Occipital plagiocephaly is abnormal flattening of the occipital bone which may be synostotic or non synostotic (deformational) in origin.

Non synostotic posterior plagiocephaly is discovered at birth and it may be attributed to an abnormal intrauterine position of the fetus which is more commonly seen with multiple fetus when one fetus or more may be pushed into a compromised position that puts pressure on the same area of the head.

Synostotic plagiocephaly is premature closure of the lambdoid suture.

There are three main points of differentiation between the two categories:

1. sutures: in craniosynostosis the sutures will be fused, which can easily be identified on CT
2. position of the ipsilateral ear (on MRI petrous bone long axis): is usually oriented posteriorly in lambdoid synostosis and anteriorly in non synostotic plagiocephaly
3. the pattern of calvarial bossing: in lambdoid suture synostosis, there is always contralateral frontal and parietal bossing, whereas in deformational plagiocephaly, there is typically ipsilateral frontal and contralateral occipital bossing

The current case is more in keeping with deformational plagiocephaly (aka positional plagiocephaly).