[Type I Arnold-Chiari malformation: diagnostic considerations in a case].

: An 18-year-old patient with a 5-year history of periodic vertigo, headache and stiff neck is reported. Routine X-ray of the skull showed a mild form of basilar impression while the CT scan demonstrated only a tri-ventricular hydrocephalus. Without using the traditional invasive techniques, diagnosis of Chiari type I malformation was nonetheless clearly pointed out by magnetic resonance imaging of the posterior fossa and spinal cord. Diagnostic problems of this clinically ambiguous and uncharacterized syndrome are discussed.