Scans
MRI scans in 3 planes with and without contrast are performed preoperatively and examined for tumour size and lateral extension. A fine cut CT of the paranasal sinuses is examined for important variations such as non aerated sphenoid sinus, nasal deformity, and pattern of septation.
Electromagnetic navigation (Medtronic) is used routinely.
Technique
A zero degree endoscope is used by the second surgeon acting as cameraman.
If a large CSF leak is likely the thigh is draped for the harvesting of fascia lata.
Adrenaline (1:1000) soaked patties are used to achieve mucosal decongestant and vasoconstriction.
The septal mucosa is infiltrated with lignocaine 1 % with epinephrine 1/100,000. This will be the donor site for the nasoseptal flap.
We routinely remove the right middle turbinate and approach pituitary tumours through the right nostril when possible. The left middle turbinate is lateralised (outfractured) by gentle pressure with an elevator.
A nasoseptal flap [
2] is routinely harvested on the right with its vascular pedicle containing the nasoseptal artery - a branch of the sphenopalatine artery. We are careful to stay below the olfactory epithelium.
We use the exact technique described by [
2]. This reveals the sphenoid os on that side which is enlarged.
A generous posterior septectomy is performed to expose the vomer. When there is likelihood of intrasellar dissection wider exposure is required for the camera and instruments and this is achieved by a wide posterior ethmoidectomy. The bony opening over the dura extends to the medial carotids. Bony septa are drilled flat mindful that the median septum usually deviates laterally to overlie the carotid artery (See Fig.
1.)
The dural opening should allow as much intrasellar access laterally as possible. We use a X shaped incision.
As soon as the dura is opened tumour usually presents itself through the dural opening unless the target is a small adenoma. Tumour is biopsied using either a ring curette or Deckers rongeurs. The tumour is debulked using ring curettes, staying in the inferior half of the tumour to avoid breaching the diaphragm (or inverted dome of tumour capsule). The capsule is held up with a small neurosurgical patty to allow full exploration of the sella. The medial cavernous sinus is examined with a Doppler probe to ensure we have explored as far lateral as possible.
After tumour excision we inject Floseal (Baxter) into the sella. (see Fig.
2). We place the septal flap over the bony and dural defect, directly onto bone. Small amounts of tisseel (Baxter) anchor the flap in place which is also then wedged in position using Nasopore forte (Polyganics).
If there has been a persistent low volume csf leak during the procedure we use an additional inlay graft of a dural substitute (Duraform, Codman). If the leak is from a visible defect in the diaphragm we place a small piece of Spongistan (Ferrosan) over the defect. If there has been a high volume csf leak we would use fat in the sella and fascia lata as inlay and onlay grafts.
If there is persistent csf rhinorrhoea we would explore the operative site to examine the cause of the leak. We have not used lumbar drains or bed rest.