title: MRI findings of radiation-induced changes of masticatory muscles: a systematic review.
abstract: BACKGROUND
  Radiotherapy to the head and neck regions can result in serious consequences to the temporomandibular joint (TMJ) and chewing muscles. Magnetic resonance imaging (MRI) demonstrates soft-tissue alterations after radiotherapy, such as morphology and signal intensity.
  
  
  OBJECTIVE
  The purpose of this review is to critically and systematically analyse the available evidence regarding the masticatory muscles alterations, as demonstrated on MRI, after radiotherapy for head and neck cancer.
  
  
  METHODS
  Electronic search of MEDLINE, EMBASE, EBM reviews and Scopus.
  
  
  METHODS
  Reports of any study design investigating radiation-induced changes in masticatory muscles after radiotherapy in patients with head and neck cancer were included.
  An electronic database search resulted in 162 papers. Sixteen papers were initially selected as potentially relevant studies; however, only four papers satisfied all inclusion criteria. The included papers focused on the MRI appearance of masticatory muscles following radiotherapy protocol. Two papers reported outcome based on retrospective clinical and imaging records, whereas the remaining two papers were case reports. Irradiated muscles frequently show diffuse increase in T2 signal and post-gadolinium enhancement post-irradiation. Also, muscle size changes were reported based on subjective comparison with the contralateral side. The quality of all included papers was considered poor with high risk of bias.
  
  
  CONCLUSIONS
  There is no evidence that MRI interpretations indicate specific radiation-induced changes in masticatory muscles. There is a clear need for a cohort study comparing patients with pre- and post-radiotherapy MRI.
authors.affiliation: Orthodontic Graduate Program, School of Dentistry, 476 Edmonton Clinic Health Academy (ECHA), University of Alberta, Edmonton, AB T6G 1C9, Canada. m.alsaleh@ualberta.ca.
authors.forename: Mohammed A Q
authors.initials: MA
authors.lastname: Al-Saleh
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Jaremko
authors.forename: Humam
authors.initials: H
authors.lastname: Saltaji
authors.forename: John
authors.initials: J
authors.lastname: Wolfaardt
authors.forename: Paul W
authors.initials: PW
authors.lastname: Major
mesh_terms: D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008410:Masticatory Muscles / Q000473:pathology* / Q000528:radiation effects*; D013704:Temporomandibular Joint / Q000473:pathology / Q000528:radiation effects