Hogan, who joined Aston Villa from Brentford in January, was stretchered off in the closing stages against Newcastle after going over on his ankle in the penalty area.
Villa went down at St James' Park to Yoan Gouffran's first-half opener before Henri Lansbury's second-half own-goal consigned Bruce's men to their fifth straight defeat.
Bruce is still waiting for a first win in 2017, dating back to Boxing Day, and that run of form has seen his side drop to within six points of the relegation zone.
The Villa manager said: "All in all a very disappointing night for everyone.
"The injury to Scott Hogan doesn't look good. He has gone up for the header and he has turned his ankle over. We will not know the extent of it until (Tuesday).
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"It's a nasty one, we will get him back to Birmingham and have him scanned. Fingers crossed.
"We have had a tough eight weeks, I have not known an eight weeks like it. We have to stay with it and hope we can break.
"I can't remember us getting the goals like Newcastle did. Newcastle needed that because up to that, before half-time, I felt we were the better side."