Lateral Skull Base Surgery (eBook)

The House Clinic Atlas

Rick A. Friedman, William H. Slattery, Derald E. Brackmann, Jose N. Fayad, Marc S. Schwartz (Herausgeber)

eBook Download: EPUB

2012 | 1. Auflage
224 Seiten
Georg Thieme Verlag KG
978-1-63853-210-1 (ISBN)

Infos

<p><strong><em>Learn surgical techniques and procedures from lateral skull base surgeons at the famous House Clinic</em></strong></p><p>Written by leading skull base surgeons from the renowned House Clinic in Los Angeles, California, <em>Lateral Skull Base Surgery: The House Clinic Atlas</em> is a much-needed reference that contains detailed descriptions of the techniques used in lateral skull base surgery. This atlas covers topics ranging from auditory brainstem implants to vestibular schwannoma, providing readers with a comprehensive overview of surgical procedures and techniques used to treat a variety of skull base diseases.</p><p>Special Features:</p><UL><LI>Online access to 8 surgical videos of the most common techniques presented in the book <LI>More than 180 high-quality illustrations depict step-by-step surgical procedures <LI>Every chapter is informed with the expertise of House Clinic skull base surgeons</LI></UL><p>This atlas offers insights and expertise from some of the most respected surgeons in the world and is an essential resource for otolaryngologists–head and neck surgeons, neurosurgeons, and fellows preparing for and performing lateral skull base surgery as well as other physicians interested in this growing specialty.</p>

Textauszug

2

 

The Subtemporal Approach

Marc S. Schwartz

 

The subtemporal approach to skull base lesions may be utilized to gain access to pathology that extends along the floor of the middle fossa, including Meckel’s cave. Trigeminal schwannomas with significant portions in Meckel’s cave are the paradigmatic lesions for this approach. The elements of the subtemporal approach described in this section may also be combined with the petrosal approach to gain access to trigeminal schwannomas with both large Meckel’s cave and posterior fossa components (dumbbell tumors) or petroclival meningiomas with significant extension along the floor of the middle fossa. Furthermore, the elements of the subtemporal approach can be combined with any of the infratemporal approaches to gain access to tumors that involve both the middle fossa and the infratemporal space, such as trigeminal neuromas extending along the third division through the foramen ovale and invasive skull base meningiomas.

Surgical Anatomy

Superficially, the subtemporal approach requires mobilization of a large portion of the temporalis muscle to achieve access to the anterior reaches of the middle fossa. The temporalis originates from a large area of the temporal bone, runs beneath the arch of the zygoma, and inserts on the coronoid process of the mandible. The anterior aspect of the temporalis originates at the frontozygomatic process, which must be fully exposed. The temporal branch of the facial nerve overlies the temporalis fascia in this area, and injury to this branch can be avoided by maintaining dissection deep to the superficial layer of fascia.

The intracranial key to the performance of the subtemporal approach is an understanding of the anatomy of the petrous apex (Kawase’s triangle). Bone removal is performed anterior to the internal auditory canal and cochlea, posterior to the mandibular branch of the trigeminal nerve, and medial to the carotid artery. The location of the carotid artery can be inferred from the greater superficial petrosal nerve, which overlies it on the floor of the middle fossa. An understanding of the anatomy of the trigeminal nerve itself is also critical, as this nerve can be traced to the foramina through which its second and third divisions pass (foramen rotundum and foramen ovale).

The subtemporal approach, as described, is considered an “extradural” approach. This is actually a misnomer, because Meckel’s cave is an intradural space. The Meckel’s cave dura, however, is an evagination of the posterior fossa dura. For that reason, this approach is extradural in relation to the middle fossa, whereas it is intradural in relation to the posterior fossa.

Monitoring

Facial nerve and vestibulocochlear nerve monitoring is used for all cases, even if pathology does not extend into the posterior fossa, due to the possibility of encountering a dehiscent geniculate ganglion or superior semicircular canal during dural elevation. For large cases, especially with significant brainstem compression, somatosensory evoked potential monitoring may be used as well.

Anesthetic Considerations

Serial compression devices are used for all patients. Cefuroxime, 1.5 g IV, is administered before the skin incision and repeated if the procedure lasts more than 8 hours. In addition to hyperventilation, intravenous mannitol is infused to facilitate brain relaxation. Muscle relaxation is not used to allow for facial nerve monitoring.

Surgical Technique

The patient is placed in the supine position and is secured to the table so that it can be safely rotated. We utilize a Mayfield headholder and rigidly immobilize the patient’s head rotated 45 to 60 degrees opposite the side of the lesion. Exposure and temporal lobe elevation may be facilitated by tilting the vertex slightly downward, although if there is extension of the lesion into the skull base and infratemporal space a more neutral position is maintained. The surgeon is seated at the head of the table. The scalp incision is similar to that made for the middle fossa approach; however, the anterior limb of the incision is carried forward to the hairline or beyond, in the case of a receding hairline (Fig. 2.1).

Fig. 2.1 Preauricular scalp incision. The anterior limb of the incision extends forward, at least to the hairline.

Extensive subgaleal elevation of the scalp is required to obtain adequate anterior exposure. Ideally, elevation is carried into the interfascial plane of the two-layer temporalis fascia. It is critical to maintain a plane deep to the fat pad that is consistently seen in this area to avoid injury of the temporal branch of the facial nerve. The root of the zygoma must also be exposed posteriorly. The temporalis fascia is incised just below the superior temporal line, and a relaxing incision is made through the fascia posteriorly. The temporalis muscle is elevated anteriorly. Subperiosteal dissection is performed to fully expose the zygoma at both its root and at the frontozygomatic process. Both the scalp and temporalis flaps can be held forward with perforating towel clips and rubber bands over a rolled sponge. Adequate retraction is necessary and can be facilitated by retracting to a Kerlix roll attached to the foot of the bed.

Although the craniotomy can be performed with bur holes and a craniotome, it is often safer to remove the bone flap entirely using cutting and diamond burs. Care is taken to achieve far-anterior and far-inferior removal of bone. The inferior extent of the craniotomy can be judged from the root of the zygoma, and anterosuperiorly the location of the sphenoid wing can be determined from the external shape of the skull. If the bone flap is performed too posterior or too superior, additional craniectomy can be performed after a cursory dural elevation. The temporalis muscle covers the entire area of bone removal and there is unlikely to be significant additional cosmetic problems (Fig. 2.2).

Extradural elevation is performed along the entire floor of the middle fossa extending anteriorly toward the temporal tip. Care is taken to identify the greater superficial petrosal nerve and the region of the geniculate ganglion, which may be dehiscent. Dissection in this area may be facilitated by exploring with a facial nerve stimulator using high stimulus intensity. Anterior exposure is augmented by coagulation and division of the middle meningeal artery at the foramen spinosum (Fig. 2.3). It may be necessary to pack this foramen to adequately control bleeding. We also use a diamond bur to fully expose the second and third divisions of the trigeminal nerve at their respective foramina. If possible, dural elevation is carried medially to the petrous apex in a manner identical to that done for the middle fossa approach. The bone in this area may be eroded by a schwannoma or other expansile tumor, and care must be taken to recognize and avoid injury to the carotid artery if it is dehiscent. The temporal lobe is elevated extradurally using a self-retaining retractor.

Fig. 2.2 Scalp and temporalis muscle flaps. The zygoma is exposed both at its root and at the frontozygomatic process. The bone flap is centered on the middle fossa and extends from the greater wing of the sphenoid to the floor of the middle fossa.

Fig. 2.3 Dural elevation along the floor of the middle fossa. Tumor can typically be palpated at the foramen ovale. The middle meningeal artery is sacrificed at the foramen spinosum.

The bone of the petrous apex, lateral to the greater superficial petrosal nerve, eustachian tube, and carotid artery, is carefully removed using diamond burs and continuous irrigation. In cases of trigeminal schwannoma, much of this bone may be eroded tumor, and not much drilling is necessary. However, it is necessary to completely remove this portion of bone, especially if there is any extension of tumor into the posterior fossa (Fig. 2.4). With meningiomas, this drilling may be more difficult, but drilling is made even more important as it will serve to partially devascularize the tumor.

Fig. 2.4 The dura propria of Meckel’s cave is exposed. This step is facilitated by the presence of a large schwannoma. Drilling of bone is performed at the petrous apex to gain access to the posterior fossa. If the tumor extends through the foramen ovale or spinosum, bone is drilled to gain access to these locations.

For trigeminal schwannomas located primarily in Meckel’s cave, access to the tumor is attained by direct dissection via the dura propria (dura of Meckel’s cave, derived from the posterior fossa) at the foramen ovale. As the temporal lobe dura is gently elevated, sharp technique is used to come through the thin tissue overlying the nerve. Tumor can be directly debulked (Fig. 2.5).

An attempt is made to preserve as many trigeminal fibers as possible. When the main trunk of the trigeminal nerve is located medial to tumor bulk, most fibers can be preserved. When tumor is medial, however, preservation of fibers is more difficult. After removal of the main bulk of tumor from Meckel’s cave, the trigeminal nerve can be followed peripherally into extradural spaces or centrally into the posterior fossa. Usually, corridors of access are widened, facilitating a limited exposure in any direction. For extension of tumor into the posterior fossa, access is improved by a more anterior to posterior trajectory (Fig....

Produkt-Details

• Erscheint lt. Verlag: 1.6.2012
• Zusatzinfo: Beilage: Videos
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► HNO-Heilkunde
• Themenwelt: Medizinische Fachgebiete ► Innere Medizin ► Pneumologie
• Schlagworte: Auditory brainstem implants • Base • Cerebellopontine Angle • clivus lesions • complications • cranial • ENT • far lateral approach • Far lateral Approach • fisch infratemporal fossa approach • infracochlear/infralabyrinthine approach • Lateral • lateral approach • lateral approach • microvascular cranial nerve decompression • Middle cranial fossa approach • neurosurgery • neurotologic surgery • neurotology • orbitozygomatic craniotomy • Otolaryngology • petroclival region • petrosal approach • petrosal approach • petrous apex • posterior fossa surgery • posterior fossa surgery • preauricular infratemporal approach • Retrosigmoid Approach • Skull • Skull base • subtemporal approach • Surgery • temporal bone resection • transcochlear approach • Translabyrinthine approach • vestibular schwannomas • Vestibular Schwannomas
• ISBN-10: 1-63853-210-9 / 1638532109
• ISBN-13: 978-1-63853-210-1 / 9781638532101