MAPT and Alzheimer disease: Interestingly, while the fraction of long and elongated aggregates was higher for the extra-synaptic aggregates in the control cases (6% synaptic vs 13% extra-synaptic), this trend reversed in AD with 7–8% of the extra-synaptic tau aggregates longer than 150 nm in length with an eccentricity greater than 0.9 (Fig. 1g).