The article critically examines the DTI-ALPS index, a non-invasive marker of glymphatic function, as reported by Yin and colleagues in children with periventricular leukomalacia (PVL). The glymphatic system, described in 2012, facilitates the clearance of solutes from the brain interstitial fluid (ISF) through the exchange of cerebrospinal fluid (CSF) and ISF. The DTI-ALPS index measures water diffusivity in perivascular spaces, which is hypothesized to reflect glymphatic function. However, the author argues that this method may not accurately represent glymphatic clearance in deep white matter, where other pathways like blood-brain barrier transport and local proteolytic degradation dominate. The limited penetration of CSF-ISF exchange into deep white matter and the dominance of other clearance mechanisms suggest that the DTI-ALPS index may not be a reliable marker of glymphatic function. The article concludes that while imaging-based assessments of perivascular spaces in white matter have gained interest, the validity of the DTI-ALPS index as a marker of glymphatic brain clearance is questionable, and further research is needed to understand the true extent and contribution of the glymphatic system to overall brain clearance capacity.The article critically examines the DTI-ALPS index, a non-invasive marker of glymphatic function, as reported by Yin and colleagues in children with periventricular leukomalacia (PVL). The glymphatic system, described in 2012, facilitates the clearance of solutes from the brain interstitial fluid (ISF) through the exchange of cerebrospinal fluid (CSF) and ISF. The DTI-ALPS index measures water diffusivity in perivascular spaces, which is hypothesized to reflect glymphatic function. However, the author argues that this method may not accurately represent glymphatic clearance in deep white matter, where other pathways like blood-brain barrier transport and local proteolytic degradation dominate. The limited penetration of CSF-ISF exchange into deep white matter and the dominance of other clearance mechanisms suggest that the DTI-ALPS index may not be a reliable marker of glymphatic function. The article concludes that while imaging-based assessments of perivascular spaces in white matter have gained interest, the validity of the DTI-ALPS index as a marker of glymphatic brain clearance is questionable, and further research is needed to understand the true extent and contribution of the glymphatic system to overall brain clearance capacity.