Two different patients with genetic disorders resulting in overgrowth of the brain.

These represent mutations in cell cycle and cell metabolism genes that lead to larger cells and/or more cells. These types of disorders tend to have mosaicism of some form, which is to say some cells have the mutation active while others don’t. The distribution of these cells can be very geographic/regional - in these two cases, one hemisphere of the brain is involved.

Compare this against a previous case with hemispheric atrophy.