[Surgical treatment of Arnold-Chiari malformation type I in an adult patient].

Background: Herniation of the cerebellar tonsils through the foramen magnum into the cervical spinal canal with obliteration of the cerebellomedullary cistern is the primary feature of Arnold-Chiari type I malformation (ACM I). It is considered to be congenital malformation, although there have been reported cases of an acquired form.

Case Report: We presented a female patient, 45-year old, with ACM I without syringomyelia as a rare and unusual clinical image, as well as the effect of decompressive surgery in the treatment of this malformation.