Indications and Preoperative Considerations
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Postoperative CSF leak is one of the most important complications secondary to endoscopic skull base surgery.
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Skull base reconstruction techniques have been instrumental for the development of endoscopic skull base surgery. Continuous research has been done during the past decade on new approaches, techniques and materials to improve its clinical results.
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Currently, the endoscopic endonasal approach is the preferred method for repair of anterior skull base and cerebrospinal fluid leakage in the majority of cases.
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Besides being less invasive than its transcranial counterpart, different clinical series have demonstrated that endoscopic skull base repair is effective in over 90% of cases for closure of CSF leaks.
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Numerous variations for the construction of skull base repair have been proposed, including:
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Autologous materials: fascia lata, fat and pericranium grafts
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Synthetic materials: Duragen, Duraseal
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Bone flaps
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Mucosal flaps: rescue flaps, turbinate flaps, Hadad–Bassagasteguy flap.
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The vascularized nasoseptal flap or Hadad–Bassagasteguy (HB) flap is one of the most important technical developments of endoscopic surgery. It has a major role in the feasibility of extended approaches to the anterior, middle and posterior fossa, reducing the risks of postoperative CSF leakage in large skull base defects, to less than 5%.
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Advantages of using a pedicled flap:
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Promotion of rapid healing.
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Provision of an effective barrier against CSF leaks.
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Wide arc of rotation: the surgeon is able to reach defects from the frontal sinus to the lower clivus.
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Different techniques may be applied for sellar reconstruction, including insertion of fat grafts and biological sealants, gasket seal and multilayer reconstruction techniques.
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The surgeon must plan the skull base reconstruction depending on:
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Etiology of the skull base defect.
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If the defect has been a consequence of tumor resection it is important to consider the pathology, the location of the lesion and if the lesion requires further debulking.
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When intraoperative CSF leakage is expected and/or observed (e.g. while resecting the suprasellar component).
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Surgical Procedure
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Different techniques are applied according to the characteristics of the lesion.
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Surgery for sellar tumors and lesions with minimal suprasellar extensions (<1 cm) ( Figure 27.1 ):
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Lumbar drain or harvesting of a nasoseptal flap are not usually required.
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Cases with no intraoperative CSF leak: sellar closure can be done with absorbable hemostatic agents, followed by a final layer of biological sealants.
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Cases with minor intraoperative leakage can be closed with a fat graft. The fat graft may be obtained from the abdomen, around the umbilicus, or waist. Usually a 1–2-cm skin incision is enough to expose the subcutaneous fatty tissue. The monopolar electrocautery is used for harvesting the graft and the skin is closed with intradermal absorbable sutures to obtain an optimal esthetic result. This step can be done at the beginning of the surgery by the neurosurgeon or assistant while the ENT or the main surgeon starts the nasal phase of the endonasal approach.
Figure 27.1
Pituitary tumor with minimal suprasellar extension. (A) A 69-year-old woman who presents with amenorrhea, galactorrhea, headaches and progressive decreased vision and elevated prolactin. The lesion continues to grow despite maximal medical therapy with anti-prolactin agents. The preoperative T1-weighted MRI shows a contrast-enhancing pituitary lesion with mass effect upon the optic nerve compatible with a pituitary adenoma (prolactinoma). (B) Surgery was recommended given the progressive symptoms, vision loss and lack of response to medical therapy. A transellar approach was planned. The sphenoid sinus is opened and the sella is drilled to expose the tumor. (C) After the sella is opened the pituitary adenoma is removed with pituitary curettes. (D) After complete lesion removal, the pituitary gland has been preserved and can be visualized. The bone defect at the sella is minimal and there is no intraoperative CSF leak. (E) Reconstruction with a fat graft over a layer of hemostatic agents. (F) An overlay of absorbable hemostats is used to cover the fat graft. (G) Fibrin sealant. (H) The postoperative T1-weighted MRI with contrast shows complete resection of the lesion with decompression of the optic nerve. The patient recovered from her symptoms. In microadenomas without intraoperative CSF leak, a fat graft is usually not necessary. *, Pituitary adenoma; rCP, right carotid prominence; CR, clival recess; S, septation; LCP, left carotid prominence; Pg, pituitary gland.
© A. Quiñones-Hinojosa.
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Surgery for intrasellar lesions with large suprasellar extensions ( Figure 27.2 ):
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Lumbar drainage insertion and confection of a nasoseptal flap are recommended. High-flow CSF leakage is expected in these cases ( Figure 27.3 ).
Figure 27.3
A lumbar drain can be placed at the end of cases with high-flow intraoperative CSF leaks to decrease intracranial pressure, promote healing and decrease the risk of postoperative CSF leak.
© A. Quiñones-Hinojosa.
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Closure is done with Gelfoam as an inlay graft, followed by fat graft to occlude the empty space in the sphenoidal sinus, and a vascularized, nasoseptal flap. When available, biological sealants are recommended as a final layer.
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In the case that no intraoperative leak is observed, Gelfoam may be used instead of the fat graft. Since it is harvested at the beginning of the procedure, the vascularized flap is used as a final layer. If a lumbar drain was placed at the start of the procedure, it can be removed immediately after surgery if a good seal has been obtained.
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