CINCINNATI — Cedric Benson got his revenge on Chicago, all right. The rest of the Bengals' offense had a sweet time, too.

Carson Palmer threw five touchdown passes — four of them in a dominant first half — and Benson ran for a career-high 189 yards and a touchdown against the team that let him go, shocking Chicago with a 45-10 victory Sunday that will go down as one of the worst days in Bears history.

The Bengals improved to 5-2 for the first time since 2005, when a fast-strike offense got them to the playoffs. There was a strong resemblance in the first half, when Cincinnati scored on all five possessions and went up 31-0. It tied for the third-most points the Bears (3-3) have allowed in an opening half.

In that half alone, Chad Ochocinco had 103 yards receiving and Benson had 98 yards rushing as the Bears gave up more points than they had in any game all season. Palmer finished 20 of 24 for 233 yards, one shy of his career high for touchdown throws.

Something wasn't right on Chicago's reshuffled defense.

The Bears have constantly rearranged their linebackers because of injuries, including Brian Urlacher's dislocated right wrist. Middle linebacker Hunter Hillenmeyer moved outside Sunday in the latest revamping, and the line was missing tackle Tommie Harris.

Even with that, it was hard to explain.

The Bengals had been an all-or-nothing offense, scoring nearly half their points in the final two minutes of halves and overtime. This time, it got going right away and didn't let up.

The focus was on Benson, who was Chicago's top draft pick in 2005 but couldn't crack the starting lineup for long or earn a spot in some of his teammates' hearts. They let him go after two stormy years, and the Bengals signed him last season.

Carrying a grudge, he played like a No. 1 pick.

Benson ran for 32 yards on the Bengals' opening drive, even taking a direct snap in the wildcat formation. Lowering his shoulder for extra yards, he topped 100 in the half, before a loss dropped him down. After his 1-yard touchdown run made it 45-3, he merely flipped the ball aside.

While Benson did the bruising work, Palmer — playing with a brace on his sprained left (non-throwing) thumb for the second straight week — piled up the points. Palmer threw short touchdown passes to different receivers on the first four drives.

Chicago hadn't given up so many first-half points since 2003.

Forced to throw, Jay Cutler had a tough time against a Bengals defense missing its best pass rusher. Antwan Odom had surgery last week for a torn Achilles' tendon. In its first game without him, Cincinnati barely missed him.

Cutler got a two-year extension last week through the 2013 season, an extra $20 million guaranteed as a sign of the Bears' faith in him. In his first game since the show of confidence, Cutler threw three interceptions, fumbled two snaps and finished 26 of 37 for 251 yards.