title: MRI Patterns of Isolated Lesions in the Medulla Oblongata.
abstract: Isolated lesions of the medulla oblongata are difficult to diagnose due to their rarity and high biopsy risk. Several individual case reports have been published, but a systematic descriptive study is lacking. Our study has three objectives that 1) provide a differential diagnosis, 2) describe magnetic resonance imaging (MRI) findings, and 3) propose a stepwise MRI-based approach to the isolated lesions of the medulla oblongata in nonstroke patients.
  
  
  
  We performed an institutional Review Board-approved retrospective analysis of 34 consecutive cases of isolated medullary lesions from nonstroke causes identified from our imaging database between January 2000 and May 2015. Eleven were excluded due to lack of pretreatment or follow-up MRI. MR studies were reviewed by two blinded neuroradiologists. The diagnosis, demographic data, and MR findings were reported using frequencies and proportions. An MRI-based diagnostic algorithm was proposed.
  
  
  
  Most lesions were neoplasms (47%), followed by vascular malformations (15%), demyelinating/inflammatory lesions (15%), others (12%), unknown (8%), and infection (3%). Five MRI patterns were identified: 1) cystic lesion, 2) exophytic noncystic lesion, 3) intrinsic lesion with T2 hypointensity, 4) enhancing intrinsic lesion, and 5) nonenhancing intrinsic lesion. All showing patterns 1 and 2 were neoplasms or cysts. All showing pattern 3 were vascular malformations. Patterns 4 and 5 comprised of multiple etiologies.
  
  
  
  Neoplasms are the most common cause of isolated medullary lesions in nonstroke patients. Other differential diagnoses include vascular malformations, demyelinating/inflammatory lesions, and infections. A stepwise MRI-based approach can help differentiate between various etiologies.
authors.affiliation: Neuroradiology Division, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA.|Department of Radiology, King Chulalongkorn Memorial Hospital the Thai Red Cross Society, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, Thailand.
authors.forename: Supada
authors.initials: S
authors.lastname: Prakkamakul
authors.affiliation: Neuroradiology Division, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA.
authors.forename: Pamela
authors.initials: P
authors.lastname: Schaefer
authors.affiliation: Neuroradiology Division, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA.
authors.forename: Gilberto
authors.initials: G
authors.lastname: Gonzalez
authors.affiliation: Neuroradiology Division, Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA.
authors.forename: Otto
authors.initials: O
authors.lastname: Rapalino
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D001927:Brain Diseases / Q000000981:diagnostic imaging*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008526:Medulla Oblongata / Q000000981:diagnostic imaging*; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult
keywords: MRI; Medulla oblongata; diagnostic algorithm; etiologies; isolated