14 Frontal and Bifrontal Approach The unilateral frontal craniotomy and its further extension, the bilateral frontal approach, are extremely versatile procedures, which can be easily tailored according to the existing pathology. The approaches are suitable for the unilateral/bilateral exposure of the lateral and anterior surfaces of the frontal lobe, as well as the most anterior aspect of the interhemispheric fissure. It is possible to extend the bilateral approach by performing a bilateral orbitotomy to take advantage of the subfrontal anatomical corridor to reach the anterior skull base, as described in detail in Chapter 30. The approach is indicated for intra-axial lesions of the frontal lobe, as well as extra-axial tumors of the frontal convexity, of the anterior aspect of the falx and anterior cranial fossa. The approach is also suitable to treat vascular lesions of A2 as well as distal frontal branches of the anterior and middle cerebral artery. • Intra-axial lesions of the frontal lobes. • Extra-axial lesions of the frontal convexity and anterior third of the falx. • Vascular lesions of the second segment (A2) and distal frontal branches of the anterior and middle cerebral artery. • Position: The patient is positioned supine with the head fixed in a Mayfield head holder. • Body: The trunk and the head are slightly elevated to facilitate the venous backflow. • Head: The head is placed in neutral position in case of bilateral approach. Alternatively, it can be slightly turned to the opposite side (about 15-20°) in case of unilateral approach. • Neck: The neck is slightly extended (about 20°), to facilitate further brain relaxation after dural opening. • Bicoronal skin incision (suggested for the frontal bilateral craniotomy): ◦ Starting point: Incision starts 1 cm anterior to the ipsilateral tragus, just above the zygoma. ◦ Course: The incision line runs to the contralateral side, just behind the hairline over the coronal suture. ◦ Ending point: It ends 1 cm anterior to the tragus on the contralateral side. Alternatively, it can be taken to the contralateral superior temporal line. • Frontotemporal skin incision (suggested for the frontal unilateral craniotomy): ◦ Starting point: Incision starts 1 cm anterior to the ipsilateral tragus, just above the zygoma. Fig. 14.1 Alternative skin incisions. ◦ Course: The incision line runs slightly curved backward until reaching the coronal suture and then turns toward the contralateral side (2 cm beyond the midline). ◦ Ending point: It ends 2 cm beyond the midline, on the contralateral side just behind the hairline. • Superficial temporal artery and its branches. • Frontal and temporal branches of the facial nerve. • Pericranial layer ◦ Pericranium is smoothly dissected from the bone and the superficial temporal fascia, taking care to preserve its anatomical integrity. ◦ It is reflected anteriorly together with the skin flap. ◦ Pericranium must be preserved as it may be needed for further reconstruction. • Muscle ◦ Frontal unilateral craniotomy Fig. 14.3 Soft tissue dissection, lateral view. ◦ Frontal bilateral craniotomy • Bone exposure The bone exposure is completed, when the following structures come into view:
14.1 Introduction
14.2 Indications
14.3 Patient Positioning
14.4 Skin Incision (Fig. 14.1)
14.4.1 Critical Structures
14.5 Soft Tissue Dissection (Figs. 14.2, 14.3)
Ipsilateral temporal muscle inter-fascial dissection is carried out according to the technique described in Chapters 6 and 8.
Abbreviations: CS = coronal suture; FB = frontal bone; FP = fat pad; PC = pericranium; STL = superior temporal line; TF = temporal fascia; TM = temporal muscle.
The superficial layer of the temporal fascia together with the fat pad is reflected anteriorly.
The deep layer is dissected from the temporal squama in a subperiosteal fashion and reflected inferiorly, in order to expose the part of temporal squama, located just below the superior temporal line, where burr holes will be made.
The procedure described for the unilateral variant has to be carried out also on the contralateral side.
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