However, this process can go wrong, and this is driven
largely by the development of the brain itself.
It’s easy to think of the skull as being
the rigid component and the brain as being
somehow more flexible soft component. But
in reality, it’s largely the other way around.
It’s the expansion of the brain which drives
the formation of the skull and the shape of
the skull. In this particular condition called
anencephaly, the forebrain has failed to fuse.
This is the equivalent of spina bifida at
the head end of the embryo. As a result, the
brain cannot properly develop at the fore
end where the cerebral hemispheres would be.
As a consequence, the bony places of the skull
have also not developed properly. This condition,
sadly, is incompatible with life after birth,
although an anencephalic foetus may survive
until delivery. This condition is hydrocephalus
or hydrocephaly. In this situation, what has
happened is that too much cerebrospinal fluid
is being produced, or more likely, it’s
not being removed efficiently enough. Therefore,
the brain is expanded beyond what it would
normally do, and when the skull begins to
form, the skull is, therefore, larger than
it would be, normally. So that’s the expansion
of the brain driven by the cerebrospinal fluid
that brings about this condition where the
baby can have a significantly enlarged head.
The treatment for this condition can be relatively
mechanical and straightforward. A drain or
shunt inserted into the spaces in the brain
can drain off the excess of cerebrospinal
fluid and lead to normal development, subsequently.
So, let me summarize what we’ve looked at
in this particular lecture. We’ve looked
at the early development and the bending,
the flexion of the brain. We’ve looked at
the regionalization of the brain itself.
We’ve seen how this can influence the development
of the skull. And we’ve noted two major
kinds of abnormality that can result from
something going wrong with these processes.
Thank you very much.