Anterior Inferior Cerebellar Research Articles

Use of indocyanine green angiography during endoscopic microvascular decompression for trigeminal neuralgia

BackgroundThe aim of this study was to assess the efficacy of indocyanine green (ICG) angiography during full endoscopic microvascular decompression for trigeminal neuralgia. MethodsWe extracted retrospective data of patients who received ICG videoangiography during full endoscopic microvascular decompression for trigeminal neuralgia. Preoperative neurovascular contact was evaluated by three-dimensional (3D) fusion images using image analysis software Ziostation2 (ZIOSOFT, Tokyo, Japan) and Intraoperative ICG angiography was used in pre and post ICG injection to identify and assess blood flow in the offending vessel for adequate transposition planification and assess for immediate post transposition blood flow or vasospasm respectively. Patients were assessed the next morning for early signs of brainstem infarction and at one month follow up. ResultsThere were 44 patients. All patients had ICG videoangiography done during the procedure. The mean age was 65.5 and male female ratio 3.4:1. Some anatomical variants were identified during this procedure. Five patients (11.3%) had a trigeminocerebellar artery, three patients (6.8%) had a developed superior petrosal vein and one patient (2.2%) had dural adhesions with encasement of anterior inferior cerebellar artery. Among the 44 patients enrolled, 34 had transposition done and 10 had combined transposition either with neurolysis or Teflon interposition. The main offending vessel was Superior cerebellar artery (SCA) in 23 patients (67.6%). In 5 (14.7%) of 34 patients who underwent Transposition, vasospasm was seen and no complications were observed in all patients but 93.1% had good pain control in postoperative. ConclusionICG angiography in endoscopic microvascular decompression is safe and effective in depicting the offending vessel, its branches and some perforators and contributes significantly to the determination of treatment strategy.

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

Anterior inferior cerebellar artery (AICA) aneurysms present a challenge for neurosurgeons and neurointerventionalists alike. Cases of AICA aneurysms managed with endovascular flow diversion at our institute are reviewed with their angiographic outcomes. 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. 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.

Sudden Sensorineural Hearing Loss from a Jugular Bulb Diverticulum

A 19-year-old woman presented with an 11-month history of sudden-onset left sided hearing loss accompanied by vertigo and headache. Audiometric testing revealed profound left- sided hearing loss. A contrast-enhanced MRI of the internal auditory canal performed 5 months after symptom onset was interpreted as showing a vascular loop, probably the anterior inferior cerebellar artery, abutting and indenting on the left vestibulocochlear nerve; and a prominent and high-riding left jugular bulb. In this study, the internal auditory canals were assessed to be of normal width, with walls that were smooth and sharply defined. A cerebral CT angiogram subsequently performed did not show any abnormal findings related to the previously identified vascular loop. On the basis of these radiologic findings, the patient was advised surgery by physicians at a tertiary- care institution, presumably to address the identified vascular loop. A second opinion was sought by the patient.
 Review of the MRI initially focused on the axial high-resolution T2-weighted sequence (T2-DRIVE), as the fast spin-echo T2-weighted sequence has been recommended as a reliable and cost-effective MR screening protocol for the detection of masses in the IAC.1 In contrast to the official radiology report, stenosis of the left internal auditory canal by a protrusion (Figure 1, white asterisk) originating from the posteromedial wall of the internal auditory canal was noted. This protrusion, which had no MR signal intensity, appeared to abut and compress the cranial nerves within the IAC. Reconstruction of the images in non-orthogonal planes aligned with the orientation and direction of the left 8th cranial nerve showed the protrusion causing upward compression on and distortion of the nerve. (Figure 2, white arrows)
 Attention was directed to the axial high-resolution T1-weighted sequence (T1W-3D FFE), which revealed that the protrusion contained an isointense soft tissue structure (Figure 3, white asterisk) located within the petrous bone medial to the posterior semicircular canal. This structure appeared to be an upward extension of the jugular bulb.
 The axial high-resolution contrast-enhanced T1-weighted sequence (T1W-3D TFE Gd) showed smooth, vivid enhancement of the identified structure (Figure 4, black asterisk), which connected with the sigmoid sinus in lower cuts. This confirmed the presence of a high-riding jugular bulb that encroached on the internal auditory canal.
 Any doubt as to its true nature was dispelled by a review of the temporal bone structures on high-resolution CT which was fortunately available in the cerebral CT angiogram. This revealed a protrusion of the high-riding jugular bulb with a waist-like margin (Figure 5A and B, black arrows), allowing further characterization of the lesion as a jugular bulb diverticulum.2
 A high-riding jugular bulb that projects into the middle ear is not an uncommon anatomic variation. On the other hand, a jugular bulb diverticulum, which is an outpouching of the jugular bulb that can extend superiorly, medially, and posteriorly in the petrous bone, is a true venous anomaly that has been described rarely in the medical literature.3,4 When symptomatic, patients with this anomaly can present with sensorineural hearing loss, tinnitus, vertigo and auricular pain.3-5 Proper identification of a jugular bulb diverticulum in the evaluation of a patient with neurotologic symptoms is necessary to avoid inappropriate medical and surgical intervention.
 As demonstrated in this patient, a jugular bulb diverticulum may not be identified by a screening MRI that utilizes only a T2-weighted sequence. T1-weighted MRI sequences with and without contrast are necessary to demonstrate its soft tissue imaging characteristics. Although not the initial imaging study of choice for sudden sensorineural hearing loss, high-resolution bone-window CT may be necessary to delineate the bony anatomy of the jugular foramen and confirm the presence of this anomaly.

Persistent trigeminal artery variant and presumed ophthalmic artery simultaneously arising from the inferolateral trunk incidentally diagnosed by magnetic resonance angiography.

To describe a case of persistent trigeminal artery variant (PTAV) and presumed ophthalmic artery (OA) simultaneously arising from the inferolateral trunk (ILT). A 53-year-old woman with an initial episode of convulsion underwent cranial magnetic resonance imaging (MRI) and MR angiography (MRA) of the intracranial region for the evaluation of brain and vascular lesions. The MR machine was a 3-T scanner. MRI revealed no pathological brain lesions. On MRA, the left anterior inferior cerebellar artery (AICA) arose from the cavernous segment of the internal carotid artery (ICA), indicative of the PTAV. The arising point was more distal than the usual point, and the presumed OA also arose simultaneously from the short common trunk, which was considered the ILT. There are two types of PTA: lateral (usual) and medial (intrasellar) PTA. The lateral-type PTA and PTAV arise from the ICA of the distal precavernous-proximal cavernous segment and take a course similar to that of the posterior fossa. The medial type arises slightly more in the distal cavernous segment than in the lateral type. The OA rarely arises from the cavernous segment of the ICA and enters the orbit via the superior orbital fissure. The origin of this type of OA is considered to be the ILT. We herein report a case of a PTAV and presumed OA arising simultaneously from an ILT. No similar case has been reported in the relevant English language literature.

Abstract 170: Flow Diversion for Distal Aneurysms of the Posterior Circulation: A Multicenter Retrospective Study

Introduction Flow diversion (FD) has emerged as an effective treatment option for intracranial aneurysms (IAs). However, there is limited evidence regarding its safety and efficacy specifically for distal aneurysms of the posterior circulation including posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), superior cerebellar artery (SCA), and the P2 and P3 segment of the posterior cerebral artery (PCA). This study aimed to investigate the outcomes of FD for these aneurysms. Methods A retrospective analysis of a multicentric observational registry was performed between 2014 and 2022. Patients harboring distal aneurysms of the posterior circulation including the PICA, AICA, SCA, and PCA P2‐3 treated with FD were included. Aneurysms characteristics and outcomes were calculated for the total series and a comparison was performed between fusiform/dissecting versus saccular aneurysms. The primary outcome was complete occlusion at last imaging follow up which was defined as per the Raymond Roy occlusion scale. Additional outcomes included the retreatment rate, and thromboembolic and hemorrhagic complications Results Overall, 36 patients with 36 aneurysms were treated with FD with a median age in years of 60.0 (interquartile range [IQR]: 52.8‐65.3 years). Of those, 13 were fusiform/dissecting while 23 were saccular IAs. Complete occlusion was achieved in 78.1% for all IAs at a median follow‐up of 14.0 months (IQR: 9.3‐48.6 months). There was no significant difference in rates of complete occlusion between fusiform/dissecting (91.7%) and saccular aneurysms (70%, p=0.151). Thromboembolic and hemorrhagic complications were observed in four cases (11.1%), and retreatment was required for four IAs (11.4%). There was no significant difference in rates of thromboembolic and hemorrhagic complications, or retreatment between fusiform/dissecting and saccular IAs Conclusion This study suggests the safety and efficacy of FD for distal aneurysms of the posterior circulation. Further larger‐scale studies are warranted to confirm these findings and to explore the long‐term safety and efficacy of FD in this specific aneurysm population.

Early detection of stroke at the sudden sensorineural hearing loss stage.

Sudden sensorineural hearing loss (SSNHL) can be a prodromal symptom of ischemic stroke, especially posterior circulation strokes in the anterior inferior cerebellar artery (AICA) area. Early diagnosis and optimal treatment for vascular SSNHL provide an opportunity to prevent more extensive area infarction. The objective of our research was to find clues that suggest stroke at the stage of isolated sudden hearing loss. We retrospectively investigated the medical records of patients who received an initial diagnosis of sudden sensorineural hearing loss upon admission from January 2017 to December 2022 at Capital Medical University Affiliated Beijing Tiantan Hospital. Among these patients, 30 individuals who developed acute ischemic stroke during their hospital stay were enrolled as the case group. To create a control group, we matched individuals from the nonstroke idiopathic SSNHL patients to the case group in terms of age (±3 years old) at a ratio of 1:4. We collected the clinical characteristics, pure tone hearing threshold test results, and imaging information for all patients included in the study. Three models were constructed to simulate different clinical situations and to identify vascular sudden sensorineural hearing loss (SSNHL). The results revealed that patients with SSNHL who had three or more stroke risk factors, bilateral hearing loss, moderately severe to total hearing loss, and any intracranial large artery stenosis and occlusion (≥50%) were at a higher risk of developing ischemic stroke during hospitalization. Consistent with previous studies, the presence of vertigo at onset also played a significant role in the early detection of upcoming stroke. Clinicians should be alert to SSNHL patients with bilateral hearing loss, moderately severe to total hearing loss and other aforementioned features. Early pure tone audiometric hearing assessment and vascular assessment are necessary for high-risk patients with SSNHL.

Improving the depiction of small intracranial vessels in head computed tomography angiography: a comparative analysis of deep learning reconstruction and hybrid iterative reconstruction.

This study aimed to evaluate the ability of deep learning reconstruction (DLR) compared to that of hybrid iterative reconstruction (IR) to depict small vessels on computed tomography (CT). DLR and two types of hybrid IRs were used for image reconstruction. The target vessels were the basilar artery (BA), superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA). The peak value, ΔCT values defined as the difference between the peak value and background, and full width at half maximum (FWHM), were obtained from the profile curves. In all target vessels, the peak and ΔCT values of DLR were significantly higher than those of the two types of hybrid IR (p < 0.001). Compared to that associated with hybrid IR, the FWHM of DLR was significantly lower in the SCA (p < 0.001), AICA (p < 0.001), and PICA (p < 0.001). In conclusion, DLR has the potential to improve visualization of small vessels.

Anterior Inferior Cerebellar Artery Aneurysm in Internal Auditory Canal: A Case of Hemorrhage Caused by Misdiagnosis.

Anterior Inferior Cerebellar Artery Aneurysm in Internal Auditory Canal: A Case of Hemorrhage Caused by Misdiagnosis.

Microvascular decompression for hemifacial spasm: Complications after 292 procedures without neurophysiological monitoring.

Hemifacial spasm (HFS) is characterized by involuntary, progressive, and intermittent spasms in the upper and lower facial muscles. Due to the high success rate, microvascular decompression (MVD) is the treatment of choice, and intraoperative neuromonitoring (INM) is considered useful for achieving safe surgery. Still, most centers do not have this technology. We analyzed 294 patients with HFS treated with MVD without INM. We only included patients with a neurovascular etiology while excluding other causes, such as tumors. As part of the postoperative evaluation, we assessed preoperative magnetic resonance imaging and pure-tone audiometry. The main complication was peripheral facial paralysis in 50 patients, followed by hypoacusis in 22 patients and deafness in 17 patients, associated with a failed surgical outcome (P = 0.0002). The anterior inferior cerebellar artery (AICA) was an offending vessel, and the involvement of more than one vessel was significantly associated with the development of facial nerve palsy (P = 0.01). AICA was also associated with hearing impairment (P = 0.04). Over 90% of immediate complications improve in the follow-up (6 months), and one patient did not show a cure for initial HFS. MVD is the method with the highest long-term cure rates for treating HFS; however, we must inquire into the multiple factors of the patient and the surgeon to predict surgical outcomes. INM is not a must during MVD for HFS. We recommend its use depending on the availability and mainly on the surgeon's skills, for surgeons.

A Case of Anterior Inferior Cerebellar Artery Syndrome Accompanied by Polycythemia Presenting Vertigo and Hearing Loss as Initial Symptoms

A Case of Anterior Inferior Cerebellar Artery Syndrome Accompanied by Polycythemia Presenting Vertigo and Hearing Loss as Initial Symptoms

Anatomic Variants in the Anterior Inferior Cerebellar Artery Encountered During Resection of Vestibular Schwannomas.

Vestibular schwannomas (VS) are often phenotypically benign lesions that may be technically challenging to resect because of involvement of neurovascular structures. The anterior inferior cerebellar artery (AICA) is commonly identified near VS, with variable position in relation to the tumor; however, little published literature describes anatomic and pathologic variants of AICA observed during VS resection. A prospectively maintained cohort of surgically managed VS with available operative reports and clinical/radiographic follow-up was queried and reviewed for noted aberrations. We identified 66 cases with noted AICA abnormalities among 880 reviewer cases, including 20 loops extending into the internal auditory canal (2.3%), 18 arteries embedded in dura (2.0%), 15 AICA branches directly within VS (1.7%), 8 main trunk arteries coursing between cranial nerves 7 and 8 (0.9%), 3 arteries embedded in temporal bone (0.2%), 1 aneurysm (0.1%), and 1 artery bifurcating cranial nerve 6 (0.1%). The median age of AICA-variant patients was 55 years (range 19-74), and 29 were female (45%). Compared with the other AICA variants, tumors embedded with AICA tended to be larger lesions on maximal axial diameter (2.9 vs 1.6 cm; P = .006), they more commonly underwent less than total resection (73% vs 28%; P = .0001), and they had higher rates postoperative House-Brackmann scores >2 (47% vs 20%; P = .005). Two patients had radiographic and symptomatic postoperative cerebral ischemia or hemorrhage-1 from a bone-encased AICA and 1 from a dural embedded variant. Anatomic variants of AICA occur in approximately 7% of VS operations. Most aberrations do not affect surgical or clinical outcomes, and the rate of major vascular injury was low. However, certain types variably add operative time and in the case of AICA encasement in the tumor, likely indicate a more aggressive tumor phenotype with lower rates of gross total resection and high incidences of facial nerve weakness.

Meckel’s cave compression with Teflon for the treatment of idiopathic trigeminal neuralgia: its possibility as a modified surgical technique

Objective: We analyzed the clinical outcomes of Meckel’s cave compression with Teflon (Rhee’s method) as a new modified and additional surgical technique for trigeminal neuralgia (TN).Methods: Between March 1996 and December 2014, out of 78 patients who were treated with microvascular decompression (MVD) or partial sensory root rhizotomy, 28 patients additionally underwent Meckel’s cave compression with Teflon. The mean age at initial treatment was 54.3 years (range: 40–69 years). The mean duration from onset to operation was 70.5 months (range: 5–360 months) and the mean follow-up period was 26 months (range: 1–77 months). Results: Fifteen patients (53.6%) had facial pain in the V2/V3 distribution. The offending or associating vessel was the superior cerebellar artery in four patients (14.3%), the superior petrosal vein in six (21.4%), the anterior inferior cerebellar artery in two (7.1%), multiple vessels in nine (32.1%), and miscellaneous arteries or veins in six (21.4%). One patient (3.6%) had no offending vessel, and seven patients were had no definite offending vessels that contacted the trigeminal root entry zone. Meckel’s cave compression with Teflon was applied to all patients: 10 (35.7%) in combination with MVD, one (3.6%) with partial rhizotomy, and 17 (60.7%) with both MVD and partial rhizotomy. TN was relieved in 26 patients (92.9%) and symptoms recurred in three patients (pain-free rate: 82.1%). The complication rate of this method appeared to be similar to other treatment procedures. Conclusion: Meckel’s cave compression with Teflon may be a safe and useful additional treatment procedure for TN.

A review of acute ischemic stroke caused by distal, medium vessel occlusions.

Acute ischemic stroke (AIS) due to distal, medium vessel occlusion (DMVO) is increasingly recognized as the next frontier for mechanical thrombectomy. Distal, medium vessel occlusions are typically defined as an occlusion in the following arteries: anterior cerebral artery, M2-M4 segments of the middle cerebral artery, posterior cerebral artery, posterior inferior cerebellar artery, anterior inferior cerebellar artery, and superior cerebellar artery. It is estimated that 25-40% of all AIS is due to DMVO. Because of the large burden of DMVO, the frequency of literature published regarding these occlusions has greatly increased in recent years. Furthermore, treatment modalities have been created specifically for DMVOs. Due to the rapidly evolving literature on this topic, remaining up to date on DMVO definitions, anatomy, management, imaging, and clinical course is difficult. In this review article, we synthesized existing literature regarding the aforementioned topics and discussed future directions.

Management of a challenging dura-embedded anterior inferior cerebellar artery loop during a retrosigmoid hearing-preserving vestibular schwannoma resection: microsurgical technique and operative video. Illustrative case.

Anatomical variants of the anterior inferior cerebellar artery (AICA), such as an anomalous "AICA loop" embedded in the dura and bone of the subarcuate fossa, increase the complexity and risk of vestibular schwannoma resections. Classically, osseous penetrating AICA loops are the most challenging to mobilize, as the dura must be dissected and the surrounding petrous bone must be drilled to mobilize the AICA away from the surgical corridor and out of harm. The authors present a rare case of a dura-embedded, osseous-penetrating AICA loop encountered during a hearing-preserving retrosigmoid approach in which they demonstrate safe and efficient microdissection and mobilization of the AICA loop without having to drill the surrounding bone. Although preoperative recognition of potentially dangerous AICA loops has been challenging, thin-sliced petrous bone computed tomography scanning and high-quality magnetic resonance imaging can be useful in preoperative diagnosis. Furthermore, this report suggests that a retrosigmoid approach is superior, as it allows early intradural recognition and proximal vascular control and facilitates more versatile mobilization of AICA loops.

Anterior inferior cerebellar artery (AICA) aneurysms: a radiological study of 15 consecutive patients.

The aneurysms of the anterior inferior cerebellar artery (AICA) are rare lesions of the posterior circulation and to treat them is challenging. We aim to present anatomical and morphological characteristics of AICA aneurysms in a series of 15 patients. The DSA and CT angiography images of AICA aneurysms in 15 consecutive patients were analyzed retrospectively. Different anatomical characteristics were quantified, including morphology, location, width, neck width, length, bottleneck factor, and aspect ratio. Eighty percent of the patients were females. The age was 52.4 ± 9.6 (mean ± SD) years. 11 patients were smokers. Ten patients had a saccular aneurysm and five patients had a fusiform aneurysm. Aneurysm in 10 patients were located in the proximal segment, in three patients in the meatal segment, and in two patients in the distal segment. Ten out of 15 patients presented with a ruptured aneurysm. The size of AICA aneurysms was 14.8 ± 18.9 mm (mean ± SD). The aspect ratio was 0.92 ± 0.47 (mean ± SD) and bottleneck factor was 1.66 ± 1.65 (mean ± SD). AICA aneurysms are rare lesions of posterior circulation predominantly found in females, present predominantly with subarachnoid hemorrhage, and are mostly large in size.

Perioperative Management and Anesthesia in Patients with Hemifacial Spasm Undergoing Microvascular Decompression: A Case Report

Introduction: Microvascular decompression (MVD) is an operation performed to treat a symptom of hemifacial spasm. Hemifacial spasm is described as a disorder of neuromuscular movement characterized by repeated to persistent involuntary contractions affecting the muscles innervated by the facial nerve.&#x0D; Case presentation: A 33-year-old woman came to consciousness with complaints of twitching on the right side of her face since 1 year ago. Initially, the complaint was felt for the first time 3 years ago, only on the upper right eyelid, but it has been getting worse over the past year. Magnetic resonance imaging (MRI) was obtained vascular loop on the right anterior inferior cerebellar artery (AICA) in level cerebellar pontine angle (CPA). MVD is a unilateral neurosurgical procedure in the axial section of the posterior fossa. Positions that can be used are supine and modified lateral decubitus or park bench. The management of anesthesia-related to posterior fossa surgery includes, first, the effect of the drug on the ability of the lungs to hold air from entering the venous circulation. Intravenous administration of anesthetics, for example, fentanyl, can maintain a higher threshold for retaining air bubbles in the pulmonary circulation compared with inhalational anesthetics.&#x0D; Conclusion: Optimal hemodynamic monitoring, good analgesia, and adequate muscle relaxation are the principles of anesthesia monitoring that aim to facilitate the operator in finding access to the disturbed nerve complex.

Location of the AICA influences the severity but not occurrence of ISSNHL: A reappraisal using high-resolution 3 T MRI

ObjectiveTo investigate the potential influence of anatomical variation in the anterior inferior cerebellar artery (AICA) on the occurrence and severity of idiopathic sudden sensorineural hearing loss (ISSNHL). MethodsNinety ISSNHL patients were enrolled. The anatomical location of the AICA was exhibited using high-resolution magnetic resonance imaging (MRI), and the various AICA types classified by previously reported Chavda and Gorrie methods were analyzed. The severity of hearing loss in the ipsilateral ear among different AICA types was compared. ResultsApproximately 85.6% of subjects had unilateral ISSNHL (uISSNHL), and the others had bilateral ISSNHL (bISSNHL). In the uISSNHL group, the ratios of different AICA types were similar between the ipsilateral and contralateral ears. The ratios of the different AICA types in the bISSNHL group were similar to those in the uISSNHL group. In the uISSNHL group, pure tone audiometry (PTA) thresholds at 2 kHz, 4 kHz and 8 kHz of patients with Chavda type II AICA were higher than those of patients with Chavda type I and type III, with a significant difference at 4 kHz between type I and type II. There was a tendency of the PTA threshold in patients with Chavda type II or Gorrie type C to gradually increase from low to high frequency zones. ConclusionWhen the AICA enters the IAC (Chavda type II) or crosses between the 7th and 8th cranial nerves (Gorrie type C), the severity and frequency of hearing impairment in ISSNHL but not the occurrence of ISSNHL will be affected.

Anatomy of the pontine arteries and perforators of the basilar artery in humans.

Cerebral blood flow constitutes a critical area of interest for neurologists, neurosurgeons, and interventional radiologists as a social burden related to ischemic stroke, hemorrhagic stroke, and vascular dementia is expected to intensify. There is a great need to develop new and effective therapies, therefore deepening understanding of cerebrovascular anatomy, physiology, and pathology is crucial. The main aim of the study was to develop a comprehensive classification of the pontine arteries considering their typology, relations to the cranial nerves, branching schemes, and superficial pontine blood supply areas. We prepared 100 anatomical specimens of the human brainstem with the basilar artery, the pontine arteries, and the terminal perforating arteries. With the use of microsurgical microscope, we analyzed morphometry of the basilar artery, origins, courses, and branching patterns of the pontine arteries as well as distribution of the terminal perforators in relation to pontine superficial vascular areas and the cranial nerves. Additionally, we studied presence of pontine branches of the superior cerebellar artery (SCA) and anterior inferior cerebellar artery (AICA). Repetitive branching patterns, origins, and courses led us to distinguish five types of the pontine arteries: type 1-the paramedian branches, type 2-the short circumflex branches, type 3-composition of the paramedian and the short circumflex branches, type 4-long circumflex branches, and type 5-median branches penetrating the pons along the basilar sulcus. Types 1, 2, and 4 were described in the literature previously, but the classification did not include the median branches (the most prevalent branches) and frequently occurring combinations of the types 1 and 2. There were seven pontine arteries on both sides on average that presented the following general pattern: the first pontine artery below the SCA is a type 4 vessel called the posterolateral pontine artery and it is followed by a type 2 vessel-the superolateral pontine artery; the next three arteries represent the types 1, 2, and 3 and supply most of the ventral pontine surface; the sixth artery-the anterolateral pontine artery-is a short circumflex branch and the seventh artery, originating below the AICA, represents long circumflex arteries. Occlusion of each of the abovementioned vessels relates to a specific pontine vascular syndrome. As explained by the phylogenesis and ontogenesis of the central nervous system, the pontine arteries are subject to variability. The SCA and the AICA took part in the pontine blood supply in 2.5% and 12.5% of cases, respectively, therefore neurovascular interventions involving the SCA, or the AICA may lead to pontine ischemia. Contact of the pontine arteries with the cranial nerves depends on the vessel type and origin location.

Predictors of Multi‐Vessel Identification, Outcome, and Optimal Surgical Timing for Microvascular Decompression in Hemifacial Spasm

Objectives and BackgroundHemifacial spasm (HFS) is a disabling condition that imposes significant burden upon patients. Microvascular decompression (MVD) surgery is the most effective and long-lasting treatment for HFS, but outcomes following this surgery may vary based on a variety of clinical and operative factors. A more thorough understanding of the variables that impact patient outcome after MVD surgery is needed. MethodsA systematic review and meta-analysis of Medline, Embase, and Central was conducted (n = 2108 screened; n = 86 included) with the goal of determining the impact of the following variables on outcome: duration of disease, geographic location, intraoperative use of an endoscope, and intraoperative finding of single versus multi-vessel neurovascular compression. ResultsMost cases of hemifacial spasm occur on the left side (53.9%, p < 0.001) and are more common in women than men (66.5% versus 33.5%, p < 0.0001). The offending vessel frequencies were: 40.8% anterior inferior cerebellar artery [AICA], 24.9% posterior inferior cerebellar artery [PICA], 17.2% multiple vessels, and 4.7% vertebral artery [VA]. Multiple vessel combinations involved: 26.5% PICA + AICA, 24.6% PICA + VA, 23.1% AICA + VA, and 4.7% AICA + PICA + VA. Relative to the Americas, AICA was less frequent in Europe (p = 0.005), while PICA more frequent in Europe (p = 0.009) and Asia (p < 0.0001). With endoscope assistance, frequency of multiple vessels identified was 31.7% (versus 14.7% with non-endoscopic, p = 0.005), and 27.4% for AICA (43.5% with non-endoscopic, p = 0.003). Spasm improvement was 94.1% near discharge and 96.0% at maximum follow-up. Complications occurred in 16.5% of cases, with spasm recurrence in 2.4%. Greatest frequency of spasm improvement (p < 0.0001) and lowest spasm recurrence rates (p = 0.0005) were reported in series from Asia. For every additional month of pre-operative spasm, the effect size of post-operative improvement decreased (p = 0.04). With every subsequent postoperative month, the effect size of spasm improvement increased (p = 0.0497). The frequency of spasm improvement was significantly higher in series published after 2005 (94.4% versus 97.4%, p = 0.005). ConclusionClinical outcomes following MVD for HFS have improved since 2005. Consideration should be given to earlier operation (shorter disease duration) and use of an endoscope may increase detection of multiple offending vessels. Further studies are needed to understand regional differences in culprit vessel incidence and surgical outcomes in the Americas, Europe, and Asia.

Neurovascular Conflict Causing Isolated 6th Nerve Palsy

There are many intracranial pathologies of isolated 6th nerve palsy but neurovascular conflicts causing isolated 6th nerve palsy is very rare condition. We present a case of isolated abducens nerve palsy due to neurovascular conflicts caused by indentation and mass effect from left vertebral artery and left anterior inferior cerebellar artery (AICA) loop on the left VI cranial nerve.