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Neuroradiology Case of the Week

Case 238

Sara Ann Majewski, MD

Clinical Presentation: This patient is a 49-year-old status post liver transplant with pain in the right face/cheek, fevers, chills and rigors. CT of the head was obtained.

Imaging Findings: Initial CT: The right maxillary sinus is opacified by a soft tissue density with a 5 mm sized radiopaque lesion which is as dense as bone. The bony wall of the right maxillary sinus shows diffuse thickening. The posterolateral aspect of the sinus wall shows some erosion.

CT 6 weeks later:  Post-surgical bony defect is seen in the anterior wall of the right maxillary sinus. Previously seen radiopaque material within the sinus lumen is not seen on the current study. Soft tissue attenuation along the wall is still seen. Bony thickening with some erosions are still seen without definite interval changes since the prior study. Small amount of soft tissue density behind the posterolateral wall of the right maxillary sinus remains and appears stable.        

Diagnosis: Chronic fungal sinusitis secondary to aspergilli

Discussion: Caldwell-Luc of the right maxilla and inferior turbinate enterostomy were performed between CT scans in our case example.
     In adults, the maxillary sinuses are the most common site for sinusitis.
     The four paranasal sinuses develop as outpouchings of the nasal mucosa. They remain connected to the nasal cavity via narrow ostia with a lumen diameter of 1 to 3 mm. The mucoperiosteum lining the sinuses is thinner with less vasculature and glands than the nasal mucosa. Cilia within the sinuses beat and sweep mucus toward the ostia. Ostia of the frontal, maxillary and anterior ethmoid sinuses open into the ostiomeatal complex, which is located middle meatus lateral to the middle turbinate. The posterior ethmoid and sphenoid sinuses open into the superior meatus and sphenoethmoid recess.
     The ostiomeatal complex is composed of the uncinate process, maxillary ostium, infundibulum, and ethmoid bulla. The cilia of the maxillary sinus beat superiorly toward the maxillary sinus ostium.
     Impaired mucus transport and sinus ventilation are major factors contributing to sinusitis. Predisposing factors to sinusitis are as follows: allergic rhinitis (rare); anatomic variants, including tonsillar and adenoid hypertrophy, deviated septum, nasal polyps and cleft palate; barotraumas; dental infections and procedures; trauma; hormonal changes associated with puberty or pregnancy; immunocompromise; irritant inhalation; mechanical ventilation; nasal dryness or packing, nasotracheal and nasogastric tubes; and upper respiratory infections. Obstruction of sinus ostia may be secondary to mucosal edema or an anatomic anomaly. Bacterial and viral infections can also lead to failure of mucus transport. The most common cause of acute bacterial sinusitis is a viral upper respiratory infection. Ciliary beating which is normally 700 per minute slows to less than 300 per minute with infection. Inflammation can cause approximately one-third of the ciliated columnar cells to undergo metaplasia to mucus-secreting goblet cells. Obstruction and decreased transport causes mucous pooling, decreased pH and decreased oxygen tension within the sinus which create a niche for bacteria.
     Seventy percent of cases of community-acquired acute sinusitis in adults and children are caused by Streptococcus pneumoniae and Haemophilus influenzae. Branhamella (Moraxella) catarrhalis causes 25 percent of pediatric acute sinus infections. Other pathogens less frequently documented include other streptococcal species, Staphylococcus aureus, Neisseria species, anaerobes and gram-negative rods. Viruses are identified in fewer than 10 percent of childhood sinus infections. Beta-lactamase producing organisms, such as H. influenzae or B. catarrhalis are found in patients with recent antibiotic use. Nasal mixed flora does not correlate with bacteria cultured directly from the sinuses, therefore nasal cultures are not used for diagnosis. Fungi are normal upper airway flora but can cause acute sinusitis in immunocompromised and diabetic patients. Aspergillus species are most common.
     Medical therapy is the first-line treatment of chronic sinusitis, consisting of oral antibiotics, steroids, and nasal saline irrigations. Decongestants provide symptomatic relief for nasal congestion. Guafenisin mucolytic can be used for large amounts of nasal secretions.
     Surgery is reserved for confirmed chronic sinusitis, per history, physical and CT as well as those who have not responded to medical therapy. Three main surgical options are available: (1) endoscopic uncinectomy with or without maxillary antrostomy, (2) Caldwell-Luc procedure, and (3) inferior antrostomy (naso-antral window).
     Comprehension of the physiologic drainage pattern of the maxillary sinus led to intranasal middle meatus antrostomy around 1970. Functional endoscopic sinus surgery (FESS) via the ostiomeatal complex was later developed and is the standard surgical treatment for chronic maxillary sinusitis. External approaches are used in complicated cases.
     As FESS is widely used, it is rare to perform a Caldwell Luc operation except in a patient who is inaccessible with an endoscope or has refractory sinusitis.
    CT scanning identifies the anatomic relationships of the key structures (orbital contents, optic nerve and carotid artery) to the diseased areas, a process that is key to surgical preparation. CT also defines the extent of disease, as well as any underlying anatomic abnormalities that may predispose a patient to sinusitis.
     The Caldwell-Luc operation was first described in the late 1890s. The Caldwell-Luc procedure is performed under general anesthesia or, less commonly, with local anesthetic and sedation or with both general and local anesthesia. It may be performed in conjunction with nasoantral window (inferior antrostomy) to facilitate postoperative surveillance. A small incision is made superficial to the canine tooth and first premolar where the cheek meets the gum. A tiny portion of gingiva is left intact above the teeth for closure. A dissection is made through the soft tissue and periosteum to bone. Then, the periosteum is separated or scraped upwards from the anterior wall of the maxilla. The infraorbital nerve, which supplies sensation to skin of cheek, is identified inferior to the mid pupillary line so as to avoid injury to it. In the canine fossa, a window is made through the anterior thin bony portion of the maxillary sinus, exposing the mucous membrane of the sinus, of which a variable portion is removed. Pus from the maxillary cavity can then be cultured. Next, the sinus is irrigated. The incision is then closed, stitching the cheek back to the gum.
     The main complications associated with the Caldwell-Luc procedure include oroantral fistula (breakdown of the gum incision with communication between the mouth and sinus), rare osteomyelitis, infraorbital nerve injury with associated hypesthesia, injury to the tooth roots and tooth discoloration. When the mucous membrane of the antrum is totally removed, the sinus eventually regenerates nonciliated epithelium. It is unable to clear mucus as a normal ciliated sinus would. It is common for mucoid pus to occur postoperatively as the sinus is no longer able to clear itself of bacteria and mucus. Incomplete removal of mucous membrane may allow regrowth of ciliated mucous membrane and the reestablishment of normal mucus flow patterns.
     FESS has many advantages. Using an endoscope, this surgery is minimally invasive. Entry is via the nose, therefore, there is much less discomfort postoperatively than with conventional surgery. The sinus, ostia and ostiomeatal complex are directly visualized with the aim of extracting diseased soft tissue and enlarging the sinus openings, hence clearing the sinus and reestablishing ventilation. The use of the endoscope permits a better view of the surgical field which is likely responsible for the lower rate of complications.  Scars and damage to the nerve supply of the teeth are avoided. The procedure is usually performed under local anesthesia, with optional sedation, and is done as an outpatient.
     The worst complication of FESS is blindness secondary to optic nerve damage, which is extremely rare. Cerebrospinal fluid leak is the most frequent major complication of FESS but is still rare. CSF leak is recognized during surgery in most cases and is simple to repair. Other rare complications include orbital hematoma and nasolacrimal duct stenosis. All of these complications can occur with invasive sinus surgery, too.

References:

1. Fagnan, L. Acute sinusitis: a cost-effective approach to diagnosis and treatment. Am Fam Physician. 1998 Nov 15;58(8):1795-802, 805-6. [Medline]
2. Patel A, Vaughan W. Sinusitis, Maxillary, Chronic, Surgical Treatment. Emedicine: May 19, 2005 (http://www.emedicine.com/ENT/topic339.htm).
3. Ramadan H. Sinusitis, Fungal. Emedicine; August 25, 2006 (http://www.emedicine.com/ENT/topic639.htm).
4. Slack R, Gates B. Functional endoscopic sinus surgery. Am Fam Physician. 1998 Sep 1;58(3):707-18. [Medline]