YOU SAID:
My brain is too large for my head.
INTO JAPANESE
私の頭には頭が大きすぎます。
BACK INTO ENGLISH
My head is too big for my head.
INTO JAPANESE
私の頭は私の頭には大きすぎます。
BACK INTO ENGLISH
My head is too big for my head.
That didn't even make that much sense in English.