Neurosurgery

Fig. 12.4. a Operative position of the patient's head (Mayfield head-clamp not shown). The head of the bed is raised 20° and the patient's head is rotated 30° away from the side of surgery. A standard curvilinear frontotemporal skin incision is made behind the hairline (broken line). A frontotemporal craniotomy is turned (broken line connecting the three burr holes), following which the lateral sphenoid wing is drilled (shaded area). bThe shaded area depicts the bone removed during the right-sided extradural skull base technique. The removed bone includes the lateral sphenoid wing, posterolateral orbital wall, posterior orbital roof, optic canal roof and ACP. The broken lines outline the orbit. c Extradural operative view of the exposed intracanalicular optic nerve and the opened SOF following complete removal of the ACP. ACP, anterior clinoid process;ON, optic nerve; SOF, superior orbital fissure.

Fig. 12.4. a Operative position of the patient's head (Mayfield head-clamp not shown). The head of the bed is raised 20° and the patient's head is rotated 30° away from the side of surgery. A standard curvilinear frontotemporal skin incision is made behind the hairline (broken line). A frontotemporal craniotomy is turned (broken line connecting the three burr holes), following which the lateral sphenoid wing is drilled (shaded area). bThe shaded area depicts the bone removed during the right-sided extradural skull base technique. The removed bone includes the lateral sphenoid wing, posterolateral orbital wall, posterior orbital roof, optic canal roof and ACP. The broken lines outline the orbit. c Extradural operative view of the exposed intracanalicular optic nerve and the opened SOF following complete removal of the ACP. ACP, anterior clinoid process;ON, optic nerve; SOF, superior orbital fissure.

Fig. 12.5. a Extradural view after completion of the skull base technique, including: (1) frontotemporal craniotomy, (2) lateral sphenoid wing removal, (3) posterior orbitotomy, (4) SOF decompression, (5) optic canal unroofing, and (6) extradural anterior clinoidectomy. The dural incision (broken line) is made in two steps: First, a frontotemporal curvilinear opening is created, centered on the Sylvian fissure, followed by a bi-section of the dural flap toward the optic sheath and extending across the falciform ligament and to the anulus of Zinn. b The same clinoidal meningioma as depicted in c, following completion of the extradural skull base technique and extending the dural incision into the optic sheath. The optic nerve is readily identified in the exposed optic canal and completely decompressed at the onset of tumor removal. Tumor resection progresses by following the exposed optic nerve proximally. The combination of early optic nerve identification and decompression leads to prevention of intraoperative optic nerve injury. cThe view of an exposed large clinoidal meningioma after the initial dural opening, using pterional craniotomy and standard frontotemporal dural opening only. Upon tumor exposure, it is noted to be covering the critical neurovascular structures (the optic and oculomotor nerves, ICA). The exact locations of the optic nerve and ICA are unknown to the surgeon, and the optic nerve remains in a compressed state. Tumor resection progresses slowly until the optic nerve and ICA are eventually identified. FL, frontal lobe; ON, optic nerve; SOF, superior orbital fissure; TL, temporal lobe.

Fig. 12.5. a Extradural view after completion of the skull base technique, including: (1) frontotemporal craniotomy, (2) lateral sphenoid wing removal, (3) posterior orbitotomy, (4) SOF decompression, (5) optic canal unroofing, and (6) extradural anterior clinoidectomy. The dural incision (broken line) is made in two steps: First, a frontotemporal curvilinear opening is created, centered on the Sylvian fissure, followed by a bi-section of the dural flap toward the optic sheath and extending across the falciform ligament and to the anulus of Zinn. b The same clinoidal meningioma as depicted in c, following completion of the extradural skull base technique and extending the dural incision into the optic sheath. The optic nerve is readily identified in the exposed optic canal and completely decompressed at the onset of tumor removal. Tumor resection progresses by following the exposed optic nerve proximally. The combination of early optic nerve identification and decompression leads to prevention of intraoperative optic nerve injury. cThe view of an exposed large clinoidal meningioma after the initial dural opening, using pterional craniotomy and standard frontotemporal dural opening only. Upon tumor exposure, it is noted to be covering the critical neurovascular structures (the optic and oculomotor nerves, ICA). The exact locations of the optic nerve and ICA are unknown to the surgeon, and the optic nerve remains in a compressed state. Tumor resection progresses slowly until the optic nerve and ICA are eventually identified. FL, frontal lobe; ON, optic nerve; SOF, superior orbital fissure; TL, temporal lobe.

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