title: Impact of body mass index on cerebellar tonsil position in healthy subjects and patients with Chiari malformation.
abstract: OBJECTIVE
  It is unclear if there is a relationship between Chiari malformation Type I (CM-I) and body mass index (BMI). The aim of this study was to identify the relationship between BMI and cerebellar tonsil position in a random sample of people.
  
  
  METHODS
  Cerebellar tonsil position in 2400 subjects from a cohort of patients undergoing MRI was measured. Three hundred patients were randomly selected from each of 8 age groups (from 0 to 80 years). A subject was then excluded if he or she had a posterior fossa mass or previous posterior fossa decompression or if height and weight information within 1 year of MRI was not recorded in the electronic medical record.
  
  
  RESULTS
  There were 1310 subjects (54.6%) with BMI records from within 1 year of the measured scan. Of these subjects, 534 (40.8%) were male and 776 (59.2%) were female. The average BMI of the group was 26.4 kg/m(2), and the average tonsil position was 0.87 mm above the level of the foramen magnum. There were 46 subjects (3.5%) with a tonsil position ≥ 5 mm below the level of the foramen magnum. In the group as a whole, there was no correlation (R(2) = 0.004) between BMI and cerebellar tonsil position.
  
  
  CONCLUSIONS
  In this examination of 1310 subjects undergoing MRI for any reason, there was no relationship between BMI and the level of the cerebellar tonsils or the diagnosis of CM-I on imaging.
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Brandon W
authors.initials: BW
authors.lastname: Smith
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Strahle
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Erick
authors.initials: E
authors.lastname: Kazarian
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Karin M
authors.initials: KM
authors.lastname: Muraszko
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Hugh J L
authors.initials: HJ
authors.lastname: Garton
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Cormac O
authors.initials: CO
authors.lastname: Maher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001139:Arnold-Chiari Malformation / Q000175:diagnosis / Q000453:epidemiology / Q000473:pathology*; D015992:Body Mass Index; D001835:Body Weight; D002531:Cerebellum / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005539:Foramen Magnum / Q000473:pathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D013115:Spinal Canal / Q000473:pathology; D055815:Young Adult
keywords: BMI = body mass index; CM-I = Chiari malformation Type I; Chiari malformation; ICP = intracranial pressure; SD = standard deviation; body mass index; diagnostic and operative techniques; obesity; syrinx