Orbital Cellulitis

Etiology

The most common cause of orbital cellulitis is bacterial rhinosinusitis. Other potential causes include[4]:

• Infection of the teeth, middle ear, or face
• Dacryocystitis
• Orbital trauma with fracture or foreign body
• Ophthalmic surgery such as strabismus surgery, blepharoplasty, radial keratotomy and retinal surgery
• Peribulbar anesthesia
• An infected mucocele that erodes into the orbit
• Immunodeficiency

Epidemiology

Orbital cellulitis is commonly seen in young children. It is seen less in older children and adults[5].

Pathophysiology

Orbital cellulitis is a rare complication of bacterial rhinosinusitis. However, in most cases of orbital cellulitis, rhinosinusitis is the source of infection. Data show that in up to 86% to 98% of cases of orbital cellulitis, there is coexisting rhinosinusitis present. Moreover, pansinusitis and ethmoid sinusitis are the forms of rhinosinusitis that most likely to lead to orbital cellulitis.[6]

History and Physical

The best indicators of orbital cellulitis is a pain with eye movements, proptosis, and ophthalmoplegia with diplopia. Chemosis (conjunctival swelling) is more commonly present in orbital cellulitis; however, it may also be seen occasionally in severe cases of preseptal cellulitis. Fever and peripheral leukocytosis with a predominance of neutrophils are also seen in orbital cellulitis. Eyelid erythema may or may not be present.[7]

Evaluation

The diagnosis of orbital cellulitis should always begin with a physical exam looking for clinical findings of orbital cellulitis but also for its serious complications. It is important that an ophthalmologist evaluate a patient with suspected orbital cellulitis for extraocular movements, visual acuity, and to assess for proptosis. In addition, an otolaryngologist should be consulted for evaluation of patients with extensive rhinosinusitis[7].

Laboratory Studies

Although low yield, it is recommended to obtain blood cultures for common bacterial pathogens and, depending on the circumstances, fungi and mycobacteria from patients with suspected orbital cellulitis prior to the administration of antibiotics.

Imaging Studies

Two main imaging tools are available such as a CT and MRI to aid in the diagnosis of orbital cellulitis. MRI has been found to be superior to CT scan because it can help in following soft tissue disease progression[8]. However, due to lack of availability of MRI, CT scanning is more commonly used. Other specific imaging modalities such as MRI or CT venography are used when complications of orbital cellulitis are suspected. Based on the studies and guidelines it is recommended that patients with suspected orbital cellulitis with any of the following features undergo a contrast-enhanced CT scan of the orbits and sinuses[8]:

• Proptosis
• Limitation of eye movements
• Pain with eye movements
• Double vision
• Vision loss
• Edema extending beyond the eyelid margin
• ANC greater than 10,000 cell/microL
• Signs or symptoms of central nervous system (CNS) involvement
• Inability to examine the patient fully (patients less than 1 year of age)
• Patients who do not begin to show improvement within 24 to 48 hours of initiating

Findings on Imaging

Common CT findings in orbital cellulitis are inflammation of extraocular muscles, fat stranding, and anterior displacement of the globe, although this may be subtle. Evidence of rhinosinusitis, with the most intense, is commonly seen in ethmoid sinuses. Complications of orbital cellulitis, for example, subperiosteal abscesses and orbital abscesses appear as low-density collections on CT scan.

Treatment / Management

Uncomplicated orbital cellulitis can be treated with antibiotics alone. Treatment regimens are usually empiric and designed to address the most common pathogens as described above because reliable culture results are difficult to obtain in the absence of surgical intervention. For patients with uncomplicated orbital cellulitis, it is suggested that antibiotics be continued until all signs of orbital cellulitis have resolved. The duration of antibiotic therapy ranges from a total of at least 2 to 3 weeks. For patients with severe ethmoid sinusitis and bony destruction of the sinus, a longer period, at least 4 weeks is recommended[7].

Appropriate antibiotic regimens for empiric treatment in patients with normal renal function include:

Intravenous (IV) Therapy

Vancomycin

For MRSA coverage

• Children: 40 to 60 mg/kg per day IV divided into 3 or 4 doses; Maximum daily dose 4 g
• Adults: 15 to 20 mg/kg per day IV every 8 to 12 hours; Maximum 2 g for each dose

Plus one of the following:

Ceftriaxone

• Children: 50 mg/kg per dose IV once or twice per day (the higher dose should be used if an intracranial extension is suspected); Maximum daily dose 4 g per day
• Adults: 2 g IV per day (2 g IV every 12 hours if an intracranial extension is suspected)

Cefotaxime

• Children: 150 to 200 mg/kg per day in 3 doses; Maximum daily dose 12 g
• Adults: 2 g IV every 4 hours

Ampicillin-sulbactam

• Children: 300 mg/kg per day in 4 divided doses; Maximum daily dose 8 g of the ampicillin component
• Adults: 3 g IV every 6 hours of the ampicillin-sulbactam combination

Piperacillin-tazobactam

• Children: 240 mg/kg per day in 3 divided doses; Maximum daily dose 16 g of the piperacillin component
• Adults: 4.5 g IV every 6 hours of the piperacillin-tazobactam combination

Metronidazole

Should be added to include coverage for anaerobes.

• Adults: 500 mg IV or orally every 8 hours
• Children: 30 mg/kg per day IV or orally in divided doses every 6 hours

Other agents that cover for MRSA infection are daptomycin, linezolid, and telavancin; however, there is little experience using them for orbital or intracranial infections. In the absence of a contraindication such an allergy, vancomycin is the preferred agent for MRSA coverage of orbital cellulitis. Linezolid is not recommended for children with CNS infections as its concentrations in the CNS have been inconsistent in children.

In case of allergy to penicillins and/or cephalosporins, treatment with a combination of vancomycin plus:

Ciprofloxacin

• Adults: 400 mg IV twice per day or 500 to 750 mg orally twice per day
• Children: 20 to 30 mg/kg per day divided every 12 hours; Maximum dose of 1.5 g orally daily or 800 mg IV daily

Levofloxacin

• Adults: 500 to 750 mg IV or orally daily
• Children 5 years or older: 10 mg/kg per dose every 24 hours; Maximum daily dose 500 mg
• Infants 6 months or older and children 5 years or younger: 10 mg/kg per dose every 12 hours

Oral Therapy

There are no controlled trials to define the ideal duration of antimicrobial therapy in orbital cellulitis or when to switch to oral treatment from intravenous. For uncomplicated orbital cellulitis with good response to IV antibiotics, it is reasonable to switch to oral therapy. If patient remains afebrile and the eyelid and orbital findings have begun to resolve substantially, which usually takes three to five days then switching to oral antibiotics is warranted. If definitive culture data are available, oral therapy should be directed against the infecting organisms. When there are no definitive culture data, appropriate empiric oral regimens include the following:

Clindamycin (alone)

• Adults: 300 mg Q8H
• Children: 30-40 mg/kg per day in 3 to 4 equally divided doses, not to exceed 1.8 g per day

Clindamycin or Trimethoprim-Sulfamethoxazole

• Adults: 1 to 2 DS tablets every 12 hours
• Children: 10 to 12 mg/kg per day of the trimethoprim component divided every 12 hours

Plus one of the following:

Amoxicillin

• Adults: 875 mg orally every 12 hours
• Children: 45 mg/kg per day in divided doses every 12 hours or 80 to 100 mg/kg per day in divided doses every 8 hours; Maximum dose 500 mg per dose

Amoxicillin-clavulanic

• Adults: 875 mg every 12 hours
• Children: 40 to 45 mg/kg per day in divided doses every 8 to 12 hours or 90 mg/kg per day divided every 12 hours (600 mg/5 mL suspension)

Cefpodoxime

• Adults: 400 mg every 12 hours
• Children: 10 mg/kg per day divided every 12 hours, not to exceed 200 mg per dose

Cefdinir

• Adults: 300 mg twice daily
• Children: 7 mg/kg twice daily, not to exceed 600 mg per day

Surgery

Surgery is almost always indicated in patients with intracranial extension of the infection. Other indications for surgery are poor or failure to respond to antibiotic therapy, worsening visual acuity or pupillary changes, or evidence of an abscess, especially a large abscess, greater than 10 mm in diameter. Smaller abscesses can be followed clinically and with repeat imaging unless impairment of vision is a concern. If either the clinical findings or CT scan show no improvement within 24 to 48 hours, surgical drainage is usually indicated. Surgery may also be indicated to obtain culture material, for example, in patients with suspected fungal or mycobacterial infection of the orbit. External approaches (through the orbit) and endoscopic transcaruncular surgery can be employed.

Differential Diagnosis

• Acute Complications of Sarcoidosis

• Adenoviral conjunctivitis

• Carotid-cavernous fistula

• Langerhans cell histiocytosis

• Orbital Inflammatory Syndrome

• Pediatric Mucormycosis

• Retinoblastoma

• Retrobulbar haemorrhage

• Sickle cell orbitopathy

• Thyroid Ophthalmopathy

• Widow Spider Envenomation