AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Background

When discussing orbital infections, understanding the clinical differences between an ocular versus an orbital infection is important. The orbit includes the bone, periorbita, ocular muscles, retroseptal fat, and optic nerve and is considered separately from the globe. The globe is contained by the sclera and lies within the fascial envelope of Tenon's capsule. (See Orbital Cellulitis in Children and CT Accurately Diagnoses Orbital Inflammation Arising From Dental Disease, on Medscape.)

An ocular infection is defined as being limited to the globe or intraocular tissue. Ocular disease, such as infectious scleritis, endophthalmitis, cytomegalovirus (CMV) retinitis, and syphilitic chorioretinitis, is typically diagnosed using direct ophthalmologic examination. Radiographic evaluation using computed tomography (CT) scanning and magnetic resonance imaging (MRI) has limited usefulness in the assessment of these disease entities, although dedicated ophthalmic ultrasonography may be a useful adjuvant.¹ (See also the eMedicine articles Scleritis, Endophthalmitis, Fungal, Endophthalmitis, Bacterial, and Retinitis, CMV [in the Ophthalmology section]; Endophthalmitis [in the Emergency Medicine section]; and Chorioretinitis [in the Pediatrics section].)

Radiographic imaging using CT scanning and MRI may help to distinguish an endophthalmitis with limited secondary extraocular inflammation from a true panophthalmitis with infected orbital tissue. In addition, diffusion-weighted imaging in MRI shows utility in assessing the optic nerves for developing ischemia or infarction, which may occur during orbital infections.^{2, 3}
 
This article focuses on the important clinical and radiographic manifestations of orbital infections—that is, preseptal versus postseptal cellulitis; viral, bacterial, and fungal infections; and infections involving contiguous orbital structures such as the lacrimal gland and duct.

For excellent patient education resources, visit eMedicine's Eye and Vision Center. Also, see eMedicine's patient education articles Eyelid Inflammation (Blepharitis), Sty, and Foreign Body, Eye.

Pathophysiology

The orbit is surrounded by an osseous bony compartment and is divided into anterior and posterior compartments by the orbital septum and globe. The anterior compartment contains the eyelids, lacrimal ducts, and anterior soft tissues. The posterior compartment is also termed the retrobulbar space and contains the extraocular muscles and fascia that form the orbital cone. The orbital cone subdivides the posterior compartment into the intraconal and extraconal spaces. The intraconal space contains the optic nerve and retrobulbar fat.⁴

Orbital infections most often occur secondarily to an underlying paranasal sinusitis; however, other etiologies include trauma, foreign body introduction, bacteremia, or skin infections.⁵ The 2 paranasal sinuses that are most often involved in orbital infections are the ethmoid and maxillary sinuses. Spread of infection from the sinuses to the orbit may occur directly through extension via the osseous structures or indirectly through the valveless venous plexus that surrounds the orbit and paranasal sinuses.⁶ Infection from the sinus may extend into and involve the subperiosteum, intraconal and extraconal spaces, and the globe. (See also the eMedicine articles Sinusitis and Periorbital Infections [inthe Emergency  Medicine section], Sinusitis [in the Radiology section], Orbital Fractures [in the Otolaryngology and Facial Plastic Surgery section], and Sinusitis, Acute and Sinusitis, Chronic [in the Infectious Diseases  section].)

Dental infections may also subsequently cause orbital infections.⁷ Routes of odontogenic infections include spread to the sinuses via the maxillary premolar and molar teeth,⁸ which are in close proximity to the maxillary sinus antral floor and orbit. Infection of the maxillary incisors,  canine  or  first  premolars may also cause an orbitofacial cellulitis, with infection spreading along the venous system.⁹

Although the orbital complications of sinus infections are usually classified as orbital cellulitis, treatment of this disease requires a more complete description. Chandler et al defined categories of orbital infections, including (1) inflammation with edema, (2) orbital cellulitis, (3) subperiosteal abscess (SPA), (4) orbital abscess, and (5) cavernous sinus thrombosis.¹⁰ One of the most important clinical and radiographic questions regarding these categories is whether the orbital infection is preseptal or postseptal.

The orbital septum originates from the linea marginalis as a continuation of the periosteum of the orbit and inserts onto the levator palpebrae aponeurosis. The orbital septum is a fibrous entity that divides the eyelid from the orbit. The superior and inferior portions of the septum arise from the periosteum of the superior and inferior orbital rims, respectively. The lateral portion of the septum arises anterior to the Whitnall tubercle, where it then merges into the lateral canthal tendon. The medial aspect of the septum arises from the posterior lacrimal crest. The central margins of the orbital septum are attached to the eyelid. In the inferior eyelid, the septum is connected indirectly to the lower aspect of the inferior tarsal plate by the capsulopalpebral complex.

The integrity of the septum alters with age. In pediatric patients, the septum is a definitive fibrofatty structure; however, in geriatric patients, only a thin remnant remains. The septum acts as a barrier between the anterior and posterior orbital structures, preventing spread of infection from the superficial tissues to the retro-orbital structures. Preseptal cellulitis is confined to the anterior preseptal superficial orbital soft tissues and can usually be treated medically with antibiotics. A postseptal (retro-orbital) infection is one that has extended posterior to the orbital septum and is clinically more worrisome and dangerous; this condition often requires patient admission to the hospital and intravenous (IV) antibiotics. If either a subperiosteal or orbital abscess is identified radiographically, the typical treatment is surgical evacuation and concurrent antibiotic therapy, although exceptions exist. (See also the eMedicine articles Cellulitis, Orbital and Cellulitis, Preseptal [in the Ophthalmology section].)

An SPA results from the development of purulent material between the orbital bones and periorbita. Because spread and expansion into the potential subperiosteal space may be rapid, the acute increase in orbital pressure and mechanical distortion may compromise the optic nerve. More importantly, purulent material is sequestered in a relatively avascular region, which may limit the effectiveness of antibiotic therapy and thus necessitate surgical evacuation. (See also the eMedicine article Acute Orbital Compartment Syndrome.)

Adjacent tissue may be involved either primarily or secondarily in orbital infections, such as the lacrimal gland, resulting in dacryoadenitis, or the lacrimal duct or sac, resulting in dacryocystitis. A diagnosis of dacryocystitis is made clinically unless adjacent periorbital cellulitis is present, limiting the ophthalmologic evaluation. Because the lacrimal sac is a preseptal structure, radiographic imaging in patients with periorbital cellulitis is a helpful adjuvant. If only the lacrimal gland is infected and inflamed, the treatment is nonsurgical because of the preseptal location. However, extension into the postseptal space with a resultant abscess may require surgical treatment (see Images 9-10).¹¹ CT imaging also allows for careful evaluation of the lacrimal sac and nasolacrimal ducts to exclude the possibility of a dacryolith, which, although rare, can lead to obstruction of the nasolacrimal ducts and toa resultant  dacryocystitis  and  orbital  infection.¹² (See also the eMedicine articles Dacryoadenitis and Dacryocystitis [in the Ophthalmology section].)

Clinically, the signs and symptoms of an orbital infection may be similar to those seen in inflammatory and neoplastic orbital diseases, including pain, periorbital edema, cellulitis, exophthalmos, visual impairment, and ophthalmoplegia.

Frequency

United States

• Orbital viral infections are rare, and herpes zoster ophthalmicus (HZO) is among the most important. HZO may cause a severe inflammatory and infectious response in the eyelids, skin, globe, and optic nerve. Although HZO is uncommon, approximately 0.5% of patients develop motility disorders, and most of these are secondary to infectious vasculitis of the cranial nerves, with rare associated infections of the orbital tissue. In immunocompromised patients, both HZO and CMV may lead to an acute retinal necrosis (ARN) and retrobulbar optic neuritis (RBON), with T2-weighted hyperintensity on MRI and contrast enhancement that extends along the optic nerves, optic tracts, lateral geniculate bodies, optic radiations, and optic cortex.¹³ (See also the eMedicine articles Herpes Zoster Ophthalmicus [in the Emergency Medicine section] and Acute Retinal Necrosis [in the Ophthalmology section].)
• Bacterial infections of the orbit are caused by paranasal sinusitis in approximately 75% of patients.¹⁴ The exact frequency of SPA that is secondary to sinusitis is difficult to ascertain because the populations studied in reviews of orbital and periorbital abscesses vary according to differences in the orientation of the investigators. Studies by otolaryngologists and ophthalmologists are usually biased toward more complicated cases that require surgical intervention.¹⁵ A 10-year review (1978-1988) of 220 patients with acute sinusitis by Patt and Manning revealed that among the study's 159 patients who had orbital and periorbital complications, 89 patients (56%) had preseptal cellulitis, 38 patients (24%) had orbital cellulitis, 30 patients (19%) had an SPA, and 2 patients (1%) had an orbital abscess (see Images 1-6).¹⁶
• Orbital infections from atypical mycobacterial infections have rarely been reported;  in 1995,  1 author noted a total of 8 cases in the literature.¹⁷
• The incidence and frequency of fungal infections, especially aspergillosis, has increased over the past century and is most commonly seen in patients who are immunocompromised.
• Aspergillosis is the second most common fungal infection (after candidiasis) in patients who are immunocompromised. As the incidence of acquired immunodeficiency syndrome (AIDS) has increased, so too has the incidence of aspergillosis in patients with AIDS.^{18, 19} The incidence of sinus infections in patients with AIDS that has been reported in the literature ranges from 20-60%, including aspergillosis sinus infections.¹⁷ Invasive orbital aspergillosis can occur as infection spreads from the paranasal sinuses into the orbits; this is the most common orbital infection that occurs in patients with AIDS. In cancer patients with aspergillosis, approximately 60% have acute leukemia, 20% have lymphoma, and 12% have chronic leukemia  (see Images 7-8).²⁰ (See also the eMedicine articles Aspergillosis [in the Pulmonology section], Aspergillosis, Thoracic [in the Radiology section], HIV [in the Ophthalmology section], and HIV Infection and AIDS [in the Emergency Medicine section].)
• Additional fungal infections include rhino-orbital cerebral mucormycosis, which is associated with extremely high morbidity and mortality. Approximately 50-70% of patients with orbital mucormycosis have diabetes, and the disease is usually associated with ketoacidosis. This orbital disease may also be seen in patients who have acute leukemia, metastatic disease, and severe burns (see Images 14-15).²¹
• Parasitic orbital infections are extremely rare; of these, Echinococcus may be the most common infective organism, spreading via a hematogenous route.
• Lyme disease is spread by the spirochete Borrelia burgdorferi; this disease is the most common arthropod-borne infection in the US.²² Orbital infection from Lyme disease may result in  keratosis, conjunctivitis, neuroretinitis, cranial neuropathy, optic nerve atrophy, and orbital myositis.^{23, 24, 25} Imaging findings may demonstrate enhancement of the extraocular muscles, which may resolve post-treatment.²⁶ (See also Lyme Disease [in the Ophthalmology section] and Tick-Borne Diseases, Lyme [in the Emergency Medicine section].)

International

Although an obvious radiographic entity, one of the leading causes of blindness in Africa is river blindness, also known as onchocerciasis. Onchocerciasis is a cutaneous filariasis that results from infection by Onchocerca volvulus. The disease manifests with ocular lesions, subcutaneous nodules, and a pruritic skin rash and is found in Mexico, Guatemala, Colombia, Venezuela, Ecuador, Surinam, Brazil, Saudi Arabia, Yemen, and tropical Africa. Of the approximately 40 million people who are infected, approximately 5% may have resultant blindness. (See also the eMedicine articles Onchocerciasis (River Blindness) [in the Dermatology section], Onchocerciasis [in the Ophthalmology section], and Onchocerciasis [in the Infectious Diseases section].)

• The disease is transmitted by black flies (Simulium genus) that breed in streams. The larvae take approximately 1 year to mature into an adult; because the larvae do not multiply within a human host, repeated infections cause heavy parasitic loads. Adult worms may be found wrapped together in subcutaneous nodules. Pregnant or gravid females may live as long as 15 years and can release 15,000 microfilariae daily. The microfilariae migrate through the skin and subcutaneous tissue (including the eye) for up to 30 months. In the orbit, onchocerciasis may start as a keratitis, iridocyclitis with resultant chorioretinitis, or optic atrophy that can lead to blindness.
• The diagnosis of onchocerciasis is made by identifying the microfilariae, usually from a skin sample. The microfilariae may also be observed in the anterior chamber of the eye with the use of a slit lamp. If no organisms are identified, an alternative method, termed the Mazzotti test, is used. Diethylcarbamazine is administered orally; if a pruritic rash appears within 24 hours, this finding is highly suggestive of onchocerciasis.
• Treatment involves diethylcarbamazine; however, this agent only kills the microfilariae, not the adult worm. In addition, the drug must be administered carefully because killing the parasites too rapidly may lead to a severe allergic reaction and, in cases of orbital involvement, further ocular damage. In ocular reactions, topical steroids can be applied as well.

Mortality/Morbidity

In orbital infections, development of an SPA requires both clinical and radiographic attention. An SPA results from the development of purulent material between the orbital bones and periorbita. Because expansion and spread into the potential subperiosteal space may be acute and rapid, the increase in orbital pressure and mechanical distortion can compromise the optic nerve, resulting in vision loss and blindness.

Additional complications from orbital infections include arterial occlusion, optic neuropathy, motility disorders, disfiguring eyelid changes, proptosis, exposure keratopathies, osteomyelitis, meningitis, pachymeningitis, cerebral abscess, and cavernous sinus thrombosis, which may result in cerebrovascular infarct or death.

Race

Blacks with sickle cell anemia are at risk for infection by Salmonella species and may have bone infarction; however, because the orbital bony structures are thin and well vascularized, osteomyelitis rarely occurs in the orbital region. A subperiosteal hemorrhage in the orbit can mimic an orbital infection (see Image 11). (See also the eMedicine article Osteomyelitis.)

Sex

No obvious sex predilection exists for orbital infections.

Age

• Most of the orbital sinusitis that occurs within the first decade of life involves the maxillary or ethmoid sinus.²⁷ The frontal sinus, which appears at approximately age 5-7 years, is not fully developed until late adolescence. Therefore, older children and adults may have an SPA related to the frontal sinus, with a greater association toward intracranial extension and complications.²⁸ However, the orbital complications of sinusitis occur more often in children than in adults.²⁹ This is because pediatric patients are more susceptible to upper respiratory tract infections, their vascular foramina are larger, the suture lines of their bones may be open, and the osseous septa of their sinuses are thinner and more porous.³⁰
• Age also affects the species of flora that is seen in bacterial sinusitis, which is secondary to the degree of obstruction of the sinus ostia, which in turn affects the gas tension within the sinus. Complete obstruction results in a predominantly anaerobic condition.
  • In a case series by Harris et al, anaerobes were not cultured at all in children younger than 9 years.³⁰ Pediatric patients younger than 9 years had simpler micropathology, with single aerobes cultured in two thirds of the patients who were examined.
  • In comparison, children older than 15 years all had polymicrobial, mixed aerobic, and anaerobic infections.³⁰ The etiology of these differences is related to the growth of the sinuses during aging. As the sinuses expand medially with age, the ostia remain approximately the same size relative to the sinuses they drain. Thus, the sinus ostia of young children are wide, and those of older children and adults are relatively narrow. This also explains why in young children, upper respiratory infections tend to involve the nose, leading to acute sinusitis, and why acute sinusitis is relatively uncommon in patients older than 16 years. (See also the eMedicine article Sinusitis, Acute, Medical Treatment.)
  • The higher incidence of complicated SPAs in older patients may be secondary to the greater likelihood of frontal sinus involvement during aging (see Images 3-4).
• In pediatric patients with leukocoria, an etiology of orbital infections may be ocular toxocariasis. Other extremely important diagnostic considerations in leukocoria include retinoblastoma, persistent hyperplastic primary vitreous, retinopathy of prematurity, congenital cataracts, and Coat disease. (See also the eMedicine articles Retinoblastoma, Retinopathy of Prematurity, and Cataract, Congenital [in the Ophthalmology section]; Retinoblastoma  [in the Radiology section]; and Retinopathy of Prematurity  [in the Pediatrics section].)

  In ocular toxocariasis, Toxocara canis granuloma is an eosinophilic abscess that contains the second stage of Toxocara larvae within it. The infection can result from the ingestion of the nematode's eggs, which are found in dog feces. Radiographic CT findings usually reveal an intravitreal density that corresponds to the detached retina and an inflammatory proteinaceous subretinal exudate. On MRI, the proteinaceous exudate may have variable hyperintensity on T1-weighted and T2-weighted scans. Postgadolinium studies may be useful for determining the presence of a focal abscess collection.³¹

Anatomy

See Pathophysiology, above.

Preferred Examination

CT scanning is often the first imaging modality that is used because of its ease and availability at most medical institutions. As noted in the Pathophysiology section, the fibrous orbital septum acts as a barrier to spread of the infection into the orbital posterior compartment. On CT scans, a preseptal cellulitis may appear as an area of increased density, with swelling of the anterior orbital tissues and obliteration of the adjacent fat planes. When the infection progresses, an increase in the density of the orbital fat may occur with gradual development of more discrete densities that, in turn, may progress to formation of an orbital abscess. If the infection is secondary to an underlying sinusitis, this may manifest as an SPA. CT scanning is also usually the first imaging modality of choice to identify an SPA, which may be located just lateral to the lamina papyracea. 

In pediatric patients and in skilled hands, ophthalmic ultrasonography may be a useful adjuvant for the rapid evaluation of preseptal versus postseptal involvement, as well as useful for a follow-up  examination.  However,  ultrasonography is limited in its ability to assess intracranial extension, the orbital apex, and paranasal sinuses.¹

MRI is useful for the detection of early inflammatory changes within the orbit, especially postgadolinium-enhanced, fat-suppressed sequences. On MRI, an orbital cellulitis appears hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences.³² MRI is also useful for assessing intracranial extension of the infection into the cavernous sinus and for evaluating cavernous sinus thrombosis. Diffusion-weighted imaging in MRI can help in the assessment of the optic nerves for developing ischemia or infarction, which can occur secondarily from orbital infections.^{2, 3} MRI may be useful for evaluating immunocompromised patients who have viral infections. Because HZO and CMV may lead to an acute ARN and RBON, MRI is more sensitive for evaluating pathophysiology in the soft tissues of the optic nerves and radiations, and this modality may demonstrate T2-weighted hyperintensity and contrast enhancement that extends alongthe optic nerves,  optic tracts,  lateral  geniculate bodies, optic radiations, and optic cortex.¹³

Plain films have limited usefulness in the diagnosis of orbital infections, especially with the advent of CT scanning.

Limitations of Techniques

Limitations of MRI include the length of time that is needed to obtain the images and the issue of motion artifacts, which may be critical factors in patients who are extremely ill with cerebral involvement. Metallic foreign bodies and the inability to perform MRI in patients with pacemakers, nonapproved aneurysm clips, or other devices that are not approved for placement in the MRI scanner are additional limitations.

Although CT scanning is useful, repeated scans can be damaging to the lens. Thus, imaging studies should be tailored appropriately.

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Other Problems to Be Considered

The confined nature of the orbital space may allow disease entities to present with overlapping clinical manifestations.³³ Orbital inflammatory diseases and infections present with findings that are similar to those of periorbital edema, proptosis, erythema, and pain.³⁴ The differential diagnostic considerations include inflammatory diseases, metastatic disease, lymphoma, and tumors such as rhabdomyosarcoma (see Images 13-14).³⁵ (See also the eMedicine article Rhabdomyosarcoma.)

CT SCAN

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

CT scanning is an extremely useful imaging modality in the setting of orbital infections, especially in detecting SPAs.

• Orbital cellulitis is usually well visualized because of the low density of fat on the images.
• On CT scans, preseptal cellulitis may appear as an area of increased density within the low-density orbital fat. This may represent the first sign of infection, in which there is obliteration of the normal fat planes and swelling of the anterior orbital soft tissues.
• As the cellulitis progresses, more discrete densities within the orbital fat may appear.
• Cellulitis is usually confined to the extraconal space; however, if the infection is allowed to progress, it can enter the muscle cone, resulting in an intraconal infection and abscess formation.
• Sinus disease from the ethmoid sinuses may extend into the orbit as an SPA, which is seen on CT examination as a thin layer of high density immediately lateral to the lamina papyracea.³⁶

Degree of Confidence

Although CT scanning is an excellent imaging modality for identifying preseptal cellulitis, SPAs, defects within the lamina papyracea, and dehiscence of the bony margins of the ethmoid sinus, this technique is not as efficacious in evaluating the orbital apex because of the surrounding bony structures that may create artifacts in the region.³⁶

False Positives/Negatives

Hematoma in the subperiosteal space can mimic the appearance of a subperiosteal abscess (see Image 11).

MRI

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

MRI is commonly used to assess orbital and soft-tissue disease³⁷ and has advantages over CT in this region because of the osseous nature of the orbital apex and its lack of signal intensity. In addition, MRI may be advantageous in evaluating any infectious process that extends from the orbital apex to the cavernous sinus. The superior ophthalmic vein and cavernous sinus may be assessed noninvasively by evaluating the vascular flow via gradient-echo imaging.³²

• On MRI, an orbital cellulitis appears hypointense on T1-weighted images and hyperintense on T2-weighted images.
• Although T1-weighted images demonstrate the normal findings of high signal intensity of orbital fat with dark inflammatory changes and although T2-weighted images demonstrate the normal findings of dark orbital fat with increased high-signal-intensity inflammatory changes, the most sensitive technique for evaluating an orbital infection may be postgadolinium, fat-suppressed imaging.³⁵
• MRI is especially useful in patients who have an aggressive fungal sinusitis, such as mucormycosis and aspergillosis, which has a propensity for extension into the orbit, cavernous sinus, and neurovascular structures. Mucormycosis is markedly angioinvasive; the fungus grows into the internal elastic membrane of the blood vessels. The fungal hyphae may then extend into and occlude the lumina of the blood vessels they have invaded.
• Diffusion-weighted imaging in MRI has shown utility in assessing the optic nerves for a developing ischemia or infarction, which may occur during orbital infections.^{2, 3}

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy.

NSF/NFD has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving  or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

ULTRASOUND

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Ultrasonography is usually performed in the ophthalmology practice by a trained technician using a high-frequency 10-MHz probe. The probe is applied over a closed eyelid with the glove in a neutral position and with gentle eye motions from left to right.

• To assess the posterior aspect of the globe, the gain settings are adjusted to dampen near field echoes.
• To assess the vitreous and central portion of the globe, the near field gain is increased.
• The center of the lens is anechoic, whereas the mid portions of the anterior and the posterior parts of the lens reflect the ultrasound beam, with the iris seen as an echogenic line on either side.
• The vitreous humor is anechoic, and the posterior echogenic limit of the globe is the retina.
• Posterior to the globe, the retrobulbar fat is echogenic, with the optic nerve seen as a hypoechoic structure that extends dorsally away from the posterior margin of the globe.³⁸

Degree of Confidence

Ultrasonography requires a dedicated ophthalmologic technician and may not allow important visualizations of the cavernous sinus and the intracranial extension of infections.

NUCLEAR MEDICINE

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Nuclear medicine images that use technetium-99m (^99mTc)–labeled leukocytes have been useful for the diagnosis of orbital implant infections in patients in whom CT scans failed to reveal radiographic abnormalities.³⁹

INTERVENTION

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Medical/Legal Pitfalls

• Physicians should remember that even in this age of antibiotic therapy, approximately 3% of patients with a paranasal sinusitis can develop an orbital complication. Failure to recognize this fact can lead to progression of the disease, including a preseptal and orbital cellulitis; abscess formation in either the preseptal, subperiosteal, or orbital regions; and retrobulbar optic neuritis.⁴⁰ The clinician should also be aware that optic neuritis can occur without gross manifestations of orbital disease.⁴¹ More importantly, the clinician should be aware that failure to diagnose the developing orbital cellulitis and failure to start appropriate therapy can allow intraconal progression of the disease, resulting in either an ophthalmic vein and/or a cavernous sinus thrombosis; both of these conditions have a high associated morbidity.
• Clinicians should keep in mind that in children, orbital inflammatory changes may be the first indication of an underlying sinus infection. Preseptal cellulitis is the first stage and is often misinterpreted as an orbital or periorbital cellulitis, even though the infection is still contained within the sinus. Initially, edema and swelling of the eyelids secondary to congested venous outflow may occur. Failure to recognize these findings early can lead to progression of the infection via the valveless venous system, with an accumulation of inflammatory tissue beneath the periosteum forming a subperiosteal phlegmon that may then collect pus and become a subperiosteal abscess.⁴²

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Media file 1:  Axial computed tomography scan of orbital and facial cellulitis.
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Media file 2:  Axial computed tomography scan of orbital and facial cellulitis.
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Media file 3:  Coronal computed tomography scan in a pediatric patient with sinusitis as well as an orbital and subperiosteal abscess.
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Media file 4:  Coronal computed tomography scan in a pediatric patient with sinusitis and orbital abscess (same patient as in Image 3).
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Media file 5:  Axial computed tomography scan in a patient with an infection caused by Streptococcus pneumoniae and a superior orbital subperiosteal abscess that resulted in blindness.
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Media file 6:  Axial computed tomography scan in a patient with an infection caused by Streptococcus pneumoniae and a superior orbital subperiosteal abscess (same patient as in Image 5).
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Media file 7:  Coronal T1-weighted, postgadolinium, fat-saturated magnetic resonance image in a patient with allergic fungal sinusitis, with extension into the orbit.
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Media type:  CT

Media file 8:  Coronal T2-weighted magnetic resonance image of a patient with allergic fungal sinusitis and extension into the orbit (same patient as in Image 7).
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Media file 9:  Coronal computed tomography scan of a patient who was on steroids and had multiple myeloma. In addition, the patient had infectious dacryoadenitis with Staphylococcus aureus infection and an abscess collection.
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Media file 10:  Coronal computed tomography scan of a patient with dacryoadenitis and Staphylococcus aureus infection, resulting in an abscess (same patient as in Image 9).
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Media file 11:  Coronal computed tomography scan in a patient with sickle cell disease. In this image, the patient has a subperiosteal bleed that mimics the appearance of an infectious subperiosteal abscess.
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Media file 12:  Axial computed tomography scan in a patient with sino-orbital lymphoma that is mimicking the appearance of a sinus infection with orbital extension.
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Media file 13:  Coronal computed tomography scan of a patient with sino-orbital lymphoma (same patient as in Image 12).
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Media file 14:  Coronal computed tomography scan in a patient with sino-orbital and cavernous sinus extension of mucormycosis.
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Media file 15:  Axial T1-weighted, postgadolinium magnetic resonance image in a patient with sino-orbital and cavernous sinus mucormycosis (same patient as in Image 14).
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Media file 16:  Axial T1-weighted, postgadolinium, fat-saturated magnetic resonance image from a 35-year-old black male with sickle cell disease and a left orbital staphylococcal infection.
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Media type:  MRI

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Differentials
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
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Article Last Updated: Dec 11, 2007