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The Extended Nasoseptal Flap

A 31 year-old male presented with diplopia and was found to have left sixth nerve palsy on physical examination.  Work-up with MRI revealed a hypointense mass on T2 images involving the mid to lower clivus with penetration of the posterior fossa dura.  The patient had no complaints of nasal obstruction, no prior nasal surgery or nasal trauma.  Intraoperative frozen section analysis revealed chordoma.

Author Note: minute 3:41 “rostrum” was spelled incorrectly.

Contributor:

Eric Wang

The Extended Nasoseptal Flap for Reconstruction of Transclival Defects
Clival chordomas, posterior circulation aneurysms, extended approaches requiring opening of the basal or pontomedullary cisterns.(2)
Relative contraindications: Le Fort fracture, nasal fracture, prior septoplasty or open septorhinoplasty.
The patient is intubated and then rotated with the head at 80 degrees from anesthesia. The patient is then positioned slightly to the right and at the head of bed for pinning in the Mayfield retractor. The patients head is then positioned with the neck in sniffing position and with lateral rotation to facilitate the transclival approach. The Mizuho bed is then lowered completely and positioned in reverse Trendelenberg at approximately 15 degrees. The nose is the packed with 1:1000 topical epinephrine soaked pledgets and the septum injected with injectable 1% lidocaine with 1:100,000 epinephrine. The abdomen is prepped for a fat graft harvest and the thigh prepped for fascia lata graft harvest. The image guidance system is registered to the patient and accuracy confirmed by the surgeon. Transcranial electrodes are placed for intraoperative neurophysiologic monitoring. The patient is then prepped and draped in standard fashion for the endoscopic endonasal approach to the skull base.
CT angiographram and MRI skull base with image guidance protocol, ophthalmologic examination, otolaryngologic examination.
Right-sided flaps are preferred for transclival approaches as it positions the pedicle away from the neurosurgeon’s dominant hand and drill during the neurosurgical portion of the procedure. The sphenoethmoid recess is visualized and the superior turbinate resected on the side of the planned flap. With the sphenoid ostium either exposed or opened, the procedure begins with the inferior incision along border of the rostrum and choana, extending down the posterior edged of the vomer, then along the hard soft palate junction out inferior meatus to the attachment of the inferior turbinate to the lateral nasal wall. The incision is extended anteriorly along the lateral nasal wall in the inferior meatus out to the piriform aperture. The anterior incision is then carried medially to the maxillary crest anterior to the incisive canal. Next, the superior incision is made beginning from the sphenoidotomy anteriorly until the head of the middle turbinate. At this point the incision is extended superiorly into the nasal vault along the cephalad border of the quandrangular cartilage. The superior and inferior incisions are then connect along anterior border of the septal cartilage to caudal septum. Next, elevation of the flap proceeds from posterior to anterior along the lateral nasal wall. This is then elevated medially until it is lifts up along the maxillary crest from posterior to anterior. The flap will be tethered at the incisive canal. Next, the flap is elevated anteriorly at the caudal septum. Care is taken not to raise this too far as this may tear the flap along the decussating fibers and incisive canal. Sharp dissection of the decussating fibers and neurovascular bundle in the incisive canal is performed in order to prevent this. Once free, from the maxillary crest, the flap is elevated posteriorly onto the rostrum of sphenoid and the posterior superior cuts are visualized. Lastly, microscissors are used to release the anterior portion of the superior incision. The flap can then be completely elevated off the rostrum toward the pedicle and tucked into the nasopharynx or middle meatus for the remainder of the case.
Advantages: Provides a large, vascularized, local flap for reconstruction of large clival defects with high flow cerebrospinal fluid leak.(2) Provides coverage of both parasellar/paraclival carotids superiorly and between the hypoglossal canals inferiorly. Can be elevated at the beginning of the procedure. This flap covers defects just below sella down to foramen magnum in 91% of cases.(1) Disadvantages: Elevating the extended portion of the flap is technically more difficult give the size and the fact that it is tethered by the incisive foramen contents. Flap necrosis is most likely at the anterolateral portion, which covers the inferior most aspect of the defect. The flap reaches from the tuberculum to foramen magnum in only 61% of cases.(1)
Major: Flap necrosis, cerebrospinal fluid leak Minor: Temporary hypesthesia/anesthesia of the anterior teeth and upper lip, prolonged postoperative intranasal healing given the large surface area, prolonged postoperative crusting.
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1. Peris-Celda M, Pinheiro-Neto CD, Funaki T, et al. The Extended Nasoseptal Flap for Skull Base Reconstruction of the Clival Region: An Anatomical and Radiological Study. Journal of Neurological Surgery Part B, Skull Base. 2013;74(6):369-385. doi:10.1055/s-0033-1347368. 2. Patel MR, Stadler ME, Snyderman CH, et al. How to Choose? Endoscopic Skull Base Reconstructive Options and Limitations. Skull Base. 2010;20(6):397-404. doi:10.1055/s-0030-1253573.

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