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OBJECTIVE: To describe a patient with a posterior inferior cerebellar artery stroke exhibiting a horizontal direction changing nystagmus with a complex clinical phenotype. MATERIALS AND METHODS: A 78-year-old man presented with acute vertigo and gait imbalance. He was dysphagic and ataxic on the left side. He had a fast, small-amplitude right-beating nystagmus in the primary gaze position and in the gaze towards the right. Towards the left, a coarse left-beating nystagmus was seen. RESULTS: Radiographic leftwards ocular deviation was evident on admission CT. Intravenous fibrinolysis was administered. 48-hour Holter-EKG, transthoracic ecochardiogram, and transcranial doppler were unremarkable. Brain MRI demonstrated an acute stroke involving the left medulla and cerebellum, mainly within the territory of the ipsilateral posterior inferior cerebellar artery. DISCUSSION AND CONCLUSIONS: Horizontal direction changing nystagmus can arise secondary to central lesions as brainstem strokes, it can be spontaneous or gaze-evoked and characteristically remains unchanged after fixation removal. In our case, the vestibular spontaneous and contralesional nystagmus was likely related to lower-brainstem damage; on the other hand, the ipsilesional gaze-evoked nystagmus might be related to lesions of the nucleus prepositus hypoglossi and/or cerebellum, both playing an important role in gaze-holding. Our findings suggest that central lesions with concurrent involvement of the ipsilateral vestibulo-ocular and horizontal gaze-holding pathways can cause direction changing nystagmus with complex phenotypes.

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Introduction: Video head-impulse tests (video-HITs) often fail to detect anterior inferior cerebellar artery (AICA) infarction due to peripheral and central vestibular system involvement. Anecdotal studies suggest that video-HITs may reveal bilateral impairment in AICA infarction. However, the diagnostic utility of video-HITs has not been established, particularly when compared to labyrinthitis, which accounts for the majority of acute audiovestibular syndrome (AAVS) cases. Methods: We reviewed the medical records of consecutive patients presenting with new-onset acute hearing loss and spontaneous vertigo (i.e., AAVS) between March 2018 and July 2023 at a tertiary hospital in South Korea. Video-HIT patterns were categorized as follows: (1) ipsilaterally positive, (2) contralaterally positive, (3) bilaterally normal, and (4) bilaterally positive. Results: Twenty-eight patients with AICA infarction (mean age ± standard deviation = 67 ± 15 years; 14 men) and 51 with labyrinthitis (63 ± 17 years, 26 men) were included in the analyses. Among the 28 patients with AICA infarction, 15 presented with AAVS in isolation, without other co-morbid neurologic deficits (15/28, 54%). The vestibulo-ocular reflex (VOR) gains of ipsilesional horizontal canals (HCs) ranged from 0.21 to 1.22 (median = 0.81, interquartile range [IQR] = 0.50-0.89). However, those for contralateral HC gain ranged from 0.57 to 1.19 (median = 0.89 [IQR = 0.73-0.97]). Collectively, HITs were bilaterally positive in 13 patients (including 12 patients with bilaterally positive HITs for the horizontal canal), normal in eight, ipsilesionally positive in six, and contralesionally positive in one patient with AICA infarction. The VOR gains were typically decreased ipsilaterally in 28 (28/51, 55%), normal in 17 (17/51, 33%), and decreased bilaterally in six patients with labyrinthitis (6/51, 12%). Logistic regression analysis revealed that bilaterally positive HITs (p = 0.004) and multiple vascular risk factors (p = 0.043) were more frequently associated with AICA infarction than labyrinthitis. Discussion: Among patients presenting with AAVS, bilaterally positive HITs can be indicative of AICA infarction in patients with multiple vascular risk factors.

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BACKGROUND: The semi-sitting position offers advantages for surgeries in the posterior cranial fossa. However, data on its safety and effectiveness for clipping aneurysms in the posterior cerebral circulation are limited. This retrospective cohort study evaluates the safety and effectiveness of using the semi-sitting position for these surgeries. METHODS: We conducted a retrospective study of 17 patients with posterior cerebral circulation aneurysms who underwent surgical clipping in the semi-sitting position in the Department of Neurosurgery at Hannover Medical School over a 10-year period. RESULTS: The mean age at surgery was 62 years (range, 31 to 75). Fourteen patients were admitted with subarachnoid hemorrhage and 3 patients had incidental aneurysmas. Fifteen patients had PICA aneurysms, and two had aneurysms of the vertebral artery and the superior cerebellar artery, respectively. The median diameter of the aneurysms was 5 mm (range 3-17 mm). Intraoperative venous air embolism (VAE) occurred in 4 patients, without affecting the surgical or clinical course. VAE was associated with a mild decrease of EtCO2 levels in 3 patients and in 2 patients a decrease of blood pressure occurred which was managed effectively. Surgical procedures proceeded as planned in all instances. There were no complications secondary to VAE. Two patients died secondary to respiratory problems (not related to VAE), and one patient was lost to follow-up. Eleven of fourteen patients were partially or completely independent (Barthel index between 60 and 100) at a median follow-up duration of 13.5 months (range, 3-103 months). CONCLUSION: The semi-sitting position is a safe and effective technique for the surgical clipping of aneurysms in the posterior cerebral circulation. The incidence of VAE is comparable to that seen in tumor surgery. However, it is crucial for the surgical and anesthesiological team to be familiar with potential complications and to react immediately in case of an occurrence of VAE.

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The cerebellum, a major feature of the hindbrain, lies posterior to the pons and medulla and inferior to the posterior part of the cerebrum. It lies beneath the tentorium cerebelli in the posterior cranial fossa and consists of two lateral hemispheres connected by the vermis. The cerebellum is primarily supplied by three arteries originating from the vertebrobasilar system: the superior cerebellar artery (SCA), the anterior inferior cerebellar artery (AICA), and the posterior inferior cerebellar artery (PICA). However, variations of the cerebellar arteries may occur, such as duplication of the SCA, SCA creating a common trunk with the posterior cerebral artery, triplication of the AICA, and agenesis of PICA, amongst others. Knowledge of the arterial anatomy of the cerebellum is crucial, as inadequate blood supply to this region can result in diminished motor functioning, significantly impacting the quality of life for patients. The present study demonstrated the importance of adequate anatomical knowledge of the arteries supplying the cerebellum. The PubMed and Embase databases were searched to gather articles on the anatomical characteristics and variations of the arterial supply of the cerebellum. It is the most comprehensive and up-to-date review available in the literature. The possible variations of these vessels may be clinically silent or present with clinical symptoms such as neurovascular compression syndromes of the cranial nerves and aneurysms. With a comprehensive understanding of the cerebellar arterial system, physicians can enhance their diagnostic and treatment capabilities, ultimately leading to more effective management of cerebellar vascular-related issues and other neurological deficits.

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Background: Distal posterior inferior cerebellar artery (PICA) aneurysms are exceedingly rare intracranial aneurysms. In the acute phase of rupture, interventions commonly involve parent artery occlusion through endovascular treatment or direct trapping surgery. There is no consensus on the best treatment of chronic ruptured or unruptured aneurysms, and stent-assisted coil embolization has not yet been reported in the chronic phase of rupture. Case Description: We present a case of a 46-year-old female with a recurrent distal PICA aneurysm at 18 months following the initial treatment for subarachnoid hemorrhage and was treated by stent-assisted coil embolization with Neuroform Atlas (Stryker, USA), with a favorable outcome. Conclusion: Distal PICA aneurysms occur at the apical curvature, where primitive arterial anastomoses existed during development, pointing to the potential vulnerability of the vessel wall at these sites. Stent-assisted coil embolization has shown effectiveness in preserving the parent artery for chronic ruptured and unruptured distal PICA aneurysms. Nonetheless, the narrowness and tortuosity of the PICA present obstacles to treatment. In our case, the procedure was feasible utilizing the Neuroform Atlas (Stryker, USA) with the Transcell approach. A thorough grasp of the characteristics of stents and their application is pivotal for achieving effective treatment outcomes.

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The vertebrobasilar system is made up of the two vertebral arteries that unite to form the basilar artery near the base of the skull. Aneurysms in the vertebrobasilar system are distinct from other cerebral aneurysms due to their unique morphologic characteristics. They can be large and bulging (massive), pressing on the brainstem. Alternatively, they might be weak and splitting apart (dissecting) or have an elongated shape (fusiform). On the other end of the spectrum, Vertebral artery aneurysms (VAAs) can also be small and rounded (saccular). These aneurysms can occur at the vertebral artery itself or where it joins the posterior inferior cerebellar artery (PICA). Anatomically, they are situated near the brainstem and cranial nerves, deep within the posterior fossa. The cerebrospinal fluid is kept in transit and flux by the ventricular system's chambers circulating the fluid within themselves. An intraventricular hemorrhage (IVH) can occasionally result from vertebral artery aneurysmal ruptures that result in bleeding into the subarachnoid space and then extravasate into the ventricles. Persistent and poorly controlled hypertension affects about 50% of individuals with IVH. In this case report, we study a 74-year-old woman who complained of a sudden onset headache that had been bothering her for three days at the medical emergency room. She had been diagnosed with systemic hypertension eight years prior and had not taken her medicines as prescribed. She was discovered to have rigidity in her neck and a blood pressure reading of 170/100 mmHg, which had been followed by an episode of vomiting. Radiological investigations revealed a VAA that had a high risk of rupturing and causing an IVH.

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Background The cerebellopontine angle (CPA) cistern houses vital neurovascular structures such as cranial nerves V, VII, and VIII and the anterior inferior cerebellar artery (AICA), often leading to neurovascular compression syndromes due to its complex anatomy. Although vascular compression is a recognized cause of certain neuralgias, its association with otologic symptoms such as tinnitus, hearing loss, and dizziness remains uncertain. Hence, this study aims to determine the prevalence of the AICA vascular loop in the CPA cistern on MRI in patients with asymptomatic audiovestibular symptoms. Methodology Adult patients who underwent MRI, including the posterior fossa's high-resolution volumetric T2 sequence (three-dimensional constructive interference in steady state (3D-CISS)), were assessed. Patients with a history of audiovestibular symptoms (tinnitus/dizziness/vertigo/sensorineural hearing loss), intracranial tumor, vascular lesions, intracranial surgery, brain radiation therapy, traumatic brain injury, poor image quality, and MRI scans without 3D-CISS sequences were excluded. Two radiologists independently reviewed 114 (228 sides) MRI studies for the vascular loop of AICA in the CPA cistern and the extension of the AICA loop into the ipsilateral internal acoustic meatus which was graded by Chavda's classification. Results The prevalence of vascular loop of AICA in the CPA cistern was as high as 47.6% in asymptomatic patients. Grade I Chavda vascular loop was the most common type followed by type II, with type III being the least common type. Conclusions Knowledge regarding the high prevalence of the AICA loop in the asymptomatic population and the lack of significant correlation between the presence of the AICA loop and otovestibular symptoms should be considered in preoperative planning for decompression procedures.

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Haemolytic Uraemic Syndrome (HUS) is a rare medical condition characterised by microangiopathic haemolytic anaemia, thrombocytopenia, and acute kidney injury. Neurological complications are documented but rarely involve the cerebellum. We present a unique case of a 23-month-old male with HUS triggered by Escherichia coli-O157 (E.coli-O157) infection leading to an isolated cerebellar stroke.The patient initially presented with fever, bloody stools, and seizures. Confirmation of E.coli-O157 infection was obtained, and MRI revealed an isolated cerebellar stroke. Treatment included supportive care, anticoagulation for a right atrial thrombus, with gradual improvement observed.This case highlights the unusual occurrence of isolated cerebellar stroke in HUS patients, emphasising the importance of promptly recognizing manifestations of the central nervous system and the necessity for a multidisciplinary approach. Finally, a comprehensive literature review was conducted to identify cases of HUS patients with cerebellar involvement.

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BACKGROUND AND OBJECTIVE: Aneurysms of the posterior cerebral circulation constitute a burdensome condition with high mortality and morbidity. In the modern era, there has been a trend toward favoring an endovascular approach over microsurgery for aneurysm cases. Nevertheless, this transition has yet to be mirrored in low-to-middle-income countries where endovascular therapy may not be widely available. Herein, we aim to illustrate our experience treating these challenging conditions in patients from low-income backgrounds and discuss the relevance of the clinical setting in the treatment decision. METHODS: The authors conducted a retrospective review of the health records of patients who received microsurgical treatment for aneurysms in the posterior circulation, including the basilar artery (BA), posterior cerebral artery (PCA), and posterior inferior cerebellar artery (PICA) in an institution providing treatment to people of low-income backgrounds. Epidemiological data, microsurgical technique, and neurological function were retrieved and analyzed. RESULTS: Surgical clipping was employed for 12 patients (75% female) harboring 15 aneurysms (87% in the posterior circulation and 62% ruptured at presentation). Aneurysms were predominately located in the BA (69%), followed by the PCA (15%) and PICA (15%). Among neurological complications, 25% of patients developed oculomotor nerve palsy. The mortality rate was 17% owing to complications such as cerebral vasospasm, infarction, and severe intracranial hypertension. At the 6-month follow-up, 90% of patients had a good clinical outcome (modified Rankin scale scores of 0-2). CONCLUSION: The present case series illustrates the manifest role of microsurgical techniques for posterior circulation aneurysms, particularly in a scenario where endovascular techniques are not easily accessible. Importantly, this clinical setting pressure could exhort trainees to strive for microsurgical mastery and gain a competitive advantage.

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INTRODUCTION AND IMPORTANCE: Embolization of an arteriovenous malformation (AVM) via the anterior inferior cerebellar artery (AICA) is difficult. The "pressure cooker" technique in the AICA via a marathon microcatheter can be effective. CASE STUDY: A 43-year-old man with a cerebellar hematoma involving the brainstem. Angiography revealed an AVM supplied by the right AICA. Embolizing the AVM by casting an Onyx-18 liquid embolic system assisted by the "pressure cooker" technique was planned. An Apollo microcatheter was used for Onyx casting, and a Marathon microcatheter was used to establish a coiling plug to prevent Onyx reflux. The AVM was obliterated. Postoperatively, burr hole drainage of the cerebellar hematoma was performed. Postoperative computed tomography showed that the cerebellar hematoma and hydrocephalus had resolved. Magnetic resonance imaging revealed that there was no new serious infarction from damage to the cerebellum or brainstem. The patient recovered well. CLINICAL DISCUSSION: During Onyx casting, the drawback is that reflux can occlude normal vessels. The "pressure cooker" technique was useful for preventing Onyx reflux and for driving the Onyx to penetrate the AVM. However, it was difficult to use this technique in slim AICA; the Marathon microcatheter had a thinner tip than other microcatheters, and it can be used to establish the "pressure cooker" technique. This technique provides more solutions for AVMs in transarterial embolization through small feeding arteries. CONCLUSION: In a selective case, it was feasible to use the "pressure cooker" technique in the AICA via a Marathon microcatheter to embolize the AVM.

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Posterior inferior cerebellar artery (PICA) aneurysms are relatively uncommon among intracranial aneurysms and present unique challenges due to their complex anatomical origins. PICA aneurysms arise from the vertebral artery (VA), basilar artery, or anterior inferior cerebellar artery and can have complex anatomical sites and structures. A 31-year-old female known case of trigeminal neuralgia, currently asymptomatic for the same, experienced acute vertigo, headache, and altered sensorium. On the basis of the magnetic resonance imaging of the brain with angiography, she was diagnosed with a PICA aneurysm, necessitating immediate intervention. The patient subsequently underwent endovascular coiling of the aneurysm. The successful management of this unusual case emphasizes the significance of prompt diagnosis and early intervention in managing posterior inferior cerebellar artery aneurysms, leading to a favourable outcome. The patient is on regular follow-ups and has satisfactory progress.

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Persistent trigeminal artery (PTA) is the most common remnant of the primitive carotid-vertebrobasilar anastomoses, which typically form and obliterate during the early stages of human embryonic development. While PTA can be non-pathologic and is usually an incidental finding, it is also associated with various other vascular abnormalities, such as arteriovenous malformations and fistulae, but most commonly cerebral aneurysms. In these cases, aneurysms are usually reported in the anterior cerebral circulation or in the PTA trunk itself; to date, only one report exists of an associated aneurysm in the posterior circulation (basilar artery). These associated vascular pathologies are not only a source of morbidity and mortality but can also complicate subsequent endovascular treatment due to different flow patterns and increased vessel tortuosity. In this case report, we present the first reported case of PTA-associated aneurysm in the anterior inferior cerebellar artery and its resulting impact on the endovascular treatment of this aneurysm.

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Objective: The double origin of the posterior inferior cerebellar artery (DOPICA) is a rare variant of PICA. Vertebral artery dissecting aneurysm (VADA) with DOPICA is an extremely rare occurrence. Herein, we report a case of VADA located between DOPICA that was successfully treated with endovascular internal trapping. Case Presentation: A 48-year-old male, found collapsed at his workplace, was admitted to our hospital for emergency medical assistance. Head CT revealed a subarachnoid hemorrhage (Fisher group 3), and cerebral angiography revealed right VADA with DOPICA. The VADA was located distal to the proximal component of the posterior inferior cerebellar artery (PCPICA) and just proximal to the hypoplastic distal component of PICA (DCPICA). Emergency endovascular internal trapping was performed using a total of 13 coils from the distal end of the VADA to just the distal of the branching point of PCPICA. VADA was not visualized, and antegrade flow through DOPICA to the basilar artery was confirmed. Head magnetic resonance angiography (MRA) showed antegrade flow via DOPICA, and the patient was discharged home on Day 46 with a modified Rankin Scale 0. Conclusion: Endovascular internal trapping for VADA with DOPICA was considered useful, especially when VADA is distal to PCPICA and proximal to DCPICA.

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Vertebral artery dissections (VAD) pose a significant risk for strokes, particularly in young adults. This case report details the presentation and management of a 48-year-old patient who was diagnosed with an extracranial VAD following cervical spine manipulation (CSM). The patient's symptoms included acute right-sided ataxia, giddiness, vertigo, nausea, vomiting, and persistent pain behind the right ear, prompting immediate evaluation. After ruling out acute intracerebral hemorrhages, a computed tomography angiogram (CTA) of the head and neck identified a severe narrowing of the right distal vertebral artery with a string sign at the level of the right C1 loop (V3 segment), indicating an extracranial VAD. This finding was further supported when ultrasound (US) imaging revealed a high resistance flow pattern in the right distal vertebral artery. Furthermore, T2 and diffusion-weighted magnetic resonance imaging (MRI) confirmed a 1.8 cm VAD/hematoma and a 1.4 cm acute/subacute infarct in the right posterior inferior cerebellar artery (PICA) territory. This research accentuates the importance of recognizing and addressing that neck pain can be a symptom of musculoskeletal dysfunction or could have neurovascular origins. In this case, the patient's neck pain may have been musculoskeletal or could have been due to a previous dissection. Thus, differentiation should be considered before cervical spine manipulation.

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Flow diversion (FD) has revolutionized the treatment of cerebral aneurysms. Since the introduction of the Pipeline Embolization Device, there has been a significant shift in the management of cerebral aneurysms, with increasing emphasis being placed on use of endoluminal reconstruction as a means of long-term, durable treatment of aneurysms. Increasingly, FD stents are being used as primary treatment for aneurysms, including those that present with subarachnoid hemorrhage.1 Improper use of FD stents, however, may create havoc, as access to the aneurysm sac is blocked with the placement of these devices. Aneurysms that are incompletely treated with FD may continue to grow and rupture. The inability to use coils or endosaccular devices for treatment of these aneurysms means the only options for treatment are placement of additional FD devices, deconstructive strategies with or without bypass, or microsurgical clipping,2 thereby making an aneurysm that may have been straightforward to treat with another strategy a complex lesion to treat with the presence of the FD stent. Although deconstructive techniques can be used for treatment of failed aneurysm occlusion with flow diversion, where possible, surgical clipping can result in the simplest, most durable solution. Herein we present (Video 1) a case of a patient with a posterior inferior cerebellar artery aneurysm treated previously with FD using a single pipeline embolization device without aneurysm occlusion over 1 year of follow-up who was treated with retrosigmoid craniotomy and clipping of aneurysm. Nuances of the approach selection, clipping of the aneurysm, and preservation of the stent are discussed.

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Vertebral artery （VA）Aneurysms involving the origin of the posterior inferior cerebellar artery (PICA) ,occasionally, induce cerebellum and brainstem infarction due to intraluminal thrombus and calcific VA stenosis. At times, vessel occlusion and revascularization is necessary for successful obliteration of these aneurysms.2 The occipital artery (OA) is often the preferred donor graft for lesions of the posterior fossa. Although most OA-PICA bypasses can be performed using the p3 segment as the recipient site for an end-to-side anastomosis, a more feasible alternative to conventional OA-p3 PICA bypass in cases of high-riding caudal loops , aberrant anatomy or p3 multiple perforators is to free the p1 PICA, transpose it away from the lower cranial nerves, and perform an end-to-end OA-p1 PICA bypass instead. This video captures the dissection of the OA using an orientational anterograde harvesting technique and the end-to-end anastomosis of the OA to the PICA at the p1 segment. This was performed in a 56-year-old man who presented with posterior circulation ischemia from a fusiform aneurysm with calcific vertebral artery stenosis located at the origin of the right PICA. The patient tolerated the procedure well and suffered no major complications related to the operation. He did experience some mild, posterior neck rigidity at the time of his 6-month follow-up, likely due to nerve injury that occurred while harvesting the OA. Overall, the patient remains in good neurologic status 1 year after the operation. The operation proved the feasibility of end-to-end bypass in OA-p1 PICA.

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INTRODUCTION: The anterior inferior cerebellar artery (AICA) plays a crucial role in cerebellar blood supply, and AICA aneurysms are relatively rare, comprising less than 1-1.5% of all brain aneurysms. Understanding their clinical scenarios, management approaches, and outcomes is essential. This systematic review analyzes data from 86 studies to comprehensively explore AICA aneurysms. MATERIALS AND METHODS: The process of obtaining relevant research, which includes patients with AICA aneurysms, was carried out using the PubMed, Web of Science, and Scopus databases. This review exclusively included extensive papers written in English. The search included the MeSH phrases "Anterior inferior cerebellar artery aneurysm" and "AICA aneurysm." Microsurgical and endovascular treatments were compared using statistical analysis, exploring demographics, risk factors, treatment modalities, and clinical outcomes. RESULTS: The review includes 85 case reports and one retrospective study, totaling 140 patients. The study reveals a diverse patient profile with a slight female predominance (65%), a mean age of 50.7 years, and an 82.86% prevalence of no identified risk factors. Ruptured aneurysms accounted for 55%, with microsurgery and endovascular procedures accounting for 70.71% and 27.86%, respectively. The mortality rate was 2.86%, and no significant differences were found in rebleed, recurrence, or mortality rates between treatment groups. CONCLUSION: Microsurgical and endovascular interventions demonstrate comparable effectiveness, with microsurgery showing superiority in specific situations. Therefore, tailoring treatment is crucial to individual patient needs. Subgroup analyses highlight demographic-specific trends, guiding clinicians in managing this rare pathology.

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In this case, a 61-year-old patient presented with Horner's syndrome of the left eye, left-sided truncal ataxia, left-sided pain/paresthesia of the face as well as right-sided loss of pain and temperature of the arms and legs. MRI findings displayed a clear 4 mm acute left lateral medullary infarct of the left posterior inferior cerebellar artery (PICA) vascular territory, indicative of lateral medullary syndrome (LMS). The presence of pre-existing medical conditions such as uncontrolled diabetes, late-stage syphilis, and a mechanical aortic valve complicated this clinical picture. The presence of ipsilateral corticospinal deficits in this patient revealed Opalski syndrome, a rare variant of LMS. This case report highlighted the importance of correlating imaging and physical examination of stroke findings.

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The anterior inferior cerebellar artery (AICA) is situated within the posterior cranial fossa and typically arises from the basilar artery, usually at the pontomedullary junction. AICA is implicated in various clinical conditions, encompassing the development of aneurysms, thrombus formation, and the manifestation of lateral pontine syndrome. Furthermore, owing to its close proximity to cranial nerves within the middle cerebellopontine angle, AICA's pulsatile compression at the root entry/exit zone of cranial nerves may give rise to specific neurovascular compression syndromes (NVCs), including hemifacial spasm (HFS) and geniculate neuralgia concurrent with HFS. In this narrative review, we undertake an examination of the influence of anatomical variations in AICA on the occurrence of NVCs. Significant methodological disparities between cadaveric and radiological studies (CTA, MRA, and DSA) were found, particularly in diagnosing AICA's absence, which was more common in radiological studies (up to 36.1%) compared to cadaver studies (less than 5%). Other observed variations included atypical origins from the vertebral artery and basilar-vertebral junction, as well as the AICA-and-PICA common trunk. Single cases of arterial triplication or fenestration have also been documented. Specifically, in relation to HFS, AICA variants that compress the facial nerve at its root entry/exit zone include parabola-shaped loops, dominant segments proximal to the REZ, and anchor-shaped bifurcations impacting the nerve's cisternal portion.

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Hemodynamic factors are associated with the progression of cerebral aneurysms. We report a 78-year-old woman with an anterior inferior cerebellar artery aneurysm and proximal stenosis of the anterior inferior cerebellar and basilar arteries. The aneurysm exhibited growth on annual follow-up imaging. Aneurysmal rupture occurred 4 years after diagnosis. Coil embolization resulted in aneurysm occlusion with parent artery preservation. Aneurysms adjacent to a more proximal region of severe stenosis in the parent vessel should be considered at high risk for growth or rupture. Such aneurysms require careful monitoring. Particular attention should be paid to posterior circulation aneurysms that occur at anatomically vulnerable sites.