Makarov, the former mayor of the Siberian city of Tomsk, was arrested in December on corruption-related charges, which he has dismissed as politically motivated.
His lawyers in May lodged a complaint with the Strasbourg-based European Court of Human Rights.
Makarov has since been in jail awaiting a court verdict and is recovering from a heart attack suffered during his detention.
His press secretary, Nadezhda Dreval, told RFE/RL's Russian Service that the court has asked Russia to explain its decision to keep Makarov in detention.
"The court will take the state of his health into account and speed up this process," Dreval said. "The European Court is likely to deliver a ruling by the end of the year. Now, the government of the Russian Federation must outline its position, answer 15 questions all connected to [Makarov's] detention -- why was custody chosen instead of house arrest, and why was Aleksandr Sergeyevich's state of heath not taken into account."
Makarov is charged with receiving bribes in exchange for lucrative construction contracts, as well as abuse of office and drug possession. He was subsequently suspended from his post.
Hearings into Makarov's case are not expected to begin before mid-December. His lawyers are currently reading the case file, which fills up 50 volumes of 250 pages each.