Worried about hard lump on head

[dyno7]

My son has a condition known as Schizencephaly caused by a stroke in utero. He has a cleft in his brain on the right side and which he presents with hemiparises on his left side. Fortunately it only affects his motor skills and not his cognitive ability. However, when he was about 6 months I noticed that there was a noticeable bulge on the right side of his head near the temple. About two weeks ago I noticed the bulge has gotten larger (about the size of a silver dollar). It's very hard , almost like bone. It doesn't seem to bother him and he doesn't show any difference in his behavior or regression. I spoke to his pediatrician and he refered me to a neurosurgeon but I can't get in to see him for another month. What could the lump be? Is it something that would need to be surgially removed?
Thanks, Amanda

[Dr. Joshua]

Hi, thanks for your question. From your description alone it's not possible for me to say what it could be, but I'm happy that you have an appointment with a neurosurgeon. A physical examination and possibly some imaging such as CT is needed for the diagnosis. Please come back and let me know what the neurosurgeon says.