Utility of T1- and T2-Weighted High-Resolution Vessel Wall Imaging for the Diagnosis and Follow Up of Isolated Posterior Inferior Cerebellar Artery Dissection with Ischemic Stroke: Report of 4 Cases and Review of the Literature

https://doi.org/10.1016/j.jstrokecerebrovasdis.2017.06.038Get rights and content

Background

An accurate diagnosis of isolated posterior inferior cerebellar artery dissection (iPICA-D) is difficult due to the limitation of spatial resolution on conventional magnetic resonance imaging (MRI) techniques to detect subtle vessel wall abnormalities. The recent development of MRI techniques, including high-resolution vessel wall imaging (HRVWI), has resulted in the improved diagnostic accuracy and efficiency of iPICA-D. In fact, T1-weighted HRVWI, which can reveal intramural hematomas in the posterior inferior cerebellar artery (PICA), is useful for the diagnosis of iPICA-D. However, the utility of T2-weighted HRVWI has not been previously reported. The aim of this study was to investigate the diagnostic utility of T1- and T2-weighted HRVWI for the diagnosis of iPICA-D.

Methods

We retrospectively evaluated MRI findings including intramural hematomas, dilations, and chronological changes in 4 patients with iPICA-D admitted to our hospital and related facility from January 2015 to August 2016. In addition to T1-weighted HRVWI, T2-weighted HRVWI was performed on isovoxel three-dimensional (3D) fast spin-echo or 3D sampling perfection with application-optimized contrast using different flip-angle evolution. We also reviewed cases of nonhemorrhagic iPICA-D with ischemic onset in which the MRI findings were described.

Results

In all 4 patients, in addition to the intramural hematomas on T1-weighted HRVWI, T2-weighted HRVWI clearly showed the fusiform dilation of the external diameter of the PICA. T2-weighted HRVWI was more useful than other techniques, including T1-weighted HRVWI, for the evaluation of arterial shape changes.

Conclusions

Like T1-weighted HRVWI, T2-weighted HRVWI is useful for the diagnosis and assessment of chronological changes in vessel wall abnormalities during the follow-up period.

Introduction

The etiological mechanisms of posterior inferior cerebellar artery (PICA) territory infarctions mainly comprise atherosclerotic occlusive lesions of the vertebral artery, cardioembolism, and in situ branch artery disease of the PICA.1, 2 Cases of dissection of the PICA not involving the vertebral artery (isolated PICA dissection [iPICA-D]) have also been reported.3 Previously, iPICA-D was recognized as a rare phenomenon in the literature. However, recent studies have demonstrated that 6.0% of isolated PICA territory infarctions4 and 5.4% of posterior circulation ischemic strokes caused by arterial dissection5 were attributable to iPICA-D, suggesting that iPICA-D is a more common cause of PICA territory infarction. Generally, digital subtraction angiography (DSA) was considered essential for the diagnosis of iPICA-D; however, recent advancements in magnetic resonance imaging (MRI) techniques, especially high-resolution vessel wall imaging (HRVWI) such as T1-weighted volume isotropic turbo spin-echo acquisition, have enabled clinicians to depict minute intramural hematomas and thus improve the diagnostic accuracy and efficiency of iPICA-D.6, 7 Nevertheless, the utility of T2-weighted HRVWI for the diagnosis and management of iPICA-D has not been thoroughly evaluated. We herein report the clinical course and MRI findings, including intramural hematomas, dilations, and chronological changes, on T1- and T2-weighted HRVWI in 4 patients with iPICA-D. We also discuss the contribution of MRI findings to the diagnosis of iPICA-D with a review of the literature.

Section snippets

Materials and Methods

This was a retrospective study performed to evaluate MRI findings of iPICA-D. The privacy of patients was completely protected. This study was approved by the Ethic Committee of Nagoya City University. From January 2015 to August 2016, 4 patients were diagnosed with iPICA-D according to the Spontaneous Cervicocephalic Arterial Dissections Study (SCADS) criteria8 (Table 1). T1- and T2-weighted HRVWI was performed with a three-dimensional (3D) variable refocusing flip angle turbo spin-echo

Case 1

A 36-year-old man with hypertension and hyperlipidemia developed a sudden headache and right posterior neck pain followed by vertigo the next day and was admitted to our hospital. On admission, he had no neurological deficits; however, brain MRI detected a hyperintense area in the right lower cerebellar hemisphere on diffusion-weighted imaging (Fig 1, A). The right PICA was not depicted on MRA because of a stenosis (Fig 1, B). In contrast to T2*WI, an intramural hematoma was detected on

Discussion

In this study, in contrast to conventional MRI techniques, HRVWI could clearly detect abnormal imaging findings related to iPICA-D (including intramural hematomas on T1-weighted HRVWI and fusiform dilations on T2-weighted HRVWI) as well as chronological changes in these findings in all 4 cases. These HRVWI findings solely fulfilled the SCADS diagnostic criteria (definite dissection) and contributed to the achievement of a correct diagnosis of cerebellar or medullary infarction of the PICA

Conclusion

HRVWI is a useful technique with which to detect specific abnormal imaging findings related to iPICA-D, including intramural hematomas on T1-weighted HRVWI and dilation on T2-weighted HRVWI. We propose that in addition to T1-weighted HRVWI, T2-weighted HRVWI should be performed for the diagnosis of iPICA-D. These HRVWI techniques enable noninvasive diagnosis and follow-up of iPICA-D.

References (17)

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    This retrospective study was approved by the Ethics Committee of Nagoya City University, and the privacy of all patients was completely protected. T1- and T2-weighted HRVWI were performed on previously reported three-dimensional (3D) variable refocusing angle turbo spin-echo techniques including isovoxel 3D fast spin-echo (isoFSE) using a 3-T imager (Trillium Oval; Hitachi Medical Corporation, Tokyo, Japan), variable density incoherent spatiotemporal acquisition (VISTA) using a 1.5-T and 3-T imager (Intera; Philips, Amsterdam, Netherlands) or 3D sampling perfection with application-optimized contrast using different flip-angle evolution (SPACE) using a 1.5-T imager (MAGNETOM Avanto; Siemens Healthcare, Erlangen, Germany).9,10 HRVWI was scanned along the sagittal plane parallel to the ACA.

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    This finding is subject to chronological change of signal intensity due to paramagnetic effect by hemoglobin metabolism during disease course and may potentially be overlooked in the acute and subacute states even with the use of T1-weighted HRVWI. On the other hand, the utility of T2-weighted HRVWI in the acute and subacute stages has only been evaluated in a few case reports [7,8]. The aim of this study was to compare the utility of aneurysmal dilations on T2-weighted HRVWI with that of IMH on T1-weighted HRVWI, discrepancies between combination of BPAS and MRA, mainly during the acute and early subacute stages of iPICA-D.

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