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Diagnostic Accuracy and Interpretation Reliability of Pelvic MR Neurography in Meralgia Paresthetica
Avneesh Chhabra, MD; Allan J. Belzberg; Eric Howard Williams, MD; J.A. Carrino, MD
Johns Hopkins University, Baltimore, MD, USA
Purpose: To evaluate the diagnostic accuracy and interobserver/intraobserver reliability of pelvic MR Neurography in patients with meralgia paresthetica.
Method and Materials: Two radiologists, blinded to the clinical diagnosis, independently reviewed 41 pelvic MR Neurography (MRN) studies performed on a 3T scanner. A qualitative analysis of bilateral lateral femoral cutaneous nerves (LFCN) was performed on a scale of 0-3 (0=normal, 1= slightly hyperintensity, 2=moderate hyperintensity and 3= fluid like signal intensity) around the inguinal ligament, and for presence or absence of neuroma / mass lesion along the course of the nerves. 13 patients (Male/Female=4/9, mean age±SD = 93± 9 years) had a clinical diagnosis of meralgia paresthetica and 28 (Male/Female=11/17, mean age±SD= 47 ± 15 years) served as the control group and underwent pelvis MRN for other clinical indications, such as sciatica, femoral neuropathy, or pudendal neuralgia. Sensitivity (Sen), specificity (Spe), positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were calculated. Linear weighted kappa was calculated to measure interobserverand intra-observer reliability. Chi2 and Fischer’s test were used to evaluate the significance of the signal abnormality of the LFCN.
Results: Cases and controls were not statistically different regarding age and sex (p> 0.05). Sen, Spe, PPV,NPV and diagnostic accuracy were 67%, 76%, 47%, 87% and 73% for reader 1 and 50%, 84%, 50%, 84% and 76% for reader 2, respectively. Inter-observer and intra-observer reliability was good to very good (kappa ranging from 0.50 to 0.74) and the percentages of agreement were between 81% and 98%. The signal intensity of the LFCN in patients with meralgia paresthetica was statistically different compared to the control group and/or the contralateral side (P<0.05). Neuroma was seen in 3/13 cases and none of the controls, and no other mass lesion was seen along the course of the nerves.
Conclusion: MRN is accurate and reliable technique to investigate patients with meralgia paresthetica.
Clinical Relevance/Application: Pelvic MR Neurography is a valuable complementary technique in the diagnosis of meralgia paresthetica.
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