Sonography has been proven to be highly accurate in the diagnosis of a Morton's neuroma. At sonography, a Morton's neuroma is seen as a hypoechoic, ovoid, interdigital mass at or just proximal to the metatarsal heads (Fig. 31) . Most symptomatic neuromas are larger than 5 mm, and this diameter has been proposed as a threshold size for symptomatology [77,78]. Performing Mulder's clinical test while scanning may provide increased conspicuity and diagnostic confidence .
The intermetatarsal bursa is present in each interspace, dorsal to the interdigital nerve intermetatarsal ligament, and can pose a potential diagnostic problem in MRI and sonographic imaging for a suspected Morton's neuroma [80,81]. This fluid may occur independently or be associated with a Morton's neuroma (Fig. 32) . The presence of an adjacent intermetatarsal bursa may cause the true size of the Morton's neuroma to be overestimated on sonogra-phy . Compressibility of the bursa at sonography may aid in diagnosis (Fig. 33).
Sonography has been used successfully for the diagnosis of Morton's neuroma, with reported sensitivities of 85% to 98% [77,82-84]. MRI has a comparable high sensitivity (87%) and specificity (100%) in the depiction of Morton's neuroma . A recent study by Sharp and colleagues  showed MRI and sonography to be similar in Morton's neuroma detection, but sonography was less accurate for small lesions. The authors believe that sonography is the imaging modality of choice for Morton's neuroma detection. Missed neuromas may be attributed to sonographer experience and technique.
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