Alluni was sentenced to seven years in jail in September 2005 on charges of collaborating with al-Qaida.
Aljazeera correspondent Michel al-Kik said if the revision took place, Alluni's lawyers would be able to ask for his realease on bail on health grounds.
Haitham Manna, the spokesman for the Paris-based Arab Commission for Human Rights, said he had visited Alluni in jail with Fatima al-Zahra, Alluni's wife.
Manna said Alluni was being held in unusual conditions - he was being held in a separate cell - and his health condition remained critical. Alluni suffers from high blood pressure and problems with his spine.
According to Manna, the prison authorities have refused to send Alluni to hospital, saying he would be treated by prison doctors.
Aljazeera's envoy to Spain, Muhamad Kraishan said Alluni's lawyers were hopeful the appeal could lead to Alluni's case being dropped.
Kraishan said: "Recently, a sentence against a Basque activist had been scrapped because one of the judges that sentenced him was a prosecutor during the investigation..
"The same case applies to Alluni. One of the judges in the court which sentenced him was a prosecutor during the investigation with Taysir, an unprecedented violation according to lawyers here in Spain," he said.
Earlier this month, the Spanish constitutional court accepted a request from Alluni's lawyers to appeal against the sentence. The court said there were enough reasons to accept the appeal.
The Spanish High Court sentenced Alluni on 26 September 2005 to seven years imprisonment. He was fined for cooperating with what it termed as terrorism organisation. He was sentenced along with 18 other co-defendants in what was Europe's largest al-Qaida trial. The same court acquitted him of being a member of al-Qaida.
Alluni gained international recognition as a journalist when he secured an interivew with Osama bin Laden, al-Qaida's leader, in 1998, and for his coverage of the Afghanistan and Iraq wars.
Aljazeera has always maitained its correspondent is innocent of the charges, while human rights groups have criticised the trial for being politically motivated.