Other risk factors for Alzheimer’s Disease and dementia, including the cholesterol transporter isoform ApoE4 (Liu et al., 2013), age-related deterioration of arterial integrity and disruption of elasticity (Weller et al., 2009), or changes to CSF production (Silverberg et al., 2001, Silverberg et al., 2003), have been implicated in the disruption of perivascular clearance, specifically including Aβ clearance (Hawkes et al., 2012). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.