4.1. Limitations of Supraorbital Craniotomy through the Eyebrow Incision Entering through the third eyebrow historically led to postoperative loss of supraorbital sensation or to a palsy of the frontalis branch of the facial nerve (see Table 1). Placement of the incision lateral to the supraorbital notch is important in preserving function of the supraorbital nerve. Avoiding the use of cautery laterally over the temporalis fascia and muscle can also avoid injury to the frontalis nerve. The use of neuronavigation can help prevent a breach of the frontal sinus during the craniotomy. Avoidance of the frontal sinus will lower the risk of CSF leak or postoperative wound infection. A lateral frontal sinus may even be considered a contraindication for this approach.

In the setting of vascular pathologies, there may be some difficulty with using two suction tubes in managing prematurely ruptured aneurysms or to obtain proximal control [13, 22, 46, 47]. Some have even recommended against this approach for vascular lesions for this reason [47]. A prominent orbital rim may impede the surgical degree of freedom, and some authors have advocated the addition of an orbital osteotomy to improve surgical freedom and access for vascular pathologies [16, 48]. A similar concept led to similar adaptations to traditional approaches to frontal base and parasellar lesions in the past [46, 49�C52].

A number of authors have described different vascular pathologies safely treated through this approach, but we feel it should be limited to those with significant experience with the approach, and it may not be the best approach for some lesions (such as in subarachnoid hemorrhage, giant aneurysms, or vascular lesions in the posterior circulation) in comparison to more traditional approaches (see Table 1) [13, 22, 46, 47]. Numerous shortcomings have been overcome since the introduction of this approach in the 1980s. Probably the biggest limitation was the problem of lighting with the operating microscope down such a narrow corridor. Endoscopes have dramatically improved visualization of this region through this approach and allow for safer dissection with better visualization through this smaller incision than can often be achieved with the microscope alone. Endoscopic-assisted surgery is a common adjunct to the modern skull-based surgeon wishing to employ this keyhole approach in his armamentarium, and is discussed in more detail in what follows.

4.2. Head Positioning Brefeldin_A with the Keyhole Supraorbital Craniotomy and Subfrontal Approach Proper positioning of the head for the keyhole supraorbital craniotomy can play an important role in surgical access of skull base lesions. Extension of the neck permits frontal lobe relaxation in combination with mannitol. Contralateral rotation of the head is also performed [2�C5, 9, 13, 48]. The degree of head rotation is related to the anatomic location of the pathology in the subfrontal corridor.