Anterior Inferior Cerebellar Artery Strokes Based on Variant Vascular Anatomy of the Posterior Circulation: Clinical Deficits and Imaging Territories

The cerebral artery in cynomolgus monkeys (Macaca fascicularis)

Cerebral artery structure has not been extensively studied in primates. The aim of this study was to examine the cerebrovascular anatomy of cynomolgus monkeys (Macaca fascicularis), which are one of the most commonly used primates in medical research on human diseases, such as cerebral infarction and subarachnoid hemorrhage. In this study, we investigated the anatomy and diameter of cerebral arteries from 48 cynomolgus monkey brain specimens. We found three anatomical differences in the vascular structure of this species compared to that in humans. First, the distal anterior cerebral artery is single. Second, the pattern in which both the anterior inferior cerebellar artery and posterior inferior cerebellar artery branch from the basilar artery is the most common. Third, the basilar artery has the largest diameter among the major arteries. We expect that this anatomical information will aid in furthering research on cerebrovascular disease using cynomolgus monkeys.

Clinical Significance of Middle Cerebellar Peduncle Ischemia After Translabyrinthine Vestibular Schwannoma Resection

OBJECTIVE

To assess clinical symptoms, signs, and radiographic evolution of middle cerebellar peduncle (MCP) diffusion restriction (DR) abnormalities following vestibular schwannoma (VS) resection.

STUDY DESIGN

Retrospective chart and imaging review.

SETTING

Tertiary-referral neurotology and neurosurgery practice.

PATIENTS

All consecutive patients who underwent translabyrinthine VS resection over a 2-year period (August 2017-May 2019).

INTERVENTION

Translabyrinthine craniotomy for VS resection.

MAIN OUTCOME MEASURES

Magnetic resonance imaging (MRI) obtained on postoperative day 1 were reviewed for DR within the pons and cerebellum, with 3 months follow-up MRI to assess for evolution of these vascular changes.

RESULTS

Of the 31 patients who met inclusion criteria, MRI demonstrated MCP DR consistent with acute ischemia in 29% (9/31). Of those, two showed corresponding T2 signal abnormalities on follow up MRI consistent with cerebrovascular accident (CVA) within the MCP. Both had severe gait ataxia and dysmetria requiring acute rehabilitation admission and significantly larger tumors (p = 0.02). The remaining seven were asymptomatic, and DR abnormality resolved without lasting radiographic changes. Brainstem compression was present in 100% of patients with postoperative MCP DR (mean MCP ipsilateral:contralateral ratio 0.59 ± 0.19), and 68.1% of those without (mean MCP ratio 0.71 ± 0.25), a difference that was not statistically significant (p = 0.14). In the two patients with CVA, MCP asymmetry persisted, whereas the asymmetry resolved in all others.

CONCLUSIONS

Asymptomatic acute MCP ischemia discovered incidentally does not require intervention. However, when the ischemic area is large and patients are symptomatic, especially if an acute rehabilitation admission is required, surgeons should suspect true CVA.

Case report: the etiology of anterior inferior cerebellar artery infarction: what does basi-parallel anatomic scanning magnetic resonance imaging tell us?

Background

The precise etiology of anterior inferior cerebellar artery (AICA) infarction is difficult to identify because of the high anatomic variability of vertebrobasilar arteries and the limitations of conventional vascular examinations. Basi-parallel anatomic scanning magnetic resonance imaging (BPAS-MRI) can reveal the outer contour of the intracranial vertebrobasilar arteries, which may be helpful to distinguish the arteriosclerosis from congenital dysplasia and dissection.

Case presentation

In this study, we reported 3 cases of AICA infarction and discussed the diagnostic value of BPAS-MRI in the evaluation of vascular etiology.

Conclusions

The BPAS-MRI could be considered as an important supplementary in the diagnosis of vascular etiology of infarction in AICA territory.

Junctional dilatation of the basilar tip: A Normal anatomical variant with a benign natural history

PURPOSE

The intracranial arterial vasculature has numerous anatomical variants, which vary from largely benign to having remarkable clinical implications. The significance of a lesser known variant described as a junctional dilatation of the basilar artery tip has not yet been described in the literature.

METHODS

Retrospective query of radiology imaging reports was performed for vascular specific imaging of the head, which included descriptions related to the basilar junctional dilatation variant from 2005 to 2019 at a single institution. Imaging studies were individually scrutinized for true presence of the variant, and were assessed for any change in appearance over time. Primary data-points collected included length of time between imaging studies with stable appearance, intracranial aneurysm incidence, and frequency of hemorrhage associated with aneurysm rupture.

RESULTS

Fifty patients with multiple vascular exams were found to have the typical appearance of the basilar junctional dilatation variant. The variant was found to be stable over time in all patients, without interval expansion or basilar tip aneurysm development. Interval follow-up ranged from 1 to 156 months, with a mean follow-up length of 3.83 years, and total patient-years of follow-up of 192. No adverse neurological events were found which could be attributed to the basilar junctional dilatation variant.

CONCLUSION

Junctional dilatation of the basilar artery tip is a benign, normal variant of the posterior intracranial arterial circulation. It is important for both radiologists and clinicians to recognize its characteristic appearance and benign nature, as misdiagnosis may lead to unnecessary work-up, imaging, and/or treatment.

Vascular loop in the cerebellopontine angle: clinical-radiological correlation

BACKGROUND

The brainstem, situated in the posterior fossa, connects the brain to the spinal cord. Owing to its location, the nerves of the brainstem are closely related with vascular structures.

OBJECTIVES

To correlate the finding of vascular loops in the cerebellopontine angle on imaging with symptoms indicative of vestibulocochlear involvement.

MATERIALS AND METHODS

This retrospective descriptive study included all patients evaluated between 2011 and 2017 with findings suggestive of vascular loops in the cerebellopontine angle for whom the clinical history and imaging studies were available.

RESULTS

A total of 102 patients (63 women and 39 men) had vestibulocochlear involvement. The most common clinical indication was dizziness (41.18%). A unilateral vascular loop was found in 43 patients (right: 21.57%, left: 20.59%) and bilateral loops were found in 59 (57.84%) patients. The most common type of vascular loop was type II (right: 69.14%; left: 58.75%). The most common origin of vascular loops was the anterior inferior cerebellar artery (right: 66.67%, left: 65.00%). No associations were observed between vascular loops and sensorineural hearing, nystagmus, or vertigo. There was an association with tinnitus.

CONCLUSIONS AND SIGNIFICANCE

The presence of vascular loops is not associated with most auditory symptoms. Nevertheless, all findings on imaging studies must be reported. The interpretation of the findings of imaging studies must be correlated with the clinical symptoms after other more common causes that can explain the symptoms have been ruled out.

Bilateral middle cerebellar peduncle lesions: Neuroimaging features and differential diagnoses

OBJECTIVES

Lesions limited to the bilateral middle cerebellar peduncles (MCPs) are uncommon. This retrospective study investigated diseases with a proclivity for the bilateral MCPs and explored the associations between their neuroimaging features and clinical findings for the differential diagnosis of such lesions.

METHODS

We enrolled 26 patients who were admitted to our department between January 2016 and March 2019 with bilateral MCP abnormalities on magnetic resonance imaging (MRI). The demographic, clinical, and neuroimaging characteristics, and the biomarkers and diagnoses were evaluated.

RESULTS

Although all patients exhibited symmetrical bilateral MCP hypointensities on T1-weighted imaging and hyperintensities on T2-weighted and fluid-attenuated inversion recovery imaging, they were diagnosed with different conditions. Diagnoses included acute cerebral infarction (ACI) (n = 9, 34.62%), Wallerian degeneration (WD) (n = 8, 30.77%), multiple system atrophy (MSA) (n = 6, 23.08%), neuromyelitis optica (NMO) (n = 1, 3.85%), heroin-induced leukoencephalopathy (n = 1, 3.85%), and primary central nervous system lymphoma (PCNSL) (n = 1, 3.85%). Patients with ACI exhibited bilateral MCP-restricted diffusion hyperintensities on diffusion-weighted imaging and corresponding stenosis or occlusion of the vertebrobasilar system. The initial MRI of patients with WD depicted pontine infarctions, while symmetrical MCP lesions were observed on follow-up MRI. Symmetrical MCP lesions, cruciform hyperintensity, and marked atrophy in the posterior fossa were characteristic manifestations of MSA. Longitudinally extensive myelitis affecting more than three vertebral segments on cervical MRI and positive serum AQP4-IgG may be indicative of NMO. Heroin-induced leukoencephalopathy was characterized by extra-symmetrical lesions in the posterior limbs of the internal capsules, while the anterior limbs were spared. PCNSL was indicated by a significant and characteristic "fist" sign on contrast-enhanced MRI.

CONCLUSIONS

Bilateral MCP lesions were most frequently observed in cerebrovascular diseases, followed by neurodegenerative diseases, inflammatory diseases, toxic encephalopathies, and lymphomas. Our findings demonstrate that bilateral MCP signal abnormalities are more common in patients with ACI and WD, with fewer degenerative processes than previously believed. The high frequency of WD may be attributed to the specific awareness of this pathology. WD can also present with stage-related restricted diffusion and should not be mistaken for a new infarction. The symmetrical bilateral MCP hypointensities on T1-weighted imaging and hyperintensities on T2-weighted imaging often raise concern regarding a demyelinating process. Our findings emphasize that neurologists should consider the aforementioned conditions and correlate the specific neuroimaging characteristics and medical history before arriving at the final diagnosis.

Neuroangiography: Review of Anatomy, Periprocedural Management, Technique, and Tips

Neuroangiography (NA) is a minimally invasive procedure used to diagnose patients with neurovascular diseases. Noninvasive imaging has improved dramatically in recent years and is utilized more frequently; however, further evaluation with NA is still required in certain cases. NA indications include intracranial (cerebral aneurysms, arteriovenous malformations, dural arteriovenous fistula, cerebral vasculitis, cerebral vasospasm, ischemic stroke, nontraumatic subarachnoid hemorrhage, intracerebral hemorrhage, Moyamoya, vein of Galen malformation, intracranial tumors, and pseudotumor cerebri) and extracranial (internal and common carotid artery stenosis, vertebral artery stenosis, carotid artery blowout, vertebral artery blowout, epistaxis, oropharyngeal bleeding, and carotid body tumor) pathologies which can help with diagnosis and potential subsequent endovascular treatment. A thorough understanding of normal and variant cervical/cranial vascular anatomy is required. In addition, periprocedural management, catheter technique, equipment needed, and underlying disease pathology are paramount to successful and safe outcomes. This article will review basic neurovascular anatomy, periprocedural management, NA technique, and tips for safe and successful outcomes.

A Classification for the Anterior Inferior Cerebellar Artery-Subarcuate Artery Complex Based on the Embryological Development

Objective  To hierarchize the anterior inferior cerebellar artery (AICA)-subarcuate artery (SAA) complex's variations in the surgical field. Background  The AICA's "subarcuate loop" (SL) presents multiple variations, closely related to the SAA. AICA-SAA complex's variations may represent major issues in cerebellopontine angle (CPA) surgery. As the spectrum of configurations is originated during the development, a systematized classification was proposed based on the interaction between the petrosal bone and the AICA in the embryonic period. Methods  The variations were defined as follow: Grade 0: free, purely cisternal AICA, unidentifiable or absent SAA; Grade 1: purely cisternal AICA, loose SL, SAA > 3 mm; Grade 2: AICA near the subarcuate fossa, pronounced SL, SAA <3 mm; Grade 3: "duralized" AICA, unidentifiable SAA, or included in the petromastoid canal (PMC); and Grade 4: intraosseous AICA, unidentifiable SAA, or included in the PMC. The classification was applied to a series of patients assessed by magnetic resonance constructive interference in steady state sequence. Surgical examples were also provided. Results  Eighty-four patients were evaluated, including 161 CPA. The proportions found in the gradation remained within the range of previous publications (Grade 0: 42.2%; Grade 1: 11.2%; Grade 2: 35.4%; Grade 3: 10.6%; and Grade 4: 0.6%). Moreover, the degrees of the classification were related to the complexity of the anatomical relationships and, therefore, to the difficulty of the maneuvers required to overcome them. Conclusion  The proposed AICA-SAA complex classification allowed to distinguish and objectify pre- and intraoperatively the spectrum of variations, to thoroughly plan the required actions and instrumentation.

[Drilling of the subarcuate fossa to release the anterior inferior cerebellar artery in a surgery of a vestibular Schwannoma]

Introducción:

El abordaje suboccipital retrosigmoideo es la vía principal para la resección de los Schwannomas vestibulares (SV). La relación vascular más constante de los nervios del conducto auditivo interno es la arteria cerebelosa anteroinferior (ACAI); pudiendo su recorrido presentarse como un serio obstáculo para la resección completa de la lesión.

Descripción del Caso:

Paciente varón de 38 años, con diagnóstico presuntivo de SV por resonancia magnética (Grado T3B). Se realiza cirugía por vía retrosigmoidea. Se observa a la ACAI totalmente recubierta por tejido dural y óseo, cuya liberación fue posible mediante fresado en la fosa subarcuata. Se logra una exéresis completa del tumor. El paciente evolucionó durante el estado posoperatorio sin déficit neurológico agregado.

Discusión:

La ACAI ha sido descripta en escasas publicaciones fijada a la duramadre y/o incrustada en el hueso de la fosa subarcuata, impidiendo la resección completa de SV, especialmente de la porción intracanalicular. Sin embargo, su liberación supone riesgo adicional de lesión vascular.

Conclusión:

La lesión de la ACAI puede ser causal de alta morbilidad, por lo que el neurocirujano debe estar preparado para reconocer y resolver este tipo de situaciones.

Delayed Establishment of Collateral Circulation from Posterior Meningeal Artery After Proximal Occlusion of Posterior Inferior Cerebellar Artery: Case Report and Literature Review

BACKGROUND

A dissecting aneurysm on the posterior inferior cerebellar artery (PICA) is a rare entity, and endovascular embolization is often adopted. During the procedure, if the parent artery is occluded, the distal PICA is usually supplied by the ipsilateral anterior inferior artery or contralateral PICA. In extremely rare circumstances, the distal PICA can establish collateral circulation by transdural anastomosis with the posterior meningeal artery (PMA).

CASE DESCRIPTION

A 29-year-old woman was admitted complaining of thunderclap headache, nausea, and vomiting for 3 hours. Head computed tomography and digital subtraction angiography revealed subarachnoid hemorrhage and a dissecting aneurysm located at the tonsillomedullary segment of PICA. The parent artery distal to the aneurysm had no collateral circulation from the adjacent arteries. Selective endovascular coiling of the aneurysm with preservation of the parent artery was adopted for treatment. The patient experienced an uneventful postprocedural recovery. To our surprise, follow-up digital subtraction angiography 6 months later revealed complete occlusion of the aneurysm and parent artery at the site of aneurysm formation. A rare anastomosis between the distal PICA and PMA was established.

CONCLUSIONS

A report about this rare condition suggested that after occlusion of the PICA trunk, the distal PICA can form collateral circulation with the PMA. A potential collateral circulation may be present in advance between the PICA and PMA. When ischemia occurs in the distal PICA, this collateral circulation may open and could be reconstructed and enlarged to provide blood supply.