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J Neurosurg Case Lessons
J Neurosurg Case Lessons
J Neurosurg Case Lessons
Journal of Neurosurgery: Case Lessons
2694-1902
American Association of Neurological Surgeons

39222541
10.3171/CASE24239
CASE24239
Functional-NeurosurgeryFunctional NeurosurgeryVascular-DisordersVascular DisordersCase Lesson
Vestibular paroxysmia caused by a subarcuate artery: illustrative case
Sakaji Kensuke MD 1
Omodaka Shunsuke MD, PhD 1
Kanamori Masayuki MD, PhD 1
Takai Shunsuke MD 2
Sawada Akari MD 2
Suzuki Jun MD, PhD 2
Katori Yukio MD, PhD 2
Endo Hidenori MD, PhD 1
1 Departments of Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
2 Otolaryngology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
Correspondence Shunsuke Omodaka: Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan. omodakashunsuke@yahoo.co.jp.
INCLUDE WHEN CITING Published September 2, 2024; DOI: 10.3171/CASE24239.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

02 9 2024
02 9 2024
8 10 CASE2423916 4 2024
10 6 2024
© 2024 the authors
2024
the authors
https://creativecommons.org/licenses/by-nc-nd/4.0/ CC BY-NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

BACKGROUND

Vestibular paroxysmia is defined by spontaneous, recurrent, short, paroxysmal episodes of vertigo. The authors present a case of vestibular paroxysmia caused by neurovascular compression of the vestibulocochlear nerve due to the subarcuate artery, which was successfully treated with microvascular decompression.

OBSERVATIONS

A 46-year-old man ﬁrst experienced vertigo attacks 5 years earlier. The attacks became more frequent, and left-sided tinnitus developed over the past 4 months, prompting a referral to our hospital. Carbamazepine treatment alleviated symptoms but had to be discontinued due to rash. Brain magnetic resonance imaging and angiography revealed that the left anterior inferior cerebellar artery was pressing on the cisternal segment of the left vestibulocochlear nerve. The authors diagnosed vestibular paroxysmia caused by neurovascular compression and performed microvascular decompression. During the operation, a subarcuate artery was identified as the offending vessel, with a prominent indentation on the vestibulocochlear nerve. The vertigo was completely relieved following surgery.

LESSONS

Neurovascular compression of the vestibulocochlear nerve by the subarcuate artery can result in vestibular paroxysmia.

https://thejns.org/doi/abs/10.3171/CASE24239

microvascular decompression
neurovascular compression
subarcuate artery
vestibular paroxysmia
ABBREVIATIONS

AICA = anterior inferior cerebellar artery
MRI = magnetic resonance imaging
VP = vestibular paroxysmia.
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pmcVestibular paroxysmia (VP) is a rare disease characterized by spontaneous, recurrent, short, paroxysmal attacks of vertigo with or without tinnitus that respond well to oxcarbazepine or carbamazepine.1 Neurovascular compression of the vestibular nerve, primarily by the anterior inferior cerebellar artery (AICA), has been proposed as the underlying cause of VP.1 We present the first case of VP caused by neurovascular compression of the vestibulocochlear nerve due to the subarcuate artery, which was successfully treated with microvascular decompression.

Illustrative Case

A 46-year-old man was referred to our hospital after experiencing recurrent paroxysmal attacks of nonspinning vertigo for 5 years. The attacks became more frequent, and simultaneous left-sided tinnitus, appearing and disappearing with the attacks, had developed over the past 4 months. This vertigo lasted approximately 30 seconds, occurred more than 10 times daily, and was unrelated to head position, headache, straining, strong sound stimulus, or hyperventilation. There were no complaints of repetitive hearing loss or aural fullness occurring at the same time as the vertigo. He had no other significant medical, psychiatric, and head trauma history. Neurological examination, including positioning and positional nystagmus testing, was unremarkable. Pure tone audiometry was normal without low-tone threshold elevations. Cervical vestibular evoked myogenic potential testing showed threshold elevation in the left ear. Carbamazepine treatment significantly alleviated the symptoms but had to be discontinued due to rash. We diagnosed deﬁnite VP using the criteria proposed by the Bárány Society in 2016.1 The diagnosis of VP is primarily based on the patient’s history, which would include at least 10 attacks of spontaneous spinning or nonspinning vertigo, attacks lasting less than 1 minute, stereotyped phenomenology, response to carbamazepine or oxcarbazepine treatment, and a condition not better explained by another diagnosis.1 Brain magnetic resonance imaging (MRI) and angiography revealed that the left AICA impinged on the cisternal segment of the left vestibulocochlear nerve (Fig. 1). Based on the left-sided tinnitus, cervical vestibular evoked myogenic potential testing abnormality, and MRI findings, we suspected a left-sided VP caused by neurovascular compression and thus performed microvascular decompression. A left retrosigmoid craniectomy was performed with the patient under general anesthesia. The portion of the left AICA running between the facial and vestibulocochlear nerves was anchored by the internal auditory artery, which originated from the loop of the AICA, so the mobility of the AICA was extremely limited. In contrast, a subarcuate artery compressed the distal intracisternal part of the vestibulocochlear nerve (Fig. 2 left). The artery was coagulated just proximal to the subarcuate fossa and cut to release the vestibulocochlear nerve, revealing a prominent indentation on the nerve (Fig. 2 right). Remission of the vertigo was observed immediately following surgery, and the patient remained vertigo free at the 12-month follow-up review. Audiometric examinations following surgery conﬁrmed normal hearing. FIG. 1. Left: Axial constructive interference in steady state MRI reveals the left AICA (arrowhead) in contact with the ipsilateral facial nerve (solid arrow) and vestibulocochlear nerve (dotted arrow) at the cisternal portion. Right: A three-dimensional fusion image of MRI and computed tomography angiography reveals that the AICA (arrowhead) runs between the facial (solid arrow) and vestibulocochlear (dotted arrow) nerves.

FIG. 2. An intraoperative view of the left facial and vestibulocochlear nerves in the cerebellopontine angle before (left) and after (right) microvascular decompression. The AICA runs between the facial and vestibulocochlear nerves and is anchored by an internal auditory artery (arrow) that emerges from the loop of the AICA. A subarcuate artery originating from the AICA runs along the distal intracisternal part of the vestibulocochlear nerve (asterisk). Following the microvascular decompression, impingement of the nerve is clearly visible (arrowheads). VII = facial nerve; VIII = vestibulocochlear nerve.

Patient Informed Consent

The necessary patient informed consent was obtained in this study.

Discussion

Observations

To the best of our knowledge, this is the ﬁrst report to show that the subarcuate artery causes neurovascular compression of the vestibulocochlear nerve, leading to VP.

The cause of VP is a neurovascular conﬂict with the vestibular nerve.2 The pathological vessel-nerve contact causes demyelination and neural hyperexcitability, resulting in ephaptic depolarization.3–5 In the vestibular nerve, the transitional zone, where oligodendrocytes become Schwann cells, is located distal to the root entry zone. The distance of the most distal part of the transitional zone from the brainstem has been measured to be between 6 and 15 mm.6, 7 This transition zone is typically found near the internal acoustic porus. Thus, the majority of the intracisternal range of cranial nerve VIII is covered by the central myelin zone made up of oligodendrocytes, and both the central myelin and transition zones are thought to be especially vulnerable to deficits caused by neurovascular compression.5, 8 In contrast, the transitional zone in the trigeminal and facial nerves is usually located near the brainstem.9 The AICA (75%) is the most common causative vessel in patients with VP, but the posterior inferior cerebellar artery (5%) and vein (10%) and the vertebral artery (10%) can also be involved.5 There is only one case report showing that the subarcuate artery causes neurovascular compression syndrome in patients with hemifacial spasms.10 In our case, we performed microvascular decompression because preoperative imaging indicated that the AICA was the offending vessel in the neurovascular conflict. During the operation, contrary to our expectations, a subarcuate artery was discovered to compress the distal intracisternal part of the vestibulocochlear nerve with marked impingement, and the patient’s symptoms disappeared immediately after decompression of this offending artery. Although the effect of the AICA manipulation, which was minimal because the AICA was anchored by the internal auditory artery, cannot be ruled out, the subarcuate artery was the main cause of VP. This case suggests that focal compression of a small group of fibers can cause focal demyelination and ephaptic transmission, which are the proposed mechanisms underlying neurovascular compression syndromes.

The subarcuate artery typically originates in the lateral pontine portion of the AICA, just distal to the point of passage beneath the facial-vestibulocochlear nerve complex. It enters the dura of the subarcuate fossa through a small depression located superolateral to the internal acoustic meatus on the posterior surface of the petrous bone and travels to the subarcuate canal to supply the antrum.11 The risk of hearing loss is almost eliminated when differentiated from the auditory artery.11 In this case, the subarcuate artery was easily identified because of its typical course toward the subarcuate fossa, and the internal auditory artery was adequately developed. The vestibulocochlear nerve could be safely decompressed by cutting the subarcuate artery, without causing hearing impairment. A potential vessel-nerve contact is detected in > 95% of VP cases and 35%–45% of non-VP subjects using 1.5-T MRI, representing high sensitivity and low specificity for detecting the offending vessel in VP.2, 5, 12 The subarcuate artery is typically not visible on preoperative imaging. Surgically treatable VP can be present in patients with no vessel-nerve contact on preoperative imaging. Furthermore, even in patients with offending vessels on preoperative imaging, the surgeon must focus on exploring the entire nerve to locate the culprit vessel, such as the subarcuate artery. Despite all the advances in neuroradiology imaging, surgical exploration remains the most effective method of ruling out nerve compression in neurovascular compression syndromes.

Lessons

Neurovascular compression of the vestibulocochlear nerve by the subarcuate artery can result in VP. Because the vestibular nerve has a longer vulnerable section than the trigeminal and facial nerves, the surgeon should focus on exploring the entire nerve to find the culprit vessel in patients with VP.

Acknowledgments

We thank Enago for English proofreading.

Dr. Omodaka is the recipient of a grant from the Japan Society for the Promotion of Science (grant no. 24K12214).

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Omodaka, Sakaji. Acquisition of data: Omodaka, Sakaji, Kanamori, Sawada. Analysis and interpretation of data: Omodaka, Sakaji. Drafting the article: Omodaka, Sakaji, Takai. Critically revising the article: Omodaka. Reviewed submitted version of manuscript: Omodaka, Takai, Suzuki, Katori, Endo. Approved the final version of the manuscript on behalf of all authors: Omodaka. Statistical analysis: Sakaji. Study supervision: Omodaka, Takai, Katori, Endo.

Correspondence

Shunsuke Omodaka: Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan. omodakashunsuke@yahoo.co.jp.
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