D.D.of water bag skull

1-Look first to the falx, if it is present or not.

2-If it is not present, look to thalami if they are fused or not.

3-If the falx is not present and is associated with fused thalami, in addition that the remaining brain tissue seen anteriorly, the condition is alobar holoprosencephaly.

4-If the falx is seen normally without disruption, look to the periphery of the skull if there remained brain tissue or not, you usually see it present suggesting that the condition is severe hydrocephalus.

5-If the falx is disrupted look to the thalamus if it is fused or not.

6-If it is fused even partially, it will be semi lobar holoprosencephaly.

7-If it is not fused, think about hydranencephaly which is usually associated with remaining brain tissue in the temporal and occipital areas.