A1 Segment Research Articles

Rescue stenting after artery occlusion as a complication of an intrasaccular device-assisted coiling embolization: illustrative case.

Endovascular embolization of wide-necked aneurysms can be challenging. The development of intrasaccular devices like the Contour has enabled us to approach these aneurysms effectively by reducing recanalization rates and eliminating the need for dual antiplatelet therapy, which is particularly beneficial in the case of ruptured aneurysms. Although complications from using these devices are rare, it is crucial to address them properly. In this case, the authors highlight how to manage artery thrombosis caused by device protrusion during aneurysm embolization. This report describes a complication in a male patient with a ruptured anterior communicating artery wide-necked aneurysm. Following Contour-assisted coiling of the aneurysm, a realignment of the detachable apex of the device occluded the A2 segment of the right anterior cerebral artery. After the failure of intra-arterial and intravenous tirofiban infusion as well as mechanical thrombectomy, a self-expanding open-cell stent was deployed in the involved vessel, achieving successful reperfusion. The Contour device has a detachable zone that can cause occlusion of the parent vessel after deployment. The use of a stent as a rescue maneuver may be useful if reperfusion of the vessel cannot be achieved through other methods such as aspiration or full-dose antiplatelet therapy.

Clip Reconstruction of a Previously Coiled Recurrent Middle Cerebral Artery Sidewall Aneurysm and an A1 Segment Sidewall Aneurysm in a Patient With Human Immunodeficiency Virus-Associated Vasculopathy: 2-Dimensional Operative Video.

Clip Reconstruction of a Previously Coiled Recurrent Middle Cerebral Artery Sidewall Aneurysm and an A1 Segment Sidewall Aneurysm in a Patient With Human Immunodeficiency Virus-Associated Vasculopathy: 2-Dimensional Operative Video.

Bihemispheric Right Anterior Cerebral Artery, Fenestrated Origin of the Left Pericallosal Artery, Fenestrated Basilar Artery, Double Right Posterior Cerebral Artery.

Anatomical variations of the cerebral vasculature are frequently encountered. The archived magnetic resonance angiogram of a 62-year-old male patient was studied anatomically on planar slices and 3-dimensional volume renderings. Numerous anatomical variants were found in that single case. In the vertebrobasilar system were found: the proximal basilar artery fenestration, with a unilateral origin from that fenestration of an anterior inferior cerebellar artery, and the unilateral origin of the superior cerebellar artery from the P1 segment of the main posterior cerebral artery (PCA). There were also unilateral variants of the right internal carotid artery (ICA): a subvariant of an accessory PCA leaving the ICA as a hyperplastic anterior choroidal artery and united to the main PCA by a short communicating branch, distinctive of the posterior communicating artery in that side (unilateral double PCA); a right bihemispheric anterior cerebral artery (ACA) but with complete agenesis of the contralateral A1 ACA segment; from the right ACA continued an anatomically normal ipsilateral A2 segment and a short transverse contralateral A2 that, in turn, sent off long pericallosal and callosomarginal arteries; and fenestrated origin of the left pericallosal artery. Therefore, an arterial variant in one of the main cerebral circulations could not exclude anatomical variants in the other cerebral circulatory beds.

Internal carotid artery stenosis: hemodynamics in the ipsilateral ACA affects CT angiography manifestations.

This study aimed to evaluate whether CT angiography (CTA) manifestations in anterior cerebral artery a1 segment (A1) were related to the hemodynamics in patients with internal carotid artery stenosis (ICAS). A total of 97 cases were selected. The degree of ICAS and symmetry of A1 were evaluated by CTA examination. Hemodynamic indexes were detected by transcranial Doppler (TCD). The differences in CTA presentations of A1 and hemodynamics between the vessels on the stenotic and contralateral sides were analyzed according to the different degrees of stenosis. The degree of ICAS according to the different manifestations of A1 and the hemodynamics of A1's adjacent vessels were also analyzed. In the case of unilateral ICAS, the difference in Vm of A1 between the stenotic and the contralateral side was the most significant relative to the stenosis degree. When unilateral ICAS was ≥70%, the presentation of A1 on the stenotic side was more slender or non-visualized compared to that on the contralateral side, while in cases with unilateral stenosis <70% or bilateral stenosis with a similar degree of stenosis, A1 were mainly symmetrical. When A1 on the side of ICAS was slender or non-visualized, the Vm of A1 was significantly slower than that on the contralateral side (P < 0.001). The CTA manifestations of A1 on the side of ICAS embodied the overall changes of the intracranial hemodynamics after ICAS. A combination of TCD and CTA examination of A1 can assist in judging the location and degree of ICAS.

Chordal force profile after neochordal repair of anterior mitral valve prolapse: An ex vivo study

ObjectiveThis study aimed to biomechanically evaluate the force profiles on the anterior primary and secondary chordae after neochord repair for anterior valve prolapse with varied degrees of residual mitral regurgitation using an ex vivo heart simulator. MethodsThe experiment used 8 healthy porcine mitral valves. Chordal forces were measured using fiber Bragg grating sensors on primary and secondary chordae from A2 segments. The anterior valve prolapse model was generated by excising 2 primary chordae at the A2 segment. Neochord repair was performed with 2 pairs of neochords. Varying neochord lengths simulated postrepair residual mitral regurgitation with regurgitant fraction at >30% (moderate), 10% to 30% (mild), and <10% (perfect repair). ResultsRegurgitant fractions of baseline, moderate, mild, and perfect repair were 4.7% ± 0.8%, 35.8% ± 2.1%, 19.8% ± 2.0%, and 6.0% ± 0.7%, respectively (P < .001). Moderate had a greater peak force of the anterior primary chordae (0.43 ± 0.06 N) than those of baseline (0.19 ± 0.04 N; P = .011), mild (0.23 ± 0.05 N; P = .041), and perfect repair (0.21 ± 0.03 N; P = .006). In addition, moderate had a greater peak force of the anterior secondary chordae (1.67 ± 0.17 N) than those of baseline (0.64 ± 0.13 N; P = .003), mild (0.84 ± 0.24 N; P = .019), and perfect repair (0.68 ± 0.14 N; P = .001). No significant differences in peak and average forces on both primary and secondary anterior chordae were observed between the baseline and perfect repair as well as the mild and perfect repair. ConclusionsModerate residual mitral regurgitation after neochord repair was associated with increased anterior primary and secondary chordae forces in our ex vivo anterior valve prolapse model. This difference in chordal force profile may influence long-term repair durability, providing biomechanical evidence in support of obtaining minimal regurgitation when repairing mitral anterior valve prolapse.

Histopathology of the Mitral Valve Residual Leaflet in Obstructive Hypertrophic Cardiomyopathy

BackgroundMitral valve (MV) elongation is a primary hypertrophic cardiomyopathy (HCM) phenotype and contributes to obstruction. The residual MV leaflet that protrudes past the coaptation point is especially susceptible to flow-drag and systolic anterior motion. Histopathological features of MVs in obstructive hypertrophic cardiomyopathy (OHCM), and of residual leaflets specifically, are unknown. ObjectivesThe purpose of this study was to characterize gross, structural, and cellular histopathologic features of MV residual leaflets in OHCM. On a cellular-level, we assessed for developmental dysregulation of epicardium-derived cell (EPDC) differentiation, adaptive endocardial-to-mesenchymal transition and valvular interstitial cell proliferation, and genetically-driven persistence of cardiomyocytes in the valve. MethodsStructural and immunohistochemical staining were performed on 22 residual leaflets excised as ancillary procedures during myectomy, and compared with 11 control leaflets from deceased patients with normal hearts. Structural components were assessed with hematoxylin and eosin, trichrome, and elastic stains. We stained for EPDCs, EPDC paracrine signaling, valvular interstitial cells, endocardial-to-mesenchymal transition, and cardiomyocytes. ResultsThe residual leaflet was always at A2 segment and attached by slack, elongated and curlicued, myxoid chords. MV residual leaflets in OHCM were structurally disorganized, with expanded spongiosa and increased, fragmented elastic fibers compared with control leading edges. The internal collagenous fibrosa was attenuated and there was collagenous tissue overlying valve surfaces in HCM, with an overall trend toward decreased leaflet thickness (1.09 vs 1.47 mm, P = 0.08). No markers of primary cellular processes were identified. ConclusionsMV residual leaflets in HCM were characterized by histologic findings that were likely secondary to chronic hemodynamic stress and may further increase susceptibility to systolic anterior motion.

Anterior Cerebral Artery Associated “Limb-Shaking TIA” A3 Branch Stenosis Corrected With Submaximal Intracranial Angioplasty (P8-5.030)

<h3>Objective:</h3> NA <h3>Background:</h3> Limb-shaking TIA is a rare presentation of severe carotid stenosis presenting with jerking movement affecting the contralateral arm, hand, or leg of the hypo perfused motor cortices. We report a patient who experienced left leg shaking TIA due to stenosis of the anterior cerebral artery (ACA) branch A3 corrected by submaximal intracranial angioplasty. <h3>Design/Methods:</h3> <h3>Case report:</h3> 61-year-old lady with a history of diabetes, hypertension, and coronary heart disease presented to the ED with left-sided weakness and slurred speech of 1-day duration. The patient had intermittent episodes of weakness and trouble speaking for days prior in addition to transient intermittent episodes of shaking and weakness of her left leg that lasted for few seconds for the last couple of months. The patient was on Aspirin, Clopidogrel and Atorvastatin at home. NIHSS in the ED was 4. CT head: right ACA sub-acute infarction. CTA head and neck: No large vessel disease. Brain MRI: Diffusion positive infarct within the paramedian right frontal lobe. Echocardiogram was unremarkable. Hemoglobin A1c 5.6 and LDL of 54. Digital Subtraction Angiography DSA showed right ACA A3 segment 90% stenosis. Intensive medial management was recommended. As patient continued to have worsening in her symptoms, submaximal angioplasty of the right A3 ACA long segment lesion was done using balloon angioplasty. <h3>Results:</h3> Limb shaking TIA is typically secondary to significant MCA, ICA or rarely ACA stenosis. Diagnosis can be challenging and confused with focal seizures. Treatment with carotid endarterectomy or stenting is usually successful for most patients. For intracranial atherosclerosis initial management is optimizing medical management. Our patient was symptomatic despite optimal medical therapy. Submaximal angioplasty was utilized to successfully restore blood flow with balloon angioplasty of the A3 segment of the right ACA. <h3>Conclusions:</h3> Revascularization of symptomatic intracranial stenosis with submaximal angioplasty can be considered in selected patients who fail medical management. <b>Disclosure:</b> Dr. Altarazi has nothing to disclose. Dr. Sankaraneni has nothing to disclose.

Acute Paraparesis Syndrome after a Ruptured Aneurysm of the Azygos Anterior Cerebral Artery (P12-5.016)

<h3>Objective:</h3> To describe a rare case of acute paraparesis syndrome (APS) after a ruptured aneurysm of the azygos anterior cerebral artery (ACA). <h3>Background:</h3> The incidence of APS within 24 hours after subarachnoid hemorrhage is very rare. Additionally, the pathophysiology of this syndrome remains poorly defined. Nonetheless, the literature suggests it could emerge from a bilateral ACA vasospasm, acute hydrocephalus, or global cerebral edema and can be associated with poor clinical status. The azygos ACA is a rare variant whose unique anatomy intensifies the hemodynamic stress on the arterial wall, making aneurysm formation closely associated with this anomaly. <h3>Design/Methods:</h3> A 72-year-old man with a past medical history of hypertension presented to the hospital with the complaint of acute paraparesis after a thunderclap headache and transitory loss of consciousness. The physical exam showed paraparesis with brisk patellar and Achilles reflexes and a neutral response to bilateral plantar stimulation. No abnormalities were noticed on the cranial nerves, coordination, and sensory examination. <h3>Results:</h3> Routine laboratory studies were normal. Brain computed tomography revealed an acute punctate hemorrhage of an aneurysm located in the frontal interhemispheric fissure. Magnetic Resonance Imaging (MRI) of the spine was unremarkable. Brain MRI showed unspecific white matter abnormalities, and an MR angiography showed a 4.3 mm saccular aneurysm in the right ACA A3 segment in the bifurcation of an azygos ACA. The patient underwent coiling of the aneurysm and was able to walk unassisted nine weeks after the procedure. <h3>Conclusions:</h3> Acute paraparesis syndrome is a rare manifestation of a ruptured anterior communicating artery or anterior cerebral artery aneurysm. Here, we present an atypical etiology of APS caused by a ruptured aneurysm of the azygos ACA. To the best of our knowledge, this is the first description of an APS after a ruptured aneurysm of the azygos ACA. <b>Disclosure:</b> Dr. Moreno-Zambrano has nothing to disclose. Dr. Jimenez Zambrano has nothing to disclose. Jose Francisco Ortega Tola, MD has nothing to disclose. Dr. Yepez has nothing to disclose. Wilson Cueva has nothing to disclose.

Hemodynamic characteristics and mechanism for intracranial aneurysms initiation with the circle of Willis anomaly

Clinically, circle of Willis (CoW) is prone to anomaly and is also the predominant incidence site of intracranial aneurysms (IAs). This study aims to investigate the hemodynamic characteristics of CoW anomaly, and ascertain the mechanism of IAs initiation from the perspective of hemodynamics. Thus, the flow of IAs and pre-IAs were analyzed for one type of cerebral artery anomaly, that is, anterior cerebral artery A1 segment (ACA-A1) unilateral absence. Three patient geometrical models with IAs were selected from Emory University Open Source Data Center. IAs were virtually removed from the geometrical models to simulate the pre-IAs geometry. For calculation methods, a one-dimensional (1-D) solver and a three-dimensional (3-D) solver were combined to obtain the hemodynamic characteristics. The numerical simulation revealed that the average flow of Anterior Communicating Artery (ACoA) is almost zero when CoW is complete. In contrast, ACoA flow increases significantly in the case of ACA-A1 unilateral absence. For per-IAs geometry, the jet flow is found at the bifurcation between contralateral ACA-A1 and ACoA, which exhibits characteristics of high Wall Shear Stress (WSS) and high wall pressure in the impact region. It triggers the initiation of IAs from the perspective of hemodynamics. The vascular anomaly that leads to jet flow should be considered as a risk factor for IAs initiation.

5613251 RAPIDLY PROGRESSING MOYAMOYA SYNDROME IN SICKLE CELL DISEASE -- CASE REPORT

Introduction: Moyamoya syndrome (MMS) is an uncommon cerebrovascular complication of Sickle Cell Disease (SCD) characterized by progressive narrowing of large intracranial vessels and development of small-vessel collaterals. This association leads to a significant risk of ischemic stroke and poor neurologic outcomes. Case description: We present a case of a 5-year-old female child, with irregular follow-up at Pediatric Hematology Consultation due to Sickle Cell Disease, who presented to our hospital with a first ischemic stroke. The magnetic resonance angiography (MRA) showed narrowing of the terminal portions of the right internal carotid artery, the proximal segments of the right middle and anterior cerebral arteries and the A1 segment of left anterior cerebral artery, with multiple collaterals, aspects highly suggestive of MMS. She initiated hydroxycarbamide, acetylsalicylic acid and chronic red blood cell exchange (RBCX) aiming HbS<30% and 3 months later she presented with a new transient ischemic stroke. She was submitted to right encephaloduroarteriosynangiosis (EDAS) and was stable, without new ischemic events, until 1 year later when she presented with a new transient ischemic stroke of the left cerebral territory. Since then, she had multiple recurrent ischemic events with total recovery of neurologic deficits. MRA and Computed tomography (CT) showed multiple diffuse areas of cerebral infarction and bilateral severe segmental stenosis of internal carotid, middle and anterior cerebral arteries. Discussion/Conclusion: The literature review suggests that early detection and surgical revascularization in addition to RBCX could significantly reduce stroke recurrence and improve neurocognitive outcome. However, in this case, despite the recommended treatment, it was not possible to prevent the rapid progression of MMS, revealing the complexity of the approach to these patients.

Diagnosis of Small Unruptured Intracranial Aneurysms

PurposeDifferentiating normal anatomical variants such as an infundibulum or a vascular loop from true intracranial aneurysms is crucial for patient management. We hypothesize that high-resolution 7 T magnetic resonance imaging (MRI) improves the detection and characterization of normal anatomical variants that may otherwise be misdiagnosed as small unruptured aneurysms.MethodsThis is a retrospective, single-center study. All patients were scanned on a clinically approved 7 T MRI scanner and on a 3 T scanner. Image analysis was performed independently by three neuroradiologists blinded to clinical information. The presence of an unruptured intracranial aneurysm (UIA) and level of diagnostic certainty were assessed and the interrater agreement was calculated. If an aneurysm was present, the anatomic location and shape were recorded and compared.ResultsIn total, 53 patients with equivocal cerebrovascular findings on 1.5 T or 3 T MRI referred for a 7T MRI examination were included. Aneurysms were suspected in 42 patients examined at 3 T and in 23 patients at 7 T (rate difference 36%, 95% confidence interval, CI, 19–53%, p-value < 0.001). Major disagreement between the field strengths was observed in the A1 segment of anterior cerebral artery/anterior communicating artery (A1/ACOM) complex. The interrater agreement among the readers on the presence of an aneurysm on 7 T MRI was higher than that for 3 T MRI (0.925, 95% CI 0.866–0.983 vs. 0.786, 95% CI 0.700–0.873).ConclusionOur analysis demonstrates a significantly higher interrater agreement and improved diagnostic certainty when small intracranial aneurysms are visualized on 7 T MRI compared to 3 T. In a selected patient cohort, clinical implementation of 7 T MRI may help to establish the definitive diagnosis and thus have a beneficial impact on patient management.

Clinical Analysis of Embryonic Posterior Cerebral Artery

Objective: To understand the clinical characteristics of patients with embryonic posterior cerebral artery and its correlation with abnormal vascular development. Methods: The clinical data of 396 patients with embryonic posterior cerebral artery confirmed by magnetic resonance angiography (MRA) and computed tomography angiography (CTA) were analyzed. Results: Two-hundred patients had clinical manifestations of posterior circulation ischemia, including recurrent dizziness, vertigo, and tinnitus; 45 had headaches, 97 had limb weakness, and 16 patients had syncope or impaired consciousness. Seventy-six patients with circulatory infarction were admitted to the hospital. There were 251 patients with history of hypertension, 74 with diabetes, 113 with hyperlipidemia, 13 with dominant vertebral artery, 10 with intracranial aneurysm, and 19 with absence of A1 segment of the anterior cerebral artery (considering developmental variation). Conclusion: Embryonic posterior cerebral artery develops abnormally during the embryonic period, often accompanied by abnormal vascular access. Due to abnormal hemodynamics, the incidence of posterior circulation ischemia, aneurysm, and infarction increases in such patients.

The Features of the Circle of Willis on Multislice Computed Tomography in Humans Without Cerebral Vascular Malformations

Abstract: A study of 135 cases without cerebral vascular malformations who were scan MSCT of cerebral arteries at Bach Mai hospital during the period from January 2019 to December 2019. Result: mean diameter of cerebral artery segments: left and right A1 segments: 2.28 ± 0.47 and 2.19 ± 0.53 mm; AcomA: 1.71 ± 0.68 mm; left and right M1 segments: 2.82 ± 0.46 mm and 2.8 ± 0.49 mm; left and right PcomA: 1.62 ± 0.5 mm and 1.67 ± 0.48 mm; left and right P1 segments: 2.22 ± 0.49 mm and 2.22 ± 0.56 mm; left and right P2 segments: 2.32 ± 0.38 mm and 2.35 ± 0.36 mm; BA: 3.41 ± 0.69 mm. The diameters of the cerebral arteries were similar in both sexes, with no difference on the right and left sides of the ring of Willis. The diameter of the edges of the Willis circle varied from aplastic and hypoplastic, which was mainly seen in the AcomA, PcomA, the A1 segment of the anterior cerebral artery, and P1 of the posterior cerebral artery. The transformations of the Willis ring included 17 forms, of which four simple transformations of the anterior part, four simple transformations of the posterior part, and nine combined transformations between the anterior and posterior parts. Mainly found aplasia or hypoplasia of the AcomA 14.1% and the PcomA 12.6%. Conclusion: the index of normalization of the segments of the Willis polygon and its variant forms contributed to bolder intervention planning in cerebrovascular disease treatment.&#x0D; Keywords: Circle of Willis, Cerebral arteries, MSCT.

A new genus, Tuberocandona gen. nov. (Crustacea, Ostracoda, Candonidae) and past to present ostracod species diversity in Texas (USA)

A new ostracod genus, Tuberocandonagen. nov., was collected from Honeycut Hollow Springs, Texas, USA Morphological comparisons and cladistic analyses showed that the new genus displays several different features (e.g. presence of two tubercules on each of the valves, numbers of A1 segments, shape of A2 claws, shape and presence of two claw-like setae on the clasping organs, absence of d2 and dp setae on T2 and T3, absence of alpha and beta setae on Md, shape of hemipenis) from other genera of the tribe. Including the new species, the number of non-marine ostracods known from inland waters of Texas is now 118 species in 45 genera. With the aim of documenting ostracod biodiversity in Texas (USA) by including fossils, we sought documents published from 1927 to 2022 and were able to list 673 ostracod taxa belonging to 142 genera. Among the fossils, 73 ostracods were the oldest records during the Pennsylvanian period (ca. 310 mya), while there were only 42 taxa reported from the Holocene. The Eocene had the highest number of ostracods (126 taxa). In comparison, the living species had only 18 of 673 taxa that were considered nonmarine forms. There are only six species in common with the fossils and recent records. These results suggest the potential for relatively high ostracod species richness and diversity in Texas. This is indeed strongly supported by the present study and the described new genus and its type species (Tuberocandona leonidasisp. nov.).

ICA agenesis with transcavernous anastomosis: a systematic review.

To present two cases of Internal Carotid Artery (ICA) agenesis and conduct a systematic review to assess for associations with other anomalies and intracranial aneurysms. We performed a retrospective review of published cases of patients with ICA agenesis with intercavernous anastomosis in MEDLINE database on August 2022 using search terms "internal carotid artery", "agenesis" and "transcavernous anastomosis". We also included two cases of ICA agenesis with type D collateral that we encountered. Total of 46 studies that included 48 patients and two of our cases resulted in 50 patients. Only 70% of studies reported the location of a collateral vessel of which more than two-thirds were on the floor of sella. More than half of the vessels connected cavernous segments of ICA. A1 segment ipsilateral to the side of ICA agenesis was absent in most of the cases but was not true for all cases. Aneurysm was seen in more than one-quarter of the patients. It can also mimic microadenoma as in prior reported cases as well as in one of our cases. ICA agenesis with type D collateral is a rare anomaly but clinically relevant due to the increased risk of an aneurysm or mimic microadenoma or false alarm for occlusion of ICA but knowledge of this rare variant can help in better management of these patients.

Abstract Number: LBA15 Transient Ischemic Attack Uncovering An Absent ICA

Introduction Absence of the Internal Carotid Artery (ICA) is a rare cerebrovascular anomaly signified by agenesis, aplasia, or hypoplasia of the ICA and its’ bony canal. Agenesis refers to complete absence whereas aplasia refers to some partial remanent of the ICA or the carotid canal however, these terms are often used interchangeably. There are 6 types of ICA agenesis/aplasia of which type A consists of collateral flow supplied to the MCA via the P‐comm and ACA via the A‐comm. The prevalence of such a condition is reported at around .01% of the population. Patients are usually asymptomatic due to robust collaterals but, in some cases, can present with focal neurologic deficits. Here, we present a case of a patient who endured a transient ischemic attack and was subsequently found to have type A Right ICA aplasia on cerebrovascular imaging. Methods Case Report Results A 24‐year‐old Right‐handed Female with no past medical history except for tobacco use presented with transient left arm monoparesis. The patient had received chiropractic treatment involving hyperextension of her neck to the left just prior to symptom onset which transiently caused her left arm to become plegic and she resolved back to her neurologic baseline within 10 minutes. Neurologic exam was normal and non‐contrast head CT was negative however, demonstrated significant hypoplasia of the right carotid canal (Figure 1‐A). Contrast enhanced CT Angiogram of the head and neck demonstrated lack of contrast opacification of the Right Internal Carotid artery with absent Right carotid bulb and opacification of only the Right ECA (Figure 1‐B). MRI of the brain did not demonstrate any acute infarction. Gadolinium enhanced MRA of the Head and Neck confirmed absence of the Right internal carotid (Figure 2‐A) with prominent Right P‐comm and absent Right A1 segment (Figure 2‐B). Due to this variant anatomy, the postulated mechanism of patient’s TIA was thought to be related to transiently decreased cerebral perfusion caused by partial mechanical compression of her vertebral arteries asymmetrically affecting the Right MCA distribution due to sole supply from the Right posterior communicating artery. Conclusions This case illustrates a fascinating variation from normal embryologic angiogenesis and highlights the importance of collateral blood flow through the circle of Willis in patient’s with congenitally absent internal carotid arteries. Particularly, this patient’s presentation demonstrates the risk that vascular compromise of posterior circulation vessels may play in patients with Type A ICA agenesis/aplasia and their subsequent risk of incurring transient ischemic events.

Abstract Number ‐ 220: Internal Carotid Artery Hypoplasia of Unique Anatomical Variance

Introduction Hypoplasia of the internal carotid artery (ICA) is incomplete development of the ICA with the presence of empty carotid canal. Despite anecdotal data reporting less than a 0.01% of developmental anomalies of ICA, the true incidence remains unknown. Many cases are asymptomatic and thus escape diagnostic detection or appropriate intervention. In 1968, Lie and Hage described collateral circulation in ICA developmental anomalies through the Circle of Willis, persistent embryonic vessels, or skull base arteries/anastomosis or rete mirabile. While collateral systems exist, subsequent cerebrovascular insufficiency and vascular malformations may occur as a result. To our knowledge, there is an incomplete body of literature surrounding the implications of ICA hypoplasia of varying anatomy. Methods We present a case report of left ICA hypoplasia and a comprehensive literature review. Results A 70‐year‐old woman with hypertension, nicotine dependence, and chronic obstructive pulmonary disease (COPD) presented with COPD exacerbation and disorientation. Computed tomography (CT) head angiography showing left cervical/petrous ICA aplasia with presence of a small carotid canal. The left external carotid and vertebral artery originate at the aortic arch. Majority of the blood supply to the left anterior cerebral artery (ACA) and middle cerebral artery (MCA) is suppliedby the right anterior communicating artery (AComA), posterior communicating artery (PComA). There is also a small left supraclinoid and carotid terminus that reconstitute predominantly by right A1 segment and PComA (Figure 1). Conclusions Although ICA hypoplasia may be an incidental finding, accurate and promptrecognition is essential for the consideration of endovascular implications, screening for vascular malformations, understanding cerebral vascular flow, managing cerebrovascular risk, and avoiding misinterpretation of clinical and imaging patterns.

Abstract Number ‐ 165: Are Smaller Stentrievers the Answer for Achieving Procedural Success in Distal Vessel Occlusions (DiVO)?

Introduction Distal vessel occlusions (DiVO) represent the next frontier of interventional stroke care. Although many experts agree the current generation of stentrievers appear to be ill‐suited to address challenges presented by DiVO, some practitioners advocate utilizing smaller devices.We sought to examine whether smaller diameter devices (3,4 or 5 mm) had any edge over standard sized 6 mm device. Methods A prospectively maintained neuro‐endovascular database was queried for patients between January 2013 to August 2022. Patients included in the analysis had undergone mechanical thrombectomy of distal circulation defined as M2, M3, P2, P3, A2 and A3 segments of the MCA, PCA, and ACA respectively.Primary outcomes measured were TICI post procedure, mRS at discharge and mRS at 90 days. Results A total of 33 patients with DiVO were identified out of a database containing 826 mechanical thrombectomies. There were no other differences in baseline characteristics such as presentation NIHSS (p = 0.58) or comorbid medical conditions. We found no differences in post procedure recanalization TICI between large device and small devices cohorts (p = 1.00), symptomatic ICH (p = 0.52), mRS at discharge (p = 0.154) and mRS at 90 days (p = 0.22). Conclusions There do not appear to be any clinical or radiographic difference in utilizing smaller diameter stentrievers in setting of DiVO.

Abstract Number ‐ 159: Intubation for Patients Undergoing Mechanical Thrombectomy of DiVOs is Associated with Increased Symptomatic ICH

Introduction Distal vessel occlusions (DiVO) represent the next frontier of interventional stroke care. Some practitioners advocate for intubatingDiVOpatients to facilitate roadmapping techniques and vessel selection to assure procedural success. However, prior work studying thrombectomy in large vessel occlusion (LVO) suggests intubation is associated with worse outcomes. We sought to examine whether this relation also exists inDiVOpatients. Methods A prospectively maintained neuro‐endovascular database was queried for patients between January 2013 to August 2022. Patients included in the analysis had undergone mechanical thrombectomy of distal circulation defined as M2, M3, P2, P3, A2 and A3 segments of the MCA, PCA, and ACA respectively.Primary outcomes measured were NIHSS at 24 hours and at discharge. Secondary outcomes measured was the occurrence of symptomatic ICH post procedure. Results A total of 33 patients fit inclusion criteria among our database containing 826 mechanical thrombectomies. While there were more males in the endotracheal intubation group (p = 0.03), there were no other differences in baseline characteristics such as hypertension, diabetes, or prior antiplatelet medication use. Amongst the intubated cohort, we found increased rate of symptomatic intracerebral hemorrhage (ICH) (p = 0.03), worse NIHSS at 24 hours (p = 0.01), and worse NIHSS at hospital discharge (p = 0.002). Conclusions Endotracheal intubation for mechanical thrombectomy inDiVOpatients also appears to be associated with increased rates of symptomatic ICH which drives worse outcomes at 24 hours and discharge.

Abstract Number: LBA7 Outcomes of Endovascular Thrombectomy Versus Medical Treatment in Ischemic Strokes Secondary to Medium Vessel Occlusion

Introduction Acute ischemic stroke (AIS) from arterial occlusions are treated with emergent endovascular thrombectomy (EVT) when clinically appropriate. Clinical outcomes of EVT in medium vessel occlusion (MVO) compared to large vessel occlusion (LVO) have neither been well established nor compared to alternate medical management. Our aim was to evaluate outcomes of patients with AIS secondary to MVO undergoing EVT. Methods We conducted a retrospective chart review of patients presenting to our comprehensive stroke center with MVO‐associated AIS undergoing EVT or aggressive intra‐arterial thrombolytic treatment with concurrent administration of IV eptifibatide. We assessed occlusion site, NIHSS (presentation, 7 day or discharge, 3 months), modified Rankin Scale (baseline, 90‐day), and intracranial hemorrhage (ICH) rate. MVO was defined as occlusion of pure M2 middle cerebral artery without M1 segment involvement, anterior cerebral artery A1 segment or more distal, and posterior cerebral artery P1 segment or more distal. Mann‐Whitney U test, Fisher exact test statistic, and T‐test statistic were used for analysis. Social science statistics software was used for data analysis. Results From August 2020 to December 2021, out of 175 patients who underwent EVT, 50 had MVO (n = 33 M2 occlusion, n = 12 M3 occlusion, n = 1 for P1, P2, A1, A2, A3 each). Twelve subjects with MVO received aggressive medical management with concurrent IV eptifibatide. Subjects between arms were similar at baseline (median NIHSS 11 [95% CI 10.75, 14.32]; mean age 71.5 [95% CI 69.24, 73.77]; male 48.39% [n = 30]). The difference between initial NIHSS and discharge NIHSS was statistically significant in the EVT arm (Z‐Score = 4.03; p‐value &lt; .00001) but not in the medical arm (Z‐score = 1.96; p‐value 0.05). Hemorrhagic transformation occurred in 28% (n = 14) of EVT arm and 16.67% (n = 2) of medical arm. This was not statistically significant (Fisher value: 0.71). Median 90 day mRS was 1 (95% CI [0.89, 2.11]). The difference between 90 day mRS was not significantly different (Z‐score = ‐1.20; p‐value 0.23). Conclusions In our patient cohort, endovascular therapy was safe in medium vessel occlusion and may have more favorable clinical outcomes as illustrated by higher delta NIHSS in the endovascular thrombectomy group. Larger, prospective studies are needed to validate our results.