Neurovascular Compression Syndromes

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

Objective

To 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).

Methods

Ninety 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.

Results

Approximately 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.

Conclusion

When 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.

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

Background

Where 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.

Methods

The 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).

Results

Out 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).

Conclusion

From 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.

In vitro and in vivo experiments of a novel intra-arterial neurovascular decompressor for treating neurovascular compression syndromes: a brief report

Objectives: Neurovascular compression syndromes (NVCS) could be cured with an intravascular device that releases compression of the root entry zone of cranial nerves by changing the course of offending vessels. The purpose of this study was to report our results of in vitro and in vivo experiments with a novel intra-arterial neurovascular decompressor (IA-NVD) for NVCS. Methods: A nitinol-based IA-NVD was developed to release pressure applied to the root entry zone of cranial nerves by changing the course or angle of an offending vessel, which can possibly cure NVCS. We performed in vitro tests for safety and feasibility and preliminary in vivo tests up to 4 weeks for safety. Results: The bending stiffness of the device was similar to but slightly stronger than that of current, closed-cell intracranial stents. Hemocompatibility tests showed no significant thrombogenesis in whole blood. After the 4-week follow-up, all animals (20-month-old female Gottingen mini-pigs weighing 15-18 kg, n = 4) had a normal upright position and gait. Scanning electron microscopy images and H&E staining of arteries containing the devices showed good neointima formation on the devices. Intima hyperplasia occurred over wires and connecting tubes, but it did not interrupt the patency of the arterial lumen. Discussion: An IA-NVD was created and tested to demonstrate its functionality and biocompatibility in the present experiments. The device may be safely applied to intracranial arteries, providing us a chance to test the efficacy of an upgrade version of the device on changing the course of an artery that compresses a cranial nerve. Abbreviations: CN = cranial nerve; EVT = endovascular treatment; H&E = hematoxylin and eosin; HFS = hemifacial spasm; IA-NVD = intra-arterial neurovascular decompressor; MVD = microvascular decompression; NVCS = neurovascular compression syndrome; REZ = root entry zone; SEM = scanning electron microscopy; TN = trigeminal neuralgia.

Abducent nerve palsy treated by microvascular decompression: a case report and review of the literature

Too few cases of isolated abducent nerve palsy caused by neurovascular compression syndrome have been reported. We here report on a case of abducent nerve palsy caused by neurovascular compression syndrome that was successfully treated by microvascular decompression (MVD). A 46-year-old male presented with a 6-month history of right-sided persistent abducent nerve palsy. High-resolution magnetic resonance imaging revealed a neurovascular contact of the vertebral artery with the right abducent nerve. MVD was performed via a retrosigmoid craniotomy, with remarkable improvement of the palsy. Our report suggests that MVD might be considered as an optional treatment if the symptoms progress or persist.

MRI and neurophysiology in vestibular paroxysmia: contradiction and correlation

BACKGROUND

Vestibular paroxysmia (VP) is defined as neurovascular compression (NVC) syndrome of the eighth cranial nerve (N.VIII). The aim was to assess the sensitivity and specificity of MRI and the significance of audiovestibular testing in the diagnosis of VP.

METHODS

20 VP patients and, for control, 20 subjects with trigeminal neuralgia (TN) were included and underwent MRI (constructive interference in steady-state, time-of-flight MR angiography) for detection of a NVC between N.VIII and vessels. All VP patients received detailed audiovestibular testing.

RESULTS

A NVC of N.VIII could be detected in all VP patients rendering a sensitivity of 100% and a specificity of 65% for the diagnosis of VP by MRI. Distance between brain stem and compressing vessels varied between 0.0 and 10.2 mm. In 15 cases, the compressing vessel was the anterior inferior cerebellar artery (75%, AICA), the posterior inferior cerebellar artery in one (5%, posterior inferior cerebellar artery (PICA)), a vein in two (10%) and the vertebral artery (10%, VA) in another two cases. Audiovestibular testing revealed normal results in five patients (25%), a clear unilateral loss of audiovestibular function in nine patients (45%) and audiovestibular results with coinstantaneous signs of reduced and increased function within the same nerve in six patients (30%). From the 20 TN patients 7, (35%) showed a NVC of the N.VIII (5 AICA, 1 PICA, 1 vein).

CONCLUSIONS

Only the combination of clinical examination, neurophysiological and imaging techniques is capable of (1) defining the affected side of a NVC and to (2) differentiate between a deficit syndrome and increased excitability in VP.

The anatomical classification of AICA/PICA branching and configurations in the cerebellopontine angle area on 3D-drive thin slice T2WI MRI

BACKGROUND

With the technical advance of magnetic resonance imaging (MRI), we have been able to observe not only the small cranial nerves arising from the brain stem but also the branches of vertebrobasilar artery in the cerebellopontine angle (CPA) cistern.

PURPOSE

The purpose was to demonstrate the courses and configurations of the anterior inferior cerebellar artery (AICA) or posterior inferior cerebellar artery (PICA) branch including the internal auditory artery in the CPA cistern and evaluate the relationship between the facial-vestibulocochlear (VIIth-VIIIth) nerves and AICA/PICA on high-resolution, thin-slice, three-dimensional T2-weighted MRI using driven equilibrium pulse.

MATERIAL AND METHODS

Thirty-three men and 27 women aged 8-85 years old with sensory hearing loss or vertigo, and/or tinnitus were evaluated by thin-slice (0.75 mm) T2-weighted MRI. Five subjects (3 men, 2 women) without any auditory symptoms were also examined.

RESULTS

Thin-slice T2WI drive MRI revealed several variations of the AICA/PICA coursing, such as a loop formation (n=30, 48 sides) or the IAC extension (n=19, 30 sides). Contact with the vestibulocochlear nerve was seen in 31.7% subjects (n=19, 27 sides). The AICA/PICA branching and shape patterns relative to the CPA and IAC were classified into four major types: type 1A, nonloop AICA/PICA in the CPA cistern; type 1 B, nonloop AICA/PICA (internal auditory artery) entering the IAC; type 2A, loop-type AICA/PICA in the CPA cistern; and type 2B, loop-type AICA/PICA entering the IAC.

CONCLUSION

There was statistically significant association between types 1A and 2A (P<.01) regarding the existence of any auditory 3 symptoms. The results of our study suggest that this classification is simple and very useful for the elucidation of the mechanism of auditory symptoms and deciding the therapeutic strategies.

TMS Neuro-Cardiovascular Coupling in Vascular Compression Cranial Neuropathy

Background:

Neurovascular compression (NVC) may cause cranial mononeuropathy but lacks a definitive diagnostic investigation. We hypothesized that the arterial pressure wave (APW) would interact at the neurovascular interface in NVC to inhibit transmission of transcranial magnetic stimulation (TMS) stimuli to affected muscles.

Methods:

We report a novel neurophysiological method coupling cardiovascular physiology with TMS. The electrocardiogram (ECG) and arterial pressure wave (APW) were coupled to triggering of cortical TMS in a patient with NVC-induced spinal accessory (CNXI) mononeuropathy. Outcome measures included motor evoked potential (MEP) amplitudes and firing probabilities of normal and affected trapezieus (TPZ). Values at intervals in proximity to the APW (40/80/120/160ms) were compared to baseline (800ms) using ANOVA and student t-test.

Results:

Electrocardiogram triggered TMS of CNXI pathways with 100% reliability. MEP amplitudes were decreased in proximity to the APW, particularly at 120ms (0.21±0.04 mV versus 0.39±0.10mV, p=0.003). TPZ firing probabilities were similarly inhibited (43.8% versus 88.2%, p=0.009). No effect of APW proximity was observed on the unaffected side (p=0.868). Procedures were well tolerated.

Conclusions:

Vascular compression causes CNXI mononeuropathy. Transcranial magnetic stimulation-cardiovascular coupling may evaluate neurovascular junction interactions and non-invasively diagnose NVC.

Neurovascular relationships in the posterior cranial fossa, with special reference to trigeminal neuralgia. 1. Review of the literature and development of a new method of vascular injection-filling in cadaveric controls

Vascular compression of cranial nerves adjacent to the brain stem has been implicated in a wide variety of disorders affecting their function. The considerable conflicts in published results relate primarily to flaws in study design. The design required of an adequate study is defined and a technique is presented, in 16 fresh human cadavers, of reliable and physiological injection-filling of both the cerebral arterial and venous systems. It allowed for the accurate observation of the normal neurovascular relationships in the posterior cranial fossa during operative simulation. Part 2 of this article concerns the use of this design in the study of trigeminal neuralgia, a disorder thought to relate to vascular compression of the fifth cranial nerve.

Hemifacial spasm: a review

Hemifacial spasm can be diagnosed by observation and clinical history. It is thought to arise primarily from compression of the facial nerve at the pons, usually by an adjacent artery. Although many approaches to treatment have been tried, the most effective is microvascular decompression of the facial nerve at the pons. That operation has well-recognized risks, including ipsilateral deafness. The latter complication ordinarily can be avoided by the use of intraoperative monitoring of auditory evoked potentials.

Radiographic position of the trigeminal nerve in the skull for angiographic determination of arterial-nerve relationship in trigeminal neuralgia: results of a radiologic-anatomic study

The positions of 20 trigeminal nerves in the skulls of 12 cadavers were evaluated radiographically. Small metal clips were attached to the nerves and radiographs were obtained in straight AP, Towne and lateral projections. It was found that the trigeminal nerve had a fairly constant position in the skull with respect to the internal auditory meatus in the AP and Towne projections and the petrous ridges in the lateral view. This information can be used during vertebral angiography to predict whether an arterial loop is sufficiently close to the trigeminal nerve root for arterial compression of the nerve, causing trigeminal neuralgia, to be a realistic possibility.