Subarachnoid hemorrhage due to nonbranching aneurysm of the middle cerebral artery in a young adult with a history of Kawasaki disease
A 20-year-old male experienced a sudden onset of headache, nausea, and vomiting. He was brought to a nearby hospital, where a head computed tomographic (CT) scan revealed SAH. He was immediately transferred to our hospital for emergency treatment. He had a history of Kawasaki disease, which was believed to be cured. He had severe atopic dermatitis and was allergic to pollen, dogs, cats, and soba. There was no relevant family medical history and no previous history of forceps delivery, major head injury, and infectious or valvular disease. On arrival at our hospital, his Glasgow Coma Scale score was 14 points (E3V5M6). Physical and neurological examination revealed no specific abnormal deficits. Laboratory blood tests also revealed no abnormalities. Plain CT of the brain showed SAH, localized in the right sylvian fissure, and evidence of skull fracture []. Subsequent CT angiography indicated an aneurysm of the right M2, which was not at a bifurcation site []. Magentic resonance (MR) angiography revealed that the aneurysm had a stalk-like narrow neck. A pseudoaneurysm was suspected on the basis of the atypical location and shape of the aneurysm, his age, and his medical history of Kawasaki disease. Preoperative echocardiography rejected the presence of bacterial endocarditis and other heart abnormalities. As far as we could examine, there were no other vascular abnormal findings other than the aneurysm described here including aneurysms of other locations.\nThe sylvian fissure was identified and opened to expose the two parallel M2 branches. The M1 and the parental artery were then subsequently secured. A thin-walled, pseudo-looking aneurysm was found buried in the frontal lobe, but it appeared to be clippable []. A 5-mm bayonet-type clip (Sugita 2, Mizuho) was chosen and several attempts were made to close the ruptured hole without narrowing the parental artery []. A doppler study confirmed good flow through the artery, and the aneurysm appeared to be completely obliterated. The thin aneurysm wall was partially trimmed for pathological analysis and Neoveil™ was wrapped around the neck. The aneurysm wall appeared extremely thin and fragile and was surrounded by some clots.\nHistopathological examination revealed that the aneurysm wall primarily consisted of thinkened tunica intima. Granulation tissue presented with edematous chronic inflammatory cell invasion and intermediate invasion of macrophages, fibroblasts, myofibroblasts, and vascular endothelial cells. There was mild invasion of lymphocytes and plasmacytes, but no neutrophils []. Lack of black Elastica van Gieson (EVG) staining demonstrated complete absence of elastic lamina. EVG staining, Masson's trichrome staining, and smooth muscle actin (SMA) immunohistochemistry also demonstrated the lack of smooth muscle cells in the tunica media. There was no atherosclerotic change in the tunica intima, which is usually observed in cerebral aneurysms [].\nAfter surgery, the patient regained consciousness and exhibited a full postoperative recovery. Two weeks later, CT angiography showed complete amelioration of the aneurysm and normal flow of the parent artery []. Plain CT after sugery also confirmed an intact brain []. His postoperative course was uneventful without any neurological deficits, and he was discharged 2 weeks after admission.