OBJECTIVE
Although the diagnosis of ulnar neuropathy at the elbow (UNE) has been made by clinical examination and electrodiagnostic studies, magnetic resonance imaging (MRI) has been increasingly used for evaluation because of limitations such as difficulty in localization. In this retrospective study, the authors aimed to investigate correlations between MRI and nerve conduction study (NCS), especially for the segmental study and the inching study in patients with UNE.
METHODS
194 patients who were diagnosed or suspected with UNE through electrodiagnostic studies at the single center from 2014 to 2018. Patients whose location of the lesion is difficult to identify through electrodiagnosis and who had peripheral polyneuropathy were excluded. Clinical records, electrodiagnostic findings, and MRI findings were reviewed in 46 patients who had symptoms of ulnar neuropathy and underwent elbow MRI. Motor NCS was performed by electrical stimulation of bilateral ulnar nerves with recording motor latency, amplitude, and conduction velocity. Sensory NCS (antidromic) was performed by electrical stimulation of unilateral or bilateral ulnar nerves with recording peak latency, and amplitude. The 5-point (From 0 to 4) severity grade was evaluated based on the signal alteration and/or swelling in fat-suppressed T2 weighted axial sequence by one blinded radiologist. The location of the lesion was defined as three sections with from above elbow 2cm to above elbow 6cm, from above elbow 2cm to below elbow 2cm, and from below 2cm to below 6cm. The electrodiagnostic findings of both segmental NCS (below elbow 4cm, medial epicondyle, above elbow 6cm) and inching NCS at 2-cm intervals were also grouped into three sections. The Spearman’s rank test was used to evaluate the correlation between the severity grade on MRI and each electrodiagnostic parameter.
Results
The severity grade based on MRI finding showed correlations with the minimum amplitude on the inching study (r=-.512, p-value<0.001), the minimum velocity on the inching study (r=-.583, p-value=0.000). After the segmental studies, the amplitude (r=-.423, p-value=0.004) and conduction velocity (r=-.526, p-value<0.001) which were chosen at the lesion based on MRI have correlations with the severity grade of MRI findings. With the inching studies, the amplitude (r=-.456, p-value=0.002) and the conduction velocity (r=-.548, p-value<0.001) which were chosen at the lesion on MRI showed correlations with the severity grade of MRI findings.
Conclusion
The results of this study demonstrate that the electrodiagnostic outcomes have correlations with the severity grade which reflects structural changes on Magnetic resonance imaging. Using both Electrodiagnostic studies and MRI make diagnosis, localization, and severity of UNE more efficient and it is necessary to verify the relevance and localization of the patient's symptoms through further prospective studies.
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Table1. Location relationship of lesion between MRI and electrodiagnostic study in diagnosing UNE (n=46) *Among the 46 patients, 6 patients were classified as ‘undetermined group’ based on MRI findings. 20 patients showed correlated location between MRI and electrodiagnostic studies (20/40=50%).
Table2. The Relationship between the severity grade on MRI and the parameters on NCS *p<0.05 by Spearman correlation analysis.
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