Feil Syndrome in 1912. KFS includes short neck, low hair line, restriction of neck motion and fusion of at least two cervical segments. Original classification as described by Feil is based on the extent of fusion but is not clinically useful.
Etiology is unknown.
What is known is that there is a failure of the normal segmentation of cervical somites during the third and eighth weeks of gestation. Some hidden anomalies can be fatal. Generally flexion and extension are better preserved than side- bending and rotation. Patients have the ability to compensate at the unfused segments. These inter-spaces can become extremely hypermobile.