title: The natural history of the Chiari Type I anomaly.
abstract: OBJECTIVE
  Since the advent of MR imaging, an increasing number of asymptomatic or oligosymptomatic patients have been diagnosed with Chiari malformation Type I (CM-I). The decision of whether or not to operate is more difficult in these patients than in those with clear symptoms because of the lack of information about the natural course of this disease.
  
  
  METHODS
  The authors report on their experience in a series of 22 patients with CM-I who were evaluated at the authors' institution, and for whom a conservative approach to treatment was adopted. The patients ranged in age from 1 to 16 years (mean 6.3 years) at diagnosis. Neuroradiological and complete clinical examinations were performed in all patients 6 months after the first observation and every year thereafter. The follow-up period ranged from 3 to 19 years (mean 5.9 years).
  
  
  RESULTS
  Chiari malformation Type I was incidentally detected on MR images in 11 of 22 patients. The remaining 11 patients had minimal clinical signs at presentation that were not regarded as necessitating immediate surgical treatment. Seventeen patients (77.3%) showed progressive improvement in their symptoms or remained asymptomatic at the last follow-up whereas 5 patients (22.7%) experienced worsening, which was mild in 2 cases and required surgical correction in the remaining 3 cases. On MR imaging a mild reduction in tonsillar herniation was appreciated in 4 patients (18.18%), with complete spontaneous resolution in 1 of these. In 16 patients, tonsillar herniation remained stable during follow-up.
  
  
  CONCLUSIONS
  The authors' data confirm the common impression that in both asymptomatic and slightly symptomatic patients with CM-I, a conservative approach to treatment should be adopted with periodic clinical and radiological examinations.
authors.affiliation: Department of Pediatric Neurosurgery, Catholic University Medical School, Largo A. Gemelli 1, Rome, Italy. federicanovegno@hotmail.it
authors.forename: Federica
authors.initials: F
authors.lastname: Novegno
authors.forename: Massimo
authors.initials: M
authors.lastname: Caldarelli
authors.forename: Antonio
authors.initials: A
authors.lastname: Massa
authors.forename: Daniela
authors.initials: D
authors.lastname: Chieffo
authors.forename: Luca
authors.initials: L
authors.lastname: Massimi
authors.forename: Benedetta
authors.initials: B
authors.lastname: Pettorini
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Tamburrini
authors.forename: Concezio
authors.initials: C
authors.lastname: Di Rocco