Clinical differentiation of primary degenerative and multi-infarct dementia: a critical review of the evidence. Part II: Pathological studies.

A critical examination of representative pathological studies published over the past four decades reveals that this literature fails to provide sufficient support for the antemortem differentiation of primary degenerative dementia (PDD) from multi-infarct dementia (MID) on the basis of clinical criteria. Similar conclusions with respect to clinical studies and articles are presented in Part I of this overview. Among the difficulties commonly encountered in the literature are sampling bias, retrospective design, nonblind assessments, inadequate sample size, failure to consider overlap (i.e., mixed cases), absence of pathological verification in the clinical studies and post hoc reasoning. The necessity to assure that one is dealing with a case of PDD as opposed to some other dementing process is self-evident. However, these reviews show that this capability has not been adequately established with respect to the differential diagnosis of PDD and MID; the evidence to date indicates that the clinical diagnosis of MID, in particular, should be made with caution until more conclusive methods become available.