Interestingly, unlike β-amyloid plaque pathology, tau pathology is relatively sparse in NPH cortical biopsies8, although some studies have found trace tau pathology at higher levels14, which is consistent with the fact that most patients coming to shunt surgery do not show severe cognitive impairment (those patients who are pre-AD are likely to be at a Braak stage with sparse to no neocortical tangles). This evidence concerns the gene MAPT and Alzheimer disease.