Efficacy of MR imaging in patients suspected of having Morton's neuroma

The purpose of our study was to evaluate the role of MR imaging in patients with suspected Morton's neuroma and to assess the value of various MR sequences in this diagnosis.

Thirty-two consecutive patients with suspected Morton's neuroma were studied using a 1.0-T MR scanner. Axial T1- and T2-weighted spin-echo, short inversion time inversion recovery, and enhanced T1-weighted fat-suppressed spin-echo images were obtained on each patient. Eighteen intermetatarsal spaces in 16 of the 32 patients were evaluated surgically. Contrast-to-noise ratios for Morton's neuroma versus surrounding fat were calculated and standardized for imaging times.

In 15 of 18 intermetatarsal spaces, a Morton's neuroma was surgically proven. Thirteen true-positive, two false-negative, three true-negative, and no false-positive MR diagnoses were given. In six of 15 proven neuromas, the clinical examiner was not able to identify the correct intermetatarsal space. The MR diagnoses in the 16 remaining patients who did not undergo surgery were Morton's neuroma (n = 8), stress fracture (n = 1), foreign body reaction (n = 1), tendon sheath ganglion (n = 1), postoperative changes (n = 2), and no abnormality (n = 3). Standardized contrast-to-noise ratios (+/- SD) were 2.42 +/- 0.72 for T1-weighted images; 1.43 +/- 1.13 for T2-weighted images; 1.26 +/- 1.47 for short inversion time inversion recovery images; and 0.83 +/- 0.59 gadolinium-enhanced fat-suppressed images. The differences were statistically significant for the T1-weighted spin-echo images versus the three other sequences (p = .001-.018), but not among the other sequences (p = .209-.710).

MR imaging is accurate in diagnosing Morton's neuroma and may be important for correct localization. A limited examination employing axial T1-weighted spin-echo images is adequate; additional sequences should be employed only for differential diagnosis.