What are the key radiological and clinical features of Alexander disease, including head size, typical age of onset, and patterns of white and gray matter involvement?

Alexander disease is characterized by a normal to large head size and typically presents before the age of 1 year. Radiologically, there is predominant frontal white matter involvement with no significant gray matter involvement. Key diagnostic features include the presence of Rosenthal fibers and a characteristic MRI pattern with frontal lobe predominance. Clinically, it may present with developmental delay and seizures. Common pitfalls include confusing it with other leukodystrophies, but the frontal predominance and lack of gray matter involvement are distinguishing features.