Spontaneous mirror dissections of cervicocephalic arteries. Pathomechanical considerations

Abstract

While so-called twin or mirror aneurysms constitute an established subgroup of multiple aneurysms, simultaneous spontaneous mirror dissections of cervicocephalic artery have not yet been reported as a particular entity. Among the patients treated at our institution since 1989, we identified 74 patients with spontaneous, nontraumatic dissections. Six of these cases presented with simultaneous bilateral dissections and four of the six patients had mirror dissections. Acute or chronic headache was present in all four cases. Additional clinical presentations consisted of impaired consciousness, cranial nerve palsy, and tinnitus. Angiography revealed irregular stenosis, dilatation or aneurysms located in the cervical ICA (internal carotid artery), VA (vertebral artery), or MCA (middle cerebral artery) without evident location bias. Although mirror dissections seems to be an exceptional finding, they may shed light on the vulnerability of different arterial segments to specific diseases. Similar to arterial aneurysm formation, pathogenesis of mirror dissection may involve an underlying "shared defect" in the endothelial cells, since these cells demonstrate a bilateral distribution during embryological development. This particular distribution therefore also provides a chronicle trail of the first trigger striking during embryonic development and demonstrates the segmental vulnerability to highly specific triggers.

Figure 1

Case 1. MRI (A-D,Tl-weighted fat-suppressed images (SPIR) pre contrast) reveals an intramural crescent shaped hyperintensity indicative of mural hematoma on the cervical segments of both internal carotid arteries (ICA). Lateral projection of the left (E) and right (F) common carotid artery angiography demonstrates irregular stenosis and dilatation of the ICA lumen which confirmed the diagnosis of bilateral mirror-like segmental ICA dissections. A pseudoaneurysm was opacified near the cranial base on the left ICA.

Figure 1

Case 1. MRI (A-D,Tl-weighted fat-suppressed images (SPIR) pre contrast) reveals an intramural crescent shaped hyperintensity indicative of mural hematoma on the cervical segments of both internal carotid arteries (ICA). Lateral projection of the left (E) and right (F) common carotid artery angiography demonstrates irregular stenosis and dilatation of the ICA lumen which confirmed the diagnosis of bilateral mirror-like segmental ICA dissections. A pseudoaneurysm was opacified near the cranial base on the left ICA.

Figure 2

Case 3. (A) CT scan reveals an extensive frontotemporal hematoma and diffuse SAH. AP view of right (B) and left (C) ICA angiography demonstrates a pseudoaneurysm on the right MCA and a fusiform aneurysm on the left, thereby indicating bilateral segmental dissections of the MCA. Notice the diffuse irregular stenosis in the anterior circulation bilaterally, corresponding to atheromatous changes as verified during surgery.