One of the greatest rhymes is rock history!

   Now I guess I'll have to tell 'em
   That I got no cerebellum

But even more strangely, he did have this:

> He was born with a parasitic twin growing out of his back, which was incompletely formed and surgically removed

Can you provide a reference for this? I searched and found nothing.

I think it was a joke - The Ramones have a song with lyrics about a missing cerebellum, but it's a song about a fictional character with a lobotomy.