Anterior Inferior Cerebellar Artery Loop Research Articles

Prevalence of Anterior Inferior Cerebellar Artery Vascular Loop in Cerebellopontine Angle With Three-Dimensional Constructive Interference in Steady State (CISS) Sequence MRI.

Background The cerebellopontine angle (CPA) cistern houses vital neurovascular structures such as cranial nerves V, VII, and VIII and the anterior inferior cerebellar artery (AICA), often leading to neurovascular compression syndromes due to its complex anatomy. Although vascular compression is a recognized cause of certain neuralgias, its association with otologic symptoms such as tinnitus, hearing loss, and dizziness remains uncertain. Hence, this study aims to determine the prevalence of the AICA vascular loop in the CPA cistern on MRI in patients with asymptomatic audiovestibular symptoms. Methodology Adult patients who underwent MRI, including the posterior fossa's high-resolution volumetric T2 sequence (three-dimensional constructive interference in steady state (3D-CISS)), were assessed. Patients with a history of audiovestibular symptoms (tinnitus/dizziness/vertigo/sensorineural hearing loss), intracranial tumor, vascular lesions, intracranial surgery, brain radiation therapy, traumatic brain injury, poor image quality, and MRI scans without 3D-CISS sequences were excluded. Two radiologists independently reviewed 114 (228 sides) MRI studies for the vascular loop of AICA in the CPA cistern and the extension of the AICA loop into the ipsilateral internal acoustic meatus which was graded by Chavda's classification. Results The prevalence of vascular loop of AICA in the CPA cistern was as high as 47.6% in asymptomatic patients. Grade I Chavda vascular loop was the most common type followed by type II, with type III being the least common type. Conclusions Knowledge regarding the high prevalence of the AICA loop in the asymptomatic population and the lack of significant correlation between the presence of the AICA loop and otovestibular symptoms should be considered in preoperative planning for decompression procedures.

A Surgical Case of Hemifacial Spasm Due to Tentorial Meningioma -peritorcular type- in Posterior Fossa

Hemifacial spasm is commonly caused by compression of the facial nerve due to overlying vessels, and also due to various types of tumor or aneurysm, and other factors. It occurs, although rarely, as a secondary effect of cerebellar or brainstem shift resulting from a tumor. In such a case, the presence of a large tumor often leads to additional neurological deficits. We present a case of hemifacial spasm caused by a peritorcular type of large tentorial meningioma in the posterior fossa. A 68-year-old woman presented with right facial numbness 4 months ago and right hemifacial spasm 2 weeks ago. Upon visiting our hospital, she displayed no neurological deficits other than the right hemifacial spasm. MRI revealed a peritorcular type of large tentorial meningioma in the posterior fossa with perifocal edema. The right cerebellopontine cistern was narrowed, and the cerebellar tonsil was herniated. The right facial nerve ran adjacent to the anterior inferior cerebellar artery (AICA). Angiography showed that only the left posterior meningeal artery (PMA) flowed to the tumor. The loop of the right AICA extended into the right cerebellopontine cistern. After embolization of the PMA, the tumor was surgically removed, leading to an improvement in the patient's hemifacial spasm. Postoperative MRI confirmed complete removal of the tentorial meningioma without any contact with the right facial nerve. The hemifacial spasm was caused secondarily by the cerebellar or brainstem shift due to the large tentorial meningioma in the posterior fossa. This large tumor had not produced any other neurological deficits before the hemifacial spasm appeared. We report this case because it is extremely rare.

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.

Nervus intermedius: Microsurgical and anatomic relationships to the cerebellopontine angle neurovascular complex.

The nervus intermedius (NI) comprises fibers originating from the trigeminal, superior salivary, and solitary tract nuclei, which join the facial nerve (cranial nerve [CN] VII). Neighboring structures include the vestibulocochlear nerve (CN VIII), the anterior inferior cerebellar artery (AICA), and its branches. Microsurgical procedures at the cerebellopontine angle (CPA) benefit from understanding NI anatomy and relationships, especially for the microsurgical treatment of geniculate neuralgia, where the NI is transected. This study sought to characterize common relationships between the NI rootlets, CN VII, CN VIII, and the meatal loop of AICA at the internal auditory canal (IAC). Seventeen cadaveric heads underwent retrosigmoid craniectomy. Following complete unroofing of the IAC, the NI rootlets were individually exposed to identify their origins and insertion points. The AICA and its meatal loop were traced to assess their relationship with the NI rootlets. Thirty-three NIs were identified. The median number of NI rootlets was 4 per NI (interquartile range, 3-5). The rootlets mainly originated from the proximal premeatal segment of CN VIII (81 of 141, 57%) and inserted onto CN VII at the IAC fundus (89 of 141, 63%). When crossing the acoustic-facial bundle, the AICA most frequently passed between the NI and CN VIII (14 of 33, 42%). Five composite patterns of neurovascular relationships were identified regarding NI. Although certain anatomical trends can be identified, the NI has a variable relationship with the adjacent neurovascular complex at the IAC. Therefore, anatomical relationships should not be used as the sole method of NI identification during CPA surgery.

Anterior inferior cerebellar artery loop and tinnitus—is there any association between them?

BackgroundWhere there is no identifiable cause of otologic symptoms like hearing loss and tinnitus, it is believed that etiology could possibly involve a vascular loop in AICA compressing the vestibulo-cochlear nerve within the internal auditory canal. In this study, we aim to evaluate whether there is any association of AICA vascular loops with unexplained tinnitus.MethodsThe present prospective study was conducted in the Department of ENT, SMGS Hospital, GMC Jammu, from October 2020 to March 2022 on 131 subjects with unexplained tinnitus. All subjects were subjected to contrast enhanced MRI brain (3D fast spin echo T2W1 with drive equilibrium pulse) for evaluation of AICA using Chavda classification—type 1 (lying in CP angle, but not entering IAC), type 2 (entering IAC but extending < 50% of length of IAC), and type 3 (extending > 50% of length of IAC).ResultsOut of 131 unexplained tinnitus cases, 76 patients (58%) had AICA loop on MRI. Out of 16 patients with right sided tinnitus, 11 patients had AICA on same side, while 5 patients had AICA on the opposite (left) side. Out of 26 patients with left-sided tinnitus, 12 patients had AICA on same side, while 14 patients had AICA on the opposite (right) side, these findings being statistically insignificant (p = 0.153).ConclusionFrom our study, we can conclude that the presence of AICA vascular loop either on CP angle or within IAC in tinnitus patients is an incidental finding and has no role in its etiology.

Vascular loops in cerebellopontine angle in patients with unilateral idiopathic sudden sensorineural hearing loss: Evaluations by three radiological grading systems.

ObjectiveWe aimed to investigate the impact of the position, configuration and neurovascular contact of the anterior inferior cerebellar artery (AICA) in cerebellopontine angle (CPA) and internal auditory canal (IAC) on the clinical features of patients with unilateral idiopathic sudden sensorineural hearing loss (ISSNHL).MethodsOne hundred and thirty‐six patients with unilateral ISSNHL were enrolled. All patients received detailed history inquiry and standard treatments. Pure tone audiometry and magnetic resonance imaging (MRI) of CPA‐IAC were performed. The MRI findings of both ears were evaluated by the Chavda, Gorrie and Kazawa systems. The association between radiological findings and clinical data were analyzed.Results(1) No significant interaural difference in the position, configuration and neurovascular contact of AICA was observed. (2) There was no significant association between the AICA loop and concomitant vertigo or pre‐treatment audiometric configuration in the affected ear. (3) Concomitant tinnitus seemed to be affected by the configuration of AICA categorized by Kazawa system, while the Chavda and Gorrie classification of AICA loop was unassociated with tinnitus. (4) Hearing outcomes were not compromised by the position or configuration of AICA based on the Chavda and Kazawa systems. Patients with Gorrie type B tended to have better hearing recovery than those with type C.ConclusionsIn patients with ISSNHL, the position, configuration and neurovascular contact of AICA in the CPA‐IAC were unassociated with the side of hearing loss, audiometric configurations, or concomitant vertigo. The neurovascular contact graded by Gorrie system might be associated with hearing outcomes.

Vascular Loop of Anterior Inferior Cerebellar Artery Causing Disabling Tinnitus, Vertigo, and Hearing Loss - A Review

The vascular anatomy of the anterior inferior cerebellar artery (AICA) is highly variable. In respect to the neurovascular relationship in the internal auditory canal (IAC), the AICA is intimately related with vestibulocochlear and facial nerve. Vascular loop of AICA, especially located in the IAC, is rare. This vascular loop of the IAC may result in the compression over the vestibulocochlear nerve. Microvascular compression of the eighth cranial nerve is an important cause for disabling tinnitus, vertigo, and hearing loss. Disabling tinnitus and vertigo due to intrameatal vascular loop of AICA compression, the vestibulocochlear nerve can be treated with help of drilling the internal acoustic meatus and separate the vascular loop from the vestibulocochlear nerve. The intrameatal AICA and vestibulocochlear nerve conflict produce specific pathological features and their surgical treatment is also invariably challenging. Decompression of the vestibulocochlear nerve by the opening of the IAC and transposition of the AICA is thought to be an effective treatment modality for radiologically confirmed cases with clinical presentations of unilateral sensorineural hearing loss and pulsatile tinnitus. The aim of this review article is to describe the details of vascular anatomy, etiopathology, clinical presentations, diagnosis, neurophysiology, and current treatment of the vascular loop of AICA in IAC which often pose challenge to the clinicians.

Evaluation of the Relationship Between the Internal Acoustic Canal Anatomy and Loops of the Anterior Inferior Cerebellar Artery Using 3-Tesla Magnetic Resonance Imaging

Background: Anatomical variations in vascular structures are frequently encountered. In the cerebellopontine region, anatomical variations, especially variations in the anterior inferior cerebellar artery (AICA) in relation to cranial nerves passing through the internal acoustic canal (IAC), are common. Magnetic resonance imaging (MRI) provides detailed information for the evaluation of the cerebellopontine region and the IAC anatomy. Objectives: This study aimed to examine the relationship between the IAC anatomy and AICA loop variations and to investigate the frequency of anatomical variations and its correlation with demographic variables. Patients and Methods: In this study, 253 patients (age &gt; 18 years), who underwent 3-Tesla MRI of the temporal bone between July 2019 and December 2019, were retrospectively evaluated. The exclusion criteria were images of poor diagnostic quality due to technical or patient-related reasons and the presence of a localized tumor that could disrupt the IAC. Four patients were excluded from the study because they had tumors related to IAC. The AICA variations were categorized according to the Chavda classification. The IAC size, canal diameter, canal length, and meatus width were measured, and the canals were characterized as cylindrical, funnel-shaped, and bud-shaped. Results: A total of 249 patients were included in this study. The Chavda type I vascular loop was the most common type on both sides. The mean size measurements of IACs were significantly higher in the group of vascular loops compared to the group without vascular loops. The presence of a vascular loop was significantly more common in funnel- and bud-shaped IACs compared to cylindrical IAC. Also, there was a negative correlation between the patient’s age and all IAC dimensions. Conclusion: The results of the present study showed that the AICA loop variations were closely related to the size and shape of the IAC.

Etiopathology and Prevalence of Pulsatile Tinnitus in a Tertiary Care Referral Hospital.

The diverse etiopathogenesis of pulsatile tinnitus (PT) makes it a difficult condition to diagnose and treat. To describe the clinical features, investigations and diagnosis of patients presenting with pulsatile tinnitus (PT). Retrospective chart review in an otology unit of a tertiary care referral centre. All medical records of patients who had a complaint of pulsatile tinnitus during the period 1st January 2014-1st May 2020 were included in the study. Data regarding history, characteristics of tinnitus, examination findings, investigations and diagnosis were collected and analyzed. Sixty-four patients with complaints of PT presented to our clinic during this time period and were included in the study giving a prevalence of 0.09%. Definite diagnosis was made in 62 (96.8%) cases with a detailed history, clinical examination and tailored investigations. Pathologies diagnosed were paraganglioma (25%), superior semicircular canal dehiscence (20.3%), anterior inferior cerebellar artery loop (7.8%), sigmoid sinus wall dehiscence (10.9%), sigmoid sinus diverticulum (6.25%), jugular bulb anomalies (7.8%) and hyperpneumatised petrous apex (3.1%) among others. Rare causes encountered were IgG4 disease, far advanced otosclerosis, vestibular aqueduct dehiscence and idiopathic intracranial hypertension. Pulsatile tinnitus is a rare complaint in the Otology clinic. Almost all cases of PT can be diagnosed correctly and appropriate treatment initiated with a logical approach to investigations.

Clinical perspectives of anterior inferior cerebellar artery: a review

&lt;p class="abstract"&gt;The anterior inferior cerebellar artery arises at the cerebellopontine angle (CPA), usually from the lower one third of the basilar artery. However, the vascular anatomy of the anterior inferior cerebellar artery (AICA) is highly variable. In respect to the neurovascular relationship in the internal auditory canal (IAC), the AICA is intimately related with vestibulocochlear and facial nerve. Microvascular compression of the vestibulocochlear nerve by AICA is an important etiology for tinnitus, hearing loss and vertigo. The vascular loop or aneurysm of the AICA will compress the vestibulocochlear nerve in the internal auditory canal. The AICA loop should be separated from the vestibulocochlear nerve. Magnetic resonance angiography (MRA) is helpful to reveal the vascular pathology of the AICA and confirm the causes for disabling otological symptoms. After confirmation of the vascular pathology of AICA, surgery is usually planned. The intrameatal AICA and vestibulocochlear nerve conflict produce specific pathological features and their surgical treatment is also invariably challenging. The objective of this review article is to discuss the details of vascular anatomy, etiopathology, clinical presentations, diagnosis, neurophysiology and current treatment of the vascular anomalies of AICA in IAC which often pose challenge to the clinicians.&lt;/p&gt;

Descriptive and topographical analysis of the labyrinthine artery in human fetuses.

Hearing or/and balance impairments may be caused by disorders of the labyrinthine artery (LA) and their branches. Most findings regarding the LA anatomy have been acquired through investigation of the cerebellopontine angle (CPA) in animal or adult human specimens. Eighty-eight CPAs and LAs of human fetuses were investigated using angio-techniques and microdissections. We found 15 intricate forms of distribution of LA. The LA usually originated from the extra-meatus loop in the anterior inferior cerebellar artery (AICA). The distribution of its terminal branches was 53.42% uni-arterial, 44.31% bi-arterial, and 2.27% tri-arterial systems. In the uni-arterial system, the LA described an anterior superior path to the cochlear nerve (CN) and originated its terminal branches in the gap between CN and the inferior part of the vestibular nerve. In the bi-arterial system, the anterior LA was located anterior and superior to the CN while the posterior LA appeared posterosuperior to the superior part of the vestibular nerve. In the tri-arterial system, the terminal branches originated directly from the AICA loop. Our results provide anatomical support to explain how compressions in the LA branches inside the internal acoustic meatus, as evoked by Schwannomas in the VII and VIII nerves, can lead to hearing and balance loss. The zone of the posterior vestibular nerve appeared to be a "safe area" for invasive procedures in these specimens.

Chronic Vestibular Syndrome Associated with Anterior Inferior Cerebellar Artery loop into the Internal Acoustic Meatus (P5.6-033)

Chronic Vestibular Syndrome Associated with Anterior Inferior Cerebellar Artery loop into the Internal Acoustic Meatus (P5.6-033)

Vascular Offenders in Trigeminal Neuralgia: A Unified Classification and Assessment of the Outcome of Microvascular Decompression

Vascular loop compression remains the most accepted theory for trigeminal neuralgia (TN). Apart from the normal adjoining vascular loops, certain unusual vascular loops incriminated in TN such as vertebrobasilar dolichoectasia and pure venous compressions do not truly fit into the traditional classification. Moreover, vascular diseases such as cavernoma and aneurysms causing TN are considered as secondary TNs. There is a lack of unified classification for TN with underlying vascular offenders, otherwise amenable to microvascular decompression. We classified vascular offenders in TN (n= 53) into the usual offenders such as superior cerebellar artery or anterior inferior cerebellar artery loop with (n= 4) or without (n= 34) superior petrosal vein loop (n= 38, group I). The unusual vascular offenders (n= 15, group II) comprised unusual arterial loops (n= 4, IIa), pure venous compressions (n= 8, IIb) and vascular diseases (n= 3, IIc). The clinical symptoms, pain severity scores, and surgical outcomes were compared. A right-sided preference and male predominance typified the unusual group. The incidence of atypical pain and sensory impairment was higher in group II. Group II also showed a less favorable immediate pain outcome, particularly the patients in group IIb. Group IIb also showed a higher incidence of postoperative hemorrhagic complications. However, long-term outcomes did not differ significantly. Unusual vascular offenders in TN do constitute a significant population. They differ from the usual group with respect to the type of pain, gender, and side of involvement and tend to have more complications with similar pain outcomes after microvascular decompression.

Anatomical location of AICA loop in CPA as a prognostic factor for ISSNHL.

The cerebellopontine angle (CPA) is a triangular-shaped space that lies at the junction of the pons and cerebellum. It contains cranial nerves and the anterior inferior cerebellar artery (AICA). The anatomical shape and location of the AICA is variable within the CPA and internal auditory canal (IAC). A possible etiology of idiopathic sudden sensorineural hearing loss (ISSNHL) is ischemia of the labyrinthine artery, which is a branch of the AICA. As such, the position of the AICA within the CPA and IAC may be related to the clinical development of ISSNHL. We adopted two methods to classify the anatomic position of the AICA, then analyzed whether these classifications affected the clinical features and prognosis of ISSNHL. We retrospectively reviewed patient data from January 2015 to March 2018. Two established classification methods designed by Cahvada and Gorrie et al. were used. Pure tone threshold at four different frequencies (0.5, 1, 4, and 8 kHz), at two different time points (at initial presentation and three months after treatment), were analyzed. We compared the affected and unaffected ears, and investigated whether there were any differences in hearing recovery and symptoms between the two classification types. There was no difference in AICA types between ears with and without ISSNHL. Patients who had combined symptoms such as tinnitus and vertigo did not show a different AICA distribution compared with patients who did not. There were differences in quantitative hearing improvement between AICA types, although without statistic significance (p = 0.09–0.13). At two frequencies, 1 and 4 kHz, there were differences in Chavda types between hearing improvement and no improvement (p < 0.05). Anatomical variances of the AICA loop position did not affect the incidence of ISSNHL or co-morbid symptoms including tinnitus and vertigo. In contrast, comparisons of hearing improvement based on Chavda type classification showed a statistical difference, with a higher proportion of Chavda type 1 showing improvements in hearing (AICA outside IAC).

Microvascular Decompression of Facial Nerve and Pexy of the Left Vertebral Artery for Left Hemifacial Spasm: 3-Dimensional Operative Video.

A 73-yr-old man presented with intractable left hemifacial spasm of 4 yr duration. Brain magnetic resonance imaging showed significant compression of left facial nerve by the left vertebral artery (VA) and anterior inferior cerebellar artery (AICA).The patient underwent a left retrosigmoid craniotomy and a microvascular decompression of the cranial nerve (CN) VII. Intraoperatively, we found that the distal AICA had a protracted subarcuate extradural course.1 This was relieved by intra/extradural dissection. The left VA and the AICA loop were compressing the root exit zone of CN VII. The VA was mobilized, and pexy into the petrosal dura was done with 8-0 nylon sutures (Ethilon Nylon Suture, Ethicon Inc, a subsidiary of Johnson & Johnson, Somerville, New Jersey). Once this was done, the lateral spread disappeared.2 The AICA loop was decompressed with 2 pieces of Teflon felt (Bard PTFE felt, Bard peripheral Vascular Inc, a subsidiary of CR Bard Inc, Temp, Arizona). After this, wave V of the brainstem auditory evoked potential (BAEP) disappeared completely, with no recovery despite the application of the nicardipine on the internal auditory artery (IAA). The IAA appeared to be stretched by the microvascular decompression. Arachnoidal dissection was done to release the CN VIII and an additional felt piece was placed to elevate the AICA loop; the BAEP recovered completely. The patient had a complete disappearance of the hemifacial spasm postoperatively, and hearing was unchanged.This 3-D video shows the technical nuances of performing a vertebropexy, release of the AICA from its extradural subarcuate course, and the surgical maneuvers in the event of an unexpected change in neuromonitoring response. The suture technique of vertebropexy is preferred to a loop technique, to avoid kinking of the VA.3Informed consent was obtained from the patient prior to the surgery that included videotaping of the procedure and its distribution for educational purposes. All relevant patient identifiers have also been removed from the video and accompanying radiology slides.

Vestibular nerve compression: role of auditory brainstem response and cervical vestibular evoked myogenic potentials

&lt;p&gt;The objective of the study was to evaluate the role of ABR and cVEMP in the diagnosis of vestibular compression syndrome (VCS) and to study the association of test results with the MRI findings. This is a case-report of four patients with VCS using case-study approach.&lt;strong&gt;&lt;em&gt; &lt;/em&gt;&lt;/strong&gt;Four patients with varying degrees of indentation of vestibulo-cochlear nerve by the anterior inferior cerebellar artery (AICA) loops were studied. Episodic rotatory vertigo was reported by three cases and two cases complained of tinnitus but the characteristic low-frequency ‘type-writer’ type of tinnitus was seen in only one. All cases showed evidence of retrocochlear pathology on ABR although two had normal peripheral hearing status. The cVEMP abnormalities noted were absence of cVEMP and reduced amplitude of cVEMP as compared to instrument-specific age-matched norms; only one case with no indentation of vestibulo-cochlear nerve had normal cVEMP tracings. Presence of AICA loops on the MRI by itself need not necessarily indicate vestibular compression syndrome. However when MRI excludes any other pathology in cases with symptoms such as unilateral sensorineural hearing loss, tinnitus, vertigo; vestibular compression could be the etiology. The likelihood of abnormal test findings is greater when the loop causes indentation of the nerve. &lt;/p&gt;

Diagnostic Yield of a Routine Magnetic Resonance Imaging in Tinnitus and Clinical Relevance of the Anterior Inferior Cerebellar Artery Loops

To assess the diagnostic yield of a routine magnetic resonance imaging (MRI) scan in patients with (unilateral) chronic tinnitus, to define the frequency of incidental findings, and to assess the clinical relevance of potentially found anterior inferior cerebellar artery (AICA) loops. Retrospective cohort study. Tertiary Tinnitus Care Group at the University Medical Center Utrecht. Three hundred twenty-one patients with chronic tinnitus. Routine diagnostic magnetic resonance imaging (MRI) and diagnostic auditory brainstem responses (ABR) when an AICA loop was found. Relationship between abnormalities on MRI and tinnitus. In 138 patients (45%), an abnormality on the MRI scan was described. In only 7 patients (2.2%), the abnormality probably related to the patient's tinnitus. Results were not significantly better in patients with unilateral tinnitus (abnormalities in 3.2%). Incidental findings, not related to the tinnitus, were found in 41% of the patients. In 70 patients (23%), an AICA loop was found in the internal auditory canal. No significant relationships were found between the presence of an AICA loop and the side of the tinnitus, abnormalities on the ABR or complaints specific to nerve compression syndrome. A routine MRI is of little or no value in patients with tinnitus with persistent complaints. Anterior inferior cerebellar artery loops are often encountered on an MRI scan but rarely relate to the tinnitus and should thus be considered incidental findings. It is advised to only perform an MRI when on clinical grounds a specific etiology with tinnitus as the symptom seems probable.

Preoperative MRI in neurovascular compression syndromes and its role for microsurgical considerations

BackgroundNeurovascular compression (NVC) in the posterior fossa is characterized by complex, three-dimensional (3D) neurovascular relationships at the root entry zones (REZ) and other parts of cranial nerves, resulting in syndromes such as trigeminal neuralgia (TN), hemifacial spasm, vertigo and glossopharyngeal neuralgia. Microvascular decompression (MVD) requires microsurgical experience and 3D orientation within the cisternal spaces to achieve adequate clinical results. The vascular structures in anatomical relation to the trigeminal nerve root at the lateral pontine aspect of the brainstem should be examined and maximally decompressed to minimize the risk of recurrent TN. Indication was traditionally based on clinical decisions, only. New MR techniques have become available, and their chances and potential impact should be evaluated in this study. MethodsIn our study we examined 7 consecutive patients with TN and one patient with vertigo analyzing the details of NVC with high resolution magnetic resonance (MR) imaging in correlation to the intraoperative findings. All 8 patients underwent 1.5T MRI with T2 fast spin echo. The MRI data were retrospectively analyzed and compared to the intraoperative findings with the focus on the length of the corresponding cranial nerve and topography of the NVC site, the distance of the location of the NVC from the surface of the brainstem. ResultsThe superior cerebellar artery (SCA) was the most common causative vessel in 5 of 8 cases (62.5%), the anterior inferior cerebellar artery (AICA) in 2 of 8 cases (25%) and veins in 1 of 8 cases (12.5%). The cisternal length of the examined trigeminal nerve on the high resolution MR images at the affected side ranged from 8.1mm to 10.8mm and on the unaffected contralateral sides from 9.4mm to 11.4mm. The vestibular nerve in one vertigo patient had an equal cisternal length of 18.0mm on either side, whereas the distance of the neurovascular conflict site was 8.0mm from the surface of the flocculus. The distance of the neurovascular conflict location site to the brainstem ranged from 1.4mm to 8.5mm on the reviewed MR image slices. One patient with vertigo showed an AICA loop in the MR images, which was confirmed intraoperatively. All causative vessels on the trigeminal nerve performed loops from cranially to caudally. All 7 patients (100%) with TN and one vertigo patient were symptom-free since discharge. ConclusionWe show that high resolution MR images provide reliable and detailed information on corresponding intraoperative anatomy. Especially in unusual cases, the application of such MR techniques and preoperative evaluation may contribute to indication, planning, and also for teaching purposes.

The Association of Anterior Inferior Cerebellar Artery in IAC with Tinnitus and Hearing Loss

Objective: Tinnitus is a common disorder, but the etiology of this disorder remains unknown. The objective of this study was to assess the correlation between anatomic type and the thickness of the anterior inferior cerebellar artery (AICA) loop with tinnitus, using 3D-fast imaging employing steady state acquisition magnetic resonance image (MRI). Method: Seventy-four patients with tinnitus and 82 asymptomatic controls were included in this study. Otologic symptoms, which were measured based on the results of a pure tone audiometry, were reviewed. We evaluated the position and thickness of the AICA vascular loop in 3D-FIESTA MRI using 2 scoring systems. The first system was Chavda classification based on the anatomic location of the AICA loop. The second scoring system was used to measure the thickness of the AICA loop. The AICA loops were classified into 2 groups based on thickness, thinner than adjacent facial nerve and thicker than the facial nerve. Results: Ears with type I, II AICA loops showed significantly higher rates of tinnitus than those with type III. There was no association between the type of AICA loop and subtype of tinnitus (pulsatile, nonpulsatile). There was no association between the type of tinnitus and hearing loss. Ears with thinner AICA loop had a higher rate of tinnitus than those with thicker AICA loop. Conclusion: The type I, II and thinner AICA loop was significantly correlated with tinnitus. Compression of VIIIth cranial nerve by AICA loops at a cerebellopontine angle and impaired blood flow through thevessel may be the pathophysiology of tinnitus.

MRI assesment of internal acoustic canal variations using 3D-FIESTA sequences

Magnetic resonance imaging (MRI) of the internal acoustic canal is the standard diagnostic tool for a wide range of indications in patients. This study aims to investigate the vascular variations and compression of the cranial nerves (CNs) VII and VIII at the cerebellopontine angle in patients with neuro-otologic symptoms using 3D-fast imaging employing steady-state acquisition (FIESTA) MR imaging. One hundred and eighty-seven patients (374 temporal bones) were examined on a 1.5-T MRI. In addition to conventional MR sequences, a 3D-FIESTA MR imaging was acquired. Magnetic resonance images thus obtained were evaluated with special regard to the presence of vascular contact to the CNs VII and VIII, as well as the presence of the vascular variations of the anterior inferior cerebellar artery (AICA) causing the compression of CNs. The Chi-squared test was used for statistical analysis. No statistically significant differences were found between the presence and absence of the AICA loop and/or vascular contact for the clinical symptoms of patients (P > 0.05). The cisternal and canalicular segments of CNs VII and VIII and adjacent vascular variations are well identified using 3D-FIESTA, especially by determining the relationship of the AICA variations between CNs.