Tonsillar ectopia and Chiari malformations: monozygotic triplets. Case report.

A unique case of monozygotic triplets, each of whom exhibits variable degrees of tonsillar ectopia, is reported. Patient X presented with a Chiari I malformation and associated syringomyelia; examination of patients Y and Z showed 4 mm and 2.5 mm of tonsillar ectopia, respectively. No such case has been reported in the literature. The discussion defines the current magnetic resonance criteria for diagnosis of hindbrain malformations and addresses the question of whether these disorders represent a spectrum or separate disease entities, with specific emphasis on genetic predisposition. Due to the 100% concordance in this case the presence of a common hereditary factor in the etiology of these malformations is highly suggested.