The cerebrospinal fluid (CSF) is a continuous source of fluid and ions for the brain. During an acute ischemic stroke, a cervical or cerebral artery is occluded possibly leading to brain edema.

A team of researchers found out that the glymphatic flow may play an essential role in early brain edema formation.

They occluded the middle cerebral artery in mice and used magnetic resonance (MR) and multimodal optical imaging and realized that within minutes of ischemic stroke, CSF flowed rapidly into brain tissue along perivascular spaces. Radionuclides confirmed that CSF was the earliest contributor of fluid and ions.

Basically the space left unoccupied after vessels constrict in acute stroke is filled by an inrush of CSF that nearly doubles flow speed.