Objective: To provide evidence that venous congestion and drainage patterns are responsible for the manifestations of cavernous sinus area dural arteriovenous malformations (CSdAVMs). Design: Retrospective observational case series. Participants: Records of 85 patients with complete clinical and angiographic evaluations of CSdAVMs were evaluated for the clinical features of the disorder. A neuroradiologist analyzed patterns of venous drainage to and from the cavernous sinus without knowledge of the clinical features. Four venous drainage patterns (reversal of flow from the CSdAVMs into the anterior cavernous sinus, ophthalmic vein thrombosis, drainage into the inferior petrosal sinus or drainage into the superior petrosal sinus) were statistically tested for their predictive value of signs and symptoms using logistic regression. Main Outcome Measures: The power of prediction of orbital congestion, elevated IOP, extraocular muscle dysfunction, optic neuropathy, venous-stasis retinopathy, choroidal effusion, anterior chamber shallowing, bruits, cranial nerve paresis, and central nervous system dysfunction from four patterns of venous drainage. Results: Reversal of drainage into the anterior cavernous sinus and ophthalmic veins was highly predictive (P = 0) of orbital congestion, which was seen in 77 (91%) patients. In contrast, eight (9%) patients without orbital congestion had shunts that did not drain into the anterior cavernous sinus and ophthalmic veins. Cavernous sinus dural arteriovenous malformation drainage into the anterior cavernous sinus and ophthalmic veins also predicted elevated IOP (P = 0.0023) and optic neuropathy (P = 0.047). Ophthalmic vein thrombosis significantly predicted cases with choroidal effusion (P = 0.002) and anterior chamber shallowing (P = 0.01). Third nerve paresis could be predicted from flow toward the inferior petrosal sinuses (P = 0.017). Central nervous system symptoms or dysfunction, occurring in 7 (8%) patients, was predicted by venous drainage into the superior petrosal sinus (P = 0.0008). Conclusions: The clinical features found in patients with CSdVAMs are related to the abnormal venous drainage and can be predicted by these venous drainage patterns. Venous congestion and hypertension seem to cause the clinical dysfunction in this disorder.