The present study verified excellent surgical outcomes when using a superciliary approach for unruptured supraclinoid ICA aneurysms with a maximum diameter up to 12 mm in patients aged 37 to 75 years. Successful aneurysm clipping was achieved in all patients with minimal surgical morbidity and less invasiveness than a pterional approach.
While the keyhole concept of a superciliary approach is already used for tumorous and vascular lesions of the anterior cranial fossa and parasellar region27,30)
, it is still not a popular neurosurgical practice due to certain significant shortcomings. As the size of the cranial opening is small, this reduces the intraoperative light and sight, and limits the maneuverability of the surgical microinstruments, necessitating almost coaxial control of the microinstruments. Also, the supraorbital location of the mini-craniotomy only allows a subfrontal approach, whereas a pterional craniotomy with modifications allows pterional, subfrontal, and multidirectional approaches.
Yet, despite such shortcomings, this study highlighted the usefulness of a superciliary approach for unruptured ICA aneurysms. In the case of supraclinoid ICA aneurysms, they are located in the center of the small and deep surgical field, however, ACoA and MCA aneurysms are situated in the corner of the surgical field, which requires more technical development and a longer learning period. Moreover, most ICA aneurysms can be clipped using a subfrontal unidirectional perspective. Thus, a 90-minute simple and straightforward procedure can provide satisfactory treatment of the aneurysms.
When considering the meta-analysis by Raaymakers et al.28)
, which reported 0.8% mortality and 1.9% permanent major morbidity related to the surgical clipping of non-giant anterior circulation aneurysms, the zero-percent major complication rate in the current series underscores the safety of the superciliary approach for unruptured ICA aneurysms.
When comparing the less invasive superciliary approach with a pterional approach, the present study found statistically significant advantages to the superciliary approach in terms of a shorter operative duration, no intraoperative blood transfusion, and no occurrence of postoperative EDHs. Le Roux et al.14)
previously reported a 13.2% incidence of blood transfusions during conventional surgery for unruptured aneurysms. Plus, postoperative EDHs after conventional craniotomies are not uncommon and can be a serious complication. In a report by Fukamachi et al.5)
, EDHs occurred in 46.8% of patients after conventional aneurysm surgery, where 2.1% required reoperation to remove the hemorrhage.
Avoiding damage to the temporalis muscle is another advantage of a superciliary approach, whereas a pterional craniotomy causes temporalis atrophy and varying degrees of pseudoankylosis of the temporomandibular joint7,9,22)
. Kawaguchi et al.10)
reported limited mouth opening in 20% of patients 1 month after a pterional craniotomy. Conversely, palsy of the frontalis muscle is a potential problem with a superciliary approach. Although, in a previous report by the current authors, only 5.9% of patients were found to experience long-lasting palsy for more than 6 months following a superciliary procedure27)
Thus, this minimally invasive superciliary approach offers many convincing benefits over a conventional pterional craniotomy, including a smaller incision without scalp shaving, much smaller craniotomy reducing the risk of a postoperative EDH, reduced trauma to the body reducing the postoperative pain, shorter operative duration, reduced blood loss, reduced risk of infection in the operative field, faster postoperative recovery, and earlier return to normal life.
Furthermore, the reduced patient repulsion to surgical treatment due to the minimally invasive nature of the superciliary surgical procedure also has a positive effect on the decision of treatment modality, surgical or endovascular. Surgical treatment can invariably be an easier option for cases that are technically challenging or not amenable to endovascular therapy, for example, cases involving difficult navigation of the microcatheter due to acute angles or the morphology of the aneurysm, very small aneurysms (defined as <3 mm in diameter), wide-necked aneurysms necessitating stent-assisted or balloon-assisted technology, and aneurysms with an arterial branch incorporated into the sac1,8,11,12,15,17-21)
The selection of an appropriate surgical approach, superciliary keyhole approach versus pterional approach, depends on the surgeon's discretion and experience. Aneurysm complexities difficult to handle via a superciliary keyhole approach may include large size, previous coiling, adherence of the AChA, and atherosclerotic calcification31)
Although the current study is limited based on a retrospective review of a case series from a single institution, it is the first large case series highlighting unruptured supraclinoid ICA aneurysms as an optimal application for a superciliary approach. The current case series covers various aneurysms arising in the supraclinoid ICA, including PCoA origin, AChA origin, ICA bifurcation, and the dorsal wall of the ICA, although aneurysms originating from the ventral wall of the ICA have not been included due to their rarity.