title: Intramuscular schwannoma: clinical and magnetic resonance imaging features.
abstract: BACKGROUND
  Schwannomas that arise within the muscle plane are called intramuscular schwannomas. The low incidence of these tumours and the lack of specific clinical features make preoperative diagnosis difficult. Herein, we report our experience with intramuscular schwannomas. We present details of the clinical presentation, radiological diagnosis and management of these tumours.
  
  
  METHODS
  Between January 2011 and December 2013, 29 patients were diagnosed and treated for histologically proven schwannoma at the National University Hospital, Singapore. Among these 29 patients, eight (five male, three female) had intramuscular schwannomas.
  
  
  RESULTS
  The mean age of the eight patients was 40 (range 27-57) years. The most common presenting feature was a palpable mass. The mean interval between surgical treatment and the onset of clinical symptoms was 17.1 (range 4-72) months. Six of the eight tumours (75.0%) were located in the lower limb, while 2 (25.0%) were located in the upper limb. None of the patients had any preoperative neurological deficits. Tinel's sign was present in one patient. Magnetic resonance (MR) imaging showed that the findings of split-fat sign, low signal margin and fascicular sign were present in all patients. The entry and exit sign was observed in 4 (50.0%) patients, a hyperintense rim was observed in 7 (87.5%) patients and the target sign was observed in 5 (62.5%) patients. All patients underwent microsurgical excision of the tumour and none developed any postoperative neurological deficits.
  
  
  CONCLUSIONS
  Intramuscular schwannomas demonstrate the findings of split-fat sign, low signal margin and fascicular sign on MR imaging. These findings are useful for the radiological diagnosis of intramuscular schwannoma.
authors.affiliation: Division of Musculoskeletal Oncology, National University Hospital, Singapore ; Pramukhswami Medical College & MS Patel Cancer Centre, Karamsad, Gujarat, India.
authors.forename: Abhijeet Ashok
authors.initials: AA
authors.lastname: Salunke
authors.affiliation: Department of Orthopaedic Surgery, National University Hospital, Singapore.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Jun Hao
authors.initials: JH
authors.lastname: Tan
authors.affiliation: Department of Hand and Reconstructive Microsurgery, National University Hospital, Singapore.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Hand and Reconstructive Microsurgery, National University Hospital, Singapore.
authors.forename: Tun-Lin
authors.initials: TL
authors.lastname: Foo
authors.affiliation: Department of Radiology, National University Hospital, Singapore.
authors.forename: Louise Elizabeth
authors.initials: LE
authors.lastname: Gartner
authors.affiliation: Division of Musculoskeletal Oncology, National University Hospital, Singapore.
authors.forename: Mark Edward
authors.initials: ME
authors.lastname: Puhaindran
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019042:Muscle Neoplasms / Q000000981:diagnostic imaging*; D009442:Neurilemmoma / Q000000981:diagnostic imaging*; D011184:Postoperative Period; D012189:Retrospective Studies; D012846:Singapore
keywords: intramuscular; magnetic resonance imaging; schwannoma