The glymphatic system, first described in 2012, is a pathway for the clearance of solutes from the brain interstitial fluid (ISF) via perivascular pathways, involving glial cells. It is associated with sleep and is crucial for clearing waste products like amyloid-β and hyperphosphorylated tau. The DTI-ALPS index, developed in 2017, is a non-invasive MRI technique to assess glymphatic function in cerebral white matter. It measures water diffusivity in perivascular spaces, but its validity is questioned due to limited penetration into deep white matter and potential confounding factors like motion and blood flow. Studies using DTI-ALPS have linked impaired glymphatic function to various conditions, including neurodegenerative diseases and stroke. However, the index's ability to accurately reflect glymphatic function remains uncertain, as CSF-ISF exchange is minimal in deep white matter, where other clearance pathways dominate. The DTI-ALPS index may reflect white matter features rather than glymphatic function, as shown by correlations with other DTI parameters and age. The glymphatic system's role in overall brain clearance is still debated, with ongoing research needed to understand its true contribution. While new imaging tools for brain clearance research are promising, caution is required due to existing controversies and the complexity of clearance mechanisms. The DTI-ALPS index may not be a reliable marker for glymphatic function, especially in conditions like periventricular leukomalacia. Further studies are needed to clarify the glymphatic system's role in neurological diseases and to develop more accurate imaging methods.The glymphatic system, first described in 2012, is a pathway for the clearance of solutes from the brain interstitial fluid (ISF) via perivascular pathways, involving glial cells. It is associated with sleep and is crucial for clearing waste products like amyloid-β and hyperphosphorylated tau. The DTI-ALPS index, developed in 2017, is a non-invasive MRI technique to assess glymphatic function in cerebral white matter. It measures water diffusivity in perivascular spaces, but its validity is questioned due to limited penetration into deep white matter and potential confounding factors like motion and blood flow. Studies using DTI-ALPS have linked impaired glymphatic function to various conditions, including neurodegenerative diseases and stroke. However, the index's ability to accurately reflect glymphatic function remains uncertain, as CSF-ISF exchange is minimal in deep white matter, where other clearance pathways dominate. The DTI-ALPS index may reflect white matter features rather than glymphatic function, as shown by correlations with other DTI parameters and age. The glymphatic system's role in overall brain clearance is still debated, with ongoing research needed to understand its true contribution. While new imaging tools for brain clearance research are promising, caution is required due to existing controversies and the complexity of clearance mechanisms. The DTI-ALPS index may not be a reliable marker for glymphatic function, especially in conditions like periventricular leukomalacia. Further studies are needed to clarify the glymphatic system's role in neurological diseases and to develop more accurate imaging methods.