The patient is positioned supine with the body elevated 10–15° to reduce the venous cranial pressure. The head is fixed sharply in a Mayfield clamp with rotation to the contralateral side and hyperextension of the neck in a way that the zygoma is the highest point (Fig. 22.3a, b). Hyperextension is very important because it leads to frontal lobe retraction simply by gravity. The degree of head rotation depends on the target zone to be reached. Usually, we use 30° rotation in suprasellar lesions and 45° rotation for anteriorly located olfactory groove lesions. In midline tumors, we always come from the right side. In medial sphenoid wing meningiomas, we approach from the side of the lesion. After disinfection, the patient is draped. Microscope and endoscopes are draped as well and are ready to use. The microscope stands behind the surgeon in order to bring it easily out of the surgical field when the endoscopes are used for visualization. The video monitors displaying the MR data, and the endoscopic images are positioned in front of the surgeon to enable an ergonomic work (Fig. 22.4). A Gilsbach frame (Aesculap AG, Tuttlingen, Germany) is used for skin retraction and as a handrest (Fig. 22.5a). The endoscopes are used freehand for inspection, but are fixed to a mechanical holding arm (Karl Storz GmbH & Co. KG, Tuttlingen, Germany) when bimanual dissection and tumor removal are required (Fig. 22.5b).

At first, the skin incision is marked. It is placed exactly in the eyebrow and starts laterally to the supraorbital fissure avoiding injury to the supraorbital nerve (Fig. 22.6a). The incision follows the eyebrow to the lateral end, sometimes even a little bit longer (app. 4 cm). Then the orbicularis oculi muscle and the fat tissue overlying the periosteum are incised. The skin is retracted upward away from the orbit. The superior temporal line indicating the attachment of the temporal fascia is identified (Fig. 22.6b). A periosteal flap based to the orbit is circumcised and elevated (Fig. 22.6c). The lateral incision follows the superior temporal line. Sometimes the supraorbital nerve can be identified at the medial end of the incision (Fig. 22.6d). The temporal fascia and the temporal muscle are detached from the temporal line and adjacent bone. They are retracted laterally with fish hooks (Fig. 22.6e). A small burr hole is placed as far as possible behind the temporal line for cosmetic reasons (Fig. 22.6f). It should be exactly made just over the frontal skullbase. If it is too deep, the orbit will be entered. Then a 2.5 × 2 cm craniotomy is made with the aid of a craniotome as close to the skullbase as feasible (Fig. 22.6g, h). The frontal sinus should be avoided whenever possible. The craniotomy should be approximately 2 cm in height (Fig. 22.6i). If it is too small, the microscopic visualization of the skullbase may be compromised, and the margins of the craniotomy may interfere with the bimanual dissection using the microinstruments. After elevation of the bone flap, the dura is detached from the frontal skullbase (Fig. 22.6j). The inner edge of the craniotomy and prominent protuberances of the orbital roof are drilled away to provide more space for visualization and dissection (Fig. 22.6k). A curved dural incision based to the orbit is finally performed to complete the approach (Fig. 22.6l).

A cotton patty is placed on the frontobasal cortex, and the frontal lobe is carefully retracted from the skullbase with a suction and anatomical forceps. After olfactory tract and optic nerve have been identified, the optic cistern is opened, and CSF is released abundantly to relax the brain. Alternatively, the Sylvian fissure can be opened to drain CSF. If the head is positioned correctly, the frontal lobe falls back by gravity and provides space for the microsurgical manipulations (Fig. 22.7). Retractors should be avoided whenever possible. Sometimes, we use a retractor only to fix the patty which protects the frontal lobe. Excessive retraction of the frontal lobe has to be avoided because it can avulse the olfactory fibers at the cribriform plate.

After tumor resection, the dura is closed with a running suture (Fig. 22.8a). To achieve a watertight closure, TachoSil® (Nycomed Austria GmbH, Linz, Austria) can be placed on the suture line, if needed (Fig. 22.8b). This is especially helpful when the frontal sinus was opened during the craniotomy to avoid rhinorrhea. A piece of Gelfoam is placed in the craniotomy defect and the bone flap is fixed with mini plates (Fig. 22.8c). For cosmetic reasons, the bone flap has to be in close contact to the upper margin of the craniotomy to avoid a visible indentation in the forehead later on. When the bony defect caused by the craniotome is at the lower aspect of the craniotomy hidden under the eyebrow, it usually remains invisible. When the temporal muscle and scalp are very thin, the initial burr hole and the lower craniotomy defect should be covered with a mini plate or filled with bone cement to avoid a visible indentation after scar formation (Fig. 22.8d). The wound is closed in layers – periost, muscle, subcutis, and skin. The periosteal suture is important to cover the bony defect caused by the craniotome (Fig. 22.8e). The periost is sutured additionally to the temporal fascia. For skin closure, we use running resorbable sutures (Fig. 22.8f). The patient is observed overnight in the intensive care unit. The day after surgery, a CT scan is performed to rule out any complication and to check the position of the bone flap (Fig. 22.9a). Usually, the cosmetic result after an eyebrow approach is excellent (Fig. 22.9b)