SLR - January 2011 - Sara Karamloo
Reference: Espinosa, N., Schmitt, J.W., Saupe, N., Maquieira, G.J., Bode, B., Vienne, P., Zanetti, M. (2010). Morton Neuroma: MR Imaging after Resection—Postoperative MR and Histologic Findings in Asymptomatic and Symptomatic Intermetatarsal Spaces. Radiology, 255, 850-856.
Scientific Literature Reviews
Reviewed by: Sara Karamloo, DPM
Residency Program: Yale New Haven / VA CT
Podiatry Relevance:
Recurrence of Morton’s neuroma after surgical excision is commonly encountered by the podiatric physician, however, diagnostic imaging does not always correspond with histologic findings upon re-excision.
Methods:
Fifty eight patients (being seen for initial surgical excision of a morton's neuroma), including 46 women and 12 men were included in this study, thereby evaluating ninety Morton neuromas removed between February 2000 and February 2006. Extensive inclusion and exclusion criteria were fulfilled by patients prior to obtaining informed consent for enrollment into the study. The average age was 51 years and patients were divided into 2 groups post-operatively: asymptomatic and symptomatic. All patients underwent open resection of the neuroma through a dorsal approach, with subsequent histologic evaluation of the removed specimen in the pathology department. Pre and post-operative MRI were obtained in all patients to assess structural alterations and the size of the lesion in the intermetatarsal space following neuroma excision, leading to a diagnosis of recurrent neuroma, scar or bursitis. MRIs were read by two separate musculoskeletal radiologists, who were blinded to the symptomatic or asymptomatic nature of the patient, in order to calculate interobserver reliability. Furthermore, each specimen was fixed in formalin and embedded in paraffin to be cut into slices and evaluated for presence of intra- or peri-neural fibrosis in the pathology department, for diagnosis of recurrent Morton‘s neuroma.
Results:
Histologic examination of the 90 removed specimens confirmed presence of the common digital nerve in all. At follow up, clinical exam revealed that of the ninety removed neuromas , 68 intermetatarsal spaces or 76% were asymptomatic, whereas 22 intermetatarsal spaces or 24% remained symptomatic, making this the calculated prevalence of recurrence for this study. Seven of the patients in the symptomatic group underwent repeat surgery and histologic examination did not reveal neural tissue, rather fibrous tissue was found in all of the specimens with pronounced bursitis detected in one. On post-op MR imaging, a presumed Morton’s neuroma was detected in 18 (26%) of the asymptomatic spaces and 11 (50%) of the symptomatic spaces, whereas a presumed scar was detected in six (9%) of the asymptomatic spaces and two (9%) of the symptomatic spaces, followed by findings consistant with intermetatarsal bursitis detected in six (9%) of the asymptomatic spaces and six (27%) of the symptomatic spaces. Inter-observer agreement between the two radiologists was substantial (κ = 0.64) for the presumed recurrent neuromas.
Conclusions:
Due to the finding of fibrous, rather than neural tissue, on histologic examination of specimens from repeat neuroma surgery, it is important to proceed with caution when Morton’s neuroma-like abnormalities are noted on MR imaging following resection.