21 Extradural Subtemporal Transzygomatic Approach The subtemporal transzygomatic approach combines some of the nuances of a classic subtemporal exposure with the possibilities of a pure skull base approach, suitable for the treatment of extradural tumors of the middle-upper clivus extending into the ipsilateral paraclival area and middle fossa. Sectioning of the mandibular branch (V3) of the trigeminal nerve and petrous apicectomy can further enlarge the surgical exposure as well as the maneuverability area and improve vascular control on the internal carotid artery. • Extradural lesions of middle-upper clivus with lateral extension. • Position: The patient is positioned supine with the head fixed by a Mayfield head holder. • Body: The body is rotated 30°. • Head: The head is extended 20°, rotated 60° to the contralateral side and tilted 10° toward the floor. • Shoulder: A roll is placed under the ipsilateral shoulder. • Please note that the zygoma has to be the highest point in the surgical field. Two main options are available for the skin flap. • Question-mark shaped unilateral temporal incision ◦ Starting point: Incision starts 1 cm in front of the tragus at the level of the zygoma. ◦ Course: Incision line runs posteriorly around the superior margin of the ear; turns anteriorly after reaching the posterior aspect of the pinna. ◦ Ending point: It ends on the midline, just behind the hairline. • Coronal bilateral incision ◦ Starting point: Incision starts 1 cm in front of the tragus at the level of the zygoma. ◦ Course: Incision line runs medially, parallel and behind the hairline. ◦ Ending point: It ends at the contralateral superior temporal line. • Superficial temporal artery. • Frontal and temporal branches of the facial nerve. Fig. 21.1 Question-mark shaped unilateral temporal incision. • Myofascial level ◦ The myofascial level is incised parallel to the course of the skin incision. ◦ The flap is reflected anteriorly with the skin. • Muscles: Step 1 ◦ Temporal muscle: inter-fascial dissection is carried out as it is already described (see Chapters 6 and 8). ◦ Deep temporal muscle fascia is detached from the inner surface of the zygoma. ◦ Masseter muscle is detached from the inferior margin of the zygoma. • Cuts ◦ I: Posterior cut is made in front of the mandibular fossa. ◦ II: Anterior cut is made at the basis of the zygomatic temporal process. • Muscles: Step 2 ◦ Temporal muscle is incised posteriorly along the posterior margin of the skin incision. ◦ Temporal muscle insertion is cut along the superior temporal line. • Bone exposure The bone exposure is completed, when the following structures come into view: ◦ Temporal squama, outer surface of sphenoid greater wing, pterion, inferior aspects of frontal and parietal bone located below the superior temporal line. • Frontal branch of the facial nerve. A temporal, low-positioned craniotomy, including the greater sphenoid wing and the squamosal part of the temporal bone is performed. • Burr holes ◦ I: At the McCarty keyhole. ◦ II: At the posterior aspect of temporal squama just below the superior temporal line. ◦ III: At the greater wing of the sphenoid bone at the zygomatic level.
21.1 Introduction
21.2 Indications
21.3 Patient Positioning
21.4 Skin Incision (Fig. 21.1)
21.4.1 Critical Structures
Abbreviations: Incision (red dotted line); midline (black continuous line); zygomatic profile (black dotted line). E = ear; N = nasion; Z = zygoma.
21.5 Soft Tissue Dissection and Zygomatic Osteotomy (Figs. 21.2, 21.3)
21.5.1 Zygomatic Osteotomy
21.5.2 Critical Structures
21.6 Craniotomy/Craniectomy (Fig. 21.4)
21.6.1 Temporal Craniotomy
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