PROCEDURE OF THE DAY
Functional Endoscopic Sinus Surgery (FESS) is a surgical modality for some diseases of the nose and paranasal sinuses. It is a relatively recent surgical procedure that uses the help of nasal endoscopes (which make use of Hopkins rod lens telescopes): these are endoscopes which have diameters of 4mm and 2.7mm and come in varying angles of vision from 0 degrees to 30, 45, 70, 90, and 120 degrees. These provide good illumination and can be introduced into the nose after anesthetising.
It has now become the main-stay in the surgical treatment of sinusitis and nasal polyposis including fungal sinusitis: this technique of functional endoscopic sinus surgery came into existence because of pioneering work of Messerklinger and Stamberger (Graz, Austria.) Other surgeons have made additional contributions (first published in USA by Kennedy in 1985).
The surgical technique usually adopted is the Messerklinger technique.
Frontal, Maxillary, and Anterior Ethmoid sinuses drain into the middle meatus. Posterior ethmoids drain into the superior meatus. Sphenoid drains into the sphenoethmoid recess.
There are four sinuses dealt with by means of this surgery: The frontal sinus with frontal recess dissection, the maxillary by uncinectomy and antrostomy, the anterior and posterior ethmoids which require careful dissection to the skullbase and orbital lamina, and finally the sphenoid sinus which is managed via a sphenoidotomy.
One of the most accepted means of functionally enlarging the maxillary ostium is to perform an uncinectomy via the "swing door" technique. This initially removes the vertical process of the uncinate via backbiter inferiorly and sickle knife superiorly. The uncinate is swung medially and then severed at its lateral attachment. This is followed by a submucosal removal of the horizontal process of the uncinate and subsequent trimming of the mucosa to fully visualize the maxillary os.
Controversy exists as to whether or not the maxillary ostium should be enlarged or not depending on the disease status of the maxillary sinus. However, the medical literature would support a wide antrostomy and complete clearance down to healthy mucosa if fungal mucin is present within the sinus. In this circumstance, the ostium is enlarged superiorly to orbital floor and posteriorly to posterior fontanelle to allow wide access for clearance.
Complete maxillary debridement can be accomplished via either trans-ostial clearance which can be quite tedious. A newer technique, canine fossa trephination, can accomplish this same task faster and with few side effects.
More recently, the paranasal sinuses have been found to be a relatively low-morbidity approach to selected tumors of the anterior and posterior cranial fossa.
Endoscopic access to pituitary tumors has been found to be quite useful as well. Using endoscopes for hypophysectomy allows excellent visualization within the sella and more complete tumor removal than would be available via microsurgical technique.
This can be divided into: 1. approaches to the anterior cranial fossa 2. approaches to the mid cranial fossa 3. approaches to the posterior cranial fossa 4. access to the infratemporal fossa (incl. pterygopalatine fissure) 5. access to the sella turcica 6. orbital access 7. optic nerve access
Word of Caution
Extreme care is required with this surgery due to the paranasal sinus' proximity to the orbits, brain, internal carotid arteries, and optic nerves. However, even with these possible serious risks, there are many benefits to be reaped by a patient with appropriate indications from a well-performed ESS. As the degree of difficulty increases with these surgeries, a surgeon with appropriate experience must be present to manage the procedure. This is especially true in approaches to neurosurgical procedures.
Planum Sphenoidale marks the posterior limit of the anterior skull base. This bony structure is the plane created by the medial confluence of the lesser wing of the sphenoid bone.
Fovea Ethmoidalis is the true roof of the ethmoid cavities and the bony marker of the skull base. It extends from the orbital lamellae laterally to the lateral lamella of the cribriform medially.