Morton neuroma: evaluated with ultrasonography and MR imaging.

Objective: The purpose of this study was to compare the diagnostic accuracy of both ultrasonography (US) and magnetic resonance imaging (MRI) for the assessment of Morton neuroma.
Materials and Methods: Our study group was comprised of 20 neuromas from 17 patients, and the neuromas were confirmed on surgery following evaluation with US, MRI, or both US and MRI. The diagnostic criterion for Morton neuroma, as examined by US, was the presence of a round or ovoid, well-defined, hypoechoic mass. The diagnostic criterion, based on MR imaging, was a well defined mass with intermediate to low signal intensity on both the T1- and T2-weighted images. The retrospective comparison between the sonographic and MR images was done by two experienced radiologists working in consensus with the surgical and pathologic correlations.
Results: The detection rate of Morton neuroma was 79% for 14 neuromas from 11 patients who had undergone US followed by an operation. The detection rate was 76% for 17 neuromas from 15 patients who had undergone MRI and a subsequent operation. The mean size of the examined neuromas was 4.9 mm on the US images and it was 5.1 mm on the MRI studies. Ten neuromas (71%) were 5 mm or less as measured by US, and three neuromas were not detected, whereas on the MRI analysis, 10 neuromas (59%) were 5 mm or less and four neuromas were not visualized. Among the patients examined during postoperative follow-up, symptoms were completely relieved in 85% and the symptoms were partially relieved in 15%.
Conclusion: US and MR imaging are comparable modalities with high detection rate for the evaluation of Morton neuroma.