There can be certain conditions that initially mimic "Parkinsonism", but can't be called Parkinson's disease. A label of PD is usually given only when a DAT scan shows extensive loss of dopamine producing neurons, and as we all have brain stem damage in different areas and structures, each case of PD is slightly different, and some cases can't be labelled as PD proper, because they lack certain symptoms which are indicative of loss of Dopamine transport. " there is still a "grey area" (pun intended) in which the symptoms can be properly termed as PD.