Number of dogs within degrees 0, 1, 2 for Chiari-like malformation (CM) and Syringomyelia (SM).

CM0 - no CM; CM1 - cerebellum indented by supraoccipital bone; CM2 - cerebellum impacted or herniated into foramen magnum; SM0 - normal; SM1 - central canal dilation or a separate syrinx, which has an internal diameter of less than 2 mm or a pre-syrinx alone; SM2 - syringomyelia (central canal dilation which has an internal diameter of 2 mm or greater, a separate syrinx, or pre-syrinx with central canal dilation). Syringomyelia may be late onset condition so SM0 dogs less than 3 years of age were excluded from statistical calculations for syringomyelia as their clear status could not be assured. Conversely SM1 and SM2 dogs less than 3 years old were included as identifying conformational and genetic indicators of this severe phenotype was a paramount goal of the study.