MR imaging of the muscular component of myocutaneous flaps in the head and neck

BACKGROUND AND PURPOSE: Myocutaneous flaps are commonly used for reconstruction in head and neck surgery. The purpose of this study was to characterize the MR imaging findings of the muscular component of these flaps, with an emphasis on enhancement patterns. Recognition of these imaging findings is important in differentiating postoperative changes from recurrent tumor. METHODS: MR studies were evaluated in 25 patients who had undergone 27 flap reconstructions after resection of a head and neck tumor. Twenty were free flaps and seven were pedicled rotation flaps, and a dominant component of all flaps was muscle. MR images were reviewed for signal intensity, enhancement characteristics, and morphology over a period of 7 to 79 months. RESULTS: On baseline postoperative images, 21 flaps showed moderate or intense enhancement of the muscular graft component relative to nonenhancing native muscle, three flaps showed mild enhancement, and three showed no enhancement. On follow-up images, 18 flaps that initially had intense enhancement showed persistent intense enhancement, and three showed decreasing enhancement. Two flaps with initial mild enhancement were unchanged on follow-up, and one became nonenhancing. None of the initially nonenhancing flaps subsequently enhanced. T1 signal intensity of muscular graft components was always isointense with normal muscle, whereas T2 signal intensity was variable and tended to be stable. Ninety-three percent of our muscular flap components showed striations typical of normal muscle and were best identified on T1-weighted images. No significant imaging differences were found between pedicled and free flaps. CONCLUSION: Most muscular flap components show moderate or intense enhancement on fat-suppressed contrast-enhanced MR images that may persist for many months and be quite striking. Radiologists should be familiar with the typical postoperative appearance of predominantly muscular flaps to avoid misdiagnosis as tumor extension or recurrence.