To answer your question gliosis does not occur randomly.It is always the result of some insult to the normal brain tissue like trauma,ischemia or stroke.It is a part of normal repair process of the neuronal tissue. Or it may result as a part of any of the inflammmatory neurological diseases like multiple sclerosis,parkinsons,alzheimers and others.And surgery is usually not the typical treatment for a gliosis.It can be managed conservatively like in this case with the help of anti epileptic drugs.Many people dont remember any such injury or small stroke like events occur which may go unnoticed and lead to reactive gliosis.Having said this i admit that i havent read the book and i cannot comment further.Hope my answer is satisfactory.