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- Diff Dx: in Infants:
    - pterygium colli;
    - bronchial cleft cysts;
    - tumor:
           - cystic hygroma;
           - thyroid teratomas;
           - tumors of spinal cord and or posterior cranial fossa;
           - chordoma;
    - congenital anomalies of C-spine:
           - unilateral absence of lateral mass of Atlas;
           - posterior fossa masses;
           - Klippel feil syndrome
    - opthalmologic dz that may require child to tilt head to see normally;
           - superior oblique palsy of the ocular muscle;
    - syringomyelia;
    - dystonia musculorum deformans