[Anatomical Variations to the Vertebral Artery and Posterior Inferior Cerebellar Artery are Associated with the Partial Persistence of Primitive Lateral Basirovertebral Anastomosis].

The angioarchitecture of the hindbrain is homologous to that of the spinal cord, and its vascular system can be analyzed at the longitudinal and axial structures. During embryonic development, there are two main longitudinal arteries: the longitudinal neural artery and the primitive lateral basilovertebral anastomosis. Commonly observed variations are formed by the fenestration and duplication of either the vertebrobasilar artery, or cerebellar artery, which can be observed when the primitive lateral basilovertebral anastomosis partially persists. Understanding the pattern and development of blood supply to the hindbrain provides useful information of various anomalies in the vertebrobasilar junction and cerebellar arteries.

[Basilar Artery, Anterior Inferior Cerebellar Artery, Superior Cerebellar Artery].

The basilar artery(BA)is formed by the fusion of two longitudinal arteries, and incomplete development may lead to BA fenestration. The BA provides many short perforating arteries and long lateral pontine arteries to the brain stem. The anterior inferior cerebellar artery(AICA)usually branches from the proximal third of the BA and primarily perfuses the ventral, inferior and lateral aspect of the cerebellum and inner ear organ. However, there are many variations to the AICA that depend on the degree of posterior inferior cerebellar artery development. The superior cerebellar artery(SCA)branches into not only to the rostral, ventral aspect of the cerebellar hemisphere, but also to the deeper cerebellar nucleus and brain stem. Duplications within this vessel are frequently identified, but it is not missing.

Posterior Inferior Cerebellar Artery Aneurysm Shaped Like a "Calabash Gourd" and Mimicking a Tumor.

Posterior inferior cerebellar artery aneurysms are likely to be fusiform, yet they hardly enlarge to mimic a tumor in the posterior fossa on radiology. They constitute about 3%-4% of all cerebral aneurysms. A 65-year-old woman presented with tremor in her right upper limb for 1 year and intermittent dizziness for 8 months. Interestingly, magnetic resonance imaging revealed 2 unanimously enhanced masses like mother and daughter located in the right cerebellum hemisphere. The lesion was resected via surgery, and histopathology established the diagnosis of an aneurysm. Her tremor and dizziness subsided 3 months after the surgery, and at her 2-year follow-up she was well with no further neurologic deficits.

Flow Diversion for Treatment of Anterior Inferior Cerebellar Artery Aneurysms: Mechanism and Pitfalls from a Novel Management Strategy.

BACKGROUND: Anterior inferior cerebellar artery (AICA) aneurysms present a challenge for neurosurgeons and neurointerventionalists alike. METHODS: Cases of AICA aneurysms managed with endovascular flow diversion at our institute are reviewed with their angiographic outcomes. RESULTS: Both direct and indirect flow diversion provide complete aneurysm occlusion at follow-up. We propose a stratified method of approaching AICA aneurysms based on location, rupture status, and neck size. CONCLUSIONS: Careful evaluation of preoperative parameters is paramount in deciding between a surgical or a neuroendovascular approach. Low-profile stents in the future may assist in direct flow diversion of AICA trunk aneurysms. In addition, neurosurgeons need to be well versed in endovascular approaches.

Preserving the cerebellar hemispheric tentorial bridging veins through a novel tentorial cut technique for supracerebellar approaches.

OBJECTIVE: The objective of this study was to describe the distribution pattern of cerebellar hemispheric tentorial bridging (CHTB) veins on the tentorial surface in a case series of perimedian or paramedian supracerebellar approaches and to describe a novel technique to preserve these veins. METHODS: A series of 141 patients with various pathological processes in different locations was operated on via perimedian or paramedian supracerebellar approaches by the senior author from July 2006 through October 2022 and was retrospectively evaluated. During surgery, the number and locations of all CHTB veins were recorded to establish a distribution map on the tentorial surface, divided into nine zones. Patients were classified into four groups according to the surgical technique used to manage CHTB veins: 1) group 1 consisted of CHTB veins preserved without intervention during surgery or no CHTB veins found in the surgical route; 2) group 2 included CHTB veins coagulated during surgery; 3) group 3 included CHTB veins preserved with arachnoid and/or tentorial dissection from the cerebellar or tentorial surface, respectively; and 4) group 4 comprised CHTB veins preserved using a novel tentorial cut technique. RESULTS: Overall, 141 patients were included in the study. Of these 141 patients, 38 were in group 1 (27%), 32 in group 2 (22.7%), 47 in group 3 (33.3%), and 24 in group 4 (17%). The total number of CHTB veins encountered was 207 during surgeries on one side. According to the distribution zones of the tentorium, zone 5 had the highest density of CHTB veins, while zone 7 had the lowest. Of the patients in group 4, 6 underwent the perimedian supracerebellar approach and 18 had the paramedian supracerebellar approach. There were 39 CHTB veins on the surface of the 24 cerebellar hemispheres in group 4. The tentorial cut technique was performed for 27 of 39 CHTB veins. Twelve veins were not addressed because they did not present any obstacles during approaches. During surgery, no complications were observed due to the tentorial cut technique. CONCLUSIONS: Because there is no way to determine whether a CHTB vein can be sacrificed without complications, it is important to protect these veins in supracerebellar approaches. This new tentorial cut technique in perimedian or paramedian supracerebellar approaches makes it possible to preserve CHTB veins encountered during supracerebellar surgeries.

Bypass Surgery for Vertebral Artery and Posterior Inferior Cerebellar Artery Fusiform Aneurysms: Surgical Technique and Key Lessons.

Fusiform vertebral artery (VA) aneurysms are challenging to treat due to their pathophysiology, morphology, and anatomic location.1,2 Endovascular treatments are considered to be a widely adopted safe option for this pathology.1 Open microsurgical treatment is considered for complex anatomy, important branch involvement, poor collateral flow, or failed endovascular therapy.3-7 This report aims to show the flow-replacement strategy and bypass technique for a VA aneurysm with complex anatomy and branch involvement. A 24-year-old man presented to our clinic with a bilateral fusiform VA aneurysm discovered during workup of progressive headaches. Further investigation revealed that the left-side aneurysm was mostly thrombosed and the posterior inferior cerebellar artery arose from the aneurysm dome with a fusiform enlargement within a few millimeters from the branching point. After evaluating all management options, the patient decided on surgical treatment of the left VA aneurysm. We performed an occipital artery to posterior inferior cerebellar artery end-to-side anastomosis distal to the fusiform enlargement, followed by trapping of the aneurysm and dome resection (Video 1). Antegrade flow to the distal VA was reestablished using a radial artery interposition graft, thus preventing any flow alterations that may cause growth or rupture of the contralateral aneurysm caused by increased hemodynamic stress if the ipsilateral VA flow is not preserved.8 After in-hospital physical rehabilitation, the patient was discharged with a modified Rankin Scale score of 1. The contralateral aneurysm is managed with serial imaging and treatment will ensue if there is clinical-radiologic evolution. The patient consented to the procedure and publication of his image.

Endoscopic endonasal transclival clipping of a cerebellar arteriovenous malformation feeding vessel and associated aneurysm; a 2D operative video.

Positioned along the ventral surface of the pons, proximal superior cerebellar artery (SCA) aneurysms account for only 1.7% of all intracranial aneurysms [1]. Unlike more commonly encountered basilar artery aneurysms, patients often experience good outcomes when treated via endovascular coiling or surgical clipping [1,2]. These lesions frequently have a lateral projection and paucity of perforator arteries [2]. With further development of endoscopic endonasal techniques, access to this region is possible via a direct frontal exposure to the ventral brainstem, basilar artery and branching vessels. To date, there are only a limited number of reports describing an endoscopic endonasal transclival (EETC) approach for surgical clipping [3-5]. In this operative video, we detail the surgical clipping of a cerebellar arteriovenous malformation feeding vessel and an associated aneurysm using the EETC approach in a 59-year-old woman who presented with sudden onset of a severe headache. The feeding vessel and aneurysm's midline location, just below the take-off of the SCA made it a good candidate for this surgery. Major steps included in this video include 1) transsphenoidal exposure of and subsequent drilling of the clivus, 2) dural opening into the pre-pontine cistern and dissection of the aneurysm, 3) clipping of the aneurysm, and 4) multi-layered closure of the skull base defect. Overall, the patient tolerated the procedure well and was found to have no residual filling of the aneurysm or the AVM feeding vessel at 2-year follow-up. EETC is a viable surgical option for the treatment of aneurysm located along the midline of the pre-pontine cistern.

Use of Proximal Suboccipital Segment of Occipital Artery as Donor for Posterior Circulation Revascularization Surgery: Technical Note.

BACKGROUND: The distal suboccipital segment of the occipital artery is commonly used as a donor vessel for aneurysms of the posterior circulation requiring revascularization techniques. Isolating this segment of vessel can be challenging due to its course in and out of the various layers of the suboccipital musculature. METHODS: We describe the use of the proximal suboccipital segment of the occipital artery within the occipital groove at the lateral skull base as a donor segment for an interposition graft in revascularization surgery. We present a case detailing the use of this technique for treatment of a dissecting PICA aneurysm and photographs from cadaveric dissections demonstrating relevant anatomy. RESULTS: Our patient is a 62-year-old man who presented with a high-grade subarachnoid hemorrhage from a proximal dissecting-type aneurysm of the posterior inferior cerebellar artery (PICA). Endovascular options were limited to coil sacrifice of the parent vessel, and thus the patient was taken for a far lateral craniotomy, trapping of the aneurysm, and revascularization of the PICA territory via a saphenous vein interposition graft sewn proximally and distally to the occipital artery within the occipital groove and a cortical segment of the affected PICA, respectively. Postoperative imaging demonstrated filling of the PICA territory via the graft, and the patient ultimately recovered from his subarachnoid hemorrhage. CONCLUSIONS: The use of the proximal suboccipital segment of the occipital artery is a viable option for a donor in posterior fossa revascularization surgery.

Medullary branches of the vertebral artery: microsurgical anatomy and clinical significance.

BACKGROUND: Since the medullary arteries are of a great neurologic and neurosurgical significance, the aim was to perform a detailed microanatomic study of these vessels, as well as of the medullary infarctions in a group of patients. METHODS: The arteries of 26 halves of the brain stem were injected with India ink and gelatin, microdissected and measured with an ocular micrometer. Neurologic and magnetic resonance imaging (MRI) examinations were performed in 11 patients. RESULTS: The perforating medullary arteries, averaging 6.7 in number and 0.26 mm in diameter, most often originated from the anterior spinal artery (ASA), and rarely from the vertebral (VA) (38.5%) and the basilar artery (BA) (11.6%). They supplied the medial medullary region. The anterolateral arteries, 4.8 in number and 0.2 mm in size, most often arose from the ASA and PerfAs, and nourished the anterolateral region. The lateral arteries, 2.2 in number and 0.31 mm in diameter, usually originated from the VA and the posterior inferior cerebellar artery (PICA). They supplied the lateral medullary region. The dorsal arteries, which mainly arose from the PICA and the posterior spinal artery (PSA), nourished the dorsal region, including the roof of the 4th ventricle. The anastomotic channels, averaging 0.3 mm in size, were noted in 42.3%. Among the medullary infarctions, the lateral ones were most frequently present (72.8%). CONCLUSION: The obtained anatomic data, which can explain the medullary infarctions symptomatology, are also important in order to avoid damage to the medullary arteries during neurosurgical and neuroradiologic interventions.

Posterior inferior cerebellar artery originating from the posterior meningeal artery mimicking dural arteriovenous fistula.

PURPOSE: Many variations in the origin of the posterior inferior cerebellar artery (PICA) have been reported. To our knowledge, only one case of a PICA originating from the posterior meningeal artery (PMA) has been reported. METHODS: We describe a case with a PICA that was supplied retrograde from the distal segment of the PMA, mimicking a dural arteriovenous fistula on magnetic resonance angiography (MRA). RESULTS: A 31-year-old man was admitted to our hospital with a sudden occipital headache and nausea. MRA showed a hyperplastic left PMA, continuing to an abnormal vessel that was suspicious for venous drainage. Digital subtraction angiography revealed the left PMA originated from the extradural segment of the vertebral artery and then connected to the left PICA near the torcula. The cortical segment of the PICA flowed retrograde, which appeared as venous reflux on MRA. A second PICA originated from the extradural segment of the left vertebral artery and perfused the tonsillomedullary and televelotonsillar segment of the left PICA territory. CONCLUSION: We present an anatomical variant of the PICA mimicking a dural arteriovenous fistula. Digital subtraction angiography is useful for diagnosis of the cortical segment of the PICA flowing retrograde from the distal segment of the PMA because signal intensity in MRA of retrograde flow tends to decrease and diagnosis may be difficult. During endovascular treatment and open surgery, we should note that ischemic complications may occur due to the potential anastomosing channels between cerebral and dural arteries.

Revascularization of a Complex Case of Vertebrobasilar Insufficiency with Occipital Artery-Anterior Inferior Cerebellar Artery Bypass.

Atherosclerotic disease is the most common etiology in causing posterior circulation strokes and can be found within the intracranial vertebrobasilar system.1 Endovascular and surgical approaches to treat this disease have been defined with both advantages and disadvantages.2,3 We present a case of surgical revascularization of a complex case of vertebrobasilar insufficiency with occipital artery (OA)-anterior inferior cerebellar artery (AICA) bypass (Video 1). A 56-year-old gentleman presented with severe, disabling, and progressive symptoms of vertebrobasilar insufficiency refractory to maximal medical management. Symptom onset was 2 years prior after suffering a left lateral medullary stroke due to a left vertebral artery (VA) occlusion. Angiography showed left VA occlusion after the origin of the posterior inferior cerebellar artery (PICA) and a hypoplastic right VA mostly ending in a PICA with a small and critically stenosed branch to the basilar artery. An initial attempt to revascularize the chronic totally occluded left VA using a combination of anterograde and retrograde (via PComm) approaches was unsuccessful. The decision was made to proceed with an OA-AICA bypass. The end-to-side anastomosis was conducted in the right cerebellopontine cistern and was uncomplicated. Postoperative angiography demonstrated a patent bypass with brisk OA-to-AICA flow with retrograde filling of the basilar artery and its branches. No perioperative strokes. The patient remained free of recurrent symptoms of vertebrobasilar insufficiency at 6 months' follow-up.

Midline Suboccipital Unilateral Trans-Cerebellomedullary Fissure Approach for Clipping of Ruptured VA-PICA Aneurysm: Two-Dimensional Operative Video.

The vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysm poses a technical challenge for microsurgical clipping due to its anatomical complexity, which requires dissection of lower cranial nerves. Endovascular treatment is regarded as a feasible first-line therapeutic option for VA-PICA aneurysm because it has an acceptable aneurysm occlusion rate and is less invasive. However, microsurgical clipping remains an effective treatment option. We present the case of a 62-year-old man who presented with subarachnoid hemorrhage (SAH) due to a ruptured VA-PICA aneurysm. Neuroradiologic examination revealed a 2-3 mm medially pointing left VA-PICA aneurysm with acute obstructive hydrocephalus due to massive SAH in the posterior cranial fossa. As the patient had acute obstructive hydrocephalus and a relatively small aneurysm, we selected clipping over endovascular treatment. Because the aneurysm was located close to the midline and anterolateral to the medulla oblongata, we approached it from the midline. A midline suboccipital craniotomy, C1 laminectomy, and drilling of the left condylar fossa were performed; a unilateral cerebellomedullary fissure opening was added; and the aneurysm was clipped. Postoperative neuroradiologic examinations revealed complete obliteration of the aneurysm. As shown in this video, unilateral cerebellomedullary fissure opening combined with adequate removal of the condylar fossa provides a wide operative field in the cerebellomedullary cistern while avoiding strong retraction of the cerebellum. We believe that this technique makes VA-PICA aneurysm clipping safe and successful. Patient consent was obtained to perform the surgery and to publish the surgical video (Video 1).

Endovascular Treatment Strategies for Aneurysms of the Origin of the Posterior Inferior Cerebellar Artery.

BACKGROUND: Treatment of aneurysms at the origin of the posterior inferior cerebellar artery (PICA) is challenging. Surgery is difficult due to the deep location and proximity to cranial nerves and endovascular treatment is complicated due to the often tortuous anatomy of the PICA and its small diameter. The purpose of this study is to report our experience with the endovascular treatment of aneurysms at the origin of the PICA. METHODS: Consecutive patients with aneurysms at the origin of the PICA who were endovascularly treated at our department were identified from our registry of neuro-angiographies. Clinical, angiographic, and treatment data were analyzed. Endpoints included successful occlusion and recurrence. RESULTS: Twenty-nine patients were included. 79.3% of the aneurysms were wide-neck with a dome-to-neck ratio <2.65.5% of all endovascular procedures were performed by coiling alone. The procedural rupture rate was 18.75% for endovascularly treated aneurysms presenting with subarachnoid hemorrhage (SAH). Successful embolization was achieved non-significantly more often in the coiling-only group (94.7% vs. 70%, P = 0.066). Aneurysm recurrence after successful occlusion was observed in one case. CONCLUSIONS: Though aneurysm and parent vessel characteristics were challenging successful occlusion was achieved in a high rate of treatments, often with standalone coiling. Adjunctive techniques like retrograde stenting seem promising to further enhance endovascular results. Interestingly aneurysms arising solely from the origin of the PICA without the V4-segment involved presented with SAH significantly more often and wide-neck aneurysms presenting with SAH had a significantly higher periinterventional rupture rate.

Microsurgical Anatomy of the Cerebellar Interpeduncular Entry Zones.

OBJECTIVE: The cerebellar interpeduncular region, particularly the middle cerebellar peduncle (MCP) and interpeduncular sulcus (IPS) are significant surgical relevance areas due to the high prevalence of vascular and tumoral pathologies, such as cavernomas, arteriovenous malformations, and gliomas. We defined safer access areas of the MCP and the IPS, according to the surface anatomy, involved vessels, and fiber tracts of the cerebellar interpeduncular region. METHODS: Fifteen formalin-fixed and silicone-injected cadaveric heads and 23 human brainstems with attached cerebellums prepared with the Klingler's technique were bilaterally dissected to study the vascular and intrinsic anatomy. RESULTS: Surface anatomy: The mean length of the IPS was 12.73 mm (standard deviation [SD],2.15 mm), and the average measured angle formed by the IPS and the lateral mesencephalic sulcus was 144.53°. The mean distance from the uppermost point of the IPS to cranial nerve IV was 2.63 mm (SD, 2.84 mm). Vascular anatomy: The perforating branches of the superior cerebellar peduncle, IPS, and MCP originated predominantly from the caudal trunk of the superior cerebellar artery. The inferior third of the superior cerebellar peduncle and IPS was the third most pierced by perforating arteries, and for the MCP, was its superior third. Crossing vessels: The branches of the pontotrigeminal vein and the caudal trunk of the superior cerebellar artery crossed the IPS mostly. The superior third of the IPS was the most crossed by arteries and veins. CONCLUSIONS: The middle thirds of the IPS and MCP as entry zones might be safer than their superior and inferior thirds due to fewer perforating branches, arterial trunks, and veins crossing the sulcus as fewer eloquent tracts.

Infarto cerebeloso bilateral agudo en territorio de la arteria cerebelosa posterior inferior: reporte de caso / Acute bilateral cerebellar infarction in territory of the posterior inferior cerebellar artery: a case report

Antecedentes: Los infartos cerebelosos suponen una entidad rara con una incidencia baja del total de ictus isquémicos. El territorio más prevalente de los infartos cerebelosos son los de la arteria cerebelosa posterior inferior (PICA). Cuando los infartos se limitan al cerebelo, los pacientes típicamente experimentan síntomas no específicos, esto hace considerar otros diagnósticos de forma errónea. Descripción del caso clínico: paciente femenina de 54 años, con antecedente de hipertensión arterial, quien presentaba cefalea insidiosa y progresiva acompañado de vértigo, alteración en la marcha y deterioro progresivo del estado de conciencia. Se realizó imagen de Resonancia Magnética Cerebral (IRM), la cual reveló zonas hiper intensas bilaterales en región cerebelosa que delimitaban territorio vascular de la arteria cerebelosa posterior inferior además dilatación moderada del sistema ventricular. Fue intervenida quirúrgicamente, realizándose craniectomía suboccipital descompresiva; posterior a la cirugía presentó mejoría clínica. Conclusiones: El ictus isquémico cerebeloso bilateral es una forma infrecuente de ictus y su presentación clínica es muy diversa. El desarrollo de las neuroimágenes, juegan un papel importante para ayudar a los médicos a seleccionar el tratamiento adecuado. Alrededor de la mitad de los pacientes con infartos cerebelosos que presentan deterioro neurológico progresivo y son tratados con craniectomía suboccipital descompresiva tienen buenos resultados. El pilar fundamental de este caso fue el hacer un diagnóstico temprano de esta entidad, ya que permitió prevenir las posibles complicaciones graves asociadas al infarto cerebeloso, las cuales ocurren durante la primera semana del ictus y, por lo tanto, asegurar un pronóstico favorable para el paciente...(AU)

Endovascular treatment of posterior inferior cerebellar artery trunk aneurysm.

BACKGROUND: The posterior inferior cerebellar artery (PICA) generally originates from the vertebral artery (VA) and is the most complex cerebellar artery. Aneurysms can occur at any site along the PICA trunk. Although most PICA aneurysms are located at the VA-PICA junction, a small proportion is located at the PICA trunk. Endovascular treatment (EVT) of aneurysms in the PICA trunk may be difficult and complex. METHODS: We performed a review to expound upon EVT of PICA trunk aneurysms. RESULTS: The PICA can be divided into five segments (p1-5); the p1-3 segments are proximal segments, and the p4-5 segments are distal segments. Most PICA trunk aneurysms are dissecting aneurysms. Sometimes, the PICA can give rise to flow-related aneurysms in association with cerebellar arteriovenous malformations. Most aneurysms of the PICA trunk require aggressive treatment, especially those that have ruptured. Currently, the EVT mainly includes selective coiling with/without stent assistance and parent artery occlusion. Recently, some new devices, such as flow diversion and Barricade and Kaneka ED coils, can be used to treat PICA trunk aneurysms. The risk of complications with EVT seems to be higher; however, most complications are only transient or mild, and some are even clinically silent. In addition, open surgery is still an important option. CONCLUSION: For PICA trunk aneurysms, the treatment choice should be assessed on a case-by-case basis. The rate of permanent morbidity of the EVT is low. EVT is an effective method for treating PICA trunk aneurysms.

Mechanical Embolectomy for Superior Cerebellar Artery Embolism.

ABSTRACT: Acute embolism of the superior cerebellar artery is rarely reported. The treatment is mainly medication, decompressive craniectomy is performed when necessary, and mechanical thrombus removal is not recommended. This article describes the admission of a 69-year-old man with acute superior cerebellar artery embolization. Compared with the imaging data of the patient 2 weeks before the onset of the disease, cerebral angiography revealed that there was a mural thrombus covering the opening of the superior cerebellar artery. it is also a bold attempt for this patient to undergo mechanical thrombectomy. The patient finally recovered well from neurological symptoms. This case report details the causes of the rare mural thrombosis leading to superior cerebellar artery embolism, and also has a new understanding of arterial embolism in acute stroke.

Microsurgical Treatment of Vertebral Artery Dissection: Surgical Strategies and Treatment Outcomes.

BACKGROUND: Vertebral artery dissection (VAD) is a rare cerebrovascular disease that can lead to permanent morbidity or mortality. Open surgery for VAD is challenging; therefore, most cases are managed via endovascular techniques. There are several surgical methods for VAD treatment, including trapping or proximal occlusion with or without bypass; however, the standard treatment protocol is not well established. The aims of this study were to demonstrate surgical strategies, surgical outcomes, and complications of each method and to propose an algorithm to select the appropriate procedure. METHODS: This study included 22 patients with VAD who underwent open surgical treatment between January 2015 and December 2019 and were retrospectively reviewed and evaluated for postoperative outcomes and complications. RESULTS: Proximal occlusion, trapping, occipital artery-posterior inferior cerebellar artery (PICA) bypass with blind-alley formation, and occipital artery-PICA with trapping were performed in 13, 2, 5, and 2 patients. The surgical procedure depended on the type of VAD: pre-PICA, PICA, post-PICA, and non-PICA. All VADs were completely obliterated after surgery. Obliteration occurred immediately for 18 patients (81.8%) and within 1 week for 4 patients (18.2%). There was no postoperative bleeding or PICA infarction. Favorable outcome at 3 months after operation was achieved in 100% for good-grade patients and 86.4% overall. CONCLUSIONS: Open surgery can be a safe and effective treatment of VAD when surgical strategies are carefully selected. Angioarchitecture and the type of VAD influence the selection of the surgical method.

Culprit vascular patterns and surgical outcomes of hemifacial spasm caused by an AICA segment passing between cranial nerve VII and VIII: A series of 25 cases.

OBJECTIVE: To report the vascular anatomic characteristics and surgical outcomes of hemifacial spasm (HFS) caused by an anterior inferior cerebellar artery (AICA) segment passing between cranial nerve VII (CN VII) and cranial nerve VIII (CN VIII). PATIENTS AND METHODS: This case series study retrospectively reviewed records of 1040 consecutive patients treated with MVD for HFS in our hospital in 10 years. 25 patients had the culprit vessel recorded as an AICA segment passing between CN VII and CN VIII. Vascular anatomic characteristics were reviewed from intraoperative microscopic videos. The clinical outcomes were followed up at 3-month and 1-year time points. RESULTS: The culprit AICA segments feature 3 discrete anatomic patterns. The patterns denoted as pattern A, B, and C were identified in 19(76%), 3(12%), and 3 (12%) of the 25 patients respectively. Postoperative spasm relief were achieved in 19(76%), 22(88%), and 23 (92%) of the patients at immediately after surgery, 3-month, and 1-year follow-up respectively. 3(12%) of them have permanent postoperative cranial nerve deficits, including one patient with hearing loss and 2 patients with vocal cord palsy. CONCLUSIONS: Though an AICA segment passing between CN VII and CN VIII is common, very rarely it was deemed the culprit for HFS in our patients. We used fREZ centered definition and operation. We found the culprit AICA segments feature 3 discrete anatomic patterns. We observed good spasm relief outcome and relatively fewer complications with CN VII and CN VIII. Identifying the 3 anatomic patterns may help with a smooth decision-making when vascular compression by an AICA segment passing between CN VII and CN VIII is suspected.