at the elbow in different UNE severity groups.
Variable | Mild ( |
Moderate ( |
Severe ( |
|
---|---|---|---|---|
CSA-prox (mm2) | 5 (4–6) | 6.5 (5.25–8.5) | 6 (5.25–9.75) | 0.03 |
CSA-epi (mm2) | 6 (4.5–7.5) | 6.5 (5.25–10) | 13 (7.5–15.75) | 0.04 |
CSA-dist (mm2) | 4 (3–6) | 5.5 (4.25–6.75) | 9 (5–10.5) | 0.01 |
CSA-max (mm2) | 7 (6–9) | 10 (7–14.37) | 13.5 (10.5–16) | 0.003 |
UNE: ulnar neuropathy at the elbow; CSA: cross-sectional area; prox: proximal; epi: epicondyle; dist: distal; max: maximum.
An ROC analysis provided the sensitivity and specificity of the ultrasonographic measurements. The CSA-max had the largest area under the curve and the greatest sensitivity and specificity (Table
ROC analysis of ultrasonographic measurements.
Variable | AUC | Cut-off value | Sensitivity | Specificity |
---|---|---|---|---|
CSA-prox (mm2) | 0.73 | 5 | 79% | 51% |
CSA-epi (mm2) | 0.83 | 5 | 82% | 65% |
CSA-dist (mm2) | 0.74 | 5 | 72% | 71% |
CSA-max (mm2) | 0.90 | 6 | 93% | 68% |
ROC: receiver operating characteristic; CSA: cross-sectional area; prox: proximal; epi: epicondyle; dist: distal; max: maximum; AUC: area under the curve.
ROC curve for ultrasonographic measurements CSA: cross-sectional area.
An MRI was performed in 21 UNE patients and 20 healthy individuals. Nineteen symptomatic patients (90.4%) and four (20%) normal volunteers had increased signal intensity of the ulnar nerve. In patients with UNE, ulnar nerve hyperintensity was followed by ulnar nerve swelling (9/21, 42.8%), combination of ulnar nerve hyperintensity and swelling (9/21, 42.8%), and ulnar nerve compression (7/21, 33.3%). In addition, ulnar nerve hyperintensity showed the greatest sensitivity (90%) and specificity (80%) than the other measured MRI variables (Table
Sensitivity and specificity of MRI measurements.
Variable | Sensitivity | Specificity |
|
---|---|---|---|
Ulnar nerve hyperintensity | 90% | 80% | <0.001 |
Ulnar nerve swelling | 42% | 100% | 0.01 |
Ulnar nerve hyperintensity and swelling | 42% | 100% | 0.01 |
Ulnar nerve compression | 33% | 100% | 0.06 |
MRI: magnetic resonance imaging.
The present study revealed that the ulnar nerve CSA at all the four levels (-prox, -epi, -dist, and -max) was significantly greater in UNE patients than in the healthy individuals. These findings are similar to those of the previous studies [
In the present study, we found that the cut-off value of >5 mm2 for CSA-prox, -epi, and -dist had sensitivity of 72–82% and specificity of 51–71% in UNE diagnosis. The study by Bayrak and colleagues yielded relatively similar sensitivity and specificity of the CSA-prox and -dist; however, the cut-off values were higher (8 and 9 mm2) compared to those of our study [
The present study also showed that the ulnar nerve enlargement, evaluated by CSA at all the four levels (-prox, -epi, -dist, and -max), was significantly linked to UNE severity. An association between the ulnar nerve and severity of nerve conduction abnormalities in UNE has been established in some previous studies [
In our study, MRI analysis revealed that ulnar nerve hyperintensity had greatest sensitivity (90%) and specificity (80%). Similarly, high sensitivity of increased signal of the ulnar nerve (97%) in MRI was reported by Britz and coworkers [
This study has certain limitations. A clear limitation is the small sample size for both patients and controls. Further similar studies with larger sample size would be valuable in definition of both ultrasonography and MRI cut-off points discriminating between different UNE severity grades. Furthermore, in some cases of the control group we used both arms as independent observations (artificial power increase) [
In conclusion, as a useful complementary tool, ultrasonography of the ulnar nerve using maximum CSA (CSA-max) is both sensitive and specific in UNE diagnosis and discriminating the severe UNE cases from the mild and moderate grades. Furthermore, ulnar nerve MRI particularly targeting at the increased signal of the ulnar nerve can be a useful diagnostic test for evaluation of UNE, particularly in conjunction with clinical and electrophysiological data.
This paper is based on Elyar Sadeghi-Hokmabadi’s specialty dissertation (89/3-7/9) submitted to the Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.