Table 4.

Borden’s classification (1995)

Type I	Drainage directly into dural venous sinuses or meningeal veins
Type II	Drainage into dural sinuses or meningeal veins with retrograde drainage into subarachnoid veins
Type III	Drainage into subarachnoid veins without dural sinus or meningeal venous drainage (cortical venous reflux only)
Type IV	Drainage into one or more large venous lakes (dural or subdural) that act as a mass lesion (supra- or infratentorial venous lake)