Reconstruction of Transcribriform Skull Base Defects

Extradural pericranial flap reconstruction of endoscopic endonasal transcribriform defects.

Repair of endoscopic anterior craniofacial resection, endoscopic transplanum dural defects, endoscopic transclival defects, repair of dural defects for sinonasal malignancy.

Absolute: Prior forehead laceration, prior direct brow lift, radiation to scalp, small anterior craniofacial defects where nasoseptal flap is available for reconstruction
Relative: Radiation for sinonasal malignancy or radiation for anterior fossa pathology

N/A

The patient is intubated orally with a regular endotracheal tube, which is secured to the left lower lip. The head of bed is rotated 90 degrees from the anesthesia team and the right arm is padded to protect the ulnar nerve and tucked at the patient’s side. The patient is then pinned and positioned using the Mayfield retractor in slight extension, axial rotation, and sniffing position, so as to facilitate the endoscopic endonasal transcribriform approach. Oxymetazoline (0.3%) or topical epinephrine (1:10,000) soaked pledgets are placed in the nasal cavity for decongestion. The image guidance system is registered to the patient and accuracy confirmed by the surgeon and vasoconstriction. Transcranial electrodes are placed for intraoperative neurophysiologic monitoring. The thigh prepped for fascia lata graft harvest. Finally, a coronal incision is drawn with extension to the antihelix bilaterally. The patient is then prepped for coronal approach and the endoscopic endonasal approach.

CT and MRI with Stryker skull base protocol are obtained. Institutional review of preoperative biopsy slides or a repeat biopsy should confirm the diagnosis and determine the need for further immunohistochemical or molecular work-up as indicated. Depending on the diagnosis, an additional metastatic work-up may be indicated.

After complete resection of the tumor and margins, a coronal incision is made from the vertex, just anterior to helical root bilaterally. In standard open fashion, the pericranial flap is raised. First, the surgeon incises the skin, subcutaneous tissue and galea aponeurotica. The loose areolar tissue is bluntly dissected and elevated so that the pericranium can be identified and preserved below and all superficial layers are bluntly dissected laterally over the temporalis muscle insertions to the cranium. The skin incision is then opened down to the helical roots bilaterally and elevated anteriorly using blunt dissection until the superficial temporal fat pads are identified bilaterally. Cold knife technique is used to incise the superficial temporal fat pads along the superficial layer of the deep temporal fascia overlying the temporalis muscles in order to preserve the temporal branch of the facial nerve bilaterally. Next, the pericranium is incised 3-5 centimeters posterior to the vertex to provide length. Incisions are then made parallel to the temporalis muscles insertions down to the superior orbital rim bilaterally. The flap is then elevated down to the supraorbital rim and nasion in the midline. Care is taken to free the supraorbital vessels from the foraminae (either with blunt technique or osteotomies as required). In the setting of prior radiation, surgery or trauma near the pericranial flap, an ultrasound probe can be used to confirm an intact pedicle and appropriate flow.

Major: Flap necrosis due to strangulation or twisting of pedicles, cerebrospinal fluid leak (6.7%), injury to the temporal branch of the facial nerve, and alopecia.3,4
Minor: Temporary brow hypoesthesia, temporary brow ptosis, seroma/hematoma of scalp, prolonged skull base crusting, frontal sinus mucocele.1,3

Dr. Snyderman is a consultant for SpiWay LLC.

1. Zanation AM, Snyderman CH, Carrau RL, Kassam AB, Gardner PA, Prevedello DM. Minimally invasive endoscopic pericranial flap: a new method for endonasal skull base reconstruction. Laryngoscope. 2009;119(1):13-18.
2. Patel MR, Shah RN, Snyderman CH, et al. Pericranial flap for endoscopic anterior skull-base reconstruction: clinical outcomes and radioanatomic analysis of preoperative planning. Neurosurgery. 2010;66(3):506-512; discussion 512.
3. Snyderman CH, Janecka IP, Sekhar LN, Sen CN, Eibling DE. Anterior cranial base reconstruction: role of galeal and pericranial flaps. Laryngoscope. 1990;100(6):607-614.
4. Harvey RJ, Parmar P, Sacks R, Zanation AM. Endoscopic skull base reconstruction of large dural defects: a systematic review of published evidence. Laryngoscope. 2012;122(2):452-459.