Functional endoscopic sinus surgery--I (Anatomy, diagnosis, evaluation and technique).
It has been proved beyond doubt that the causation and perpetuation of disease in the dependent sinuses (maxillary and frontal sinuses) is secondary to disease of the ostiomeatal complex, the primary focus of which is the anterior ethmoid. Based on this concept, functional endoscopic sinus surgery (FESS) aims at correcting the underlying pathology in the ethmoids and helps to re-establish normal ventilation and mucociliary clearance of the dependent sinuses.
It has long been recognised that mechanical obstruction due to a deviated nasal septum can contribute to persistent infection in the paranasal sinuses. Septum surgery is often advised for such sinus infections. Since the 1950s, the work of Messerklinger has highlighted an even more important factor viz. disease of the ostiomeatal complex, the focal point of which is the anterior ethmoid area,,. Disease of this area can cause maxillary and frontal sinusitis and prevent their resolution in spite of 'adequate treatment' with routine measures. Messerklinger has shown that mucociliary transport in the paranasal sinuses follows a definite pattern leading towards the natural ostium. Any blockage of the normal ostium leads to disturbed mucociliary transport and subsequently infection of the sinus. The frontal and the maxillary sinuses open into the middle meatus. These openings are surrounded by the frontal recess and the ethmoidal infundibulum respectively, which build up a systcm of fissures and clefts in the middle meatus, all of which form a part of the anterior ethmoid. Thus, these sinuses drain into the middle meatus via the anterior ethmoid and hence their physiology and pathology depend on conditions in the anterior ethmoid,,.
What an infected frontal or maxillary sinus really needs for recovery is re-establishment of normal mucociliary drainage through its natural ostium, by rcmoving the disease in the anterior ethmoid around the ostium and widening it if narrowed. This concept also points out the cause of persistent infection in spite of an antral puncture, intranasal antrostomy or even a Caldwell-Luc operation in may cases of chronic maxillary sinusitis. Stammberger, has shown by video photography that even in a case with an intranasal antrostomy, the mucus bypasses this antrostomy and ascends to the natural ostium, further supporting Messerklinger's concept.
The lateral wall of the nose offers several anatomical landmarks. However, our interest is mainly focussed on the middle meatus area (See [Figure - 1]). The first structure to be seen in the middle meatus on anterior rhinoscopy is the uncinate process. This process forms the antero-medial wall of the infundibulum, which is the space anterior to the bulla ethmoidalis. The uncinate process continues posteriorly into the medial infundibular wall. When the uncinate process is incised and the medial infundibular wall removed (this is referred to as infundibulotomy) the anterior wall of the bulla ethmoidalis is visualised. Opening the anterior wall of the bulla ethmoidalis exposes the roomy cavity of the bulla and the ground lamella which constitutes the posterior boundary of the bulla ethmoidalis. Superolateral to this is a small space termed the lateral sinus. Opening the ground lamella will lead into the posterior ethmoidal cell complex. Further rcmoval of the posterior ethmoidal cells will lead to the anterior wall of the sphenoid sinus. The maxillary ostium in the middle meatus is normally hidden from view because of the infundibulum. On doing an infundibulotomy, visualisation of the ostium is possible using a 30? telescope. The fronto-nasal duct opens into the frontal recess and its ostium is often surrounded by anterior ethmoidal cells which may have to be cleared and a 30? or 70? telescope used to visualise the ostium.
Several important anatomical relations to be considered during the operation are as follows:
1) The lamina papyracea separates the ethmoids from the orbit. It is very thin and may be accidentally opened leading to a prolapse of the orbital fat into the ethmoids. This, if mistaken by the surgeon for edematous ethmoidal mucosa and removed, may lead to serious damage. It is therefore important to reconsider every surgical step, especially in difficult situations.
2) The roof of the ethmoid restricts the upper scope of the operation. It is slightly more yellowish in colour as compared to the remaining bone of the ethmoid and is particularly sensitive to pain, which is an important feature as the operation is usually performed under local anaesthesia. Medial to the roof of the ethmoids and at a slightly lower level, lies the cribriform plate.
3) The anterior ethmoidal artery may sometimes be a temporary source of bleeding. However, it usually passes through a solid osseous canal and can be well localised endoscopically.
4) Care must be taken to avoid damage to the nasolacrimal duct when the maxillary ostium is being widened anteriorly. It may be noted that its bony walls are significantly harder than the surrounding bone.
5) A well penumatized posterior ethmoid as well as a lateral sphenoid sinus may be directly in contact with the optic nerve. Hence surgery in this area should be under proper vision and with due caution.
Before subjecting patients to surgery, they are put through a definite protocol of investigations, which consists of a detailed history and clinical examination and X-rays of the paranasal sinuses. Routine Haematological investigations are done in all the patients. These patients are then subjected to an endoscopic examination of the nose and functional endoscopic sinus surgery (FESS), using the technique described below.
The operation is usually performed under local anaesthesia, except in children and apprehensive adults,,. After the patient has been sedated with intravenous pethidine and phenergan, the nose is packed with cotton pledgets soaked in 4% xylocaine and adrenaline. Care is taken to squeeze the pledgets well before introducing thcm. The pledgets are removed after 10 minutes. The patient lies supine with the head slightly tilted to the right, facing the operating surgeon (See [Figure - 2]). Hopkins rod optic telescopes with deflections of view from 0? to 70? and the Messerklinger endoscopic sinus instruments are used (See [Figure - 3]). The 0? telescope is most commonly used for visualisation during surgery and for simplicity of instrument manipulation. Other deflections are mainly used for access to the recesses in the operative field.
Before beginning the surgical procedure, a routine endoscopic examination is done to visualise the inferior meatus and turbinates, middle meatus and turbinates, the custachian tubes and to note any obvious pathology. The medial infundibular wall is first injected with 2% xylocaine with 1:1,00,00 adrenaline under endoscopic visualisation. If necessary, the middle turbinate is displaced slightly medially to allow better visualisation of the middle meatus. An infundibulotomy is then per formed by incising the uncinate process with a sickle knife. The knife is inserted into the uncinate process exactly in front of and immediately below the beginning of the insertion of the middle turbinate. The uncinate process is then removed with a pair of straight forceps, thereby gaining access to the anterior ethmoid area. The ethmoidal bulla now comes into view. The anterior ethmoid cells and ethmoidal bulla are removed with Henkel's straight forceps. Further exenteration of ethmoid air cells can be carried out step by step as necessary. The path leading to the frontal recess in seen above and this region is now explored using an upward bent forceps. In this area the 30? to 70? telescopes are usually required for visualisation.
The posterior ethmoid cells are entered by opening the ground lamella. These cells are opening the ground lamella. These cells are opened under direct vision by placing the telescope in the posterior ethmoid cells. Finally the maxillary sinus ostium is identified with a 30? telescope. Since it is often blocked by edematous inflamed mucosa it is first sounded with a curved probe and then enlarged with a curette and an Ostrom's reverse cutting forceps. Bleeding is usually minimal. If persistent bleeding is present at the end of surgery, nasal packing may be done. However, this is required in very few cases.
Usually, surgery entails rcmoval of obstructive diseased mucosa from isolated diseased cells and/or from the frontal recess and ethmoidal infundibulum. A complete endoscopic ethmoidectomy with sphenoidotomy is rarely required except in surgery for massive polyposis. However, the entire procedure has been described here for descriptive purposes.
The maxillary sinus is entered sublabially via the canine fossa using a trocar and cannula and the sinus inspected with a 30? or 70? telescope. Maxillary sinus mucosa is usually left untouched unless the lesion appears irreversible as in a large polyp or cyst.
Regular follow-up with meticulous cleaning of the operative cavity during the postoperative period is mandatory to avoid synechiae and renewed ostiomeatal obstruction. This is very essential for the success of this therapy concept. The patient is seen 2 and 4 days post-operatively and the operated area is cleaned of crusted blood. An antibiotic ointment is instilled into the operative cavity. This treatment is repeated at regular intervals as required (usually 3-5 days) for the next couple of weeks.
Thanks are due to the Dean, King Edward Memorial Hospital and Seth GS Medical College, Mumbai, for permitting us to use hospital data.