His likely comeback game will be for the Ospreys against Celtic League opponents the Borders in Swansea on February 17th. Henson was suspended for 10 weeks and two days after being cited and found guilty of elbowing Leicester prop Alex Moreno during a bitter Heineken Cup clash between the Ospreys and Tigers just before Christmas.
Although the ban has been cut, his absence from Wales's opening two RBS Six Nations games will be a severe blow to coach Mike Ruddock, who has already lost injured players Kevin Morgan, Chris Horsman, Brent Cockbain, Tom Shanklin and Ryan Jones from his plans for this season's tournament.
The appeal committee was chaired by Brian McLoughlin, of the Irish Rugby Football Union, assisted by former Ireland and Lions prop Phil Orr and the Scottish Rugby Union's Peter Brown. They accepted Henson's change of plea to guilty that he had struck Moreno with his elbow.
Henson was accompanied at the hearing at European Rugby Cup Limited's central Dublin offices by Ospreys manager Derwyn Jones and solicitor John Morris. Henson refused to comment as he left the hearing, but the Ospreys issued a brief statement.
"It is still disappointing, but at least there has been a reduction,'' said an Ospreys spokesman. "We felt justified in appealing the initial ban. There could have been more sympathy for Gavin, but we have accepted the panel's decision.''