Ethmoidectomy

David W. Kennedy

INTRODUCTION

Although the importance of the ostiomeatal complex in relation to the persistence of inflammation in the dependent maxillary and frontal sinuses was originally recognized by Naumann in the 1960s, it was not until the routine use of diagnostic nasal endoscopy, and the introduction of sinus CT scanning techniques, that this concept was widely accepted by otolaryngologists. Thus, prior to the widespread introduction of these diagnostic modalities, sinus surgery for chronic rhinosinusitis was traditionally aimed at the maxillary sinus or at the frontal sinus.

When ethmoidectomy was performed prior to the introduction of endoscopic surgical techniques, it was typically performed either through an external approach or by an intranasal headlight procedure. Intranasal headlight ethmoidectomy was significantly dependent on tactile feedback and was well recognized for its significant risks because of the critical adjacent anatomy. Indeed, Mosher, in the early 20th century, wrote, “If it were placed in any other part of the body it would be an insignificant and harmless collection of bony cells. In the place where nature has put it, it has major relationships so that diseases and surgery of the labyrinth often lead to tragedy. Any surgery in this region should be simple but it has proven one of the easiest ways to kill a patient.” As a result, many surgeons advocated only the external approach until visualization was improved by the introduction of the endoscope.

As a result of a lecture by Hamilton Dixon MD, microscopic intranasal ethmoidectomy was introduced during the 1970s at Johns Hopkins. However, although visualization was improved, it was difficult to reliably obtain stereoscopic visualization through the relatively narrow access provided by a self-retaining speculum, and the speculum itself was not atraumatic. Dixon in 1983 published his own results using this technique and reported no complications. However, this was not the Hopkins experience.

I introduced endoscopic ethmoidectomy into the United States in 1984 based upon work previously performed by Messerklinger, Wigand, and Draf. I organized the first course to teach these techniques to others at Johns Hopkins in 1985. Subsequently, other courses were held internationally, and the technique was widely accepted and rapidly became the standard procedure for performing this operation. However, the introduction of endoscopic techniques was certainly not without controversy.

HISTORY

The most common symptoms of ethmoid inflammatory disease are nasal congestion, nasal obstruction, and postnasal discharge, along with hyposmia. Because of the nonspecific nature of these complaints, patients frequently underwent nasal or septal surgery until such time as nasal endoscopy or CT imaging was routinely performed. The maxillary and frontal sinuses are dependent upon the ostiomeatal complex and the anterior ethmoid for their drainage, and the maxillary sinus or frontal sinus symptoms frequently predominate, so that patients with ethmoid sinus disease may present with pain in the cheek or teeth, or frontal headache. Hyposmia
may be a sensitive indicator of ethmoid mucosal inflammation, but it may also commonly result from viral infection or head trauma. Ethmoidectomy, however, not only is performed for inflammatory disease but also is frequently performed for tumors primarily in the ethmoid or as an integral part of an intranasal skull base approach, or as part of endonasal craniectomy.

PHYSICAL EXAMINATION

Evidence of ethmoid disease is not typically seen on general physical examination. However, the patient may exhibit some evidence of hyponasality. Occasionally, there may be some evidence of epiphora as a result of inflammation of the adjacent nasal lacrimal duct. In extensive ethmoid disease, such as that caused by allergic fungal sinusitis, ethmoid expansion or hypertelorism may be seen, or the root of the nose may be widened as in Woake syndrome.

Endoscopic intranasal examination frequently reveals edema of the mucosa and erythema in the area of the ethmoid bulla and hiatus semilunaris or polyps within the area of the middle meatus. When present, the discharge may be cultured under endoscopic visualization using a small malleable culture swab or suction trap.

Endoscopic examination should also include evaluation of the nasopharynx, especially in children and adolescents, where adenoid hypertrophy may result in nasal obstruction and secondary involvement of the sinuses. Nasal endoscopy should also be used to assess both the intranasal anatomy and whether the ethmoid area can be adequately accessed without doing a nasal septoplasty. In the adult, as a rule of thumb, the latter means that it should be possible to visualize the anterior attachment of the middle turbinate with a 4 mm, 0-degree telescope.

INDICATIONS

The primary indication for ethmoidectomy is chronic inflammation of the ethmoid sinus, which does not respond to appropriate medical therapy. Such medical therapy would typically include environmental control and avoidance of environmental allergies, topical nasal steroids, nasal irrigations, a trial of antibiotics, and frequently a trial of oral steroids. In chronic rhinosinusitis, and especially polyposis surgery, ethmoidectomy should be thought of as an adjunct to medical therapy, rather than as an alternative to medical therapy. Ethmoidectomy may be indicated in the management of complications of acute rhinosinusitis, such as a periorbital abscess or intracranial infection.

Ethmoidectomy is also indicated during sinonasal tumor surgery, as a necessary step during endoscopic orbital decompression and during endoscopic endonasal approaches to the skull base. Ethmoidectomy may also be used as a means of identifying the skull base prior to frontal sinus surgery.

CONTRAINDICATIONS

There are no absolute contraindications to ethmoidectomy. In small children, a very conservative approach is taken to the surgery when it is necessary. Relative contraindications include coagulation defects and acute infection in the absence of a complication or threatened complication. Special care is also required when there is a low skull base, skull base erosion, or orbital adipose tissue or muscle prolapse into the ethmoid complex. It is very important that such variations are identified preoperatively by careful review of the imaging and appropriate care is taken intraoperatively.

PREOPERATIVE PLANNING

The most important step in surgical planning is careful evaluation and conceptualization of the anatomy based upon the preoperative CT scan. This requires a systematic review of the CT scan so as to provide not only an understanding of the anatomy of the skull base and medial wall of the orbit, but also the surgeon’s conceptualization of the frontal sinus drainage pathway and the relevant anatomy of ethmoid pneumatization, including agger nasi cells, sphenoethmoidal (Onodi) cells, and infraorbital (Haller) cells (Table 13.1). Adequate conceptualization of the anatomy requires a review of imaging studies in three planes and is clearly enhanced by scrolling through the anatomy dynamically in multiple planes. A major advantage of this technology is the ability for computer-assisted image guidance to provide this capability in the operating room so that the surgeon can review the anatomy again while the patient is being anesthetized.

The vertical height of the ethmoid sinus, as well as the slope of the roof of the ethmoid, should also be carefully assessed. Failure to recognize a restricted vertical height of the ethmoid sinus posteriorly may result in inadvertent entry into the cranial cavity. In general, this area should be evaluated in relationship to the vertical height of the maxillary sinus. A restricted vertical height within the posterior ethmoid also narrows the corridor available for transethmoid access to the sphenoid sinus. In patients with prior surgery, the CT scan
allows evaluation of the altered anatomy and also provides an assessment of the degree of neoosteogenesis, an important issue in deciding both the instruments required and the potential surgical approach.

TABLE 13.1 Systematic CT Scan Review

Anterior ethmoid roof	Slope, height Anterior ethmoidal neurovascular bundle Thin and thick areas
Medial wall of the orbit	Uncinate relative position Shape, integrity Optic nerve relationships
Posterior ethmoid	Vertical height
Sphenoid sinus	Sphenoethmoidal cells Pneumatization Intersinus septa/carotid arteries
Frontal recess	Frontal sinus drainage pathway Size Neoosteogenesis
Frontal sinus	Frontal cells

MR imaging becomes important when there is opacification adjacent to an erosion of the skull base, or when there may be a tumor. MR allows the identification of meningoencephaloceles and their differentiation from mucoceles and the differentiation between tumors and opacification secondary to inflammatory disease (Fig. 13.1).

In patients with acute infection, reducing the inflammation with antibiotics will help to reduce intraoperative bleeding. In the presence of reactive mucosa or polyposis, the use of preoperative steroids has been shown to decrease intraoperative blood loss. In general, a dosage of 20 to 40 mg of prednisone orally for 3 to 7 days preoperatively will usually suffice, depending on the extent of disease. At the initiation of surgery, the patient is given IV steroids and antibiotics (e.g., dexamethasone 6 to 10 mg IV and clindamycin 600 mg IV).

Informed consent for the procedure should include all of the common potential problems (bleeding, infection, temporary decrease in sense of smell, need for revision surgery), the rare problems (CSF leak, diplopia, visual loss, and anesthetic complications), and, most importantly in chronic disease, the fact that the surgery itself is not usually curative. The key instruction in this regard is the necessity for postoperative medical therapy and debridement to resolve the frequent presence of residual asymptomatic disease post surgery, if long-term resolution of disease is to be achieved. Patients with severe polyposis are warned that they may need to remain on a slowly tapering dose of oral steroids for a prolonged period of time and should expect to remain on steroid nasal irrigations or topical nasal steroid sprays on an indefinite basis.