Diagnostic Value of Ultrasonography and Magnetic Resonance Imaging in Ulnar Neuropathy at the Elbow

Abstract

Aim. To evaluate the diagnostic value of ultrasonography and magnetic resonance imaging (MRI) in patients with ulnar neuropathy at the elbow (UNE). Methods. We prospectively performed electrodiagnostic, ultrasonographic, and MRI studies in UNE patients and healthy controls. Three cross-sectional area (CSA) measurements of the ulnar nerve at multiple levels along the arm and maximum CSA(-max) were recorded. Results. The ulnar nerve CSA measurements were different between the UNE severity grades (P < 0.05). CSA-max had the greatest sensitivity (93%) and specificity (68%). Moreover, CSA-max ≥10 mm(2) defined the severe UNE cases (sensitivity/specificity: 82%/72%). In MRI, ulnar nerve hyperintensity had the greatest sensitivity (90%) and specificity (80%). Conclusion. Ultrasonography using CSA-max is sensitive and specific in UNE diagnosis and discriminating the severe UNE cases. Furthermore, MRI particularly targeting at increased signal of the ulnar nerve can be a useful diagnostic test of UNE.

Full text

International Scholarly Research Network
ISRN Neurology
Volume 2012, Article ID 491892, 6pages
doi:10.5402/2012/491892
Research Article
Diagnostic Value of Ultrasonography and Magnetic Resonance
Imaging in Ulnar Neuropathy at the Elbow
Hormoz Ayromlou,1Mohammad K. Tarzamni,2Mohammad Hossein Daghighi,2
Mohammad Zakaria Pezeshki,3Mohammad Yazdchi,1Elyar Sadeghi-Hokmabadi,1
Ehsan Sharifipour,1and Kamyar Ghabili4
1Neuroscience Research Center, Tabriz University of Medical Sciences, Tabriz 51666-14756, Iran
2Department of Radiology, Tabriz University of Medical Sciences, Tabriz 51656-65811, Iran
3Department of Community Medicine, Tabriz University of Medical Sciences, Tabriz 51656-65811, Iran
4Medical Philosophy and History Research Center, Tabriz University of Medical Sciences, Tabriz 51656-65811, Iran
Correspondence should be addressed to Kamyar Ghabili, kghabili@gmail.com
Received 8 May 2012; Accepted 30 May 2012
Academic Editors: H. Aldskogius, C. Angelini, and D. Munoz
Copyright © 2012 Hormoz Ayromlou et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Aim. To evaluate the diagnostic value of ultrasonography and magnetic resonance imaging (MRI) in patients with ulnar neuropa-
thy at the elbow (UNE). Methods. We prospectively performed electrodiagnostic, ultrasonographic, and MRI studies in UNE pa-
tients and healthy controls. Three cross-sectional area (CSA) measurements of the ulnar nerve at multiple levels along the arm and
maximum CSA(-max) were recorded. Results. The ulnar nerve CSA measurements were different between the UNE severity grades
(P<0.05). CSA-max had the greatest sensitivity (93%) and specificity (68%). Moreover, CSA-max ≥10 mm2defined the severe
UNE cases (sensitivity/specificity: 82%/72%). In MRI, ulnar nerve hyperintensity had the greatest sensitivity (90%) and specificity
(80%). Conclusion. Ultrasonography using CSA-max is sensitive and specific in UNE diagnosis and discriminating the severe UNE
cases. Furthermore, MRI particularly targeting at increased signal of the ulnar nerve can be a useful diagnostic test of UNE.
1. Introduction
Ulnar neuropathy is the second most common cause of en-
trapment neuropathy after carpal tunnel syndrome [1]. The
ulnar nerve could be trapped in every part of upper limb
including wrist, elbow, or arm. Therefore, diagnosing the
site of ulnar nerve injury is of great clinical and therapeutic
importance. Ulnar neuropathy at the elbow (UNE) where the
nerve passes through the cubital tunnel is the most common
place of the ulnar nerve entrapment [2]. The diagnosis of
UNE is based on obtaining medical history, clinical exam-
ination, and electrodiagnostic studies [1]. Due to false neg-
ative or nonlocalizing results of the electrodiagnostic stud-
ies, ultrasonography of the ulnar nerve has been recently
recommended as an accurate noninvasive additional tool.
However, ultrasonography still has no role in guidelines or
practice parameters due to controversial results both in UNE
patients and healthy individuals [3]. On the other hand,
magnetic resonance imaging (MRI) is being increasingly
used in the evaluation of ulnar neuropathy [4]. To date, few
investigations have targeted at assessing the diagnostic value
of MRI in UNE with debatable results [5–7]. To the best of
our knowledge, the diagnostic value of both ultrasonography
and MRI in UNE has not been hitherto investigated in a
single study. Therefore, we aimed at evaluating the diagnostic
value of ultrasonography and MRI in patients with UNE and
also comparing the ultrasonographic and MRI alterations
of the ulnar nerve in patients with different grades of UNE
severity determined by electrodiagnostic studies.
2. Materials and Methods
2.1. Patients and Controls. 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

2ISRN Neurology
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 electrophys-
iological 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 con-
trols with no signs or symptoms of UNE or had systemic
diseases associated with polyneuropathy were recruited for
both ultrasonography and MRI studied.
2.2. Electrodiagnostic Studies. Electrophysiological studies
included needle electromyography (EMG), and nerve con-
duction studies of the median and ulnar nerves were per-
formed in all patients. The studies were performed with Ni-
colet Viking IV electrodiagnostic system and TOENINNIES
NeuroScreen Plus equipment. Ulnar sensory and motor
nerve conduction studies were performed with the elbow
flexed at 90◦.Toevaluatethemotorconductionvelocity
(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 10cm 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 [1].
(i) Mild involvement, presence of one of the following:
(a) 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);
(b) reduced amplitude of sensory nerve action po-
tentials (SNAPs) at IV and/or V finger (com-
pared with the unaffected side or normative
value).
(ii) Moderate involvement, presence of one of the follow-
ing:
(a) point 1 plus 2 of the previous grade;
(b) motor conduction block from IDI or ADM at
the elbow;
(c) 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.
(iii) Severe involvement, presence of one of the following:
(a) complete motor conduction block alone across
the elbow from IDI or ADM plus other abnor-
malities (point 3 of previous grade);
(b) reduced amplitude of proximal CMAP across
the elbow from IDI or ADM >50%;
(c) severe axonal involvement of ulnar nerve with
SNAPs abnormalities and abnormal EMG of
ulnar hand muscles (acute and chronic dener-
vation potentials).
2.3. Ultrasonographic Evaluation. 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.
2.4. Magnetic Resonance Imaging Examination. Axial, coro-
nal, 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 [7]. To reduce false positive
rates, the ulnar nerve was assessed in 20 healthy controls who
underwent a similar MRI study through the radiohumeral
joint.
2.5. Statistical Analysis. Data were presented as mean ±
standard deviation or as median (interquartile range). All

ISRN Neurology 3
Tab le 1: Baseline characteristics and CSA of the ulnar nerve at the elbow in the patients and controls.
Variable Patients Controls Pvalue
Age (years) 48.6±13.542.1±12.90.62
Gender (male : female) 16 : 9 15 : 8 0.85
Number of patients/examined elbows 25/29 23/35 —
Side affected: n(%) NA
Right 10 (40%) —
Left 11 (44%) —
Bilateral 4 (16%) —
UNE severity: n(%) 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.
Tab le 2: CSA of the ulnar nerve at the elbow in different UNE severity groups.
Variable Mild (n=13) Moderate (n=8) Severe (n=8) Pvalue
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.
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, t-test for independent groups to compare
quantitative variables, and Repeated Measures Analysis to
evaluate the vital indices in both groups. The sensitivity
and specificity of ultrasonography and MRI were studied by
means of a receiver operating characteristic (ROC) curve. A
Pvalue less than 0.05 was considered statistically significant.
3. Results
Twenty-nine elbows with UNE were studied. Table 1 shows
the baseline characteristics of the patients and controls
included in this study. The median ulnar nerve CSA
(square millimeters) at all the four levels (-prox, -epi, -dist,
and -max) was significantly greater in UNE patients than
in controls (P<0.001, Tab l e 1 ). The median ulnar nerve
CSA at all the four studied levels (-prox, -epi, -dist, and -
max) in the patient group was significantly different between
the UNE severity grades (P<0.05, Tab l e 2 ).
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 (Tab l e 3 ,Figure 1). Moreover, ROC analysis
revealed the CSA-max cut-offpoint of 10 mm2to define the
Tab le 3: ROC analysis of ultrasonographic measurements.
Variable AU C Cut-offvalue 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.
severe UNE. This value yielded sensitivity and specificity of
82% and 72%, respectively. The same analysis did not result
in significant cut-offvalues to define mild and moderate
UNE (P>0.05).
AnMRIwasperformedin21UNEpatientsand20
healthy individuals. Nineteen symptomatic patients (90.4%)
and four (20%) normal volunteers had increased signal in-
tensity 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 (Tabl e 4 ).

4ISRN Neurology
0 0.2 0.4 0.6 0.8 1
1-specificity
0
0.2
0.4
0.6
0.8
1
Sensitivity
Source of the curve
CSA-prox
CSA-dist
CSA-epi
CSA-max
Reference line
ROC curve
Figure 1: ROC curve for ultrasonographic measurements CSA:
cross-sectional area.
Tab le 4: Sensitivity and specificity of MRI measurements.
Variable Sensitivity Specificity Pvalue
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.
4. Discussion
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
[1,8–11]. However, the median ulnar nerve CSA-max of
both UNE patients and healthy individuals in the present
study (9 and 5 mm2, resp.) is less than that of some similar
studies [1,9,11–14]. The indicated values correspond to
those of the similar study by Mondelli and colleagues [8].
In a recent review, Beekman et al. attributed this variation
in normal CSA values of the ulnar nerve to different factors
including selection of controls and use of the unaffected arm
of UNE patients as control [3]. In the present study, we
believe that low CSA-max values in the UNE patients might
stem from higher number of the cases with mild UNE (45%
of all patients) compared with moderate and severe cases of
UNE. Nevertheless, we do not have an explanation for the
low CSA-max values in the healthy individuals.
In the present study, we found that the cut-offvalue of
>5mm
2for 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; how-
ever, the cut-offvalues were higher (8 and 9 mm2)compared
to those of our study [9]. In contrast to the present study,
Bayrak et al. reported higher sensitivity and specificity
(∼82%) for CSA-epi cut-offvalue of >10 mm2[9]. Never-
theless, lower sensitivity (46%) was indicated for CSA at
the epicondyle (CSA-epi) cut-offvalue of >8.8 mm2in
the investigation by Mondelli and coworkers [8]. They
attributed the low sensitivity of CSA-epi to recruitment of
only electrophysiologically confirmed UNE patients, the
presence of many cases of neurologically mild UNE, and the
measurement of the CSA at a fixed point on an axial scan
[8]. On the other hand, the diagnostic value of the CSA-max
in UNE has been studied in several investigations. The
present study showed that the cut-offvalue of >6mm
2for
CSA-max had sensitivity of 93% and specificity of 68% in
UNE diagnosis. These findings are consistent with those of
the study by Bayrak and colleagues (sensitivity/specificity:
95%/71%) for the cut-offvalue of >11 mm2[9]. Other
studies reported that the cut-offvalue of >8.3–10 mm2for
CSA-max had sensitivity of 88–100% and specificity of 88–
98% in UNE diagnosis [1,11,15]. The diagnostic value of
the CSA-max in UNE has been recently analyzed and readers
are referred to the review by Beekman and colleagues [3]. As
the aforementioned, lower cut-offvalues of the ulnar nerve
CSA (-prox, -epi, -dist, and -max) in the present study might
be attributed to the greater number of the cases with mild
UNE compared with the moderate and severe cases of UNE
as well as to the low CSA values in the healthy individuals.
The present study also showed that the ulnar nerve en-
largement, 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 [3,16–18]. However only four
investigations reported such an association between the CSA
and UNE severity [1,8,9,11]. To the best of our knowl-
edge, the present study is the first investigation yielding the
association between CSA at all the four levels (-prox, -epi,
-dist, and -max) and UNE severity. Moreover, our study
aimed at determining the CSA-max cut-offpoints discrim-
inating between different grades of UNE severity. Accord-
ingly, CSA-max cut-offpoint of 10 mm2defined the severe
UNE cases with sensitivity of 82% and specificity of 72%.
Nevertheless, the present study failed to determine signif-
icant CSA-max cut-offvalues to define mild and mod-
erate UNE cases. Among the previous similar trials, only one
study was designed to find CSA cut-offpoints defining the
severity of UNE [1]. Volpe and colleagues found two CSA-
max cut-offvalues of >10 mm2and >15 mm2for the mild
and moderate UNE diagnosis with a very good diagnostic
performance [1]. Nonetheless, the cut-offpoint of >20 mm2
for the severe UNE showed sensitivity of 39% and specificity
of 84% in their study [1]. Their findings are in contrast to
ours in this regard.

ISRN Neurology 5
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 cowork-
ers [6]. In addition, isolated ulnar nerve swelling and com-
bination of ulnar nerve hyperintensity plus swelling yielded
a low sensitivity and high specificity in the present study. In
contrast, considering the isolated swelling or combination of
ulnar nerve hyperintensity plus swelling, MRI had excellent
sensitivity and specificity in UNE diagnosis in the previous
studies [5,7,19]. Altogether, it seems that sensitivity, speci-
ficity, and accuracy of the increased signal intensity of the
ulnar nerve in this study are higher than those of the
ulnar nerve size. This finding is consistent with that of the
previous investigations by Britz et al. and B¨
aumer and col-
leagues [6,19]. On the contrary, large number of healthy
individuals (≥50%) with increased signal intensity of the
ulnar nerve raised doubts about the diagnostic value of
hyperintensity in MRI when compared with the ulnar nerve
size or combination of increased size and signal intensity
[5,20]. As only one-fifth of the normal volunteers in our
study had increased signal intensity of the ulnar nerve, we
believe that increased signal of the ulnar nerve is more sensi-
tive and specific than enlargement of the ulnar nerve in MRI.
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-offpoints
discriminating between different UNE severity grades. Fur-
thermore, in some cases of the control group we used both
arms as independent observations (artificial power increase)
[3]. Moreover, we did not study underlying abnormalities
and anatomical variations in patients with UNE. In addition,
the diagnosis of UNE based on the electrodiagnostic studies
is not an accurate “gold standard” method; current methods
for diagnosing UNE are limited [5]. Also, our study did
not focus on localizing or nonlocalizing abnormalities in the
electrodiagnostic studies. On the other hand, the advantage
of the current study is that this is the first investigation to
assess the diagnostic values of both ultrasonography and
MRI in UNE.
In conclusion, as a useful complementary tool, ultra-
sonography 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.
Acknowledgments
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.
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