borderline dandy walker varient

every time my 12 year has a brain mri.. its suggest dandy walker varient and his docters claim he would have to be mentally retarded in order to have this..which he is not... but... has been dx with aspergers, spina bifida occultta, tethered cord  with syrinx and scoliosis. his symtoms (symptoms) are poor gait, weakness in hand feet and legs, synscope, headaches, learning difficulties, ataxia and tremor.. to me it sounds like it has to do with both the brain and spine.. my question is there a mild form of dandy walker?? and how come the dr's areent seening this??

[Melbee2]

also he has degenerative myopia