PSP, MSA, CBD is a clinical diagnosis and can only be officially confirmed after an autopsy. This makes it hard along with how rare and little is known about them to diagnose early or proper. One of the hallmark symptoms is the eye issues and freezing of eyes for PSP. This normally presents later in the disease and is often a reason for later diagnosis. They are currently working on ways to find better markers for diagnosing and hope to one day be able to better diagnose PSP, MSA, CBD.
Here is a great read about how they are constantly trying to improve the diagnosing.
We aimed to provide an evidence- and consensus-based revision of the clinical diagnostic criteria for PSP.
Here, we present new criteria aimed to optimize early, sensitive, and specific clinical diagnosis of PSP on the basis of currently available evidence.