An aneurysm at the DMCA origin was initially reported in 1962 [
8]. Most reported aneurysms related to DMCA were located at the DMCA origin [
6,
7]. Aneurysms at locations other than the DMCA origin have also been reported [
4,
6]. DMCA-related aneurysms have been suggested to be formed due to hemodynamic stress. To the best of our knowledge, 35 cases of DMCA origin aneurysm have been reported [
6‐
11]. And almost half of the cases of DMCA aneurysms have multiple aneurysms due to hemodynamic condition [
6]. Among them, only five cases of DMCA with distal MCA aneurysms have been reported [
8‐
11]. These previously reported five cases and our case are summarized in Table
1. Among them, four aneurysms were located on the distal portion of the main MCA [
12,
13,
15], and one aneurysm was located on the distal portion of the DMCA itself [
14]. In our case, the aneurysm was found at the M1/M2 junction of DMCA, and not the main trunk of the MCA. The diameter of the DMCA was almost the same as that of the main MCA. Among the four reported cases with distal aneurysms on the main MCA, the main MCA trunk was thicker than that of the DMCA in three cases. In the other case, the diameters of the main MCA and DMCA were almost the same. On the other hand, in a case of an M1/M2 aneurysm on DMCA, the diameter of the main MCA was almost the same as that of the DMCA. These previous observations and our experience suggest that an aneurysm might be formed at the thick MCA due to hemodynamic factors. All the previously reported five cases were ruptured ones. The risk of rupture of distal DMCA aneurysm seems to be high. If the aneurysm is not small, radical treatment should be considered. For the three ruptured aneurysms, common treatment such as clipping was performed, and two patients showed good recovery. Furthermore, the distal ICA was tortuous in our case. The ICA top might be stressed by blood flow. Therefore, an aneurysm was formed at the top of the ICA due to hemodynamic stress. In the six cases of DMCA with distal MCA aneurysms, half of them had another aneurysm.
Table 1
Summary of cases of duplicated middle cerebral artery accompanied with distal aneurysms
1 | 67, F | Asian (Japanese) | 0.71 | 0.37 | M1 of main MCA | ND | + | ND | ND | – | |
2 | 66, M | Asian (Japanese) | 0.92 | 0.32 | M1/M2 of main MCA | ND | + | ND | ND | AComA aneurysm | |
3 | 55, F | ND | Both arteries were similar in size | Sylvian portion of the main MCA | ND | + | Clipping | Death | Contralateral MCA aneurysm (superior trunk) | |
4 | 45, F | Asian (Japanese) | Both arteries were similar in size | Distal trunk of DMCA | ND | + | Clipping | GR | Bilateral accessory MCA | |
5 | 34, F | Black | DMCA was smaller than the main MCA | Inferior division of main MCA | ND (> 10 mm in figure) | + | Clipping | GR | – | |
Present case | 62, M | Asian (Japanese) | Almost the same | DMCA | 3 | _ | Observation | No change | Ipsilateral ICA top aneurysm | |