A Ruptured Aneurysm in Aplastic or Twig-like Middle Cerebral Artery: A Case Report with Histological Investigation

Abstract

Aplastic or twig-like middle cerebral artery (Ap/T-MCA) is a rare vascular anomaly that can cause a hemorrhagic or ischemic event. We report a 38-year-old man who presented with intracerebral hemorrhage from a ruptured aneurysm associated with an Ap/T-MCA. After aneurysm trapping and resection, histopathological examination revealed an internal elastic lamina (IEL) disruption and a thin aneurysmal wall. The patient recovered well after surgery and rehabilitation. No hemorrhagic or ischemic events have occurred during 2 years of follow-up. Ap/T-MCA-associated aneurysms exhibit a disrupted IEL and thin wall, which demonstrates the fragility of the "twig-like" vessels.

Keywords: aneurysm; anomaly; intracerebral hemorrhage; twig-like middle cerebral artery.

Fig. 1

A) A parenchymal hematoma in the right temporal lobe was seen on computed tomography. B) Cerebral angiography showed “twig-like” vessels of the M1 segment arising from A1 segment of the anterior cerebral artery with normal vessels distally. Pial anastomoses from the anterior cerebral artery were present, indicating insufficient blood supply from the middle cerebral artery. C) Three-dimensional rotational angiography showed a 1.9 × 1.9 mm aneurysm (white arrow) at a non-branching point of the twig-like vessel. D) Slab maximum intensity projection (MIP) images of rotational angiography showed the aneurysm (white arrow) located deep in the hematoma and arose from a tortuous segment of a “twig-like” vessel. E) The aneurysm (black arrow) is clearly visualized at an oblique cerebral angiography view.

Fig. 2

An intraoperative photograph shows the aneurysm (white arrow). The aneurysmal wall consisted of dark red hematoma covered by a thin fibrous wall and appeared to be a pseudoaneurysm associated with arterial dissection.

Fig. 3

A) A thick hematoma (arrows) was observed within the aneurysmal wall (hematoxylin and eosin (HE) staining, ×40). B) The smooth muscle cell layer was prominently thin (arrow) (HE staining, ×100). C) The internal elastic lamina (IEL) was disrupted in the aneurysm neck (arrow) and an mural hematoma was seen adjacent to layers of the arterial wall (Elastica van Gieson (EVG) staining, ×40). D) Higher magnification showed that the thickened intima in the neck became extremely thin (arrowheads) and without IEL in the aneurysmal wall (EVG staining, ×100). E, F) The parent artery of aneurysm (white arrow) showed a normal vascular structure with no tunica media thinning or tortuosity of the internal elastic lamina (HE staining, ×40 and EVG staining, ×40).

Fig. 4

A) Preoperative MRA showed decreased signal intensity on the right MCA area, B) which was not further affected postoperatively. C) Follow-up single photon emission computed tomography (SPECT) showed no significant reduction of CBF on the affected side other than the area of hematoma.