A total of 2,878 consecutive intracranial aneurysms were treated with EVT or surgery between January 2010 and December 2018 in a single tertiary center. Among these, patients with ruptured aneurysm and patients less than 75 years old were excluded. Finally, we included a total of 55 UIAs in 54 extremely elderly patients with more than 75 years old. The detailed patient data were retrospectively reviewed from our prospectively collected aneurysm database that included clinical information, radiological findings, outcome, and complications by two independent observers. The study protocol was approved by the institutional review board of our institution, and the requirement for written informed consent was waived.

The treatment strategy (coiling or clipping) was decided by a multidisciplinary team composed of two neurovascular neurosurgeons and a neurointerventionist. After careful review of angiographic findings and consideration of patient’s medical condition, we decided the treatment modality. If we concluded that there were no definite benefits between the two options concerning clinical outcome and postprocedural complications, coiling was primarily chosen rather than clipping. In cases with 1) MCA aneurysm with incorporated branching vessel, 2) very tortuous proximal vessels, and 3) intracranial stenosis around the aneurysm, we primarily selected clipping rather than coiling. Additionally, we considered aneurysm location, configuration, endovascular accessibility to the aneurysm, patient’s medical and neurological condition, predicted treatment risks, surgeon’s preference, and preference of the patient and family for this decision.

All clipping was conducted by conventional pterional approach and routine microsurgical procedure under general endotracheal anesthesia (GEA). Intraoperative monitoring (IOM) system including somatosensory and motor evoked potential was routinely applied in all surgery. After neck clipping, intraoperative doppler sonography and indocyanine videoangiogram were also routinely used in all cases to confirm the patency of parent and branching vessel and rule out blood filling into the aneurysmal sac. All coiling was also performed under GEA. We did not use IOM in coiling cases. Aneurysm occlusion was confirmed by immediate postprocedural cerebral angiography. Regardless of treatment modality, all patients were routinely taken care of in the intensive care unit. If complication did not occur, the patients were transferred to general ward on postoperative day 1 and discharged within 5 hospital days.

Patients’ clinical outcomes were assessed by the modified Rankin Scale (mRS) at discharge and 3 months later. Good clinical outcome was regarded as mRS ≤2. Postprocedural symptomatic complication was defined as 1) development of new neurologic deficit, or 2) decreased 2 or more of mRS score compared with initial score.

Immediate postoperative angiographic results were evaluated by digital subtraction angiography (DSA) after EVT, and indocyanine videoangiogram or DSA after surgery. The first follow-up radiologic examination was MRA in coiling and CTA in clipping. We performed MRA or CTA at three to 12 months after the operation in an outpatient clinic. An additional imaging study was conducted according to the result of first follow-up imaging study.

We used SPSS version 24 for the statistical analysis (SPSS Inc., IBM Company, Chicago, IL, USA). Student’s t-test or Mann-Whitney U test for continuous variables and χ² or Fisher’s exact test for categorical variables were used for statistical analysis.

The details of clinical and radiological characteristics are summarized in Table 1. Fifty-five UIAs in 54 patients were treated in our institute. Of 55 UIAs, 44 were treated with coiling and 11 were treated with clipping. Forty-one out of 54 patients (74.5%) were female, and the mean age was 76.9 years old. Underlying co-morbidity was found in 45 patients (83.3%). Twenty-two patients (40.7%) had 2 or more co-morbidity. The most common co-morbidity was hypertension (40 of 54 patients, 74.1%), followed by diabetes mellitus (12 patients, 22.2%), heart problem, previous stoke history, and pulmonary problem. UIA involving anterior communicating artery (AcomA) was most common site (17 out of 55 UIAs, 30.9%), followed by posterior communicating artery (PcomA) (13 patients, 23.6%), middle cerebral artery (MCA) (11 patients, 20.0%), posterior circulation (6 patients, 10.9%), paraclinoid (6 patients, 10.9%), anterior choroidal artery (1 patient, 1.8%), and distal anterior cerebral artery (1 patient, 1.8%). The mean aneurysm size was 8.7±4.3 mm. Seventeen out of 54 UIAs (31.5%) were more than 10 mm in size.

The comparison of clinical and radiological characteristics between coiling group and clipping group is depicted in Table 2. There was no significant difference in patient baseline characteristics including mean age, sex, body mass index (BMI), and co-morbidity between the two groups. Aneurysm location was significantly different between the two groups. The proportion of MCA aneurysm was significantly higher in clipping group. The mean aneurysm size was larger in coiling group (9.24±4.55 mm) compared to those in clipping group (6.60±2.33 mm), but there was no statistical difference (p=0.07). The proportion of large aneurysm did not differ between the two groups. Total anesthesia time was significant longer in clipping group (189.54±34.27 min) than in coiling group (114.36±26.80 min, p<0.001). Postoperative complete occlusion (Raymond 1) rate was 72.7% (8 out of 11 cases) in clipping group and 61.4% (27 out of 44 cases, 61.4%) in coiling group. There was no significant difference between the two groups (p=0.483). Even though there was no statistical difference (p=0.163), aneurysm regrowing occurred only in coiling group (7 out of 38 cases, 18.4%) after mean 25.6 months follow-up period. Three (6.8%) procedure-related symptomatic complications developed in coiling group, while no symptomatic complication occurred in clipping group (p=0.373). One mortality case (9.1%) due to secondary medical problem occurred in clipping group, and there was no mortality case in coiling group (p=0.044). Good clinical outcome at 3 months was achieved in 43 out of 44 cases (97.7%) in coiling group and in 10 out of 11 cases (90.9%, p=0.154) in clipping group.