Chiari 2 without spinal dysraphism: does it blow a hole in the pathogenesis?

Chiari malformation type 2 is characterized by hindbrain protrusion and a constellation of supratentorial malformations. Chiari malformation type 2 is thought to be causally related to myelomeningocele due to intrauterine cerebrospinal fluid overdrainage. This relationship is so strong that it has become a rule. A 14-year-old girl affected by mental retardation, spastic triparesis, and epilepsy is presented. Brain magnetic resonance imaging disclosed a severe Chiari malformation type 2, whereas spine magnetic resonance imaging was unremarkable. The authors discuss previous literature describing rare cases of Chiari malformation type 2 without open spinal dysraphism and the relevance of concomitant, sometimes overlooked, neuroimaging findings, underlying how exceptions might be hurdles but might also eventually strengthen the rules.