"We are looking into it," league spokesman Greg Aiello said Tuesday night via e-mail.
The NFL's personal conduct policy states that all persons associated with the league are required to avoid "conduct detrimental to the integrity of and public confidence in the National Football League."
Once rookies are selected in the NFL draft, they are subject to the policy. Spikes, who turns 23 on Friday, was selected by the Patriots in the second round of the draft in April.
The Patriots did not comment on the video, which depicted a sexual act.
Spikes' agent, Terry Watson, described it as an "embarrassing situation."
"It was something that occurred before he became an NFL draftee and a New England Patriot. I think for anyone it would be an embarrassing situation," Watson said. "Brandon has shown to many people the kind of person he is before and after being drafted in the second round. He's hoping to put this behind him and looks forward to having a great football season."
Spikes has started all three preseason games for the Patriots. He has been credited by the team's coaches with 18 tackles, the third highest total on the club.
Mike Reiss covers the Patriots for ESPNBoston.com. Follow him on Twitter.