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J Neurosonol Neuroimag > Volume 16(2); 2024 > Article
Kim, Lee, and Bae: Anterior Inferior Cerebellar Arteries Infarction Presenting Initially as Vestibular Neuronitis with Labyrinthine Artery Thrombus

Abstract

It is difficult to distinguish acute labyrinthine artery infarction from peripheral vertigo conditions, such as vestibular neuritis and labyrinthitis. Despite comprehensive neurological examinations, differentiating between these conditions remains challenging, and standard computed tomography or magnetic resonance imaging (MRI) scans may not always reveal acute labyrinthine artery infarction. This case report suggests that a thorough evaluation using susceptibility-weighted imaging on MRI may be helpful in detecting the early signs of labyrinthine infarction.

Many patients presenting to the emergency department with dizziness report an acute onset of persistent vertigo. These individuals often exhibit spontaneous nystagmus, consistent with Alexander’s law, and show a positive head impulse test result during neurological examination. These findings suggest acute unilateral vestibulopathy, a form of peripheral vertigo. However, distinguishing this form from other causes of central vertigo can be challenging. One such condition is labyrinthine infarction, which is difficult to detect using standard imaging techniques. Herein, we report a rare case of labyrinthine infarction, with a thrombus identified on early susceptibility-weighted imaging (SWI).

CASE

A 72-year-old woman with no significant medical history presented to the emergency department with a 2-day history of vertigo. She reported acute onset of persistent spontaneous vertigo accompanied by nausea and vomiting. Initial neurological examination revealed left-beating spontaneous nystagmus consistent with Alexander’s law and a positive head impulse test with right catch-up saccades. Additionally, skew deviation was not observed. Cerebellar examination did not show lateralization, and there were no other focal neurological deficits. Laboratory tests, including complete blood count with differential, serum electrolytes, glucose, liver function tests, blood urea nitrogen, and creatinine levels, were all within normal limits.
Further evaluation with computed tomography (CT) and magnetic resonance imaging (MRI) was performed. CT angiography revealed no parenchymal hemorrhage or patent flow in the vertebrobasilar artery and both anterior inferior cerebellar arteries (AICA) (Fig. 1A, 1B). MRI identified only mild small-vessel ischemic lesions in both the centrum semiovale and subcortical white matter, with no evidence of acute hemorrhage or infarction (Fig. 1C). The patient was initially suspected to have unilateral vestibulopathy, such as vestibular neuritis, and was discharged from the emergency department with medications for symptom control.
Six days later, the patient returned to the emergency department with worsening symptoms, including persistent vertigo, dysarthria, and hearing impairment in the right ear. Neurological examination revealed mild dysarthria, ongoing left-beating spontaneous nystagmus with right catch-up saccades on the head impulse test, and mild ataxia and dysdiadochokinesia in the right upper limb. The Dix-Hallpike test, head roll test, and head shaking test yielded normal findings. After suspecting central vertigo, follow-up imaging with CT angiography and MRI were performed.
CT angiography revealed a steno-occlusion of the right AICA, which appeared normal at the initial visit (Fig. 2A, 2B). MRI demonstrated diffusion restriction in the right cerebellar peduncle, indicating an acute infarction in the AICA territory (Fig. 2C). SWI also revealed a dark signal in the right AICA. At this point, the patient was diagnosed with cerebellar peduncle infarction caused by a right AICA thrombus. Subsequently, a thorough retrograde review of the MRI scan from the initial visit revealed a small dark signal in the right labyrinthine artery on SWI (Fig. 1D). This finding led to a retrospective diagnosis of labyrinthine artery infarction at the initial visit.
The patient was diagnosed with acute right AICA infarction and was started on aspirin and clopidogrel. Further evaluation, including a stroke etiology study, conservative care, and rehabilitation, was performed during admission. The etiological study, which included blood tests, echocardiography, Holter monitoring, and patent foramen ovale evaluation, revealed no significant abnormalities, leading to a classification of undetermined etiology. As symptoms improved over the following days, the patient was discharged on antiplatelet therapy.

DISCUSSION

Despite thorough neurological examination, differentiating acute labyrinthine artery infarction from peripheral vertigo remains challenging. The current imaging techniques often fail to detect isolated labyrinthine artery infarctions, making the diagnosis via imaging studies difficult.1 Differentiation of labyrinthine infarction from vestibular neuritis should initially rely on detailed history taking along with physical and neurologic examinations.2 However, in cases of isolated labyrinthine infarction without concurrent AICA territory or brainstem infarction, neurologic examination findings can be indistinguishable from those of vestibular neuritis. Both conditions present with spontaneous nystagmus away from the lesion and positive head impulse test results.3 While the HINTS-plus can aid in differentiating conditions by detecting hearing loss, it may still be insufficient, as auditory symptoms can be subtle or transient, making it challenging to distinguish conditions solely through neurologic examination.2 Additionally, differentiation is often difficult because lesions frequently remain undetected on standard diffusion MRI. The presence of associated infarctions in the flocculus or other AICA territory areas can aid in differentiation; however, these may also go undetected.4 As a result, many cases of initially isolated labyrinthine infarction may be missed and only detected later, as neurologic symptoms progress, and AICA infarction becomes evident.5 Few cases of isolated labyrinthine infarction with MRI findings have been described in the existing reports.6 Here, we present a case initially diagnosed with clinical vestibular neuritis, which revealed a thrombus in the labyrinthine artery on SWI, indicating labyrinthine artery infarction. We suggest that a thoroughly evaluated SWI can help differentiate labyrinthine artery infarction from other types of peripheral vertigo.

NOTES

Ethics Statement
Written informed consent was obtained from the patient to report demographic data, medical conditions, neuroimaging, and treatment. This study was approved by the Institutional Review Board of St. Vincent's Hospital, Catholic University of Korea (IRB number: VC24ZISI0163).
Availability of Data and Material
The imaging data obtained or edited in this study are available from the corresponding author upon request.
Author Contributions
All the authors contributed to the work described in this article. Conceptualization: SHK, DWB; Data curation: SHK, DWB; Methodology: DWB; Supervision: DWB; Writing–original draft: SHK; Writing–review & editing: SHK, JSL, DWB.
Sources of Funding
None.
Conflicts of Interest
No potential conflicts of interest relevant to this article was reported.

Acknowledgments

None.

Fig. 1.
Initially, the computed tomography (CT) angiography and magnetic resonance imaging (MRI) were considered normal. However, upon later retrograde evaluation, a thrombus within the labyrinthine artery was identified on susceptibility-weighted imaging (SWI), suggesting labyrinthine infarction. (A, B) CT angiography showing patent right anterior inferior cerebellar arteries (AICA) (arrowhead). (C) MRI showing no diffusion restriction. (D) SWI showing dark signal on right labyrinthine artery (arrow).
jnn-2024-00156f1.jpg
Fig. 2.
Follow-up computed tomography (CT) angiography and magnetic resonance imaging (MRI) revealed an infarction in the right cerebellar peduncle, and the susceptibility-weighted imaging (SWI) demonstrated a more prominent thrombus in the right anterior inferior cerebellar arteries (AICA). (A, B) CT angiography showing steno-occlusion on right AICA (arrowhead). (C) MRI showing diffusion restriction on right cerebellar peduncle. (D) SWI showing dark signal on right AICA (arrow).
jnn-2024-00156f2.jpg

REFERENCES

1. Liqun Z, Park KH, Kim HJ, Lee SU, Choi JY, Kim JS. Acute unilateral audiovestibulopathy due to embolic labyrinthine infarction. Front Neurol. 2018;9:311.
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2. Nam HW, Yoo D, Lee SU, Choi JY, Yu S, Kim JS. Pearls & Oy-sters: Labyrinthine infarction mimicking vestibular neuritis. Neurology. 2021;97:787-790.
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3. Bery AK, Chang TP. Positive horizontal-canal head impulse test is not a benign sign for acute vestibular syndrome with hearing loss. Front Neurol. 2022;13:941909.
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4. Kim DH, Lee JH, Oh SY, Shin BS. Isolated flocculus infarction mimicking acute labyrinthitis. J Korean Neurol Assoc. 2011;29:241-245.

5. Kim JS, Cho KH, Lee H. Isolated labyrinthine infarction as a harbinger of anterior inferior cerebellar artery territory infarction with normal diffusion-weighted brain MRI. J Neurol Sci. 2009;278:82-84.
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6. Kong J, Lee SU, Park E, Kim JS. Labyrinthine infarction documented on magnetic resonance imaging. Stroke. 2024;55:e277-e280.
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