Fetal cerebral arteries in a new ultrasonographic perspective.

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Fenestrated Anterior Cerebral Artery, Anterior Communicating Artery, with Accessory Middle Cerebral Artery-A Conglomeration of Embryologically Different Entities in a Single Individual.

Cerebral arterial fenestrations are anatomic variants of undetermined significance where there is a division of a single vessel into at least 2 channels, each having endothelial and muscular layers, that coalesce to a single lumen in the distal course of the vessel. The basilar artery is the most common site, followed by the anterior communicating artery. The accessory middle cerebral artery is defined as the anomalous origin of the vessel from the anterior cerebral artery and its further course along the sylvian fissure parallel to the middle cerebral artery. The embryologic basis of all these has been explained by studies on human embryological development by Padget et al. However, simultaneous existence of all 3 anomalies in a single individual has never been reported. Here we present a case of medial sphenoid wing meningioma with these incidental findings during workup and further delineation of anatomy following surgical resection of meningioma.

Angiographic predictors of spontaneous obliteration of transarterial partially embolized brain arteriovenous malformations.

BACKGROUND: Spontaneous obliteration of cerebral arteriovenous malformations is uncommon but could occur after partial embolization. METHODS: A retrospective study of 140 patients that underwent embolization for cerebral AVMs from 2005 to August 2019 using liquid embolic agents. The angiographic outcome of patients was classified as regard complete embolization, partial embolization, and complete obliteration after partial embolization. The parameters studied included size, location, number of arterial feeders, number of draining veins, rupture status, embolic agent, and patient factors as well. RESULTS: The study patients included 74 (53%) females and 66 (47%) males. Their age ranged from 7 to 43 years old. One hundred and eight patients (77%) presented with hemorrhage. The AVM grades were grade II in 57 (40.7%) patients and grade III in 56 (39.3%) patients. Sixty-one (43.57%) patients were treated by n-Butyl Cyanoacrylate and 71 (50.71%) patients were treated with Onyx, and both materials were used together in 8 cases. Follow-up angiography was done from 6 to 36 months after embolization. The rate of complete occlusion in all patients was 61.43% (86 patients). There were three groups of patients, the first group had complete occlusion of the nidus at the time of embolization and included 68 (48.57%) patients. The second group had partial embolization with partial occlusion of the nidus 54 patients (38.57%). The 3rd group included 18 patients (12.85%) with complete nidal occlusion on follow up after partial embolization. The delay in the venous drainage of the AVM to the late arterial phase or early venous phase with flow stasis was a significant predictor of future obliteration on follow up after partial embolization. Other significant parameters that were associated with the progressive disappearance of the AVM nidus on follow up after partial embolization are presentation with hemorrhage, AVMs size less than 3 cm, the presence of single draining or double draining veins, superficial venous drainage, and one or 2 arterial feeders. CONCLUSION: Spontaneous closure of intracranial arteriovenous malformations after partial embolization may be encountered in cases of stasis of flow during embolization procedure with a delay of the venous drainage. A long-term follow-up of more cases over many years is required to confirm the validity of this conclusion.

Neuroradiological findings in Alagille syndrome.

Alagille syndrome (ALGS) is a multisystemic disease caused by mutations in genes of Notch pathway, which regulates embryonic cell differentiation and angiogenesis. Clinically, ALGS is characterized by cholestasis, cardiac defects, characteristic facial features, skeletal and ophthalmologic abnormalities. The aim of this review is to illustrate neuroradiological findings in ALGS, which are less well-known and prevalent, including cerebrovascular anomalies (such as aneurysms, dolichoectasia, Moyamoya syndrome and venous peculiarities), Chiari 1 malformation, craniosynostosis, intracranial hypertension, and vertebral anomalies (namely butterfly vertebra, hemivertebra, and craniocervical junction anomalies). Rarer cerebral midline malformations and temporal bone anomalies have also been described.

Persistent Stapedial Artery Resulting in Direct Communication Between the Middle Meningeal and Basilar Arteries: Clinical Image.

A persistent stapedial artery originates from the petrous segment of the internal carotid artery due to failure of the regression of the embryonic stapedial artery. During embryologic development, the stapedial artery supplies the middle meningeal artery through the ventral pharyngeal artery. The presence of a persistent stapedial artery can result in direct communication between the basilar and middle meningeal arteries. We present a cerebral angiogram image of an adult patient that shows a right-sided persistent stapedial artery with communication between the right middle meningeal and basilar arteries. It is important to recognize such rare anatomic variants during endovascular interventions to avoid catastrophic complications such as nontarget embolization of the posterior circulation.

Morphological Analysis of Cerebral Artery Fenestrations and Their Correlation with Intracranial Aneurysms.

BACKGROUND: Fenestrations of cerebral arteries are congenital variants that develop when primitive vessels fuse incompletely. An association between the incidence of aneurysm and a fenestrated artery has been noted in the radiological literature. However, technical limitations of radiological studies may hamper visualization of small fenestrations and aneurysms. We sought to analyze a large, postmortem collection of human brains to assess the association between aneurysm formation and the presence of fenestrations. METHODS: This study included 333 formalin-fixed brains. The arachnoid was dissected under a microscope, the cerebral arteries were completely exposed, and fenestrations and aneurysms were identified and measured. For each specimen, age, sex, and all vascular abnormalities and variations were recorded for analysis. RESULTS: Fenestrations were present in 41% of the specimens, and 37% of these were multiple. Fenestrations were 3.1 ± 2.5 mm long and most commonly occurred in the anterior communicating artery (63%). Aneurysms were present in 8% of the specimens, usually in the anterior communicating artery or the middle cerebral artery. An aneurysm correlated with a fenestration was detected in 2% of all specimens (n = 4) and was not statistically significant (P = 0.18). CONCLUSIONS: Fenestrations of the intracranial arteries are a common anatomical finding. They are present most often in the anterior communicating artery. Most aneurysms were detected in the anterior communicating artery and middle cerebral artery. We conclude that the existence of an aneurysm in a fenestrated artery is an incidental, rather than causal, relationship.

Cerebrovascular Anomalies: Perspectives From Immunology and Cerebrospinal Fluid Flow.

Appropriate vascular function is essential for the maintenance of central nervous system homeostasis and is achieved through virtue of the blood-brain barrier; a specialized structure consisting of endothelial, mural, and astrocytic interactions. While appropriate blood-brain barrier function is typically achieved, the central nervous system vasculature is not infallible and cerebrovascular anomalies, a collective terminology for diverse vascular lesions, are present in meningeal and cerebral vasculature supplying and draining the brain. These conditions, including aneurysmal formation and rupture, arteriovenous malformations, dural arteriovenous fistulas, and cerebral cavernous malformations, and their associated neurological sequelae, are typically managed with neurosurgical or pharmacological approaches. However, increasing evidence implicates interacting roles for inflammatory responses and disrupted central nervous system fluid flow with respect to vascular perturbations. Here, we discuss cerebrovascular anomalies from an immunologic angle and fluid flow perspective. We describe immune contributions, both common and distinct, to the formation and progression of diverse cerebrovascular anomalies. Next, we summarize how cerebrovascular anomalies precipitate diverse neurological sequelae, including seizures, hydrocephalus, and cognitive effects and possible contributions through the recently identified lymphatic and glymphatic systems. Finally, we speculate on and provide testable hypotheses for novel nonsurgical therapeutic approaches for alleviating neurological impairments arising from cerebrovascular anomalies, with a particular emphasis on the normalization of fluid flow and alleviation of inflammation through manipulations of the lymphatic and glymphatic central nervous system clearance pathways.

De Novo Dural Arteriovenous Fistula on Draining Veins of Previously Treated Pial Arteriovenous Malformation: a Case Report.

A 71-year-old man, with a pial micro-arteriovenous malformation (pAVM) draining into the confluence of the vein of Trolard and the vein of Labbé was surgically removed, sparing these cortical veins. 4-months MR and angiographic controls showed a de novo dural arteriovenous fistula (dAVF) draining into the previously spared cortical veins. It was removed using intraoperative motor evoked potentials (MEP). This is the first case of iatrogenic dAVF developing on the same draining vein of a previously treated pAVM. De novo dAVFs are generally iatrogenic. This case suggests that the unresected venous drainage of an AVM might be the substratum for neo-angiogenetic processes; moreover inflammation related to surgery might be the trigger factor for the development of the dAVF.

Surgical Management of Cirsoid Aneurysms of the Scalp: Ten Years' Experience.

OBJECTIVE: Cirsoid aneurysms are rare arteriovenous malformations of the scalp that present with disfigured pulsatile masses and may be associated with headache, bleeding, or tinnitus. These lesions are difficult to manage because of their complex vascular anatomy, high shunt flow, and cosmetic disfigurement; many options have been described to treat such lesions. We evaluate 10 years' experience in the surgical management of cirsoid aneurysms of the scalp. METHODS: This study included 15 patients with cirsoid aneurysm of the scalp, all of whom were treated with surgical excision only over 10 years. They were 8 females and 7 males, with a median age of 23 years. History of trauma was present in 5 patients. Frontal and parietal regions were the commonly affected sites. Superficial temporal, supraorbital, and occipital arteries were the most frequent feeding arteries. RESULTS: Excision of the lesion was performed in all patients using our modified surgical technique. All patients had good cosmetic results and there were no recurrences during an average follow-up of 25 months. CONCLUSIONS: Despite great progress in endovascular therapy, surgical excision of cirsoid aneurysms of the scalp seems to be the most effective treatment, with good results and patient satisfaction.

Changes in Angioarchitecture After Stereotactic Radiosurgery for Dural Arteriovenous Fistula.

INTRODUCTION: Dural arteriovenous fistulae (DAVF) are intracranial vascular abnormalities encountered in neurosurgery practice. Treatment options are microsurgical disconnection, endovascular embolization and/or radiosurgery. Past studies have reported the efficacy, safety, and predictors of success of radiosurgery. In this study, we investigated the angioarchitecture of fistulae at the time of radiosurgery and how the anatomy changed in the time after treatment based on angiogram follow-ups. METHODS: A retrospective analysis was performed on patients with angiographic diagnosis of DAVF treated with Gamma Knife radiosurgery (GKRS) between 2013 and 2018. Data collection included demographics, symptoms, grading scores, vascular anatomy, radiation data, treatment strategy, angiographic results, and length of patient follow-up. RESULTS: Our study reports data on 10 patients with a total of 14 fistulae. On follow-up angiography, 8 (57%) had complete occlusion of the fistula with a median time to follow up of 19.5 months. The remaining 6 (43%) were deemed as near-complete occlusion of fistula with a median time to follow up of 12.0 months. Time from radiosurgery to angiogram revealing incomplete vs. angiogram revealing complete obliteration was significantly different (p=0.045). Nearly all AVFs had decreased feeders over time after treatment with only one AVF developing an additional feeder post-treatment. Arterial feeders, drainage site, sex, Borden type, lesion volume and treatment volume had no predictive value of obliteration outcome. CONCLUSIONS: This study provides data on the angioarchitecture of fistulae treated with GKRS and also serves as an extension of previous studies reporting the safety and efficacy of GKRS treatment for DAVF in a specific patient population.

Transcirculation approach for stent-assisted coiling of intracranial aneurysms: a multicenter study.

BACKGROUND: The transcirculation approach (TCA) for stent-assisted coiling (SAC) of intracranial aneurysms may be useful for certain wide-neck bifurcation aneurysms as well as those with acute-angle efferent branches. OBJECTIVE: To describe a multicenter experience using the TCA for SAC. METHODS: A multicenter, retrospective study (2016-2020) of aneurysm treatment using SAC via the TCA. Angiographic outcome was scored using the Raymond Scale (adequate occlusion 1 and 2), and clinical outcome was scored using a modified Rankin Scale (good outcome 0-2) RESULTS: Twenty-nine patients with 29 aneurysms were included (62.1% female; average age 61; 89.7% unruptured; 13.8% previously treated; average dome size 6.4 mm; average neck 4.4 mm). Aneurysm locations included internal carotid artery-fetal posterior cerebral artery (n=4), internal carotid artery terminus (n=4), anterior communicating artery (n=8), vertebral artery-posterior inferior cerebellar artery (n=2), and basilar tip (n=11). The TCA used communicating arteries (93.1%; average 1.6 mm), intermediate catheters (51.7%), jailing technique (62.1%), and staged procedures (10.3%). The most common stent was the Neuroform Atlas (Stryker; 69%). Immediate adequate occlusion was obtained in 75.9%, and five patients with inadequate occlusion progressed to adequate occlusion at follow-up. One (3.4%) procedural complication occurred: a watershed stroke in the setting of baseline four-vessel extracranial disease. Two patients had a poor outcome unrelated to the TCA. The majority of patients (86.4%) had a good clinical outcome. One case of in-stent stenosis due to non-compliance with medication was seen, which resolved with medication resumption. CONCLUSIONS: The TCA for SAC can be performed for a variety of aneurysms with a low complication rate and good clinical outcomes.

Anatomical variants of anterior communicating artery complex. A study by Computerized Tomographic Angiography.

Advances in imaging techniques have led to the identification of normal variations and abnormalities of cerebral arteries. Although the anterior communicating artery complex (ACAC) variations are usually asymptomatic, their description is essential in the radiologic report, since they can have clinical relevance. The aim of this study is to describe arterial anomalies of the ACAC and their prevalence. A retrospective observational descriptive analysis of ACAC variations in Computerized Tomographic Angiography (CTA) was performed. All CTA (426 studies) obtained in our center from 2015 to 2017 were included. Presence of aneurysm was recorded and its relationship with arterial variants was analyzed with a Chi-square test. The most common variants found in our study are linked to the A1 segment (42.3%) of the anterior cerebral artery (ACA): absence: 10.6%, hypoplasia: 31.2%, fenestration: 0.5%. A2 segment variants were present in 15.3% (absence: 0.2%; hypoplasia 8.5%; Azygos artery: 1.4%; triple ACA: 5.2%). Anterior Communicanting Artery was typical in 92.5%, absent in 4.7%, double/fenestrated in 0.9%, triple in 0.2%, X-shape in 1.2% and Y-shape in 0.2%. Aneurysms were present in 10.7%. Anterior circulation aneurysm involved the 50% of patients with aneurysm. Although the 60.9% of them showed artery variants, they did not reach statistical significance (p = 0.6). In conclusion, the Anterior Communicating Artery Complex presents variations in its anatomy. The most common anterior circulation vascular variants are the hypoplasia and the absence of the A1 segment. There does not appear to be a clear association between intracranial aneurysms and anatomical variations.

Morphological evaluation of the distal medial striate artery. A study with cadaveric material / Evaluación morfológica de la arteria estriada medial distal. Un estudio con material cadavérico

Abstract Objective: To evaluate the morphology of the distal medial striated artery, taking into account biometric variables useful for clinical and surgical management. Methods: A descriptive transversal study was performed with a sample of brains, who underwent autopsy at the Institute of Legal Medicine and Forensic Sciences of Bucaramanga-Colombia, which were evaluated using the perfusion technique of vascular structures with polyester resin. Results: The distal medial striated artery was presented in 1.4% and 4.2% duplicated in the right and left hemispheres respectively. Agenesis was presented in 2.8% in the left hemisphere. Its origin was 44.6% of the anterior cerebral artery junction site with the anterior communicating artery and was observed in 6 cases (4.2%) presented with a common trunk with the orbitofrontal artery. The main qualitative finding was the sinuous trajectory that was observed in 57.7% on the right side and 45.1% in the left hemisphere. Also, an important alteration found at the biometric analysis was hypoplasia that could be related to the decreased blood supply to the basal nuclei. The diameter was 0.5 ± 0.2 mm and its total length was 20.3 ± 4.1 mm. Conclusions: The topographical knowledge of this structure determines the vulnerability of its morphology because it can complicate surgical procedures performed in the anterior segment of the arterial circle of the brain. Besides, the observed collateral circulation contributes to the blood supply and the perfect functionality of the subcortical nervous structures.

Resumen Objetivo: Evaluar la morfología de la arteria estriada medial distal, teniendo en cuenta variables biométricas útiles para el manejo clínico y quirúrgico. Métodos: Estudio descriptivo transversal con una muestra de cerebros que fueron sometidos a autopsia en el Instituto de Medicina Legal y Ciencias Forenses de Bucaramanga-Colombia, fueron evaluados mediante la técnica de perfusión de estructuras vasculares con resina de poliéster. Resultados: La arteria estriada medial distal se presentó en 1.4% y 4.2% duplicada en el hemisferio derecho e izquierdo respectivamente. Agenesia se presentó en 2.8% en el hemisferio izquierdo. Su origen fue 44.6% del sitio de unión de la arteria cerebral anterior con la arteria comunicante anterior y se observó en 6 casos (4.2%) que presentaban un tronco común con la arteria orbitofrontal. El hallazgo principal fue la trayectoria sinuosa que se observó en 57.7% en el lado derecho y 45.1% en el hemisferio izquierdo. También una alteración importante encontrada en el análisis biométrico fue la hipoplasia que podría estar relacionada con la disminución del suministro de sangre a los núcleos basales. El diámetro fue de 0.5 ±0.2 mm y su longitud total fue de 20.3 ±4.1 mm. Conclusiones: El conocimiento topográfico de esta estructura determina la vulnerabilidad de su morfología, porque puede complicar los procedimientos quirúrgicos realizados en el segmento anterior del círculo arterial del cerebro. Además, la circulación colateral observada contribuye al riego sanguíneo y al perfecto funcionamiento de las estructuras nerviosas subcorticales.

Endovascular Treatment of Ruptured Kissing Aneurysms Arising From the Origin of the Anterior Choroidal Artery and an Aberrant Origin of the Premamillary Artery.

BACKGROUND: The premamillary artery (PMA) usually arises from the posterior communicating artery. Thus, an internal carotid artery (ICA) origin for PMA is rare. We report a rare case of a patient who presented with subarachnoid hemorrhage resulting from kissing aneurysms arising from the origin of the anterior choroidal artery and the aberrant origin of PMA and was successfully treated with coil embolization. CASE DESCRIPTION: A conscious and alert 36-year-old woman arrived at our hospital with a severe headache. Computed tomography (CT) of the head showed a thin subarachnoid hemorrhage. CT angiography revealed kissing aneurysms arising from the ICA. Digital subtraction angiography showed that these kissing aneurysms had arisen from the anterior choroidal artery and the aberrant origin of the PMA. Endovascular coil embolization was performed for both aneurysms. Her clinical course was good, and she was discharged from our hospital 20 days after admission. CONCLUSIONS: To the best of our knowledge, the present study is the first report of a ruptured saccular PMA aneurysm arising from ICA that was successfully treated with coil embolization. Three-dimensional digital subtraction angiography and cone-beam CT were useful for confirming the precise vasculature of the PMA.

Aberrant Abducent Nerve During Microvascular Decompression for Trigeminal Neuralgiass.

BACKGROUND: Microvascular decompression (MVD) is a commonly performed procedure to treat trigeminal neuralgia and hemifacial spasm. Knowledge of the variable anatomy of the cerebellopontine angle is crucial to avoid injury to cranial nerves. CASE DESCRIPTION: A 76-year-old lady with right V1 (ophthalmic division of the trigeminal nerve) and V2 (maxillary division of the trigeminal nerve) trigeminal neuralgia, refractory to medical treatment, underwent elective MVD. Intraoperatively, a distorted course of the cisternal component of the abducent nerve was noticed, caused by an ectatic anterior inferior cerebellar artery. Careful mobilization of the offending vessel to decompress the trigeminal nerve was carried out; however, abducent nerve decompression was not attempted since its function was not compromised. Facial pain resolved postoperatively without new diplopia. CONCLUSIONS: Careful review of imaging before surgery is recommended in order to preempt such unusual anatomic variations.

Pathogenesis of non-hereditary brain arteriovenous malformation and therapeutic implications.

Brain arteriovenous malformations have a high risk of intracranial hemorrhage, which is a substantial cause of morbidity and mortality in patients with brain arteriovenous malformations. Although a variety of genetic factors leading to hereditary brain arteriovenous malformations have been extensively investigated, their pathogenesis is still not well elucidated, especially in sporadic brain arteriovenous malformations. The authors have reviewed the updated data of not only the genetic aspects of sporadic brain arteriovenous malformations, but also the architecture of microvasculature, the roles of the angiogenic factors, and the signaling pathways. This knowledge may allow us to infer the pathogenesis of sporadic brain arteriovenous malformations and develop pre-emptive treatments for them.

Morphological evaluation of the distal medial striate artery. A study with cadaveric material.

OBJECTIVE: To evaluate the morphology of the distal medial striated artery, taking into account biometric variables useful for clinical and surgical management. METHODS: A descriptive transversal study was performed with a sample of brains, who underwent autopsy at the Institute of Legal Medicine and Forensic Sciences of Bucaramanga-Colombia, which were evaluated using the perfusion technique of vascular structures with polyester resin. RESULTS: The distal medial striated artery was presented in 1.4% and 4.2% duplicated in the right and left hemispheres respectively. Agenesis was presented in 2.8% in the left hemisphere. Its origin was 44.6% of the anterior cerebral artery junction site with the anterior communicating artery and was observed in 6 cases (4.2%) presented with a common trunk with the orbitofrontal artery. The main qualitative finding was the sinuous trajectory that was observed in 57.7% on the right side and 45.1% in the left hemisphere. Also, an important alteration found at the biometric analysis was hypoplasia that could be related to the decreased blood supply to the basal nuclei. The diameter was 0.5 ± 0.2 mm and its total length was 20.3 ± 4.1 mm. CONCLUSIONS: The topographical knowledge of this structure determines the vulnerability of its morphology because it can complicate surgical procedures performed in the anterior segment of the arterial circle of the brain. Besides, the observed collateral circulation contributes to the blood supply and the perfect functionality of the subcortical nervous structures.

OBJETIVO: Evaluar la morfología de la arteria estriada medial distal, teniendo en cuenta variables biométricas útiles para el manejo clínico y quirúrgico. MÉTODOS: Estudio descriptivo transversal con una muestra de cerebros que fueron sometidos a autopsia en el Instituto de Medicina Legal y Ciencias Forenses de Bucaramanga-Colombia, fueron evaluados mediante la técnica de perfusión de estructuras vasculares con resina de poliéster. RESULTADOS: La arteria estriada medial distal se presentó en 1.4% y 4.2% duplicada en el hemisferio derecho e izquierdo respectivamente. Agenesia se presentó en 2.8% en el hemisferio izquierdo. Su origen fue 44.6% del sitio de unión de la arteria cerebral anterior con la arteria comunicante anterior y se observó en 6 casos (4.2%) que presentaban un tronco común con la arteria orbitofrontal. El hallazgo principal fue la trayectoria sinuosa que se observó en 57.7% en el lado derecho y 45.1% en el hemisferio izquierdo. También una alteración importante encontrada en el análisis biométrico fue la hipoplasia que podría estar relacionada con la disminución del suministro de sangre a los núcleos basales. El diámetro fue de 0.5 ±0.2 mm y su longitud total fue de 20.3 ±4.1 mm. CONCLUSIONES: El conocimiento topográfico de esta estructura determina la vulnerabilidad de su morfología, porque puede complicar los procedimientos quirúrgicos realizados en el segmento anterior del círculo arterial del cerebro. Además, la circulación colateral observada contribuye al riego sanguíneo y al perfecto funcionamiento de las estructuras nerviosas subcorticales.

Association of Two Primitive Carotid-Basilar Anastomoses and Cerebrovascular Abnormalities on the Brain Base: A Case Report.

Simultaneous presence of the persistent primitive trigeminal artery and so-called intermediate communicating artery was discovered in a 77-year-old cadaver autopsied due to the myocardial infarction. Many vascular variants and abnormalities such as aplasia of the right vertebral artery (VA), presence of two right posterior cerebral arteries (PCAs), partial duplication of the right superior cerebellar artery, hypoplasia of the pre-communicating part (A1) of the right anterior cerebral artery and the right PCA of basilar origin, a special configuration of the anterior communicating artery (ACoA), and a small aneurysm at the right A1-ACoA junction were associated. The finding of an incipient cerebral aneurysm at the junction of the hypoplastic A1 and embryonal configuration of the ACoA in the eight decade of life indicates that its development was caused by long-term pressure of blood flow at branching points of this artery independent from its caliber. However, it is not yet clear whether the persistence of the first and/or the second carotid-basilar anastomoses in this case was the condition for an aplasia of one VA or vice versa.

Prevalence and Clinical Implications of the Primitive Trigeminal Artery and its Variants: A Meta-Analysis.

BACKGROUND: The primitive trigeminal artery (PTA) is the most common and the largest persistent carotid-basilar anastomosis. Primitive trigeminal artery variants (PTAVs) are anastomoses between the internal carotid artery and cerebellar arteries. These vessels pose a risk of hemorrhagic or ischemic complications during neurosurgical procedures in the parasellar and intrasellar regions. The aim of this study was to determine the prevalence of both PTA and PTAVs and their clinically important anatomic features. METHODS: Major electronic databases were thoroughly searched for studies on PTA and PTAV. References in the included articles were also evaluated. Data regarding prevalence, laterality, origin, course patterns, and associated anomalies were extracted and pooled into a meta-analysis. RESULTS: A total of 39 studies (110,866 patients) were included in the meta-analysis. The total pooled prevalence estimate of PTA and PTAVs combined was 0.4% (95% confidence interval [CI], 0.3-0.5). Individually, PTA was present in 0.3% of patients and PTAV in 0.2%. Both arteries most often originated from the C4 internal carotid artery and took a course lateral to the dorsum sellae. The anterior inferior cerebellar artery type was the predominant PTAV (72.1%). Basilar artery hypoplasia was found in 42.5% of patients with a PTA. CONCLUSIONS: PTA and PTAVs are rare vessels, but they are clinically important because they can contribute to trigeminal neuralgia. Knowledge of the potential course of these arteries is essential in neuroradiology and neurosurgery, especially in minimally invasive procedures such as the endoscopic endonasal transsphenoidal approach to the pituitary gland and the percutaneous gasserian ganglion procedure.