Anteroinferior Cerebellar Artery Research Articles

The Vertebrobasilar Trunk and Its Anatomical Variants: A Microsurgical Anatomical Study.

The trunk of the basilar artery has not been included in microanatomy studies. Anatomical variants of the perforant branches of the vertebrobasilar trunk and their relationship with neural structures are very important in surgical approaches. Surgical dissection for the treatment of vascular lesions requires a perfect knowledge of the microsurgical anatomy. We conducted a descriptive analysis of 50 brains, which were fixed with formalin at 10% for 2 weeks, and the arterial system was injected with colored latex. After microsurgical dissection, it was divided into three segments: the lower portion went from the anterior spinal artery to the anteroinferior cerebellar artery, the middle segment was raised from the upper limit of the lower portion to the origin of the superior cerebellar artery, and the upper segment ranged from the previous portion until the origin of the posterior cerebral artery. The basilar artery had an average length of 30 mm. The average diameter at its junction with the vertebral arteries was 4.05 mm. The average middle segment was 3.4 mm in diameter and 15.2 mm in length. The diameter of the upper segment was 4.2 mm, and its average length was 3.6 mm. The average number of bulbar arteries was three, and their average diameter was 0. 66 mm. The number of caudal perforator arteries were five on average, with a diameter of 0.32 mm. We found three rare cases of anatomical variants in the vertebra-basilar junction. The basilar artery emits penetrating branches in its lower, middle, and upper portions. The origin of penetrating branches was single or divided after forming a trunk. However, we observed long branches from perforant arteries.

The "Deep Subarcuate Fossa" sign and three types of anomalous subarcuate loops encountered during vestibular schwannoma removal.

An anomalous subarcuate loop (SL) of the anteroinferior cerebellar artery (AICA) is a rare anatomic variation, which increases the complexity and risk of vestibular schwannoma (VS) removal. However, preoperative diagnosis of this anomaly remains difficult. The aim of this study was to report three types of anomalous SLs encountered during VS removal and to describe the "Deep Subarcuate Fossa (SF)" sign and its significance in the diagnosis and treatment of an osseous-penetrating SL. We prospectively observed 963 patients with newly/recently diagnosed VS who underwent surgical treatment performed by the senior author (P.Z.) from 2012 to 2021 and identified 16 patients with an anomalous SL. The SF was retrospectively measured on preoperative thin-slice temporal bone computed tomography in 963 patients. Three types of anomalous SLs were encountered during VS removal: the apex of the SL was embedded in the dorsal tumor capsule (type I, 1 case), the dura (type II, 8 cases), or the dura and bone (type III, 7 cases) surrounding the SF. The depth of the SF in 7 patients with a type III anomalous SL ranged from 2.3 to 7.0mm (3.56 ± 1.56mm), which was significantly larger than that in 845 patients without an osseous-penetrating SL (1.23 ± 0.43mm) (p = 0.008). When the depth of the SF exceeded 2mm, the sensitivity and precision of the diagnosis of a type III anomalous SL were 100% (7/7) and 31.8% (7/22), respectively. Three types of anomalous SLs may be encountered during VS removal, and AICA displacement is recommended before tumor removal. The "Deep SF" sign may indicate the existence of a type III anomalous SL and it can predict the depth of the AICA in the bone and guide the drilling of the bone around the vessel loop.

Hemifacial spasm caused by tortuous vertebrobasilar artery: a case report

BackgroundHemifacial spasm is a rare movement disorder. Prevalence estimates worldwide was 14.5 per 100,000 women and 7.4 per 100,000 men. Hemifacial spasm generally caused by compression of blood vessels at the root entry zone of the facial nerve in the brainstem, tortuous anteroinferior cerebellar artery (AICA) and posteroinferior cerebellar artery (PICA). Direct compression by vertebrobasilar dolichoectasia (VBD) with coincidence cavernoma is extremely rare.Case reportA 50-year-old woman with right hemifacial spasm for 1 year, with a history of hypertension for 10 years, did not take medication regularly. MRI MRA was performed showing suspicious dolichoectasia in the vertebrobasilar artery and cavernoma in the left basal ganglia. Then digital subtraction angiography was performed, it was found that the tortuous vertebrobasilar junction artery with a curve to the right caused right hemifacial spasm.ConclusionVascular imaging examination is important to do to find the cause of hemifacial spasm suspected to be due to vascular causes. The finding of two types of intracranial vascular malformations should be explored further. Therefore, the selection of therapy and management becomes more appropriate.

Sudden Sensorineural Hearing Loss Associated with the Presence of a Vascular Loop in the Internal Auditory Canal. Case Report

Abstract The vascular loop refers to a trajectory abnormality of the antero-inferior cerebellar artery or its branch in the internal auditory canal. The Chavda radiological classification identifies three types of trajectory depending on the depth of penetration of the loop at the level of the internal auditory canal. The article presents the case of a 26-year-old patient admitted to the ENT department for left ear sudden sensorineural hearing loss and dizziness. The 3D Fiesta-C axial sequence MRI shows the presence of the vascular loop inside the internal auditory canal, without exceeding half of it. The hearing loss had an unfavourable evolution, without recovery after treatment with steroids and vasodilators. Sudden sensorineural hearing loss may be a consequence of the presence of the vascular loop in the internal auditory canal. The prognosis for recovery from hearing loss is poor if the loop is at least type II.

Is there an association between the anteroinferior cerebellar artery vascular loop and asymmetrical sensorineural hearing loss?

Background: Asymmetrical sensorineural hearing loss is usually idiopathic. Vascular loops are commonly implicated in compression disorders involving lower cranial nerves, which can be relieved on surgical decompression. However, the cause–effect relationship between vestibulocochlear symptoms and vascular loops is still controversial. Objective: The objective of this study is to look for an association between the presence of anteroinferior cerebellar artery (AICA) loops and asymmetrical sensorineural hearing loss of unknown etiology. Methods: Twenty-four patients with complaints of asymmetrical hearing loss of no discernible cause underwent a magnetic resonance imaging of the brain between August 2015 and August 2017. The AICA loops were graded using two classifications, namely Chavda classification and a grading system proposed by Adam Gorrie et al. (second classification). The vascular loops were correlated with the presence of hearing loss, tinnitus, and vertigo. Results: Hearing loss did not correlate significantly with the vascular loops on grading with either Chavda or the second classification. The presence of tinnitus or vertigo too did not correlate significantly with the grading of vascular loops. The caliber of AICA too did not correlate significantly with hearing loss. Conclusion: Vascular loops do not appear to be associated with asymmetrical hearing loss and other cochleovestibular symptoms.

MICROCIRUGÍA ASISTIDA CON ENDOSCOPÍA EN LA RESECCIÓN DE TUMOR EPIDERMOIDE DEL ÁNGULO PONTOCEREBELOSO

Introduction: Intracranial epidermoid tumors are rare, slow-growing, and histologically benign congenital neoplasms. The microsurgical approach with endoscopic assistance is described as a minimally invasive technique that facilitates the work of the neurosurgeon in the complete resection of an epidermoid tumor located in the cerebellopontine angle. Clinical Case: 62-year-old woman, with a 3-year disease characterized by pain on the right side of the face. Symptoms increase in the following 2 years, becoming disabling and only partially improving with pregabalin and oxcarbazepine. Brain MRI showed a hypointense lesion with a cystic appearance at the level of the prepontine cistern with expansion to the right cerebellopontine angle that compressed the right trigeminal nerve (V). Retromastoid craniotomy and a right cerebellopontine angle approach were performed. Under the microscopic vision, the trigeminal nerve was identified which was pulled by the tumor, the cranial nerve complex VII-VIII, and vessels such as the superior petrous vein and the anteroinferior cerebellar artery. With the support of the endoscope, the tumor was better visualized in inaccessible areas, the prepontine cistern was accessed and total resection of the tumor was achieved. The patient evolved favorably with remission of pain on the right side. Conclusion: The microsurgical technique assisted by endoscopy allows safe removal of the tumor, and it is immensely helpful in the resection of tumors from regions not visible under the microscope. Keywords: Brain Neoplasms, Trigeminal Nerve, Endoscopy, Cerebellopontine Angle. (source: MeSH NLM

Image diagnosis of Trigeminal Neuralgia caused by Vascular Compression

Trigeminal Neuralgia (TGN) is a disease frequently encountered by the neurologists and neurosurgeons. The typical pain of TGN is lancinating in nature in one side of face along the distribution of Trigeminal nerve. Pain is sharp shooting and periodic in nature, aggravated by various factors, like eating, talking, laughing. A typical trigeminal neuralgia is caused by compression to the Root exit zone (REZ) by superior cerebellar artery (SCA), aberrant loop of Antero inferior cerebellar artery (AICA), dolichobasilar artery or a large sized vein. However facial pain mimicking TGN may occur by a tumor, plaque of Multiple sclerosis or may be idiopathic. So this is very important to know the cause of TGN/ facial pain for planning of specific treatment. Most of the patients remain pain free by medical management by using Carbamazepine, oxycarbazepine, Pregabalin, Gabapentin, Clonazepam etc. But medically refractory TGN can be treated by Microvascular decompression (MVD) with significantly satisfactory results if the cause is by vascular compression. However during MVD no significant blood vessels are seen and surgery become failed. Clinical examination and evaluation is very important, however to become confirmed about the pathogenesis needs imaging of brain. MRI of brain can differentiate any tumor or Plaque of MS. But conventional MRI images can not show us clearly the blood vessel causing TGN. Conventional MRA could show the blood vessels, which might be causing compression to REZ but does not confirm the fact. Constructive interference in steady state (CISS) MR images were evaluated in our 15 cases to find neurovascular relationship at the REZ. In 11 cases CISS images showed excellent visualization of fifth nerve and blood vessels causing compression to REZ in all case of TGN who underwent Microvascular decompression (MVD) with excellent result. In 2 patients we depended on clinical findings and T2 MR Images. In one of them we could find Offending vessels who were also improved clinically. In one case we did not find any significant offending vessel except a small vein and this patient did not show any improvement. In rest two cases, in one patient CISS showed a tiny vessel and after MVD the patient did not improve. In one patient no significant vessels were not seen in CISS images. We did not go for MVD for this case. So the pre-operative CISS MR images are more precise to show the neurovascular relationship and determine the offending blood vessel causing TGN. Thus we can avoid an unnecessary MVD.
 Bang. J Neurosurgery 2020; 10(1): 3-8

The specific features of the anatomical structure of the artery of labyrinth (an anatomical and topographical study)

The objective of the present work was to study syntopy of the artery of labyrinth using block-preparations of the posterior cranial fossa, variants of its branching-off from the vertebro-basiliar basin (VBB), and peculiar features of its anatomical structure. A total of 12 block-preparations of the posterior cranial fossa were available for the investigation. They were preliminarily stained with red latex and fixed in a three-point system. These procedures were followed by retrosigmoid craniotomy, opening of dura mater in the supero-lateral part of the cerebellomedulllary cistern, traction of the cerebellum, and blunt separation of the basiliar artery (BA). Variants of branching of the antero-inferior cerebellar artery (AICA) and branching of the artery of labyrinth from AICA were studied. It was shown that the artery of labyrinth branches off from the antero-inferior cerebellar artery in 100% of the cases. The latter artery formed a loop in 14% of the cases (3 ears). The average diameter of the labyrinth artery was 0.32 mm and its mean area 0.06 sq.cm. The artery of labyrinth branched off from the posterior para-stem segment of the antero-inferior cerebellar artery in 42.6% of the cases (9 ears), and from the anterior para-stem segment of AICA in 14.2% of the cases (3 ears). Within the conventional «rhombus», the artery of labyrinth was straight in 76.2% of the cases (16 ears) and arc-shaped in 23.8% (4 ears).

Cervical vertigo related cerebral blood flow change revealed by three dimensional pseudo continuous arterial spin labeling

Objective To quantitatively investigate the change of cerebral blood flow (CBF)induced by cervical vertigo by using 3D pseudo-continuous arterial spin labeling (3D PCASL).Methods This study included 17 patients without cerebral arterial stenosis on MRA as the patient group and 14 healthy volunteers as the control group.They were examined by 3D PCASL before and after the vertigo-inducing test respectively.CBF was measured in regions of interest (ROI) which were perfused by bilateral anteroinferior cerebellar artery (AICA),posteroinferior cerebellar artery (PICA),superior cerebellar artery (SCA),posterior cerebral artery (PCA),middle cerebral artery (MCA),anterior cerebral artery (ACA) and posterior pons.The change of CBF caused by the vertigo-inducing test was calculated for every ROI.Independent t test was used to compare the change of CBF between the patients and controls.Results There was significant difference of change of CBF in the ROIs of R-PICA,R-AICA,R-ACA,bilateral SCA,bilateral PCA territory and posterior pons between the patients and controls (t =2.30 to 3.99,P ＜ 0.05).CBF values in these ROIs were significantly decreased after the vertigo-inducing test in the patients.The changes of CBF in ROIs of patients and controls were as following:(1) R-PICA (-3.86 ± 6.43) vs.(0.63 ±4.37) ml/(min · 100 g) ; (2) R-AICA (-4.30 ±6.79) vs.(0.39 ±3.51) ml/(min · 100 g) ;(3) SCA:(-7.15 ±6.70) vs.(-0.27 ±3.89) ml/(min · 100 g) for the left side,(6.99 ±6.34) vs.(-0.68±3.18) ml/(min · 100 g) for the right side; (4) PCA:(-7.39 ±6.31) vs.(-0.39 ±3.24) ml/(min· 100g) for the left side,(-7.86±6.48) vs.(-1.41±2.91) ml/(min· 100 g) for the right side; (5) R-ACA (-3.50 ±4.03) vs.(0.16 ±3.07) m]/(min · 100 g) ; (6) posterior pons (-5.91 ±7.34) vs.(0.06 ± 3.41) ml/(min · 100 g).Conclusions 3D PCASL is able to detect the CBF change induced by vertigo-inducing test.Cervical vertigo onset is related to posterior circulation ischemia,which may be caused by the spinal position changes. Key words: Vertigo; Cervical spondylosis; Magnetic resonance imaging

Intraoperative decisions and surgical efficacies of trigeminal neuralgia responsible vessels

To explore the types of primary trigeminal neuralgia (TN) responsible vessels and curative efficacies of microscopic vascular decompression (MVD). A total of 162 primary TN patients underwent MVD from August 2004 to the present at our hospital.Their clinical data were collected and analyzed. There were 69 males and 93 females with an age range of 22-88 years. The most common responsible vessels were superior cerebellar artery (n = 65, 40.12%), anteroinferior cerebellar artery (n = 45, 27.78%), multiple vessels (n = 26, 16.05%), posteroinferior cerebellar artery (n = 16, 9.88%), veins (n = 6, 3.70%) and vertebral artery (n = 4, 2.47%). And the pressure points were at the root of trigeminal nerve (n = 139, 85.80%), distal part (n = 16, 9.88%) and root and distal part (n = 7, 4.32%). Postoperatively pain disappeared in all patients (including one case on second surgery). Postoperative follow-ups were conducted for 132 cases.Two cases recurred over 8 years and the recurrence rate was 1.52%. MVD is preferred method for primary TN non-responsive to pharmacotherapy. Identification and treatment of responsible vessels remain a key. Venous and distal pressure points should be taken care.

Characteristics of neurovascular compression in facial neuralgia patients by 3D high–resolution MRI and fusion technology

ObjectiveTo evaluate the anatomical characteristics and patterns of neurovascular compression in patients suffering trigeminal neuralgia, using 3D high–resolution magnetic resonance imaging methods and fusion technologies. MethodsThe analysis of the anatomy of the facial nerve, brain stem and the vascular structures related to this nerve was made in 100 consecutive patients for TN. 3D high resolution MRI studies (3D SPGR, T1 enhanced 3D MP-RAGE and T2/T1 3D FIESTA) simultaneous visualization were used to assessed using the software 3D DOCTOR. ResultsIn 93 patients (93%), there were one or several locals of neurovascular compression (NVC). The superior cerebellar artery was involved in 71 cases (76%), the other vessels including the antero-inferior cerebellar artery, the basilar artery, the vertebral artery, and some venous structures. The mean distance between NVC and nerve origin site in the brainstem was (3.76 ± 2.90) mm). In 39 patients (42%), the vascular compression was located proximally and in 42 (45%) the compression was located distally. Nerve dislocation or distortion by the vessel was observed in 30 cases (32%). ConclusionsThis 3D high resolution MRI and image fusion technology could be useful for diagnostic and therapeutic decisions in TN.

Characterization of neurovascular compression in facial neuralgia patients by 3D high-resolution MRI and image fusion technique

ObjectiveTo describe the anatomical characteristics and patterns of neurovascular compression (NVC) in patients suffering trigeminal neuralgia (TN) by 3D high-resolution magnetic resonance imaging (MRI) method and image fusion technique. MethodsThe anatomic structure of trigeminal nerve, brain stem and blood vessel was observed in 100 consecutive TN patients by 3D high resolution MRI (3D SPGR, contrast-enhanced T1 3D MP-RAGE and T2/T1 3D FIESTA). The 3D image sources were fused and visualized using 3D DOCTOR software. ResultsOne or several NVC sites, which usually appeared 0–9.8 mm away from brain stem, were found on the symptomatic side in 93% of the TN cases. Superior cerebellar artery was involved in 76% (71/93) of these cases. The other vessels including antero-inferior cerebellar artery, vertebral artery, basilar artery and veins also contributed to the occurrence of NVC. The NVC sites were found to be located in the proximal segment in 42% of these cases (39/93) and in the distal segment in 45% (42/93). Nerve dislocation or distortion was observed in 32% (30/93). ConclusionsVarious 3D high resolution MRI methods combined with the image fusion technique could provide pathologic anatomic information for the diagnosis and treatment of TN.

Cortical and cerebellar hypometabolism after bilateral antero-inferior cerebellar artery infarct

A 55-year-old man with a history of hypertension, hypercholesterolemia, and tobacco use presented with sudden onset bilateral deafness, gait ataxia, and dysarthria. Clinical examination disclosed left-sided limb ataxia, bilateral gaze-evoked nystagmus, dysarthria, and bilateral hearing loss. Brain MRI showed a bilateral anterior inferior cerebellar artery (AICA) infarction (figure, A). Fluorodeoxyglucose PET scan ([18F] FDG PET) performed because of mild frontal syndrome (euphoria and decreased spontaneous activity) showed a mild cerebellar and prefrontal cortex hypometabolism (figure, B). He recovered after 1 month without sequelae. Five months later, he complained of apathy, poor motivation, and lack of interest in previous hobbies. Neuropsychological investigations disclosed a mild impairment of processing speed, alphabetic verbal fluency, attention and executive dysfunction such as difficulties in planning and disturbed mental flexibility; semantic and episodic memory and praxis were normal. An [18F] FDG PET control showed a severe bilateral cerebellar, frontal, temporal, and parietal hypometabolism (figure, …

Patterns of neurovascular compression in patients with classic trigeminal neuralgia: A high-resolution MRI-based study

To describe the anatomical characteristics and patterns of neurovascular compression in patients suffering classic trigeminal neuralgia (CTN), using high-resolution magnetic resonance imaging (MRI). The analysis of the anatomy of the trigeminal nerve, brain stem and the vascular structures related to this nerve was made in 100 consecutive patients treated with a Gamma Knife radiosurgery for CTN between December 1999 and September 2004. MRI studies (T1, T1 enhanced and T2-SPIR) with axial, coronal and sagital simultaneous visualization were dynamically assessed using the software GammaPlan™. Three-dimensional reconstructions were also developed in some representative cases. In 93 patients (93%), there were one or several vascular structures in contact, either, with the trigeminal nerve, or close to its origin in the pons. The superior cerebellar artery was involved in 71 cases (76%). Other vessels identified were the antero-inferior cerebellar artery, the basilar artery, the vertebral artery, and some venous structures. Vascular compression was found anywhere along the trigeminal nerve. The mean distance between the nerve compression and the origin of the nerve in the brainstem was 3.76±2.9mm (range 0-9.8mm). In 39 patients (42%), the vascular compression was located proximally and in 42 (45%) the compression was located distally. Nerve dislocation or distortion by the vessel was observed in 30 cases (32%). The findings of this study are similar to those reported in surgical and autopsy series. This non-invasive MRI-based approach could be useful for diagnostic and therapeutic decisions in CTN, and it could help to understand its pathogenesis.

MICROVASCULAR DECOMPRESSION IN HEMIFACIAL SPASM RESULTING FROM A CEREBELLOPONTINE ANGLE LIPOMA

Hemifacial spasm caused by a cerebellopontine angle lipoma is extremely rare. We describe a patient with left-sided hemifacial spasm caused by vascular compression of the facial and vestibulocochlear cranial nerves by the anteroinferior cerebellar artery embedded within a cerebellopontine angle lipoma. A 77-year-old man presented with a 10-year history of left-sided facial spasms that progressively worsened over time and significantly interfered with his ability to read, drive, and interact in social situations. Neurological examination showed obvious left hemifacial spasm, including orbicularis oculi and levator labii muscles. Magnetic resonance imaging revealed characteristic abnormal signal within the cerebellopontine angle cistern that was consistent with lipoma abutting the anteroinferior cerebellar artery. Surgical exploration with standard retrosigmoid craniectomy and subarachnoid dissection of the cerebellopontine angle was performed. The offending anteroinferior cerebellar artery branch was dissected away from the VIIth and VIIIth cranial nerves. Teflon felt was interposed between the artery and nerves after the artery was dissected off the surface of the lipoma. Electrophysiological monitoring showed resolution of the abnormal hemifacial spasm response during the procedure. No attempt was made to resect the lipoma, given the risk to injury of the brainstem and perforating blood vessels. Postoperatively, the patient's symptoms were completely resolved. This case demonstrates that relief of the vascular compression, when present, of the VIIth cranial nerve is sufficient for resolution of hemifacial spasm symptoms, even when associated with nearby, benign lesions.

MICROVASCULAR DECOMPRESSION FOR TRIGEMINAL NEURALGIA

Microvascular decompression, although a well-established procedure for treating primary trigeminal neuralgia, still has no standardized protocol. The practical consequences of having the implant keep the conflicting vessels apart, whether or not in contact with the root, is still in debate. The present work was undertaken to answer this question. Patients were segregated into 2 groups: Group I (260 patients) had a Teflon prosthesis implanted without contact to the root, and Group II (70 patients) had a similar implant with contact to the root. Cure rates in the 2 groups were compared at the latest follow-up (</=15 yr; average, 8.2 yr) using Kaplan-Meier analysis. In Group I, the cure rate was 82% (214 of 260 patients), whereas in Group II, the cure rate was 67% (47 of 70 patients) (P = 0.01). Kaplan-Meier analysis of the follow-up period up to 15 years also shows a significant difference (P = 0.05). These results strongly support the goal of performing the procedure without the implant in contact with the root. This is easier with the superior cerebellar artery, because of its laxity and small number of perforating branches, than with the anteroinferior cerebellar artery, which has perforators to the brainstem and labyrinthine artery arising from its cisternal portion. The significantly better long-term cure rate when the implant is not in contact with the root favors the "pure" decompressive effect of the microvascular decompression procedure, rather than a conduction block mechanism.

A giant partially thrombosed aica aneurysm

Aneurysms of the anteroinferior cerebellar artery (AICA) are rare, comprising far less than 1% of all intracranial aneurysms. By 1989, only 33 cases had been reported in the literature1-4. Subsequently, numerous case reports and small series of AICA aneurysms have been reported1,2,5-15. Giant aneurysms of proximal portion of AICA are even more uncommon, being difficult to estimate their actual incidence. These aneurysms constitute formidable surgical challenge and a judicious preoperative planning is mandatory since surgical nuances often determined the final [...]

THE CURRENT ROLE OF MICROSURGERY FOR POSTERIOR CIRCULATION ANEURYSMS

During the past decade, management of posterior circulation aneurysms has shifted away from microsurgery. Currently, microsurgical clipping is considered a primary, competitive alternative to endovascular coiling, or more commonly, a secondary alternative when endovascular therapy is unfavorable. We present a large, multidisciplinary team experience with posterior circulation aneurysms in an institution that continues to use microsurgery as a primary treatment modality for selected aneurysms. During a 9-year period, 217 patients with 228 posterior circulation aneurysms were treated microsurgically; they included 106 basilar bifurcation, 27 posterior cerebral artery, 23 superior cerebellar artery, eight anteroinferior cerebellar artery, five basilar trunk, 47 posteroinferior cerebellar artery, and 12 vertebral artery aneurysms. Overall, 81% of patients presented with hemorrhage, and 33% of the aneurysms were large or giant in size. Direct clipping was performed in 75% of cases, and the overall rate of angiographic aneurysm obliteration was 98.1%. Sixteen patients (7.4%) died after surgery, 25 patients (11.5%) experienced transient neurological deterioration, and 17 patients (7.8%) experienced permanent neurological deterioration. At late follow-up (mean duration, 13.6 mo), 144 patients had good outcomes (Glasgow Outcome Scale scores of 5 or 4, 66%), and 184 patients (85%) either improved or were unchanged relative to their preoperative baseline. Overall, mean Glasgow Outcome Scale scores improved from 3.60 to 3.97. Despite increasing reliance on endovascular therapy with posterior circulation aneurysms, there is a role for microsurgical therapy. Microsurgery remains a competitive, primary therapy for superior cerebellar artery, P1 posterior cerebral artery, distal anteroinferior cerebellar artery, and posteroinferior cerebellar artery aneurysms. Microsurgery has become a secondary therapy for P2 posterior cerebral artery, basilar trunk, proximal anteroinferior cerebellar artery, vertebrobasilar junction, and vertebral artery aneurysms when endovascular therapy is unfavorable. The preferred therapy for basilar bifurcation aneurysms remains unclear. Collaborative, multidisciplinary teams are strengthened and results are improved by offering competitive treatment alternatives for patients to consider and select. Rather than abandoning the posterior circulation prematurely, aneurysm surgeons should maintain technical proficiency with these lesions.

Anteroinferior Cerebellar Artery Aneurysms: Surgical Approaches and Outcomes—A Review of 34 Cases

Anteroinferior Cerebellar Artery Aneurysms: Surgical Approaches and Outcomes—A Review of 34 Cases

The Anteroinferior Cerebellar Artery Embedded in the Subarcuate Fossa: A Rare Anomaly and Its Clinical Significance

The purpose of this study is to call attention to an anomaly in which a segment of the anteroinferior cerebellar artery (AICA) is embedded in the dura or bone surrounding the subarcuate fossa, a small depression in the bone posterior to the internal acoustic meatus (IAM), through which the subarcuate artery enters the bone. This anomaly places the artery at risk in removing the posterior wall of the IAM. An anomalous AICA having a segment that was embedded in the dura covering on the bone surrounding the subarcuate fossa was found during a microsurgical dissection course. The senior author (ALR) has observed this anomaly in four patients during surgery for acoustic neuromas and in three specimens in microsurgery dissection courses. To define the microsurgical anatomy of the anomalous artery further, the latex-injected specimen was dissected in a stepwise manner using x3 to x40 magnification. The anomalous AICA described in this report bifurcated into a rostral trunk and a caudal trunk near the facial-vestibulocochlear nerve complex. The caudal trunk formed a sharp lateral loop that was embedded in the dura covering the subarcuate fossa. The involved trunk continued to supply the suboccipital area normally supplied by the posteroinferior cerebellar artery, which was hypoplastic. The dura surrounding the anomalous loop was opened, and the adjacent bone was removed to free the anomalous loop from the subarcuate fossa so that the artery could be displaced medially to remove the posterior wall of the IAM. Although it has been reported that the AICA may occasionally be adherent to the dura over the subarcuate fossa, this study is the first to demonstrate an AICA that is embedded in the dura and bone of the subarcuate fossa. Mobilizing the AICA loop that is embedded in the subarcuate fossa posterior to the IAM places the involved AICA at significant risk in exposing the contents of the IAM.