Sonographic analysis of Morton's neuroma.

A prospective study was performed whereby 73 patients exhibiting clinical symptoms of 109 Morton's neuromas were examined using ultrasound. Reproducible hypoechoic densities were identified as neuromas if they measured greater than 5 mm. in transverse dimension, with those 4 mm. or less in dimensions called "suspicious" if they were well-defined and if the patient had marked pain in the examined interspace. Sixty of the neuromas were surgically excised, with 49 being managed conservatively. Of the surgical cases, all but three (95%) of the neuromas were positively identified on sonographic examination and all excised masses demonstrated pathological findings consistent with Morton's neuroma. Thirty-nine percent of the conservatively treated neuromas were negative on sonogram. The average sonographic size of the resected neuromas was 6.2 mm., while the size of those not resected averaged 4.9 mm. This study provides evidence that preoperative sonography is an additional aid in the evaluation of Morton's neuroma, and reaffirms previous evidence that symptomatic neuromas are likely to be at least 5 mm. in diameter on sonogram.