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Lalwani’s grading system for transverse-sigmoid sinus DAVFs (1993)
| Grade 1 | No venous restriction: normal antegrade venous drainage without retrograde or cortical venous drainage |
| Grade 2 | Antegrade & retrograde venous drainage with or without cortical venous drainage |
| Grade 3 | Retrograde & cortical venous drainage without antegrade venous drainage |
| Grade 4 | Cortical venous drainage only |
DAVF, dural arteriovenous fistula.
