title: Association between Noonan syndrome and Chiari I malformation: a case-based update.
abstract: BACKGROUND
  Chiari I malformations (CM-I) have been associated with a variety of developmental abnormalities in the literature. A few cases of CM-I in patients with Noonan syndrome (NS) have been reported; however, opinion remains divided as to whether the observed association is coincidental.
  
  
  CONCLUSIONS
  Six previous cases of CM-I in patients with NS have been described in the literature. Many of these had other neurological abnormalities; however, neurological problems are not a prominent part of earlier descriptions of NS. A statistically significant association between NS and CM-I is difficult to obtain at present due to availability and logistical issues with scanning many asymptomatic patients. Although we believe a link exists between CM-I and NS, there is little understanding on how NS may cause CM-I. The most logical cause would be posterior fossa abnormality; however, the most common genetic mutation in NS tends to cause frontal and facial abnormalities, and the posterior fossa tends to be relatively spared. Other genetic mutations may also affect the posterior cranium and thus create the appropriate conditions for a CM-I to develop.
  
  
  METHODS
  We report a case of CM-I in a 9-year-old patient with Noonan syndrome, severe scoliosis and syringomyelia.
  
  
  CONCLUSIONS
  We believe that CM-I is a part of Noonan syndrome; however, statistical validation of this opinion is necessary.
authors.affiliation: Department of Neurosurgery, Alder Hey Children's NHS Foundation Trust, Eaton Road, Liverpool, UK.
authors.forename: Yann Shern
authors.initials: YS
authors.lastname: Keh
authors.forename: Laurence
authors.initials: L
authors.lastname: Abernethy
authors.forename: Benedetta
authors.initials: B
authors.lastname: Pettorini
mesh_terms: D001139:Arnold-Chiari Malformation / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D002648:Child; D015897:Comorbidity; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D009634:Noonan Syndrome / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology