Different Glymphatic-Lymphatic Coupling in the Nasal Mucosa and Parasagittal Dura

Background: Glymphatic-lymphatic coupling is difficult to visualize in humans. Purpose: To evaluate the transport from the basal subarachnoid space to lymphatic vessels in the nasal mucosa and in the parasagittal dura, respectively. Methods: A highly resolved 3D compressed sensing black blood sequence with almost isotropic resolution (0.5 ×0.5 ×0.6 mm 3 ) was acquired in 26 patients before and 2 to 4, 6 to 8, 24 to 48, and 72 to 96 hours after intrathecal injection of 0.5 mL gadobutrol. T1 signal intensities were measured in CSF spaces (perisylvian, above cribriform plate, midsylvian, and parasagittal), in the olfactory bulbs, fila olfactoria, and nasal mucosa, as well as in the cortex, white matter, and parasagittal dura. Results: In the perisylvian CSF, in the CSF above the cribriform plate, in the olfactory bulbs, fila olfactoria, nasal mucosa, and in the cortex, percentage T1 signal intensities showed a rapid increase, peaking at 2 to 4 hours and 6 to 8 hours, respectively. The midsylvian and parasagittal CSF exhibited a slower increase with peak enhancement at 24 to 48 hours. Similarly, in the white matter of the temporal lobe, T1 signal intensities increased gradually, reaching their peak at 24 to 48 hours, followed by a decline after 72 to 96 hours. In the parasagittal dura, T1 signal intensities continued to rise even beyond 72 to 96 hours. Conclusions: Intrathecally injected gadolinium reaches the lymphatic vessels in the nasal mucosa earlier than those in the parasagittal dura. Transport to the nasal mucosa takes place directly via the subarachnoid space. For the transport to the parasagittal dura, findings are compatible with a trans-parenchymal transport route.