Source : Webster's Revised Unabridged Dictionary (1913)

Maniacal \Ma*ni"a*cal\, a.
   Affected with, or characterized by, madness; maniac. --
   {Ma*ni"a*cal*ly}, adv.

Source : WordNet®

maniacally
     adv : in a maniacal manner or to a maniacal degree; "he was
           maniacally obsessed with jealousy"