Traumatic neuroma.

A) Anatomy:

B) Pathology:

-After focal traumatic injury, neural axonal tissue may start repair with   proliferation at the site of trauma, resulting in a focal non-neoplastic area of enlargement called a traumatic neuroma, also known as stump neuroma or amputation neuroma.

On MR imaging, traumatic neuromas are intermediate signal on T1-weighted images, usually isointense or mildly hyperintense to muscle. They tend to be isointense to hyperintense compared to muscle on proton density- and T2-weighted images, often approaching the hyperintense signal intensity of the associated nerve.  Because intraneural fascicles may remain intact proximal to the injury site, traumatic neuromas often demonstrate clustered hypointense ring-like areas called the “fascicular sign” on T2-weighted images acquired perpendicular to the nerve, corresponding to nerve fascicles.

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C)

Tibial nerve traumatic (stump) neuroma (arrows) in a 52 year-old female, status post below knee amputation for diabetic ulcers and tibial fracture.  Axial T1-weighted and fat-suppressed fast spin echo T2-weighted images (2A) demonstrate focal enlargement of the tibial nerve with well-defined margins.  Internal signal approaches joint fluid intensity on the T2-weighted series, with a suggestion of internal fascicles on sagittal fat-suppressed fast spin echo T2-weighted images (2B), and coronal T1-weighted and fat-suppressed fast spin echo T2-weighted images (2C).  Deformity of the proximal tibia is due to chronic healed fracture.

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B)

C)

Fascicular sign in a tibial nerve stump neuroma. Patient is a 62 year-old male status post below knee amputation due to leg trauma, presenting with pain and swelling in the stump. Axial fast spin-echo inversion recovery images (3A) reveal enlargement of the tibial nerve with internal fine septations (arrows), corresponding to nerve fascicles. Note the extensive adventitial bursitis along the anterior stump (arrowheads), a likely etiology for the patient’s symptoms. Coronal (3B) and sagittal (3C) fast spin-echo inversion recovery images also visualize fascicles in the neuroma, parallel to the long axis of the nerve.

 Axial images demonstrate a well-circumscribed mass (arrows) in the expected location of the median nerve, with smooth well-defined margins. Internal signal is mildly hyperintense to muscle on T1-weighted and inversion recovery sequences.

A)

B)

Sagittal (A) and coronal (B) images reveal that the mass terminates abruptly at an area of low signal fibrosis (arrows) over the proximal carpal row. The median nerve could not be identified in the area of fibrosis, and appears to terminate in the mass.

Reference