26.1 Introduction

Periorbital cellulitis is defined as an infection of the soft tissue surrounding the eye. Although it can occur at all ages, it is prevalent in the pediatric population. In fact, orbital complications are more commonly seen in the pediatric age group, with the overall incidence of 3 to 4% in children affected by acute rhinosinusitis. ¹

Periorbital cellulitis can be subdivided into two major entities, preseptal cellulitis or postseptal cellulitis, the latter also known as orbital cellulitis. In preseptal cellulitis, the infection does not extend beyond the orbital septum and is usually due to an eyelid infection or acute rhinosinusitis, while postseptal cellulitis is generally a consequence of acute rhinosinusitis. The spreading of pathogens from the sinuses (particularly the ethmoid cells) to the nearby tissues is thought to occur directly through the lamina papyracea or through the communicating blood vessels. The lamina papyracea is a thin bony structure that contains several natural perforations. It is believed that the infection can easily spread from the ethmoid sinus to the orbit through these perforations.

Therefore, acute rhinosinusitis is the predominant cause of orbital infection in children. In general, paranasal rhinosinusitis is responsible for 66 to 75% of cases of orbital infection, and acute ethmoiditis represents the most common rhinosinusitis linked to orbital cellulitis in children. The spread of infection from the ethmoid sinus is generally very rapid, and orbital complications can develop even under antibiotic therapy. Orbital involvement can easily be suspected in the case of ophthalmoplegia and proptosis.

A diagnosis is usually reached using a combination of clinical examination and radiological findings. The Chandler classification (▶ Table 26.1) still represents the most complete and popular classification for indicating the severity of the infection. ²

26.2 Subperiosteal Abscess

The periorbita represents the periosteum separating the orbital content from the skeleton and the neighboring structures. Anteriorly, the periorbita merges with the periosteum of the external skeleton to form the orbital septum. Infections ensuing anteriorly to the septum are defined as preseptal and rarely include preseptal abscesses. On the other hand, infections developing posteriorly to the septum are defined as postseptal and are usually considered more serious. A subperiosteal abscess represents a postseptal infection developing between the bone and the periorbita. Although these abscesses derive from a direct spread of infection from acute ethmoiditis, in rare cases they can develop from acute rhinosinusitis of the frontal or maxillary sinuses. The diagnosis of subperiosteal abscess is generally radiological via an enhanced CT scan (▶ Fig. 26.1). On CT imaging, an abscess appears as a rim-enhancing collection of fluid between the periorbita and the bone. The displacement of the orbital content can also be observed with larger purulent collections, and they are more visible in the axial and coronal planes of the CT images. MRI is generally reserved for those cases where there is suspicion of an intracranial extension of the infection.

26.3 Microbiology of Orbital Cellulitis

The most common pathogens of orbital cellulitis are the Staphylococcus and Streptococcus species. Less common causative organisms include the Haemophilus influenzae, Pseudomonas, Klebsiella, Enterococcus, Peptostreptococcus, Fusobacterium, and Bacteroides species. ^{3 ,​ 4 ,​ 5} Since the introduction of the H. influenzae (Hib) vaccine in 1985, H. influenzae has become an infrequent causative organism for pediatric periorbital cellulitis. ⁶ More recently, an increase in the incidence of methicillin-resistant Staphylococcus aureus (MRSA) as a causative agent has been observed.

Bacterial growth in purulent cultures may be difficult to obtain. At our institution, only 2 out of 10 patients affected by subperiosteal abscess had positive cultures for S. pneumoniae. ⁷

26.4 Physical Examination

The ear, nose, and throat (ENT) specialist should evaluate the nasal cavity for any sign of acute rhinosinusitis (edema of the nasal mucosa and purulent secretions). If possible, nasal decongestion under endoscopic view should be performed.

An ophthalmologist should evaluate the affected eye. The lid involved is generally swollen, with loss of skin crease, and is erythematous (▶ Fig. 26.2). Visual acuity and pupil reactivity should also be evaluated. The presence of proptosis and ophthalmoplegia generally indicates postseptal orbital involvement and, therefore, the presence of a purulent collection.

Radiological assessment with a CT scan is usually obtained for every patient in whom an abscess is suspected.

A neurosurgical consultation should be requested in the presence or suspicion of any intracranial complication.

26.5 Management Options

Orbital cellulitis represents a serious infection, warranting prompt antibiotic therapy due to catastrophic complications, such as visual loss, intracranial infection, and sepsis.

Before the antibiotic era, patients affected by orbital cellulitis died from meningitis in 17% of cases or suffered from permanent visual loss in 20% of cases.

The treatment of orbital complications seems to depend on the Chandler classification stage. In fact, stages I and II of the Chandler classification are usually managed with medical therapy, while the other stages usually require a surgical approach to clear the pus collection. Stage V of this classification represents an intracranial extension of the infection rather than a mere orbital complication.

Medical therapy is usually empiric and based on a parenteral broad-spectrum antibiotic, such as combined penicillin (ampicillin-sulbactam; amoxicillin/clavulanic acid) or second- or, less frequently, third-generation cephalosporin. In cases where an association between gram-positive and anaerobes is suspected, clindamycin may be added to the combined penicillin or cephalosporin. In cases of an infection due to MRSA, vancomycin may be considered as a possible treatment.

Moreover, nasal decongestant and steroid nasal sprays may be used to reduce nasal inflammation. At our institution, we also prefer to administer IV steroids (methylprednisolone) to reduce the inflammatory component of the infection more rapidly. The use of oral or IV steroids for orbital cellulitis seems to have no particular adverse effect on children. ^{8 ,​ 9}

Children affected by periorbital cellulitis (erythema and edema of the eyelid skin) without any proptosis or impairment of eye movements can generally be managed solely by medical therapy (▶ Fig. 26.3). Even cases of young children (younger than 9 years) presenting small periorbital abscesses without any visual impairment may be treated medically.

Children presenting with small purulent collections (≤5 mm) without any visual impairment and with no ophthalmoplegia or proptosis may be treated with medical treatment alone. ¹⁰ Interestingly, Arjmand et al outlined the necessity of performing surgical drainage in cases of subperiosteal orbital abscess, since visual acuity may be unchanged even in cases of rapid progression of the infection toward a serious intracranial complication. ¹¹

On the other hand, in older children, in the presence of large purulent collections and visual impairment, medical therapy is usually not sufficient and must be associated with surgical treatment.

When a surgical approach is required to achieve the removal of the purulent collection, the decision is mainly focused on a transnasal endoscopic approach. However, in the cases in which the transnasal approach is not able to completely clear the collection, an external approach must be added to the endoscopic one. For instance, in cases of superior and superolateral collections or eyelid abscess, an external approach must be considered. Tanna et al indicated the necessity of performing an external approach when the purulent collection is located superolaterally with several orbital muscles involved. ¹²

In conclusion, urgent surgical drainage should be considered in the cases that do not improve or even worsen with adequate medical management, or in those cases presenting visual deterioration (decreased vision or color vision, or afferent pupillary defect). Nevertheless, there is no universally accepted guideline for the treatment of subperiosteal abscesses, and each case should be treated independently. Cooperation among specialists, such as the ENT surgeon, the ophthalmologist, and the pediatrician, is of paramount importance in order to decide on and tailor the best treatment.

If the patient has improved sufficiently to be discharged, the antibiotic therapy can be changed to oral therapy and usually continued for 2 or 3 weeks.