Purpose To determine the natural history of diffusion weighted imaging (DWI) abnormalities in early acute subarachnoid hemorrhage (SAH).

Methods Patients with diffuse SAH at our institution were offered enrollment in a prospective study in which serial MRI, including DWI, FLAIR, PWI, and ASL sequences, was performed at admission, 7 days, 30 days, and upon the development of signs/symptoms of vasospasm. Patient demographics, Hunt-Hess grade, modified Fisher score, and underlying lesion and treatment technique were recorded.

Results Between November 2013 and August 2017, 50 patients were enrolled, 37 women, mean age 58, 20 current smokers. Hunt-Hess grade mean was 3.0. Modified Fisher score mean was 3.5. All underlying vascular lesions were treated endovascularly: 17 ACA aneurysms, 14 ICA aneurysms (including PCOM), 10 MCA aneurysms, 3 basilar tip aneurysms, 1 vertebral aneurysm, 1 posterior fossa AVM, and 4 angiographically-negative SAHs.

31 patients (62%) had DWI abnormalities on their admission scan; all had undergone a catheter angiogram or endovascular treatment of the underlying lesion prior to the MRI. The total number of DWI abnormalities amongst these patients was 250 (214<5 mm, 22 5–9 mm, and 14≥10 mm). 70 were FLAIR hyper-intense. 28 lesions were within non-catheterized vascular territories.

At 7 days, the total number of DWI abnormalities was 267 (224<5 mm, 27 5–9 mm, 16≥10 mm), 100 FLAIR hyper-intense, 19 within non-catheterized vascular territories. 11 patients (22%) had an increase in the total number of DWI abnormalities without additional intervention. Of these, 2 patients (4%) had an increase in the number of DWI abnormalities outside of the territory of the treated lesion. Only 1 patient had a perfusion abnormality; this patient did not incur an increase in DWI burden.

Conclusion The acquisition of additional multifocal ischemic injury to the brain is common in early SAH. This phenomenon is independent of cerebral perfusion and large-vessel vasospasm.

Disclosures Y. Kayan: 2; C; Medtronic, Penumbra. J. Delgado Almandoz: 2; C; Medtronic, MicroVention, Penumbra. J. Fease: None. A. Wallace: None. J. Scholz: None. A. Milner: None. N. Banerji: None. M. Mulder: None.