Both brain volume and brain gyral patterns are under significant genetic control (PDF) , although brain volume heritability appears to be greater -- over 90%. Heritability of brain gyral patterns may be closer to 50%.
One interesting gyral pattern variation is the presence or absence of a "paracingulate gyrus" which exists in many people in parallel with the cingulate gyrus. Einstein appears to demonstrate some very interesting variations on the cingulate / paracingulate pattern.
In dementia of various types, brain volume tends to shrink significantly, along with a number of other gross and microscopic changes in morphology. All of these structural changes are also accompanied by changes in gene expression in both neurons and in glial support cells.
The question then arises as to how we might be able to influence gene expression -- in both the healthy and the diseased brain -- in order to improve brain function above and beyond what is currently being experienced.
A rich and full life benefits not only from many years of existence, but also from a depth of understanding of the world around us. Understanding exceptional brains such as Einstein's, may help us to learn what we need to do to enrich the lives of more ordinary humans.