24.1 Prevalence and Pathophysiology of Periorbital and Orbital Complications of Sinusitis

Orbital cellulitis, subperiosteal abscess, and orbital abscess are the common complications of sinusitis in children. The latter may also further exacerbate onto intracranial disorders such as brain abscess, subdural empyema, meningitis, facial osteomyelitis, and thrombosis of the cavernous sinus and cortical vein. ¹

The orbit is susceptible to contiguous spread of infection from the sinuses as it is surrounded by sinuses on three sides. Children are particularly susceptible for infection spread because of their thinner bony septa and sinus wall, greater porosity of bones, open suture lines, and larger vascular foramina. The main anatomical landmark in the assessment and diagnosis of orbital cellulitis is the orbital septum (▶ Fig. 24.1), a fascial extension of the orbital rim periosteum extending to the tarsal plates of the upper and lower eyelids.

Periorbital cellulitis (preseptal cellulitis) is usually caused by trauma to the eyelid, for example, insect bite, or bacteremia ² and usually does not result from sinusitis and complicate to a sequel of orbital complications. ³ Orbital cellulitis (postseptal cellulitis) is an invasive bacterial infection of the postseptal tissues of the eye. The most common underlying factor for the development of orbital cellulitis is presiding acute ethmoid sinusitis ^{4 , 5} and up to 76% of cases of orbital cellulitis occur as a complication of acute sinusitis. ⁶

Bagheri et al found that sinusitis was the most common cause in 53.8% of patients with orbital (postseptal) cellulitis, and in only 24.1% of preseptal cellulitis patients. Hence, surgical intervention was less common in periorbital cellulitis and was required in 14.8% of cases in comparison to 48.7% needed in orbital cellulitis. ⁷ Interestingly, orbital infections secondary to sinusitis are being reported to be 85% to 95% preseptal cellulites and 5% to 15% postseptal infections ⁸ such as subperiosteal abscess (SPA) (15%) and orbital abscess (less than 1%). ⁹ However, these rates vary between different series worldwide. For example, Kinis et al presented a series of complicated sinusitis patients with a rate of 42.3% of subperiosteal abscess and 50% preseptal cellulitis.

Depending on the severity of the presentation, eye findings may vary from soft, nontender eyelid edema to marked erythema, proptosis, chemosis, ophthalmoplegia, and decreased visual acuity. ⁵ Interestingly, while underlying sinusitis may be the cause of majority of cases of orbital cellulitis, orbital complication may be the first and only presenting sign of sinus disease. ¹ The appearance of a proptotic eye with periorbital swelling usually arise the suspicion of an infection, caused by not only acute sinusitis but also bacteremia and facial infections, nasal foreign body, a fungal infection, dacryocystitis etc. If sufficient septic clinical characteristics are not available, the differential diagnosis should include other infectious sources such as hemorrhagic cyst, pseudoaneurysm of orbital bones, a cranio-orbital cerebrospinal fluid leak, Langerhans cell histiocytosis, hemorrhagic infarct of orbital bones, orbital myositis, an aneurysmal bone cyst, ossifying fibromatrauma, and iatrogenic causes. In sinus tumors, many primary tumors (i.e., rhabdomyosarcoma or retinoblastoma) and metastasis (i.e., neuroblastoma) may be misdiagnosed as infections.

As for the pathophysiology of infectious spread, the orbit is separated from the ethmoid cells and maxillary sinus by the lamina papyracea which has congenital bony dehiscence. Infections can spread directly by penetration of the lamina or through the dehiscence. Infection may also extend directly by traversing through the anterior and posterior ethmoid foraminas. Moreover, the ophthalmic venous system has no valves, meaning the extensive venous and lymphatic communication between the sinuses and the surrounding structures enables retrograde thrombophlebitis and further spread of the infection. ¹⁰ Orbital infection may also occur via foreign body contamination or systemic hematogenous seeding, though these routes are thought to be far less common than direct local spread. ¹¹

Orbital cellulitis may further complicate into orbital SPA, a process in which pus is collected between the bony orbita frame and the periorbita. SPA most commonly arises from a complication of acute sinusitis. It is a relatively rare complication, occurring in 1% to 6% of cases. ¹¹ Intracranial extensions are even more rare, and may lead to potentially life-threatening conditions such as brain abscess, epidural empyema, and sinus vein thrombosis. They may occur directly, through necrotic areas of osteomyelitis in the posterior wall of the frontal sinus or by retrograde thrombophlebitis through the intracranial valveless venous system that interconnects the intracranial venous system with the sinus mucosal vasculature. Pediatric population is more vulnerable to CNS complications, due to the immature arachnoid ¹⁰ (▶ Fig. 24.1 and ▶ Fig. 24.2).

24.2 Classification

Hubert was the first to embark on scientific classification of orbital complications following sinusitis, based on the anatomy of the orbit, progression of infection, responsiveness to treatment, and general prognosis. ¹² This classification system was renovated by Chandler, ¹³ who recognized the orbital septum, anatomical landmark, dividing the orbit into preseptal and postseptal sites. The orbital septum is a fascial extension of the orbital rim periosteum extending to the tarsal plates of the upper and lower eyelids. Chandler’s classification describes the signs and symptoms of involvement of different regions of the orbit and does not imply a chronologic progression of symptoms.

Chandler grouped his patients under five categories (see ▶ Table 24.1 and ▶ Fig. 24.4).

Schramm further modified Chandler’s classification, focusing on patients with preseptal cellulitis with chemosis as a separate entity. Schramm suggested to consider these patients as a separate entity as they do not consistently improve with antibiotics and surgery needs to be advocated. ¹⁵ Chandler’s classification was also modified by Moloney who divided orbital complications into preseptal and postseptal complications. ¹⁶ Moreover, a recent suggestion by Le et al. was to add computed tomography characteristics such as presence of bony destruction and size of SPA (>3.8 mL) to the original Chandler criteria ¹⁷ (▶ Fig. 24.3).

24.3 Microbiology of Orbital Complications Associated with Sinusitis

The microbiology of orbital cellulitis and abscess reflects the underlying sinus involvement and pathology. Common organisms are Streptococcus pneumoniae, Moracella catarrhalis, haemophilus species, Staphylococcus aureus, group A streptococcus and upper respiratory anaerobes such as Peptostreptococcus, Fusobacterium, and Bacteroides. ^{4 , 5 , 10} Historically, Haemophilus influenzae cases were common, such as meningitis and bacteremia, ¹⁸ but with the introduction of H. influenzae type B vaccine in 1985 its incidence sharply declined. ^{19 , 20} Nowadays, Staphylococcus and Streptococcus are the most common pathogens found in the current series. ^{4 , 21}

In the recent years, community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is a rising concern as a cause of head-and-neck infections. Bedwell et al report that the incidence of MRSA varies from 23% to 72% in the United States. ^{5 , 22} Mckinley et al reported that up to 73% of Staphylococcus species found and isolated in their cohort were actually MRSA, and the latter was the next most common pathogen (36% of all cultures obtained in this study).

When the sinusitis spreads to the orbital region from the maxillary sinuses, it may also be associated with odontogenic infections in pediatric population. Typical organisms may include alpha-hemolytic streptococci, microaerophilic streptococci, and more rarely, Streptococcus pyogenes and S. aureus. In anaerobic organisms, gram-negative bacilli Peptostreptococcus spp., Fusobacterium spp., and Propionibacterium acnes were found. ²³

Tissue and pus cultures may be obtained from various sites. The yield of different culture sites was examined and the most yielded cultures were obtained intraoperatively from the orbital and sinus abscess. Sinus aspirate and nasal swabs had a yield of 81% and 83%, and blood culture yield was very low at 7%. ²¹

Intravenous antibiotic therapy should not only cover common pathogens but also penetrate central nervous system, in order to reduce the risk of intracranial complications. After obtaining microbiology culture, proper treatment should be done according to the culture results. Several protocols for empiric treatment are available in the literature: Bedwell et al suggest combining Clindamycin with third-generation cephalosporin with good CNS penetration such as cefotaxime, ceftriaxone, or cefuroxime.

The conversion to oral antibiotics takes place when the clinical examination returns to the basal state. In nonsurgical cases, amoxicillin with clavulanic acid or clindamycin is prescribed for 14 days. In surgical cases, culture-directed antibiotic is used. ⁵ In some series amoxicillin is used as oral therapy in up to 40% of cases, while cefuroxime in 13% of cases only. ²¹ Although histopathological characteristics, osteitis, and even osteomyelitis signs are present in the specimen of the excised ethmoid bone of surgical patients, a long-term course of therapy is not usually required. ⁹

Cannon et al provided preliminary data regarding oral antibiotic treatment for postseptal cellulitis; however, this treatment is still experimental and does not obviate the need for hospitalization for close monitoring. ²⁴

As for other complementary treatments, nasal vasoconstriction with oxymetazoline, although a controversial treatment, is also sometimes applied. ⁵ Corticosteroid usage, especially when central nervous system is involved, is also noncommon and controversial. They can retard the encapsulation, increase necrosis, and reduce antibiotic penetration into the abscess. However, these treatments may also have a positive effect by reducing cerebral edema, ¹⁰ and they may aid in the treatment of the adjacent sinusitis. These are also hypothesized to suppress and control the exuberant inflammatory response and prevent further spillage to the subperiosteal space. Yen et al showed no significant difference in the number of patients with SPAs requiring surgery with addition of steroids in comparison to patients who did not receive steroids. ²⁵