This 74-year-old female has been referred for MRI after having difficulty walking with occasional dizziness and a sense of falling. She has been diagnosed with an anterior communicating artery (ACom) aneurysm. As a midline lesion, an ACom aneurysm could theoretically be approached from either side. The better side of the surgical approach depends on a number of factors, which the radiologist can help bring to the surgeon’s attention. How would you help in this case?
HX: The first factor is the recognition that most aneurysms bleed from the dome and that surgical exposure is generally aimed at exposing the aneurysmal neck (image 1, green arrow) where the clip will be applied before the dome (image 2, orange arrow) is exposed. This is done to decrease the chance of re-bleeding. In this instance, the aneurysm is pointing from left to right and a left-sided approach would give the surgeon access to the neck (image 2, pink arrow) of the aneurysm without dissecting the dome, which is preferred.
A second factor is the condition of the brain parenchyma post hemorrhage. Anterior communicating artery (ACom) aneurysms will often bleed into one of the gyrus recti (image 3, green arrows). Unilateral gyrus rectus damage can be well tolerated but bilateral damage can result in cognitive sequelae. If possible it is best to operate from the side of the gyrus rectus which has already sustained damage. This preserves the undamaged gyrus rectus as the approach to the aneurysm can often require partial resection of the gyrus rectus. When reporting a CTA with an ACom aneurysm in the setting of subarachnoid hemorrhage, the radiologist should scrutinize the accompanying CT and MR and comment on the condition of the gyrus recti.
The third factor is cerebral dominance, which in a large portion of the population would be left-sided, though it can be bilateral or on the right, particularly in left-handed individuals. A non-dominant approach is often chosen in midline non-aneurysmal lesions where the above factors are not an issue. For more case review, check out MRI Online.
Dr. Stephen Pomeranz
Dr. Malcolm Shupeck