Mane's involvement in the tournament was in doubt after he limped off during Bayern's 6-1 win over Werder Bremen on Tuesday and was later was diagnosed with an injury to his right fibula. The 30-year-old will undergo further tests.
Cisse, who led Senegal at the 2002 World Cup, said he hoped the condition of the Bayern Munich attacker would improve within a few weeks and declared he was "really optimistic" that the injury would not require an operation.
"I preferred to keep him in the group," Cisse told reporters.
"Sadio Mane is an important player in our squad, it is important to continue to follow his injury, hoping that in two or three weeks there will be progress. But we are really optimistic," he said.
Mane's fitness has been a major cause of concern in Senegal, the current African champions with the nation's leader, President Macky Sall, tweeting on Wednesday: "Sadio, heart of a Lion! All my heart is with you!"
Cisse admitted the possible absence of the talisman would be a massive blow for the continent.
"Losing Sadio Mane is not an easy thing for a coach, for the team, even for African football," he said. "We don't want to think about it but inevitably we have to be prepared should Sadio Mane be absent."
"For now, we still have time ahead of us. I don't want to talk about the absence of Sadio Mane even if, in the back of my head, I'm trying to prepare for it," Cisse said.
Mane, who has scored 33 goals in 92 international matches, is joined in the squad by Abdou Diallo, another player who has recently missed game time due to injury as well as Everton midfielder Idrissa Gueye and Chelsea pair Edouard Mendy, Kalidou Koulibaly.
Left back Saliou Ciss, who is currently without a club, is omitted with Fode Ballo-Toure or Ismail Jakobs providing the options on the left.
Senegal have been drawn in Group A and play their opening game on November 21 against the Netherlands before going on to meet tournament hosts Qatar and Ecuador.