Orbital and Preseptal Cellulitis

Overview

Orbital anatomy

Orbit:

• Cavity of the skull in which the eye and its appendages are situated
• Contents are made up of the eye, fascia, extraocular muscles, cranial nerves, blood vessels, fat, and lacrimal and eyelid structures.
• Flanked by paranasal sinuses:
  • Frontal sinus (superior to the orbit)
  • Ethmoid sinus (medial to the orbit)
  • Maxillary sinus (inferior to the orbit)

Orbital septum:

• Membranous layer arising from the orbital periosteal lining 
• Extends into the tarsal plates of the eyelids 
• Two compartments formed:
  • Preseptal: anterior to the septum
  • Postseptal: posterior to the septum
• Function: 
  • Structural support to the eye
  • Acts as a barrier preventing bacterial spread

Related infections

• Preseptal cellulitis:
  • Infectious inflammation of the tissue anterior to the orbital septum
  • Involves the skin and subcutaneous tissue
• Orbital cellulitis: 
  • Infectious inflammation of the tissue posterior to the orbital septum
  • Involves the orbital fat, extraocular muscles, and bony structures

Epidemiology

• Preseptal cellulitis is more common than orbital cellulitis.
• Both conditions are more common in children.
• 80% of cases occur in children < 10 years of age.

Etiology

Microbiology:

• Staphylococcus aureus: 
  • MSSA
  • MRSA
• Group A streptococcus 
• Streptococcus pneumoniae
• Bacteroides species (sinusitis resulting from dental infections)
• Polymicrobial infection 
• Fungal causes: Mucorales and Aspergillus species (in immunocompromised patients)

Pathophysiology

• Direct inoculation:
  • More common with preseptal cellulitis
  • Mechanism:
    • Eye/eyelid trauma
    • Surgery
    • Insect/animal bites (infected)
  • Common causative pathogen: S. aureus
• Spread from other infected structures:
  • Acute sinusitis:
    • Mostly ethmoiditis, as neurovascular structures penetrate the lamina papyracea and separate the ethmoid sinus from the orbit
    • Main source of infection for orbital cellulitis
    • Up to 98% of cases of orbital cellulitis occur with a coexisting sinusitis.
    • Common causative pathogen: S. pneumoniae or β-hemolytic streptococci
  • Acute dacryocystitis 
  • Ear/dental infections
  • Skin infection (impetigo, erysipelas)
  • Herpes simplex and herpes zoster lesions
• Hematogenous spread: via blood vessels from bacteremia

Clinical Presentation and Diagnosis

Clinical features

Preseptal and orbital cellulitis have common findings:

• Eyelid swelling, pain, and redness
• On occasions, eye discharge

However, orbital cellulitis involves inflammation and swelling of the extraocular muscles and fatty tissues, which is not found in preseptal cellulitis.

Red flags that raise suspicion for orbital cellulitis:

• Ophthalmoplegia with diplopia
• Pain with eye movement
• Visual impairment
• Proptosis

Contrasting findings

Diagnostic approach

Both conditions are usually diagnosed clinically.

Imaging studies:

CT scan with contrast:

• Confirms the diagnosis of orbital cellulitis in uncertain cases
• Detects complications (e.g., orbital abscess)
• Also shows opacification of the sinuses in sinusitis

Lab tests are generally of low diagnostic value.

• Not routine in diagnosing preseptal cellulitis
• CBC: Leukocytosis may be present in both conditions.
• Blood cultures: obtained in orbital cellulitis before administration of antibiotics
• Culture of aspirated pus and other material: 
  • Obtained from source of infection or from sinus (if concomitant sinus infection present)
  • Especially helpful in immunocompromised patients in whom fungal and other rare etiologies can be detected

Management and Complications

Treatment of preseptal cellulitis

• Oral antibiotics with MRSA coverage
• Clindamycin or trimethoprim–sulfamethoxazole plus one of the following agents:
  • Amoxicillin–clavulanic acid
  • Amoxicillin
  • Cefpodoxime 
  • Cefdinir 
• Incision and drainage of eyelid abscess
• Use skin marker to outline erythema to evaluate progression and response to antibiotic treatment.
• Children < 1 year of age (examination can be limited) or those who are severely ill have to be treated as though they have orbital cellulitis.
• Lack of response within 48 hours requires CT scan to evaluate for complications.

Treatment of orbital cellulitis

• IV broad-spectrum antibiotics
• Vancomycin plus one of the following medications:
  • Ceftriaxone
  • Cefotaxime
• If there is concern for intracranial extension, add anaerobic treatment (metronidazole).
• Ampicillin–sulbactam or piperacillin–tazobactam: 
  • Not an initial option, as these drugs are not effective against MRSA 
  • Not first-line therapy, especially for intracranial extension, owing to suboptimal CNS penetration 
• Response expected in 48 hours; if no improvement, imaging is done:
  • Search for complications.
  • Investigate other noninfectious causes.
• Surgery:
  • Poor response to treatment
  • Worsening visual acuity
  • Intracranial extension
  • Purpose:
    • Abscess drainage (especially > 10 mm in diameter)
    • Biopsy to determine pathogen or presence of noninfectious cause

Complications

• More common with orbital cellulitis
• Orbital and subperiosteal abscess:
  • Collection of pus involving the orbital tissue (orbital abscess) and the bony structures supporting the globe (subperiosteal abscess)
  • Rapid development
  • Can result in vision loss
• Extraorbital extension:
  • Cavernous sinus thrombosis:
    • Rare but life-threatening
    • Superior and inferior orbital veins drain to the cavernous sinus. 
    • Infection spreads from affected areas through valveless veins.
    • Presentation can include facial and periorbital edema, ptosis, proptosis, chemosis, pain with eye muscle movement, and loss of vision.
  • Bacterial meningitis: 
    • Inflammation of the meninges
    • Results from hematogenous or direct spread
    • Presents with fever, headache, and signs of increased intracranial pressure (e.g., from vomiting)
    • Diagnosis by CSF studies (fluid obtained via lumbar puncture) 
    • Empiric antibiotics should be started immediately.
  • Brain abscess: 
    • Suppurative lesion that may occur in one or more regions of the brain
    • Caused by the direct spread of sinus, ear, or dental infections
    • Presents with fever, focal headache, signs of increased intracranial pressure (e.g., from vomiting), and focal neurologic deficits due to mass effect

Differential Diagnosis

• Erysipelas: bacterial infection of the superficial layer of the skin extending to the superficial lymphatic vessels within the skin: Erysipelas presents as a raised, well-defined, tender, bright red rash that typically appears on the legs or face but can occur anywhere on the skin. Diagnosis is based mostly on the history and physical exam. Management includes antibiotics.
• Blepharitis: ocular condition characterized by eyelid inflammation: Blepharitis can affect the eyelid skin, eyelashes, and meibomian glands. Blepharitis includes eyelid edema with itching and redness, crusts and scales around the eyelashes, and a gritty sensation. Treatment includes warm compresses, eyelid scrubs, and topical or oral antibiotics. 
• Chalazion: firm, nontender mass at the eyelid resulting from obstruction of the Zeis or meibomian glands: Chalazion is usually managed conservatively with warm compresses. Persistence of the lesion requires incision and curettage or glucocorticoid injection by an ophthalmologist.
• Hordeolum: localized infection arising from the gland of Zeis, gland of Moll, or meibomian gland: S. aureus is a common cause of hordeola. Findings of a tender, erythematous, pus-filled nodule help establish the diagnosis. Management is generally conservative, though severe cases may require antibiotics or drainage. Chalazia, on the other hand, are due to sterile, granulomatous inflammation and are not painful.