Tracking of striatal degeneration in prediagnostic Parkinson's disease: fi rst steps into a promising future

775 syndrome. The cortical predominant subtype might be related to overexpression of amyloid β, whereas the late onset, hippocampal predominant subtype could be linked to defects in clearance of amyloid β. In this respect, assessment of the prevalence of lesions that are diff erentially present in the various types of AD could bring interesting fi ndings: enlarged endosomes are seen in sporadic AD, but are absent in cases with PSEN1 and PSEN2 mutations, 7 and cottonwool plaques are generally, but not exclusively, seen in patients with the PSEN1ΔE9 mutation. 8 These lesions should now be investigated in the diff erent subtypes. Murray and colleagues’ study defi nes the diff erent subtypes statistically at the population level. We now need to discover markers that would enable identifi cation of the specifi c subtype for an individual during life. Such markers would be useful for orientation of therapeutic strategies. Murray and colleagues’ study is a major step in disentangling clinical heterogeneity in AD by use of pathological correlations. The identifi cation of three subtypes—typical, hippocampal sparing, and limbic predominant—might seem simplistic to clinicians, but it is, undoubtedly, just the beginning of a more precise understanding of the diff erent forms of AD.