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M1 Dysplastic Aneurysm

August 11, 2015


Dissecting MCA aneurysms are quite a rare disease. The case of a 21 year-old female who was pregnant when she suffered from a thunderclap headache. MRI evaluation demonstrated trace amount of blood on gradient echo images along the right Sylvian fissure. An MRI suggested dissection of the proximal aspect of M1. Due to the status of her pregnancy, an angiogram was avoided. Due to the suggestion of the dissection, consistent with pattern of blood, in this case, the patient underwent a right frontotemporal craniotomy. The Sylvian fissure was widely dissected. You can see the M1, the ICA and the A1 here. The anterior temporal artery is situated here. Initial inspection did not reveal any obvious abnormality along the M1. Further inspection was necessary to assure no other vascular abnormality was overlooked. Therefore two temporary clips were placed on the ICA and A1, so I can circumferentially dissect around the M1 and thoroughly inspect the area. Here I found a questionable abnormality. our further inspection revealed this to be the origin of the M1 perforating vessels, the lenticulostriate arteries. No aneurysm is encountered. The artery appears bulbous, but no obvious dissecting aneurysm is apparent. Further inspection, more proximally and posterior to the circumference of the M1 suggested thinning of the wall and a very bulbous morphology of the proximal M1, just at the level of the ICA bifurcation. However, no obvious hemorrhage was apparent that could be related to the aneurysm rather than the dissection. Further inspection inferior to the M1, also did not reveal any obvious aneurysm or acute bleeding. Here, further inspection of the posterior aspect of the M1 suggested a bulbous abnormality without any clear defect in the wall of the M1. I suspected that this could be the only candidate potentially accounting for her hemorrhage. Therefore muslin fibers were used to cover this potential area of hemorrhage thoroughly, causing inflammation and potentially avoiding future hemorrhage. Here is also a piece of cotton, bolstering the muslin fibers. She recovered from her surgery and underwent an uneventful delivery two years postoperative, MRI demonstrated no significant change in the morphology of the bulbous M1 segment, and the patient has not suffered from any further neurological deficits or thunderclap headaches, thank you.

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