Chapter 22. Periorbital and Orbital Infections

While the terms periorbital (preseptal) and orbital (postseptal) cellulitis sound similar, their pathogenesis, management, and complications are quite different. Periorbital infections refer to infections located anterior to the orbital septum, while orbital infections are infections located posteriorly.

Periorbital infections occur more frequently than orbital infections. Both infections are most commonly bacterial in origin and represent infections of the eyelid and the area surrounding the orbit. In general, these infections are caused by contiguous spread from adjacent infected structures, local trauma, or bacteremia. Noninfectious etiologies of periorbital and orbital cellulitis include inflammatory, allergic, endocrinologic, and neoplastic diseases.1

Prior to the advent of the Haemophilus influenzae type b conjugate vaccine in 1985, the majority of periorbital cellulitis in children was secondary to bacteremia from H. influenzae type b, which caused approximately 80% of the cases.2 The introduction of the H. influenzae type b vaccine reduced pediatric cases of periorbital and orbital cellulitis by 59%.3 Today, the most common cause of periorbital cellulitis is adjacent spread from infected neighboring structures, including skin, conjunctiva, eyelids, sinuses, respiratory tract, and teeth.4 Other causes of periorbital cellulitis include blunt or penetrating trauma, viral infections such as adenovirus or Epstein–Barr virus, and bacteremia. In immunocompromised hosts, fungal etiologies, such as aspergillosis and phycomycosis, should be considered.4,5

Orbital cellulitis is an inflammation of the orbital structures, which is most commonly a complication of sinusitis, and, in more than 90% of cases, is ethmoidal in origin.5 Other causes of orbital cellulitis include blunt or penetrating trauma, bacteremia, extension from infected adjacent structures such as dacryocystitis, or severe odontogenic infections.1,5 Because sinusitis is more common in older than in younger children, orbital cellulitis tends to be seen more commonly in older children, and the occurrence tends to peak in the winter months when sinusitis is more prevalent (Table 22–1).6

Understanding the anatomy of the eyelid and the contiguous structures can be helpful in understanding the pathogenesis of periorbital and orbital infections. The terms preseptal and postseptal are used interchangeably with periorbital and orbital but specifically refer to infections that lie anterior or posterior to the orbital septum, respectively. The orbital septum is a fibrous extension of the periosteum of the skull located anteriorly in the orbit (periorbital). The periosteum and the orbital septum serve as barriers to prevent spread of infections from the eyelids and sinuses into the orbit (Figure 22–1).

The orbit is encompassed by the upper wall of the maxillary sinus, the lower wall of the frontal sinus, and the lateral wall of the ethmoid sinus. These bony walls of the sinuses vary in thickness; however, many are thin and porous and can be easily infiltrated, allowing for spread of infection.1,7 One particularly thin sinus wall is the lamina papyracea of the ethmoid bone, a derivation from Latin meaning “a thin layer of paper.” Thus, spread of infection from the sinuses into the orbit is often a consequence of direct extension through the wall of the ethmoid sinuses.

In addition, the venous drainage system of the orbit is made of a valveless system, which allows the ophthalmic and ethmoidal veins to communicate directly. These veins, in turn, drain into the cavernous sinus, which can permit sinus infections to spread hematogenously into the orbit, leading to more complicated infections including thrombosis of the cavernous sinuses and meningitis.1,2,4

In nonbacteremic preseptal cellulitis, the infection remains anterior to the orbit and thus the aforementioned complications are less common. Often, the swelling seen in the soft tissues in periorbital cellulitis is not an actual “infection” of those tissues, but rather an inflammatory edema or sympathetic effusion, which is a reaction to a neighboring infection.2 This makes it somewhat important to ascertain the location of the inciting infection, as causative organisms may be different. For example, periorbital cellulitis as a consequence of an eyelid or face trauma such as from an insect bite or from spread of infection from adjacent structures such as hordeolum, dacryocystitis, impetigo, or conjunctivitis would be more likely Staphylococcus aureus or Streptococcus pyogenes, whereas one that is caused by a sinusitis or an upper respiratory tract infection may be more commonly Streptococcus pneumoniae, nontypable H. influenzae, and other respiratory tract pathogens (Table 22–1).5,8 Polymicrobial infections with both aerobes and anaerobes are more likely to be seen in older adolescent patients with chronic sinusitis causing orbital cellulitis and associated subperiosteal abscess.9

Differentiating between clinical signs and symptoms associated with periorbital and orbital cellulitis is critical to making a prompt diagnosis. Often, the history may not be helpful in making the diagnosis, as patients commonly might have had only vague symptoms and were not aware of any problem until the onset of overt symptoms. Patients with preseptal cellulitis may complain of symptoms associated with upper respiratory tract infection or infection of adjacent structures. The clinician should ask about recent insect bites or trauma and recent skin, soft-tissue, or eye infections such as impetigo, hordeolum, conjunctivitis, acute chalazia, acute dacryocystitis, blepharitis, or odontogenic infection.1

Symptoms associated with orbital cellulitis can be similar to those articulated by patients with periorbital cellulitis. Because direct extension may occur from adjacent structures, patients with orbital cellulitis may have similar inciting foci, such as a severe odontogenic infection or acute dacryocystitis. However, as the majority of patients with orbital cellulitis have sinusitis as the predominant cause, a history of a recent upper respiratory tract infection or symptoms suggestive of sinusitis may be present, such as headache, sinus tenderness, sinus pressure, and post nasal drip. Quite often, in patients presenting with sinusitis-related periorbital and orbital cellulitis, there is only a vague history of upper respiratory tract complaints. Fever may or may not be present.5

Periorbital and orbital cellulitis are both characterized by signs of inflammation within the periorbital tissues, including erythema, warmth, tenderness, edema, and induration (Figures 22–2 and 22–3). However, only orbital cellulitis is associated with proptosis, decreased extraocular movements or ophthalmoplegia, pain with extraocular movement, and decreased visual acuity or vision loss.6 Photophobia is more commonly seen in orbital cellulitis, although this may be associated with conditions that cause periorbital cellulitis.

The progression of disease in orbital cellulitis can be rapid and is best described by the Chandler classification system of orbital cellulitis related to sinusitis (Table 22–2).10 In stage 1, the patient presents with inflammatory edema and with findings similar to periorbital cellulitis, such as erythema, warmth, induration, and tenderness over the periorbital tissues. During stage 2, the patient develops true orbital cellulitis with chemosis (edema of the bulbar conjunctiva), proptosis, pain with eye movement, decreased extraocular movements, and decreased visual acuity. It is during this stage that there is extension of disease posterior to the orbital septum. In stage 3, subperiosteal abscess formation occurs, usually between the orbit and the periosteum of the sinuses. In this stage, an increase in extraocular pressure can occur, which may worsen proptosis and vision changes. Complete loss of extraocular movements or ophthalmoplegia is associated with stage 4: development of an orbital abscess, which is a true abscess of the orbital contents. Patients may complain of complete vision loss, and a marked proptosis is noted on examination. Finally in stage 5, the most serious complications occur, including cavernous sinus thrombosis, which may present as headache, bilateral periorbital edema, cranial neuropathies, proptosis, and ophthalmoplegia with extension into the central nervous system.1,10,11 Extension of disease into the central nervous system may also include the development of meningitis or formation of abscesses in the brain and epidural or subdural spaces.

On physical examination, it is therefore critical in any patient presenting with periorbital swelling to measure visual acuity and to assess for pain or decreased range of motion with eye movement, proptosis, chemosis, and photophobia (Table 22–3).

Fever and leukocytosis with a left shift are often, but not always, present in patients with periorbital and orbital cellulitis. Obtaining a complete blood count should be considered in any patient who appears ill; however, in either of these two conditions, it does not necessarily help the practitioner to differentiate between them. Blood cultures will commonly be negative in patients presenting with periorbital cellulitis and in most stages of orbital cellulitis. Cultures of wounds draining exudate may be helpful in infections caused by trauma or local infection; however, random cultures of the adjacent structures, conjunctiva, eyelids, or nasopharynx may be misleading and are generally not advised. Decisions to obtain needle aspirates of sinuses or abscesses associated with orbital cellulitis for diagnostic purposes should only be performed by consulting specialists if deemed necessary.

Radiological studies, such as computed tomography (CT) scan with intravenous contrast, should be performed in any patient with suspected orbital cellulitis to evaluate the extent of disease. Treatment modalities are often based on severity of symptoms as well as appearance on imaging.5,11 Findings in orbital cellulitis such as opacification of the sinuses, eyelid swelling, and proptosis are easily seen on CT scan; subperiosteal abscesses generally are found on the medial orbital wall adjacent to a medially bowed periosteum, which laterally displaces a medial rectus muscle (Figure 22–4), while orbital abscesses will appear as densities within the intraconal space.1

Prompt differentiation and diagnosis are necessary to facilitate prompt management of periorbital and orbital cellulitis. Several noninfectious conditions can mimic these diseases, producing swelling of the eyelids and sometimes erythema. A list of these conditions is provided in Tables 22–4 and 22–5.

For periorbital cellulitis, in addition to the bacterial agents, other pathogens that should be considered include viruses (e.g., adenovirus and enteroviruses) when conjunctivitis is associated with periorbital edema, and, in immunocompromised persons, fungal organisms (e.g., aspergillus and zygomycetes) should be included in the differential diagnosis of any patient presenting with periorbital edema, erythema, and tenderness.5

Type I hypersensitivity reactions, such as those to animal dander and pollen, may cause acute swelling of the eyelids but typically are not erythematous or tender to palpation. Contact blepharoconjunctivitis, which is a type IV hypersensitivity reaction, is associated with ophthalmic solutions and may cause erythema, swelling, and eczematoid changes to the associated eyelid. Acute trauma, such as a basilar skull fracture, can cause unilateral or bilateral periorbital swelling, ecchymosis, and tenderness to the eyelids. The clinician must use historical data to differentiate these from infectious etiologies.1,5

The differential diagnosis of orbital cellulitis can be quite broad and needs to be differentiated from several conditions that cause orbital inflammation. A good general rule is in patients who are afebrile and have no evidence of sinusitis or adjacent structural disease, alternative diagnoses should be considered.

As with periorbital cellulitis, nonbacterial causes such as fungal infection should be considered in the immunocompromised patient with orbital cellulitis. Inflammatory orbital pseudotumor commonly presents with proptosis, ophthalmoplegia, and periorbital swelling. These patients are generally afebrile and without evidence of sinusitis on examination or CT. Typical CT scans reveal an intraorbital mass, not consistent with an abscess. Dacryoadenitis can mimic orbital cellulitis but is associated with nonbacterial etiologies such as viral infection or inflammatory diseases such as sarcoidosis or pseudotumor.1,5,12 Ophthalmologic examinations revealing choroidal elevation or retinal detachment associated with exudates may be indicative of posterior scleritis.1

For patients presenting with cavernous sinus thrombosis, a broad workup may be necessary to find the underlying etiology. Other conditions that may present similarly to orbital cellulitis include space-occupying orbital lesions such as rapidly progressive neoplastic disorders including orbital rhabdomyosarcomas, leukemic infiltration of the orbit, or lymphoma. Other non-neoplastic lesions that may cause orbital inflammation include a ruptured dermoid cyst or a subperiosteal hematoma from trauma. These space-occupying lesions should be distinguished from orbital cellulitis based on characteristics on CT scan and/or magnetic resonance imaging; however, a biopsy may be necessary if diagnosis is uncertain.1,13

Treatment of any periorbital or orbital cellulitis should be based on the inciting focus and should be managed in consultation with ophthalmology, otolaryngology, and infectious disease specialists. See Table 22–6 for list of treatment options. For the patient older than infancy who is nontoxic, periorbital cellulitis may be managed as an outpatient, particularly if the inciting focus is known. Patients with orbital cellulitis and ill-appearing patients should be admitted to the hospital and monitored closely with serial visual acuity examinations and for administration of intravenous antibiotics. In general, for periorbital and orbital infections thought to be caused by trauma, skin, or adjacent soft-tissue infection, antibiotics should be targeted at the treatment of S. aureus and S. pyogenes, recognizing that methicillin-resistant S. aureus is now commonly found as a causative organism of these infections. Surgical drainage of any abscesses may be necessary to achieve complete resolution of symptoms. For penetrating trauma, gram-negative and/or anaerobic coverage should also be considered. Therapy for infections thought to be occurring from an odontogenic focus should be aimed at both aerobic and anaerobic mouth flora such as Streptococcus species and oral anaerobes such as Fusobacterium and Bacteroides species. For sinus-related disease, therapy should be directed at aerobic respiratory flora such as S. pneumoniae, H. influenzae, Moraxella catarrhalis, S. aureus, Streptococcus species, as well as anaerobes.4

Length of therapy is dependent on inciting focus; however, typical length of therapy for periorbital cellulitis is 7–14 days, whereas 14–21 days are usually necessary for orbital cellulitis. The decision to switch from intravenous to oral antibiotics is varied between patients and is primarily based on the resolution of symptoms, cessation of fever, and ophthalmologic examination. For patients who do not improve after 24–48 hours of appropriate intravenous therapy, consider repeating radiological studies and surgical intervention.12