山口 枝里子^{1, 2}, 土井尻 遼介^{1, 3}

Eriko YAMAGUCHI^{1, 2}, Ryosuke DOIJIRI^{1, 3}

¹岩手県立中央病院脳神経内科, ²国立循環器病研究センター脳神経内科, ³秋田県立循環器・脳脊髄センター脳卒中診療部脳血管内科

¹Department of Neurology, Iwate Prefectural Central Hospital, ²Department of Neurology, National Cerebral and Cardiovascular Center, ³Department of Cerebrovascular Medicine, Akita Cerebrospinal Cardiovascular Center

キーワード : brachiocephalic plaque, mobile plaque, microvascular flow imaging, superb microvascular imaging

脳梗塞の原因として腕頭動脈プラークが塞栓源となることがある．可動性の腕頭動脈プラークを超音波で診断し，MVFIの手法であるSMIを用いて可動性病変が鮮明に描出された症例を経験したため報告する．77歳女性．構音障害，右上肢の運動失調を主訴に来院し，National Institute of Health Stroke Scaleスコア 2点であった．頭部MRIで右小脳半球，橋，左側頭葉に多発性の脳塞栓症を認めた．塞栓源検索目的で行った経食道心エコーで腕頭動脈に可動性プラークを疑い，体表面からセクタプローブで走査したところ腕頭動脈内に可動性プラークを認めた．深度が深く，アーチファクトとの鑑別を要したためSMIを使用したところ，可動性プラークが高信号に明瞭に描出された．同部位を塞栓源と診断し，抗血小板薬を含む内科治療を行った．以後超音波でプラークの形態について経過観察を行っている．SMIは組織の動きの特徴を解析し，低速血流と組織の動きを分離する技術である．SMIで可動性プラークが明瞭となる機序としてモーションアーチファクトにより過可動性を伴うクラッタ運動，反射強度が強い点が考えられている．セクタプローブによる可動性腕頭動脈プラークの評価にSMIは有用であった．

Brachiocephalic artery plaque may be an embolic source as a cause of cerebral infarction. We report a case in which a movable brachiocephalic artery plaque was diagnosed using ultrasound and in which a movable lesion was clearly visualized using superb microvascular imaging (SMI). A 77-year-old woman presented to our hospital with dysarthria and ataxia of the right upper extremity, scoring 2 on the National Institute of Health Stroke Scale. Head magnetic resonance imaging showed multiple cerebral emboli in the right cerebellar hemisphere, pons, and left temporal lobe. Transesophageal echocardiography performed to search for the source of the embolus revealed a mobile plaque in the brachiocephalic artery, which was scanned from the body surface with a sector-type probe. The depth of the plaque was so deep that it was necessary to differentiate it from artifacts, so SMI was used. The patient was diagnosed as having an embolic source at the same site and was treated medically with antiplatelet agents. The patient has since been followed up via ultrasound to monitor the morphology of the plaque. SMI can be used to analyze the characteristics of tissue motion and separate slow blood flow from tissue motion. The mechanisms by which mobile plaques become apparent with SMI include clutter motion with hypermobility due to motion artifacts and strong reflection intensity. In the present case, SMI was useful in the evaluation of mobile brachiocephalic artery plaques using a sector-type probe.