串団子形状を呈し自然閉塞を来した解離性後下小脳動脈瘤の1例—放射線学的所見を中心に

Spontaneous Occlusion of a Dissecting Aneurysm in the Shape of “Two Dumplings on a Skewer” at Right Posterior Inferior Cerebellar Artery (PICA) : report of a case and neuroradiological findings

I．はじめに

　後頭部痛，ふらつき感，吃逆を主訴として来院した症例の頭部MRIにてPICA dissecting large aneurysmとして特異的な形状所見を得たので，文献的考察を加えて報告する．

We present a case of a spontaneous dissecting aneurysm at the vertebrobasilar artery including the right PICA in a 44-year-old man, who suffered from headache, hiccup and ataxic gait. The arteriograms showed an irregular narrowing and dilatation in the right PICA and in the vertebrobasilar artery, and showed fusi-form dilatations in the bilateral middle cerebral arteries. We observed intramural hematoma and true lumen at the right PICA dissecting aneurysm on T1-weighted images on magnetic resonance imaging (1.5T, MRI), and the intimal flap was enhanced on T1-weighted image after intravenous injection of Gd-DTPA.The shape of the intramural hematoma showed a unique “two dumplings on a skewer” appearance, and the intensity of its hematoma in the false lumen decreased in gradient from adventitia to intimal flap on Tl-weighted image on MRI. The dissecting aneurysm of the PICA was occluded spontaneously 1 month later, and it caused cerebellar infarction. However, the patient has been left only with the symptom of slight trunkal ataxia.

Various shapes of intramural hematomas on MRI have been reported by Kitanaka in association with in-tracranial vertebrobasilar dissections. We suggest that “two dumplings on a skewer” shape which corres-ponds to the flow void of the true lumen, accompanied by intramural hematoma and enhanced intimal flap, on contrast-enhanced T1-weighted image, should be regarded as a true “diagnostic sign” of a dissecting aneurysm.