Eyebrow Keyhole Approach in Aneurysm Surgery

The concept of keyhole neurosurgery is not only to perform small incision and reduce the craniotomy size for the sake of a small opening as we called “keyhole,” but it is rather to make “minimum craniotomy” required to access deep intracranial lesions at the end of the route. Standard craniotomy forms a “funnel-shaped surgical corridor” to reach deeper area of the brain. In contrast, keyhole mini craniotomy forms a “reverse funnel-shaped surgical corridor” that provides adequate working space through a small incision and bone window to reach the target. The concept of this approach is that the deep area of the brain can be accessed through smaller craniotomy since the superficial optical field is widened if the size of craniotomy is bigger (Fig. 2.1).


Basic Consept
The concept of keyhole neurosurgery is not only to perform small incision and reduce the craniotomy size for the sake of a small opening as we called "keyhole," but it is rather to make "minimum craniotomy" required to access deep intracranial lesions at the end of the route. Standard craniotomy forms a "funnel-shaped surgical corridor" to reach deeper area of the brain. In contrast, keyhole mini craniotomy forms a "reverse funnel-shaped surgical corridor" that provides adequate working space through a small incision and bone window to reach the target. The concept of this approach is that the deep area of the brain can be accessed through smaller craniotomy since the superficial optical field is widened if the size of craniotomy is bigger ( Fig. 2.1). Intracranial aneurysm surgery using eyebrow keyhole approach has been reported by Van Lindert and Perneczky in 1998, and since then, this approach has been accepted as minimally invasive approach for aneurysm clipping surgery in addition to the existing standard approach.

Preoperative Planning
The planning and execution of the approach play a critical role in performing this keyhole surgery. The smaller the craniotomy, the greater the need for precise planning and self-made completion of the approach because the corridor of surgical dissection cannot be changed during the procedure. It is necessary to have preoperative consideration about the size and aneurysm dome projection, aneurysm location, perforating arteries, surrounding important structures, and how to plan the bone flap. Using excellent diagnostic facilities of CT, MRI, and digital subtraction angiography (DSA), one has today the possibility to demonstrate small details and specific anatomical orientation of the lesion related with surgical planning. In our experience, preoperative planning for eyebrow keyhole surgery is could be mainly by using and rely on 3D CT angiography (3D-CTA). The 3D reconstruction images maybe able to shows from the skin, then skull, cerebral arteries and veins, including size and shape of the aneurysm. The preoperative planning of the keyhole craniotomy can be simulated with 3D-CTA ( Fig. 2.2).

2.3
Step of the Approach

Positioning and Preparation
The surgeon must plan and perform the proper positioning of the patient by himself. Self-made preparation and positioning are essential for creating keyhole craniotomies. After the patient is anesthetized, the patient head is positioned in supine with head holder, and the head is higher up approximately 15° to facilitate venous drainage. A slightly chin-up position is preferable to support the frontal lobe that will slightly fall down according to the gravity force. The degree of head rotation should be determined by preoperative 3D simulation, but generally the head is The supraorbital craniotomy with the lesion is prepared at various angles to have an optimal microsurgical visualization rotated between 15° and 45° toward the contralateral side, determined by the location and dome projection of aneurysm. The placement of lumbar drain or extraventricular drainage also allows for brain relaxation specially in ruptured aneurysm case with brain edema. Frontal anatomic landmarks should be precisely identified, including the foramen supraorbital, superior temporal line, orbital rim, and zygomatic arch, then drawing the skin incision plan on the skin (Fig. 2.3).

Skin Cut
The skin is cut according to the preoperative planning and anatomical orientation. The skin is cut at lateral two-thirds of the eyebrow, from supraorbital notch to the lateral part, sometimes extending few millimeters to the temporal line. To achieve a good cosmetic appearance, the incision should follow the orbital rim, in the hair line. It is advisable not to overuse bipolar coagulation to avoid damaging hair follicles and surrounding tissues. After skin incision, skin flap is dissected subcutaneously to obtain optimal exposure to surrounding muscles. We could clearly identify the frontal, orbicularis oculi and temporal muscles. After dividing the muscular layers gently, we have to identify pericranium at supraorbital edge, and it is cut perpendicularly following superior temporal line to get good bone exposure.
Skin flaps should be gently retracted with three or four temporary stiches at each upper and lower side of the flaps. The frontal muscle should be retracted upward, and the temporal muscle is detached gently from the attachment and retracted laterally to expose ipsilateral temporal line, and then keyhole area is exposed. Gentle detachment and pulling of the muscle are important to prevent local postoperative hematoma (Fig. 2.4).

Mini Craniotomy and Dural Incision
Making a single frontobasal burr hole at the frontozygomatic point just behind the temporal line by using high-speed drill. The placement and direction of the drilling procedure should be in correct man-a b Fig. 2.3 Supine positioning of the patient, slightly extended and the head is turned to contralateral, and depend on aneurysm location. In most cases, the headrest with soft cushion is used for a brief preparation; the use of head fixation clamp is not necessary ner. Wrong direction during drilling can cause the drill going into the orbit, while we actually want it to go to the anterior frontal floor. The craniotomy flap is then performed with high-speed craniotomy, starting from lateral orbital rim and following the orbital rim to medial, as long as 25-30 mm, then curving cranially about 15-25 mm, and cutting back to the burr hole site, thus creating a small bone flap. An important point is the bone cut should be very close and approaching orbital roof and if necessary additional drilling to make any prominence at the frontal floor totally flat. This may provide a few millimeters more exposure and avoid the bony prominence to obstruct surgical visualization and facilitate optimal microsurgical maneuvers using microscope and microinstruments (Fig. 2.5).
Opening the dura with semicircular shape and the base parallel along the orbital rim. The dura flap is reflected basally and fixed downward with three or four sutures so that dural window is formed in optimal opening following craniotomy corridor (Fig. 2.6).

Intradural Dissection
After opening the dura, the first-step maneuver is to gently remove sufficient cerebrospinal fluid by opening the arachnoid membrane through the chiasmatic and carotid cistern or furthermore to Sylvian fissure. Ventricular puncture and drainage sometimes may be needed in case of brain edema; the authors only use the lumbar spinal drain for very selective cases. With adequate drainage of CSF (cerebrospinal fluid), the brain becomes relaxed, then a brain spatula is put in the frontal lobe, and the purpose is to protect the cortex and not to retract the cortex. With this efficient and adequate surgical corridor, we can get to the aneurysm precisely and avoid extensive cortical retraction (Fig. 2.7).

Closure and Bone Flap Replacement
After the intracranial procedure is performed, the next step is filling the intradural space with warm normal saline. Close the dura with watertight and interrupted sutures, and then make sure that any defects are well repaired. If the frontal sinus opened during the surgery, it is a must to seal off the frontal sinus to avoid postoperative infection. Bone flap is placed back, and hold it with mini plates and be careful not to penetrate frontal sinus by the screws. Authors prefer using three mini plate fixations at medial, lateral, and upper part of craniotomy to make sure a strong fixation to prevent postoperative deformity. Reapproximate the temporal muscle to zygoma by one or two sutures. After final hemostasis control, reapproximate the subcutaneous layer by interrupted sutures; then the skin is also closed by interrupted sutures in the eyebrow ( Fig. 2.8).

Complications and How to Avoid
There are some complications that could be occurred associated with surgical technique in eyebrow keyhole approach.
1. Temporary or permanent supraorbital hypesthesia. In eyebrow keyhole craniotomy, the surgical field is very narrow, and medially the surgical field is limited by supraorbital notch that contains supraorbital nerve. Perioperative anatomical landmark should be prepared precisely to avoid damaging these structures. Certainly, keeping a distance of the craniotomy site at least 5-10 mm lateral to the orbital notch can reduce the risk of supraorbital nerve injury. Sometimes stretching the nerve during surgery is unavoidable, but preserving the nerve continuity will provide good chance to have functional recovery after surgery. 2. Frontal deformity. The frontobasal burr hole needs to be placed behind the temporal line after retracting the temporal muscle laterally. The burr hole site will be covered with the muscle to prevent deformity in this area. Proper repositioning of the bone flap is also an important step to prevent frontal deformity for a better cosmetic result. Bone flap should be fixed frontally and medially without any bony a b  The images or other third party material in this chapter are included in the chapter's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.