Purpose. To assess the MR imaging characteristics, presenting symptoms, age
and nerve distribution of fibrolipomatous hamartoma.
Design. A computer search was performed of the term fibrolipomatous hamarto
ma through the musculoskeletal section MR imaging results at our institutio
n from June 7, 1996 to January 21. 1998 followed by a search of the terms l
ipomatous hamartoma, median nerve, surrounding Fat, increased fatty signal,
coaxial, and neuroma. MR images and medical files were retrospectively rev
iewed by two experienced musculoskeletal radiologists for imaging character
istics. nerve and age distribution as well as for history of trauma. In add
ition three consultation cases from outside institutions were added for det
ermination of image characteristics.
Results. Ten fibrolipomatous hamartomas were identified: eight in the media
n nerve, one in the ulnar nerve and one in the sciatic nerve. Mean age was
32.3 years (range 4-75 years, SD 21 years). Imaging characteristics were se
rpiginous low-intensity structures representing thickened nerve fascicles,
surrounded by evenly distributed fat, high signal intensity on T1-weighted
sequences and low signal intensity on T2-weighted sequences. The amount of
fat varied; however, distribution in eight cases (80%) was predominantly be
tween nerve fibers rather than surrounding them peripherally. All had a coa
xial-cable-like appearance on axial planes and a spaghetti-like appearance
on coronal planes that was not seen in any other type of median nerve abnor
mality imaged during the study period.
Conclusion. The MR imaging characteristics of fibrolipomatous hamartoma are
pathognomonic, obviating the need for biopsy for diagnosis.