32 Functional Endoscopic Sinus Surgery
The endoscopic approach has replaced the external approach as the default approach in sinus surgery for benign disease. It is used in combination with the external approach for most sinonasal malignancies. Although life-threatening and life-changing complications of endoscopic sinus surgery are rare, extensive experience and expertise is necessary in basic endoscopic sinus surgery before training in extended applications is undertaken, usually as part of a rhinology fellowship. The role of balloon sinuplasty in sinus disease has not yet been fully defined, but it is an acceptable alternative technique to endoscopic sinus surgery for blocked ostia of the maxillary, frontal and sphenoid sinuses.
32.1 Principle
Most infections of the sinuses are rhinogenic, that is, disease spreads from the nose to the paranasal sinuses. The anterior ethmoid sinus air cells and clefts are regarded as prechambers of the frontal and maxillary sinuses. Disease of these prechambers may interfere with ventilation and drainage of the frontal and maxillary sinuses and cause acute or chronic mucosal disease. Similarly, disease of the posterior ethmoid sinuses may interfere with ventilation and drainage of the sphenoid sinus.
Endoscopic sinus surgery is minimally invasive surgery, which aims to provide ventilation and drainage of the ethmoid sinuses and the secondarily involved maxillary, frontal and sphenoid sinuses. The emphasis of surgery is to preserve, as far as possible, normal anatomy and mucosa. Mucosal stripping leaves exposed sinus bone, which does not heal with ciliated respiratory epithelium, but with either scar tissue or a low columnar non-ciliated epithelium. Scarring and absence of cilia may lead to an area of mucosa that is not self-cleaning. Mucous dries on this area and this may lead to chronic infection of mucosa and underlying bone. This in turn causes mucosal oedema which can compromise ventilation and drainage. Good surgical technique is therefore paramount.
32.2 Pathophysiology
Mucus produced in the maxillary sinus is transported from the floor of the sinus along the sinus walls, to the natural ostium by mucociliary transport. The frontal and maxillary sinuses communicate with the nose through a complex system of narrow clefts, which allow drainage and ventilation. These clefts are only a few millimetres wide and contain opposing mucosal surfaces lined with ciliated respiratory epithelium. If extensive contact of opposing mucosal surfaces occurs, whatever the cause, the ciliary beat activity may be impeded so that spaces are blocked and do not drain. Common locations for contact areas in the sinuses include the frontal recess, the ethmoidal infundibulum, the turbinate sinus (cleft between the bulla and middle turbinate) and the lateral sinus, which lies above and behind the ethmoid bulla.
Anatomical variations of the middle turbinate, uncinate process and the ethmoid bulla are common. The incidence of these variations is the same in a population with no history of sinus disease and a population with recurrent acute or chronic sinusitis. Therefore, anatomical variations, while of academic interest, are not thought to predispose to sinusitis. Persistent mucosal disease of the ethmoidal infundibulum, frontal recess and posterior ethmoids may predispose patients to recurrent maxillary, frontal sinus and sphenoid sinus infection.
32.3 Indications for Endoscopic Sinus Surgery
• Recurrent acute rhinosinusitis.
• Chronic rhinosinusitis resistant to medical therapy.
• Polypoidal rhinosinopathy resistant to medical therapy.
• Mucoceles.
• Sinus mycosis.
• Adjuvant surgery to allergy treatment.
• Antrochoanal polyps.
• Endoscopic bipolar diathermy for anterior/posterior epistaxis.
• Blockage of the nasolacrimal duct requiring endoscopic dacryocystorhinostomy.
• Endoscopic resection of inverted papilloma.
• Endoscopic ligation/diathermy of the sphenopalatine artery for epistaxis.
Extended applications include the following:
• Endoscopic arrest of cerebrospinal fluid (CSF) rhinorrhoea.
• Endoscopic orbital decompression, most commonly for dysthyroid eye disease.
• Endoscopic drainage of an orbital abscess.
• Endoscopic optic nerve decompression.
• Endoscopic pituitary surgery.
• Endoscopic Draf procedures for frontal sinus disease and laterally based frontal sinus mucoceles often because disease has been contained within the frontal sinus because of anatomical variations (such as a Kuhn cell).
• Endoscopic resection of sinoethmoid and anterior skull base malignancy, combined with an open approach.
• Endoscopic transpituitary surgery to resect clivus tumours such as chordoma.
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