Background: The circle of Willis (CoW) and cervical carotid arteries are important sources of collateral flow during acute large vessel occlusion (LVO) in the anterior circulation. We examined the anatomical components of the circle and the cervical carotid arteries to determine relationship to acute stroke severity. Methods: Consecutive patients with acute LVO who underwent EVT were assessed. Measurements were made of the luminal diameters of 16 anatomical vascular components. Admission NIHSS, ASPECTS and mCTA collateral scores were statistically analyzed for any relationship to vascular measurements. Results: 100 patients were studied. No relationship was found between the collateral Willisian pathways and measures of stroke severity. However, the ophthalmic arteries exhibited a relationship to stroke severity. In adjusted analysis, 1-mm increases in the ipsilateral and contralateral ophthalmic artery diameter were independently associated with a 4.80-point decrease and a 6.31-point increase in the NIHSS scale, respectively. Similarly, a 1.53-point increase and a 2.62-point decrease in the ASPECTS. In the neck a majority showed 0-55% stenosis, with no stenosis between 55% and 95%, and 14% at 95% to 100%. Conclusions: Stroke severity and collateral during LVO is unrelated to Willisian collateral. Ophthalmic artery calibers are related. Acute progression of 55-95% stenoses to complete occlusion occurs in LVO stroke