Vascular loop in the cerebellopontine angle: Clinical-radiological correlation.

BACKGROUND: The brainstem, situated in the posterior fossa, connects the brain to the spinal cord. Owing to its location, the nerves of the brainstem are closely related with vascular structures. OBJECTIVES: To correlate the finding of vascular loops in the cerebellopontine angle on imaging with symptoms indicative of vestibulocochlear involvement. MATERIALS AND METHODS: This retrospective descriptive study included all patients evaluated between 2011 and 2017 with findings suggestive of vascular loops in the cerebellopontine angle for whom the clinical history and imaging studies were available. RESULTS: A total of 102 patients (63 women and 39 men) had vestibulocochlear involvement. The most common clinical indication was dizziness (41.18%). A unilateral vascular loop was found in 43 patients (right: 21.57%, left: 20.59%) and bilateral loops were found in 59 (57.84%) patients. The most common type of vascular loop was type II (right: 69.14%; left: 58.75%). The most common origin of vascular loops was the anterior inferior cerebellar artery (right: 66.67%, left: 65.00%). No associations were observed between vascular loops and sensorineural hearing, nystagmus, or vertigo. There was an association with tinnitus. CONCLUSIONS AND SIGNIFICANCE: The presence of vascular loops is not associated with most auditory symptoms. Nevertheless, all findings on imaging studies must be reported. The interpretation of the findings of imaging studies must be correlated with the clinical symptoms after other more common causes that can explain the symptoms have been ruled out.

Trigeminal Neuralgia from Simultaneous Compression by Cerebellopontine Angle Epidermoid and Duplicated Superior Cerebellar Artery Loop: Two-Dimensional Operative Video of Resection and Microvascular Decompression with Endoscopic Assistance.

A 51-year-old woman presented with 2 years of progressive left facial pain and numbness in maxillary nerve and mandibular nerve distributions. Symptoms were refractory to increasing doses of carbamazepine and gabapentin. Magnetic resonance imaging showed a left cerebellopontine angle nonenhancing mass, with diffusion restriction causing trigeminal nerve compression. Fast imaging employing steady-state acquisition sequences revealed a superior cerebellar artery loop in the angle between cranial nerve V and pons. The patient agreed to resection of the mass and microvascular decompression. Retrosigmoid craniotomy was performed with sensory/motor, and facial-auditory nerves' monitoring. The mass was densely adherent to cranial nerves VII-X and the anterior inferior cerebellar artery, causing compression at the root entry zone of the trigeminal nerve. It was carefully dissected off these structures; pathology confirmed an epidermoid. A large bony tubercle obscured visualization; therefore, a 30° endoscope was used. The tubercle was drilled, and remnant portions of the mass were removed. During mobilization of the superior cerebellar artery loop, it was found to be duplicated, and polytef (Teflon) pledgets were placed for microvascular decompression. The trigeminal nerve was thus discovered intraoperatively to be trapped simultaneously between the duplicated superior cerebellar artery loop from above and the epidermoid from below. Pain relief was immediate; at 12-month follow-up, the patient was pain-free, she had minimal numbness around the angle of the lip, and medications were discontinued. Facial nerve function and hearing were intact. A pure endoscopic approach is minimally invasive with a smaller incision and has been described for microvascular decompression for trigeminal neuralgia. Cerebrospinal fluid leak rates are expected to be lower. This technique has a steep learning curve and could pose a significant challenge for resection of lesions densely adherent to neurovascular structures. A pure microscopic approach generally involves a larger incision and can be better suited for resection of cerebellopontine angle lesions where bimanual dissection would be necessary. Visualization around corners in the presence of large bony protuberances (e.g., large suprameatal tubercle) around vessels and nerves in the depths is a drawback. Combining microscopic surgery with endoscopic assistance (especially angled endoscope) negates the disadvantages of either method alone, allowing for visualization around structures in the depths of the cerebellopontine angle where microscope lighting may be reduced, and provides a means to achieve gross total resection of tumor hidden from view.

The Impact of Vascular Loops in the Cerebellopontine Angle on Audio-Vestibular Symptoms: A Systematic Review.

It has been suggested that vascular loops in the cerebellopontine angle and internal auditory canal are involved in the etiology of audio-vestibular symptoms. Several studies have focused on the compression of the eighth cranial nerve by vascular loops but have yielded contradictory results regarding their clinical significance. The aim of this study was to investigate whether vascular loops in this region correlate with audio-vestibular symptoms and which loop features - if any - can potentially lead to symptom manifestation. This systematic review was conducted according to the PRISMA guidelines. We performed on PubMed a literature search from November 2005 to October 2020. The search strategy included the following keywords ("vascular loops" OR "AICA loops" OR "vascular compression syndrome") AND ("hearing loss" OR "tinnitus" OR "vertigo"). Fifteen studies were eligible and included in the analysis. Overall, the studies encompassed a total of 11,788 patients included in this review. The significantly larger group of patients (70%), in which no correlation of symptoms with vascular loops was found, suggests that vascular loops are probably anatomic variations in a substantial majority of cases with an uncommon subset causing some audio-vestibular symptoms. Even within the papers claiming a correlation, there is a multitude of symptoms that did not correlate with vascular loops. It has been suggested by most authors that magnetic resonance imaging should be performed to exclude the role of a vascular loop in the etiology of audio-vestibular symptoms only when vascular compression syndrome is suspected based on clinical indications and not routinely. Further studies would be useful in order to detail the relationship between the vascular structures and the nervous system.

Hemangioblastoma of the Cerebellopontine Angle Evaluated with Pseudocontinuous Arterial Spin Labeling.

Hemangioblastomas of the cerebellopontine angle (CPA) that emerge extra-axially from the peripheral nervous system are extremely rare. We report a case of hemangioblastoma of the CPA evaluated by pseudocontinuous arterial spin labeling (pCASL). The high rate of tumor blood flow determined using pCASL provided additional useful information for the differential diagnosis of the CPA tumors in this patient.

Surgeons' experience of venous risk with CPA surgery.

The study aims to systematize neurosurgeons' practical knowledge of venous sacrifice as applied to the posterior fossa region and to analyze the collected data to present and preserve relevant experience and expert knowledge for current and future practicing neurosurgeons. The venous structures assessed were the superior petrosal vein (SPV), sigmoid sinus (SS), and the tentorial veins (TV). The survey is constructed to obtain surgeons' idea of assessed risk when sacrificing specific venous structures during posterior fossa surgery. They were asked how they prep for surgery, number of operations conducted, and their basis of knowledge. Collected data were mainly qualitative and analyzed with a mixed-method approach. A mean absolute deviation was calculated measuring rate of disagreement for a given substructure. Consensus existed among the participating surgeons that sacrificing the SPV and the TV was considered safe. Although, the risk of death when occluding major structures like the main trunk of the SPV, one of the SS' and or a total occlusion of all TV yielded high risk of death. The risk of infarction was often too apparent to discredit even with low risk of death among an experienced class of surgeons. Our findings provide an overview of surgical risk associated with venous sacrifice. This will minimize cases where indispensable practical knowledge on safe handling veins in the cerebellopontine angle is either to be lost or taught among few when the neurosurgeons retire. This will lower the disagreement regarding risks and increase the quality of surgical decision-making.

Surgical Anatomy of the Labyrinthine and Subarcuate Arteries and Clinical Implications.

OBJECTIVE: To study the surgical anatomy of the labyrinthine artery (LA) and the subarcuate artery (SA), their anatomic relationships, and clinical implications, as injury of the LA can result in hearing loss. METHODS: Ten formalin-fixed, latex-colored specimens were studied (20 sides). After retrosigmoid craniotomy and neurovascular dissection under microscopic magnification, 4-mm 0° and 30° endoscopic lenses were used to improve visualization. Results were statistically analyzed. RESULTS: The LA was a constant artery that followed the vestibulocochlear nerve into the internal auditory canal. The SA was an inconstant artery that ended in the dura mater around the subarcuate fossa in 35% of cases. The LA originated from the anterior inferior cerebellar artery in 89.3% of specimens and from the basilar artery in 10.7% of specimens. The SA branched off from the anterior inferior cerebellar artery when present. The origin of the LA was inferomedial to the vestibulocochlear nerve in most cases (71.4%), whereas the SA was usually lateral (70%). The distal portion of the LA was inferomedial to the vestibulocochlear nerve in 71.4% of cases. The distal portion of the SA was superolateral to the nerve in all cases (P < 0.00001). CONCLUSIONS: Knowledge of the different trajectory and anatomic relationship of the LA and the SA with the vestibulocochlear nerve is of paramount importance to differentiate them during surgery. The LA is usually inferomedial to the vestibulocochlear nerve at its distal and proximal aspects, whereas the SA usually originates lateral and ends superolateral to the nerve.

Vestibular Impairment in Hemifacial Spasm Syndrome: A Case Report.

A 52-year-old man presented with left hemifacial spasm (HFS). A magnetic resonance imaging scan showed compression of the left facial nerve at the cerebellopontine angle by a dolichoectatic basilar artery. The neurotological evaluation showed an otolithic deficit, with canalicular preservation and normal hearing. The deficit improved after surgical decompression. No previous report has described the impairment of vestibular function in patients presenting with HFS.

Veins of the Cerebellopontine Angle and Specific Complications of Sacrifice, with Special Emphasis on Microvascular Decompression Surgery. A Review.

Good knowledge of the anatomy of veins is of crucial importance for the functional surgery of cranial nerve (CN) disorders, especially microvascular decompression for trigeminal neuralgia (TN), hemifacial spasm (HFS), and vagoglossopharyngeal neuralgia (VGPN). Although controversial, veins may be involved in neurovascular conflicts and may constitute dangerous obstacles to access to the CNs. With the aim of estimating the implications of veins in those diseases and evaluating the linked surgical difficulties, we carried out a review of the literature from 2000 to the end of February 2018. For this review, articles found on PubMed that gave enough precision about veins were retained (39 articles on TN, 38 on HFS, 8 on VGPN, and 26 on complications related to venous sacrifices). Before this review, we described a simplified anatomic classification of veins, amenable to easing the surgical approach to CNs. Access to the trigeminal nerve, via the infratentorial-supracerebellar route, is almost always affected by the superficial superior petrosal venous system, whereas access to the facial and cochleovestibular complex as well as to the lower CNs, through the infrafloccular trajectory, is almost always exempt of important venous obstacles. Respective incidences of venous compression at the origin of hyperactive CN syndromes are given. The percentages of a venous conflict alone were calculated at 10.8% for TN, 0.1% for HFS, and 2.9% for VGPN. We review the complications considered in relation with venous sacrifices. Precautions to minimize these complications are given.

Evaluation of vascular variations at cerebellopontine angle by 3D T2WI magnetic-resonance imaging in patients with vertigo.

BACKGROUND: Vascular loops of the anterior-inferior cerebellar artery (AICA) at the cerebellopontine angle (CPA) are considered related to auditory-vestibular symptoms. Clinical association of these anatomical aberrations, which can be grouped together as vascular compression syndromes, is controversial. Magnetic resonance imaging (MRI) is widely used to visualize this anatomical region, given its high sensitivity and specificity. OBJECTIVE: To elucidate the clinical relationship of vertigo symptoms with vascular loop compression syndrome by evaluating the neurovascular contacts of the vestibulocochlear nerve (VCN) and AICA at the CPA and internal auditory canal via high-resolution MRI. METHODS: The study included 417 patients (178 with vertigo and 239 without vertigo) undergoing MRI for various clinical causes. MRI scans were assessed to study the presence of vascular abnormalities at the CPA. RESULTS: According to our findings, type 1 vascular variation was observed most frequently in both sides. MRI findings were similar for the patients with and without vertigo. CONCLUSIONS: Identifying the prevalence of the vascular loops of the AICA primarily depends on diagnostic technique, and our results identified a slightly higher prevalence than those of previous studies, which might be partly related to the high-sensitivity of 3-dimensional T2-weighted MRI.

Presence of vascular loops entering internal acoustic channel may increase risk of Sudden sensorineural hearing loss and reduce recovery of these patients.

OBJECTIVES/HYPOTHESIS: To analyze whether there is correlation between branching patterns of anterior inferior cerebellar artery/posterior inferior cerebellar artery (AICA/PICA) in cerebellopontine angle (CPA) area, as demonstrated by three-dimensional fast imaging employing steady-state acquisition (3D FIESTA) magnetic resonance imaging (MRI) and 1) idiopathic sudden sensorineural hearing loss (ISSNHL) outcomes and 2) recovery of ISSNHL. STUDY DESIGN: We evaluated patients with idiopathic SSNHL for branching patterns of AICA/PICA in CPA area, as demonstrated by 3D FIESTA MRI. METHODS: Sixty-eight patients with SSNHL (32 [47.1%] women; mean age 45.3 ± 14.6 [minimum-maximum: 18-77]) and 38 healthy volunteers [17 (44.7%) women; mean age 48.6 ± 14.0 (minimum-maximum: 26-81)] were included in this study. We evaluated patients for branching patterns and classified as type IA, IB, IIA, and IIB. Branching patterns were evaluated at the diseased side of the patients and both sides of the control group. Pretreatment and posttreatment audiological values were also studied. RESULTS: AICA/PICA branching patterns in control group versus study group in the affected side were: 26 (34.2%) versus 12 (17.6%) subjects had type IA; seven (9.2%) versus nine (13.2%) subjects had type IB; 31 (40.8%) versus 23 (33.8%) subjects had type IIA; and 12 (15.8) versus 24 (35.3%) subjects had type IIB branching patterns, respectively. Presence of vascular loops entering internal acoustic channel (type IIB branching pattern) was more prominent in the study group (P = 0.017). In addition, type IIB branching pattern was significantly associated with unresponsiveness to treatment (18 [75%] of 24 patients with type IIB were unresponsive and 14 [47.0%] of 30 patients with nontype IIB were unresponsive, P < 0.001). CONCLUSION: Type IIB branching pattern has been shown to be more common in patients with ISSNHL, and these patients come across with unresponsiveness to standard therapy more than the other branching types. LEVEL OF EVIDENCE: 3b. Laryngoscope, 127:210-215, 2017.

Microvascular anatomy of the cerebellar parafloccular perforating space.

OBJECTIVE: The cerebellopontine angle is a common site for tumor growth and vascular pathologies requiring surgical manipulations that jeopardize cranial nerve integrity and cerebellar and brainstem perfusion. To date, a detailed study of vessels perforating the cisternal surface of the middle cerebellar peduncle-namely, the paraflocculus or parafloccular perforating space-has yet to be published. In this report, the perforating vessels of the anterior inferior cerebellar artery (AICA) in the parafloccular space, or on the cisternal surface of the middle cerebellar peduncle, are described to elucidate their relevance pertaining to microsurgery and the different pathologies that occur at the cerebellopontine angle. METHODS: Fourteen cadaveric cerebellopontine cisterns (CPCs) were studied. Anatomical dissections and analysis of the perforating arteries of the AICA and posterior inferior cerebellar artery at the parafloccular space were recorded using direct visualization by surgical microscope, optical histology, and scanning electron microscope. A comprehensive review of the English-language and Spanish-language literature was also performed, and findings related to anatomy, histology, physiology, neurology, neuroradiology, microsurgery, and endovascular surgery pertaining to the cerebellar flocculus or parafloccular spaces are summarized. RESULTS: A total of 298 perforating arteries were found in the dissected specimens, with a minimum of 15 to a maximum of 26 vessels per parafloccular perforating space. The average outer diameter of the cisternal portion of the perforating arteries was 0.11 ± 0.042 mm (mean ± SD) and the average length was 2.84 ± 1.2 mm. Detailed schematics and the surgical anatomy of the perforating vessels at the CPC and their clinical relevance are reported. CONCLUSIONS: The parafloccular space is a key entry point for many perforating vessels toward the middle cerebellar peduncle and lateral brainstem, and it must be respected and protected during surgical approaches to the cerebellopontine angle.

Trigeminal Neuralgia Caused by Cerebellopontine Angle Arteriovenous Malformation Treated With Gamma Knife Radiosurgery.

Trigeminal neuralgia is a facial pain syndrome characterized as sudden onset and lightening-like sensation over somatosensorial branch(es) of fifth cranial nerve. Rarely, some underlying diseases or disorders could be diagnosed, such as multiple sclerosis, brain tumors, and vascular malformations. The authors present a 47-year-old man with trigeminal neuralgia over left V2 and V3 dermatomes. He had a previous transarterial embolization and long use of carbamazepine with partial response to treatment. Gamma knife radiosurgery (GKR) was planned. A marginal dose of 15 Gy was given to 50% isodose line. His pain was relieved by GKR in 1.5 years. Treatment of posterior fossa arteriovenous malformations causing trigeminal neuralgia, with GKR has a very limited use in the literature. It, however, is obvious that success rate as pain relief, in a very challenging field of functional neurosurgery, is satisfactory. Large series, however, are in need to make a more comprehensive statement about efficacy and safety of the procedure in these pathologies.

A case report of a pediatric traumatic aneurysm with arteriovenous (A-V) fistula CASE-BASED UPDATE.

BACKGROUND: Traumatic intracranial aneurysms (TICAs) are rare, representing less than 5 % of all intracranial aneurysms. Most TICAs are located within the anterior circulation, and less than 10 % of TICAs occur in the posterior circulation. Histopathologically, most TICAs are false aneurysms and have a high risk of rupture or re-bleeding. When they are discovered, careful observation or treatment may be required. Once they are enlarged, they have a high risk of rupture, and immediate treatment is essential. CASE REPORT: For the first time in the literature, we report a rare case of an 8-year-old boy with a TICA in anterior inferior cerebellar artery (AICA) and arteriovenous (A-V) fistula after severe head trauma. Trapping of AICA and resection of the aneurysm was performed. Postoperatively, he has peripheral facial palsy but is otherwise neurologically normal. CONCLUSION: Surgical treatment for traumatic aneurysms is challenging because most of TICAs are histopathologically pseudoaneurysms. It may be technically difficult to perform direct surgery of aneurysms especially located in the posterior circulation, but when the treatment is successful, the outcome was favorable.

Effectiveness and safety of microvascular decompression surgery for treatment of trigeminal neuralgia: a systematic review.

Microvascular decompression has been now accepted worldwide as a reasonable treatment for trigeminal neuralgia, yet, as a functional operation in the cerebellopontine angle, this process may be risky and the postoperative outcomes might not be good enough sometimes. To assess the effectiveness and safety of microvascular decompression for treatment of trigeminal neuralgia, we conducted a systematic review. Using the keywords "trigeminal neuralgia", "microvascular decompression", or "neurovascular conflict", manuscripts published in English-language journals and indexed in PubMed between January 1, 2000 and June 1, 2013 on the treatment of trigeminal neuralgia (TN) with microvascular decompression were considered for this study. The success and complications were analyzed. The success in this investigation was defined as complete pain free. Continuous outcomes were summarized using means or medians, and dichotomous outcomes were presented as percentage associated with 95% confidence interval. Twenty-six papers with 6,847 patients were finally enrolled in this review. Among them, the male-to-female ratio was 1:1.4, the left-to-right ratio was 1:1.6, and the pain was located in the innervation of V3 and/or V2 in most of the cases with only 2.3% (0.1-4.7) of V1 exclusively. The average age at surgery was 60.9 years (52.5-64.1) with TN symptoms duration of 24.7 months (6.1-42.1) before microvascular decompression (MVD). Operative findings confirmed the superior cerebellar artery, anterior inferior cerebellar artery, posterior inferior cerebellar artery, and multiple vascular contacts (including veins) as the most common sources of nerve compression. The average follow-up duration was 35.8 months (26.2-56.6). The success rate was 83.5% (79.6-89.1). Complications included incisional infection in 1.3% (0.1-2.5), facial palsy 2.9% (0.5-6.2), facial numbness 9.1% (1.3-19.6), cerebrospinal fluid leak 1.6% (0.7-2.5), and hearing deficit 1.9% (0.2-3.9). The postoperative mortality was 0.1% (0.02-0.2). Accordingly, MVD is the most effective treatment for patients with trigeminal neuralgia. An immediate pain free can be achieved by an experienced neurosurgeon with good knowledge of the regional anatomy. To avoid complications, each single step of the process cannot be overemphasized.

[Protection of the superior petrosal vein in microneurosurgery for acoustic neuroma].

OBJECTIVE: To explore the clinical significance of the protection of superior petrosal vein (SPV) in the microneurosurgery for acoustic neuroma. METHODS: From January 2009 to July 2011, 149 cases of acoustic neuroma microsurgery were observed. The difference in hematoma in surgical area, cerebellar hematoma and cerebellar edema were compared between a SPV without protection group (SPVWP group, n=8) and a SPV protection group (SPVP group, n=141). RESULTS: In the 149 patients with acoustic neuroma, the SPV was reserved in 141 patients. In the SPVWP group (8 patients), hematoma in the surgery area occurred in 4 patients, cerebellar edema in 5, and cerebellar hemorrhage in 3. In the SPVP group (141 patients), hematoma in the surgery area occurred in 40 patients, cerebellar edema in 56, and cerebellar hemorrhage in 12. There was significant difference in the incidence of cerebellar hemorrhage (χ(2)=3.84, P=0.05), no significant difference in the incidence of hematoma in the surgical area (χ(2)=0.646, respectively, P=0.422), and no significant difference in the incidence of cerebellar edema (χ(2)=0.611, P=0.434) between the SPVWP group and the SPVP group. CONCLUSION: In acoustic neuroma surgery, the SPV should be protected, which may reduce the risk of cerebellar hemorrhage.

Usefulness of PRESTO magnetic resonance imaging for the differentiation of schwannoma and meningioma in the cerebellopontine angle.

The principles of echo-shifting with a train of observations (PRESTO) magnetic resonance (MR) imaging technique employs an MR sequence that sensitively detects susceptibility changes in the brain. The effectiveness of PRESTO MR imaging was examined for distinguishing between cerebellopontine angle (CPA) schwannomas and meningiomas in 24 patients with CPA tumors, 12 with vestibular schwannomas, and 12 with meningiomas. Histopathological study of surgical specimens showed that 11 of the 12 schwannomas contained hemosiderin deposits and all had microhemorrhages. One meningioma contained hemosiderin deposits and two involved microhemorrhages. Abnormal vessel proliferation, and dilated and thrombosed vessels were observed in all schwannomas and in 4 meningiomas. In addition to MR imaging with all basic sequences, PRESTO MR imaging and computed tomography were performed. PRESTO imaging showed significantly more schwannomas (n = 12) than meningiomas (n = 2) exhibited intratumoral spotty signal voids which were isointense to air in the mastoid air cells (p < 0.001). These spotty signal voids were significantly associated with histopathologically demonstrated hemosiderin deposits (p < 0.001), microhemorrhages (p < 0.01), and abnormal vessels (p < 0.04). The visualization of spotty signal voids on PRESTO images is useful to distinguish schwannomas from meningiomas.