Supplemental Figure 1. A-C: MRI SWI sequence of patient #8 shows an enhancing lesion with T2/FLAIR hyperintensity and susceptibility changes in the left postcentral sulcus concerning for thrombosed vessel (white arrow block). D: Left M3-4 branch pial IIA measuring 3.0x2.5 mm which is seen filling by the left middle meningeal artery (yellow arrows).

Supplemental Figure 2.

(A-C) Case #5. MRI SWI sequence shows a linear susceptibility artifact (yellow arrow), which is contiguous with the left frontal

opercular hemorrhagic infarct shown in FLAIR sequence (B). This sulcal SWI lesion corresponds to the angiogram finding of left M3

branch fusiform infective intracranial aneurysm, measuring approximately 7.1 x 1.1mm. Another cut from SWI sequence shows left

frontal operculum infarct with hemorrhagic transformation (C).

(D-F) Case #10. MRI SWI sequence (D, E) shows sulcal SWI lesions in left paramedian parietal sulcus (yellow arrow) and right

postcentral sulcus (thick arrow). Both of the sulcal SWI lesions show contrast enhancement (F). These two contrast enhancing sulcal

SWI lesions correspond to 4.3 x 2.2mm fusiform infective intracranial aneurysm of the parieto-occipital branch (P4) segment of the

left PCA and 1.9 x 1.7mm infective intracranial aneurysm in distal right M4 branch in the parietal region of the right MCA territory.

Supplemental Table 1. Demographics and characteristics of 116 persons with infective endocarditis.

Infective endocarditis patients N=116Demographics   Median age 57.5 Male 76 (66%)Past Medical History   Atrial fibrillation 31 (27%) Prior ischemic stroke 34 (29%) Prior intracranial hemorrhage 7 (6%) Coronary artery disease 41 (35%) Hypertension 76 (66%) Diabetes mellitus 30 (26%) Hyperlipidemia 51 (44%) Chronic kidney disease 19 (16%) Current smoker 29 (25%) Congestive heart failure   Antiplatelet therapy 46 (40%) Anticoagulant therapy 26 (22%) Current intravenous drug abuse 13 (11%)Organism   Viridans streptococcus 13 (11%) Other streptococcus 17 (15%) Staphylococcus aureus 36 (31%) Enterococcus 17 (15%) Fungal 3 (3%) Others 23 (20%) Pathogen not identified 7 (6%)Valve  

Aortic valve 70 (60%) Mitral valve 60 (52%) Prosthetic valve 62 (53%)Imaging Presentation   Ischemic infarct 81 (70%) Hemorrhagic conversion of ischemic infarct 26 (22%) Intracerebral hemorrhage 17 (15%) Subarachnoid hemorrhage 10 (9%) Subdural hematoma 1 (1%) Infective intracranial aneurysm 13 (11%)Clinical Variables   Transient focal neurological deficit (<24 hour) with negative brain imaging 3 (3%) Focal neurological deficit 49 (42%) Encephalopathy 43 (37%) Asymptomatic but brain imaging abnormality (ischemia or hemorrhage) 35 (30%) Number of valve surgery 74 (64%)

Supplemental Table 2. Baseline characteristics of patients with infectious intracranial aneurysm (IIA) versus without IIA.

Risk Factor IIA (N=13) No IIA (N=61) Total N=74 P-value

Demographics         Median age (interquartile range: IQR) 56 (48-68) 58 (48-68) 0.96 Male 10 43 53 0.74Past Medical History   Atrial fibrillation 4 10 14 0.26 Prior ischemic stroke 4 14 18 0.72 Prior intracranial hemorrhage 1 3 4 0.56 Coronary artery disease 5 19 24 0.75 Hypertension 10 37 47 0.35 Diabetes mellitus 3 14 17 1 Hyperlipidemia 8 25 33 0.22 Chronic kidney disease 2 9 11 1 Current smoker 6 13 19 0.16 Congestive heart failure 2 10 12 1 Antiplatelet therapy 6 23 29 0.76 Anticoagulant therapy 3 29 32 1 Current intravenous drug abuse (IVDU) 2 10 12 1Organism   Viridans streptococcus 4 4 8 0.03 Other streptococcus 2 10 12 1 Staphylococcus aureus 2 20 22 0.32 Enterococcus 3 7 10 0.37 Fungal 0 3 3 1 Others 2 10 12 1Valvular Characteristics  

Aortic valve 11 37 48 0.2 Mitral valve 5 33 38 0.37 Prosthetic valve 6 31 37 1 Presence of 1 or more vegetations 10 52 62 0.46 Vegetation mobility presence 11 45 56 0.17 Ejection fraction (median, IQR) 60% (55-65) 55% (51-60)   0.31 Vegetation length (median, IQR) 1.2cm (0.8-2.4) 1.6cm (1.2-2)   0.47 Extravalvular extension presence 5 23 28 1 Valve Regurgitation≥2+ 8 33 41 0.62Imaging Presentation   No acute intracranial lesions 3 11 14 0.7 Ischemic infarct 9 43 52 1 Hemorrhagic conversion of ischemic infarct 5 13 18 0.25 PH2 type ECASS classification of hemorrhagic conversion 2 3 5 0.21

Intracranial hemorrhage 1 18 19 0.16 Intraparenchymal hemorrhage (IPH) 1 11 19 0.68 Subarachnoid hemorrhage 0 9 9 0.35 Subdural hematoma 0 1 1 1 Enhancing lesions 5 14 19 0.71 Ischemic stroke size (median, IQR) 20.7cc (10-65) 3.9cc (1-27)   0.17 IPH size (median, IQR) 60cc 22cc (3.4-67)   0.83Clinical VariablesNIHSS (median, IQR) 3 (1-12) 1 (0-6)   0.28Focal neurological deficit 9 35 44 0.54Altered mental status 4 17 21 1Asymptomatic but brain imaging abnormality (ischemia or hemorrhage) 4 22 26 1

Supplemental Table 3. MRI imaging characteristics of 10 persons with infectious intracranial aneurysm (IIA).

Age and Valve

involved

Neurological Presentation

MRI findings: Stroke

MRI Findings: SWI microbleeds

Infective Intracranial Aneurysm (IIA) Characteristics

Sulcal SWI

Any CMB

>5mm CMB

Enhancemen

t*

FLAIR hyperintensit

y*

1

48 year old with

prosthetic aortic valve

Acute ischemic stroke with NIHSS 17

Acute R MCA infarct with HI1 hemorrhagic conversion

Sulcal SWI lesion in left occipital lobe without contrast enhancement

Left P5 PCA calcarine branch IIA measuring 2.8x3.7 mm

+ + - - -

2

29 year old with

prosthetic aortic valve

Acute Ischemic stroke with NIHSS 3

Acute L corona radiata + R frontal infarcts

Right parietal SWI lesion, CMB (>5mm), with T2/FLAIR hyperintensity

7.6x4.3 mm fusiform irregular IIA in inferior division of R M3 branch

+ + + - -

3

33 year old with

prosthetic aortic valve

Encephalo-pathy with NIHSS 0

Acute L corona radiata infarct

An elongated susceptibility artifact with hyperintensity in L circular sulcus with minimal FLAIR signal change. R occipital subcortical SWI lesion

Two IIAs: 2 mm saccular IIA in superior division L M2 branch; 2 mm fusiform IIA in R parieto-occipital MCA.

+ + + - -

455 year old with native aortic valve

Acute ischemic stroke with NIHSS 2

Acute R MCA infarct

SWI lesion in L genu of corpus callosum with T2/FLAIR hyperintensity

1.7x1.3 mm Right P3-4 branch IIA + + - N/A -

556 year old with native aortic valve

No acute symptoms with NIHSS 0

Acute bilateral MCA infarcts

L frontal operculum hemorrhagic infarct with linear SWI lesion

7.1x1.1 mm Left M3 branch fusiform IIA + + + N/A -

6 70 year old with native aortic valve

No acute symptoms with NIHSS 3. Prior

None L medial occipital enhancing lesion with sulcal SWI lesion without T2/FLAIR changes

2 mm fusiform IIA in left M4 branch

+ + - + -

ischemic stroke

7

59 year old with

prosthetic aortic and

mitral valves

Encephalo-pathy with NIHSS 25

L frontal IPH

Multiple large CMBs with T2/FLAIR changes in R frontal lobe (operculum) + Enhancing sulcal SWI lesion without T2/FLAIR change in L precentral gyrus (one day later, developed large L frontal IPH)

Two IIAs: 3x4 mm R M3 (opercular segment) IIA; 4x5 mm L M4 superior division IIA in with 8x9 mm pseudoaneurysm

+ + + + -

850 year old with native mitral valve

TIA.Prior ischemic stroke with NIHSS 2

Enhancing sulcal SWI lesion with hyperintensity in L postcentral sulcus

3.0 x 2.5 mm L M3-4 branch pial IIA + + - + +

9

66 year old with

prosthetic aortic valve

Encephalo-pathy with NIHSS 14

Acute R MCA stroke with PH2 hemorrhagic conversion

Multiple (4) large CMBs in RMCA territory with T2/FLAIR signal changes + contrast enhancement: corresponding area of IIAs

Irregularities in a R MCA fronto-parietal branch with 3 discrete fusiform dilatations at the M4 level, each measuring 1 mm

- + + + +

10

47 year old with native aortic and

mitral valves

No acute symptoms with NIHSS 0

Acute L parietal infarct

Enhancing lesions with T2/FLAIR hyperintensity and SWI lesion in L paramedian parietal lobe (sulci) and R postcentral sulcus

Two IIAs: Fusiform IIA in P4 of L PCA measuring 4.3x2.2 mm; round IIA in distal R M4 measuring 1.9x1.7 mm

+ + + + +

NIHSS = National Institutes of Health Stroke Scale. R = right. L = left. MCA = middle cerebral artery. PCA = posterior cerebral artery. RHP = right hemiparesis. CMB = cerebral microbleed. IPH = Intraparenchymal hemorrhage. PH2 = parenchymal hematoma

type 2 hemorrhagic conversion. HI1 = hemorrhagic infarction type 1 hemorrhagic conversion. N/A = not applicable. * With CMB or sulcal SWI lesion.