Most of the cases in Salvarani and colleagues' 1 series of primary central nervous system "vasculitis" would have been more appropriately labeled "vasculopathy." Vasculitis should be regarded as a pathological diagnosis. 2 Only 49 of their 101 cases had a biopsy performed, and of these, only 31 had positive biopsy results; therefore, the majority (n ฯญ 70) of their cases were not determined to have vasculitis. There are many other causes of the angiographic findings reported, including infections, cancer, medications, migraine, and others. 2,3 In their series, there are also many hints of a difference in clinical characteristics between those diagnosed with biopsy versus angiography (eg, with altered cognition overrepresented among those diagnosed by biopsy and strokelike presentations increased in those diagnosed by biopsy), suggesting that they are studying heterogeneous disorders. It would have been helpful as well to know whether there were any age differences between those diagnosed by angiography versus biopsy.
We appreciate that the definitive diagnosis of primary central nervous system vasculitis can be difficult, and a high degree of clinical suspicion is needed. The failure to make a definitive diagnosis in clinical practice, however, should no longer be taken to provide permission to misattribute a diagnosis in clinical science. Semantics aside, our major concern is that the authors make statements about the putative efficacy of therapy based on this inadequately defined population. The statement, for example, that "[m]ost patients showed a favorable response to glucocorticoids alone or in combination with cyclophosphamide" both ignores the possibility that many of their patients with other causes of vasculopathy may improve spontaneously and implies that even patients with a positive histological diagnosis can safely receive steroids alone. It would have been helpful to know what the response rates were among those with biopsy-proved vasculitis to evaluate this statement.