A deformity, particularly one resulting from faulty development.
n. any variation from the normal physical structure, due either to congenital or developmental defects or to disease or injury.
a congenital disorder in which there is distortion of the base of the skull with protrusion of the lower brainstem and parts of the cerebellum through the opening for the spinal cord at the base of the skull (see banana and lemon signs). It is associated commonly with *neural tube defects, *hydrocephalus, and a *syringomyelia. [J. Arnold (1835–1915) and H. Chiari (1851–1916), German pathologists]... arnold–chiari malformation