The last step before reperfusion is repairing the arteriotomy, which can be performed using three surgical techniques. The first option is a conventional microsuture technique [1–5], which involves temporarily trapping the arteriotomy site and 8–0 monofilament sutures to close an arteriotomy in the ICA and 9–0 or 10–0 monofilament sutures to close an arteriotomy in the M1segment or a MCA division. This microsuturing technique requires the most time. For the second option, the arteriotomy is simply repaired using a curved or angled aneurysm clip [23, 24]. This is possible when the arteriotomy is <3 mm (Fig. 13.2a). The clip is applied tangential to the arteriotomy, thereby replacing the microsutures and reducing the operative time. While a standard aneurysm clip can be used to close an arteriotomy in the ICA, a miniclip can be used for an arteriotomy in the MCA. Finally, the third option is applicable when the arteriotomy is >3 mm and cannot be repaired using a tangential clip. This special technique allows immediate cerebral reperfusion as one or two aneurysm clips with curved blades are used as temporary compartmentalizing clips to encircle and separate the arteriotomy site (Fig. 13.2b, c). This creates a transient vascular conduit below the clip blades, allowing a cerebral blood flow during microsuturing. The clips are then removed after the repair is finished [29].

The lengthy surgical procedures involved in a conventional surgical embolectomy are unsuitable for endovascular techniques in the case of an acute ischemic stroke [1–5]. In contrast, the recently developed MIRSE technique enables rapid surgical recanalization in a minimally invasive manner within a limited therapeutic time window [23, 24]. Reflecting the acute ischemic stroke management concept of “time is brain,” MIRSE minimizes both the surgical invasiveness and the operative time for cerebral reperfusion.

Undoubtedly, the limitations of minimally invasive surgery with a small cranial opening include narrow viewing angles, reduced intraoperative light, reduced maneuverability of the microinstruments, and unidirectional application and coaxial control of the instruments. Yet, these limitations can be overcome using specialized surgical techniques and with surgical experience. Thus, the MIRSE technique consists of a superciliary keyhole approach, an arteriotomy for removing the embolus, and arteriotomy repair techniques for obtaining rapid reperfusion in the case of a small limited craniotomy.

A keyhole approach has several advantages, including rapid access to the lesion with a small operative wound, reduced wound-related pain, no intraoperative blood transfusion, minimal occurrence of postoperative epidural hematomas, an early return to work and normal life, and a decreased patient reluctance for surgery.

The MIRSE procedure begins with a superciliary keyhole approach, consisting of a 4-cm eyebrow incision starting from the midpupillary line and a supraorbital mini-craniotomy (Fig. 13.3) [23, 24]. This superciliary keyhole approach has already been used for tumorous and vascular lesions of the anterior cranial fossa and parasellar region [30–37]. While the surgical embolectomy procedures require a 4-cm or 4.5-cm eyebrow incision, unruptured aneurysms can be clipped using just a 3.5-cm eyebrow incision.

Despite the small superciliary skin incision, a relatively large craniotomy is created by cutting and splaying the underlying muscles. A high-speed drill with a footplate attachment is then used to drill a frontobasal lateral burrhole and create a supraorbital bone flap with a diameter of >2 cm. Before drilling, unidirectional skin retraction using a retractor held by an assistant can avoid skin damage and create sufficient space for the craniotomy. Six retraction sutures are positioned at the edge of the skin incision. The inner edge of the craniotomy above the orbital rim is drilled and beveled, while the frontal floor prominences are flattened. Plus, to expose the sylvian fissure area, the sphenoid ridge adjacent to the frontobasal lateral burrhole is slightly drilled.

Following the dural incision, an operating microscope is used to slide a narrow brain spatula over the base of the frontal lobe toward the carotid and optic nerve cisterns, which are then opened to drain the cerebrospinal fluid, achieve brain relaxation, and obtain an intracranial working space. To expose the supraclinoid ICA, dissecting the proximal sylvian fissure provides more frontal lobe retraction and visualization up to the carotid bifurcation. Additional dissection of the sylvian fissure exposes the M1 segment, MCA bifurcation at the MCA genu, and proximal M2 segment. As the sylvian dissection is performed along the frontal side of the sylvian veins, the division of some small fronto-sylvian veins is inevitable.

The identification of the occluded vessel segment, arteriotomy, intravascular blood clot removal, and verification of the antegrade and retrograde blood flow by opening the temporary clips proximal and distal to the arteriotomy are all performed as described above. All these tasks can be effectively performed via a keyhole approach.

Repairing the arteriotomy is the last step before cerebral reperfusion. Among the three abovementioned techniques for repairing the arteriotomy, microsuturing is the most challenging via a keyhole approach. While passing a needle through the vascular wall in a running manner is feasible using a right-hand needleholder, tying a knot, which involves four separate actions (picking up the thread with the left-hand forceps, making a loop around the tip of the right-hand forceps, picking up the short end of the thread with the right-hand forceps, and pulling the loop off the right-hand forceps), can be difficult when using microinstruments with coaxial movement through a small cranial opening.

Therefore, a new clip-knotting technique is used for tying a knot after microsuturing via a keyhole approach (Fig. 13.4) [38]. With the needleholder in the right hand, the needle and a short (5 cm) thread are passed through the vessel wall several times in a running manner along the arterial incision. After tightening the running stitch to approximate the edges of the lesion, the ends of the thread are both held with forceps using the left hand. To hold both threads in place, an aneurysm clip is then applied using a right-hand clip applier, and any remaining thread beyond the clip is cut appropriately.

If the arterial incision is <3 mm, the simplest way to repair the arteriotomy is the tangential application of a curved or angled aneurysm clip [23, 24].