I have been wondering this for years since I had a class about the kinds of states, sultanism, democracy, authoritarism and totalitarism, and based on that I came up with this idea:
Somewhere between the rise of the house of Makedon in 862 and the battle of Manzikert in 1071 AD the eastern roman empire turns into a totalitarian state, the idea is that every single element of the civil society, the culture and the economy is under strict state control, while the state administrates huge investiments all through the empire, of course adaptated to the medieval era (like building a huge series of roads through anatolia using forced labour because the emperor wants to). The aristocracy is either supportive of the state or have been crushed, while the merchant class is supressed. The Orthodox church is strictly under state control, while a secret police like the oprichnina is present on the main scholar centers to supress anti government agitators. Is such a thing possible?