Typically, Arachnoiditis is seenon Contrast MRI using a Tesla 3 or higher.
However, research indicates that MRdoes not correlate with the disease symptoms and severity . In fact,research shows poor intra reader Correlation. In one study, 5 radiologists were challenged to read the same series of MRIs. For arachnoiditis, only the 2 most senior Radiologists had good correlation as to their diagnosis, with little mutual consensus by the other 3.
This leads us to believe Arachnoiditis is under reported and its rarity is a result. It is not "rare", but "rarely diagnosed."