Polymicrogyria (PMG) is a developmental malformation of the human brain characterized by an excessive number of small convolutions (gyri) on the surface of the brain. Either the whole surface (generalized) or parts of the surface (focal) can be affected.
The specific kind that Sophie has is bilateral (both sides of the brain) perisylvian (a region of the brain, primarily associated with speech). Wikipedia lists the following list of implications:
Bilateral perisylvian polymicrogyria (BPP)-Pseudobulbar signs, cognitive impairment, epilepsy, some with arthrogryposis and/or lower motor neuron disease.
In other words, Wikipedia paints a grim picture. Word to the wise, don't rely on Wikipedia exclusively. In my search for a glimmer of optimism, I found a wonderful awareness website, and found much more information there. I think this part is key (from the website):
Perhaps, for most of us, the hardest thing of all is not knowing what it means for YOUR loved one. You see, PMG affects every single person differently. It may cause severe, even fatal problems, or it might be mild. It is not uncommon for it to even go undiagnosed when a person has a very mild form. Typically they may be just labeled “developmentally delayed” unless there is a significant incident that leads to an MRI and even then it can be difficult to diagnose.
So, at this point evidence seem to point that Sophie has a relatively mild form, to the point that it would not get diagnosed if the developmental pedeatrician didn't request an MRI. Her outward signs are few, macrocephaly (big head) for one, speech impairment and gross motor delays. She never had feeding problems, but now that we know drooling is a sign we do notice she does a bit (due to low muscle tone in the mouth area).
There are still many unknowns at this point. She will have a more thorough genetic screening, as PMG can be a symptom of certain rare conditions. She has the unique pigmentation and some metabolic issues which could also point to genetic disorders. So right now she has BPP, pending the exclusion of other conditions.
Hope that clears some things up! Feel free to ask any questions you have and I will do my best to answer.