I wasnt sure what you meant by median system because my location (USA) doesnt use that term associated with dissociative disorders. when I goggled it, google says a median internal system is where a person does not have alters but are not free of mood switching, kind of like having alters but not.

here in america this describes a normal person. here in America it is believed that even non dissociative people switch into parts of their self depending upon their emotions, things they are going through and who they are around. some locations in america call this kind of switching into parts as switching roles.

example as a mother I switch into being one way with my children, as a wife I switch into my wife way of being. I wouldnt switch into wife mode when playing with my children and would not switch into the mothering role when with my wife.

but in some some people this normal switching into these parts gets a bit confusing and hectic and out of whack where it affects every aspect of a persons life...

how does this (a median system) fit in with american diagnostics for OSDD it means sometimes a person switches so often into these normal parts of self that they end up with problems like questioning their identity, feelings of numbness, and other depersonalization\derealization symptoms, perception problems, sometimes some memory loss, and other problems you can read about in my dissociative link where OSDD is one of the listed disorders. and that each time the problems happen they last less than a month, sometimes only a few hours to days.

hope this has helped. ultimately only your treatment providers can say what kind of internal system you have and how your symptoms fit in with how and why they are diagnosing you the way that they are.