Fig. 1.1
Preseptal cellulitis in young adult secondary to hordeolum externum (a) and acute dacryocystitis (b)
The common organisms causing preseptal cellulitis in children include Streptococcus pneumoniae, Staphylococcus species and Haemophilus influenzae [3, 5]. The causative organism can be isolated by culturing the abscess material. Blood culture is indicated in acutely ill children with high fever, and suspected septicaemia though a positive yield is rare. Recently, MRSA has emerged as the most common causative organism in preseptal and orbital cellulitis [2, 14, 23]. Preseptal cellulitis needs to be differentiated from other causes of periocular swelling like allergic periocular oedema, angioneurotic oedema, thyroid eye disease, etc.
Bacteremic preseptal cellulitis is commonly treated with parenteral antibiotics. The initial choice of antibiotic can be decided by the Gram stain and microscopy results and modified based on the culture sensitivity reports. Non-vaccine strains of Streptococcus pneumoniae are the common cause of the infection in children; hence, empirical antibiotic therapy should include a third-generation cephalosporin. Hospitalisation and inpatient treatment and monitoring for the development of a life-threatening complication like meningitis are preferred in infants and neonates as their immune systems are less effective against encapsulated bacterial infection [24]. Older children and adults can be treated with oral antibiotics on an outpatient basis. Orbital spread of preseptal infection is associated with worsening of symptoms, onset of proptosis and restriction of ocular movements. Orbital imaging is indicated in patients with suspected orbital cellulitis or patients with worsening of symptoms despite continued systemic antibiotic treatment. Computed tomography (CT) scan of orbits is done to rule out orbital abscess or any occult foreign body in the setting of trauma. Non-response to treatment also calls for revaluation of the antibiotic sensitivity in patients with positive culture material. Surgical management is indicated for abscess drainage and removal of foreign body in post-trauma cases. Abscess cavity is irrigated with antibiotic solution and the wound left open for exudates to drain.
1.2.2 Orbital Cellulitis
The clinical features of orbital cellulitis include pain, eyelid oedema and erythema, conjunctival congestion and chemosis and signs of involvement of postseptal orbit like presence of proptosis and ocular motility restriction which differentiated this from preseptal cellulitis (Fig. 1.2). Afferent pupillary defect and other signs of optic nerve compression may be present in cases with orbital or subperiosteal abscess. Sinusitis is the most common predisposing factor for the development of orbital cellulitis both in children and adults [2, 5]. Other predisposing causes are trauma with orbital foreign body inoculation, dental abscess, dacryocystitis and systemic conditions like diabetes mellitus [25, 26]. Sinus infection, especially ethmoid sinusitis, can spread to the orbit readily due to the thin wall of the lamina papyracea and presence of several foramina and natural dehiscences which provide a ready communication between the orbit and sinus.
Fig. 1.2
Orbital cellulitis in children manifesting as tense eyelid edema and proptosis (a) and severe proptosis and corneal exposure (b). CT scan showing large subperiosteal (c) and intraorbital abscess (d) requiring immediate drainage
In patients with positive culture, Staphylococcus aureus has been identified as the most common aetiologic agent in adult patients with orbital cellulitis. In children, various species of Streptococcus have been reported as the most common pathogen. Other reported causative organisms include Haemophilus influenzae, Corynebacterium, Clostridium, Enterococcus, Pseudomonas and anaerobes.
The clinical features of the orbital cellulitis associated with sinusitis have been described by Smith and Spencer and modified later by Chandler [21, 22]. This classification is based on the severity of the disease process. Class I is inflammatory preseptal eyelid swelling associated with sinusitis, possibly due to congestion of the orbital venous drainage system. There are no other signs of orbital involvement like proptosis and ophthalmoplegia at this stage. In class II, there is involvement of the orbit as suggested clinically by the presence of proptosis, ophthalmoplegia and signs of optic nerve compression. Radiologically, orbital involvement can be seen as streaking of the orbital fat and diffuse soft tissue thickening on CT scan. Localised collection of the purulent material from the sinus can occur in the subperiosteal space (class III) or into the orbit (class IV). Orbital abscess is diagnosed on imaging and appears as a hypodense collection along the orbital walls or into the extra- and intraconal spaces. Presence of orbital abscess is suspected in patients with non-respose to treatment or worsening of signs and symptoms with increase in pain, tenderness and tense orbit with motility restriction and possible decreased vision with signs of optic nerve compression. Cavernous sinus involvement can occur due to the posterior spread of the infection through the venous system and is the most serious complication of orbital cellulitis (class V). Onset of cavernous sinus thrombosis is associated with high fever with or without signs of CNS involvement like altered sensorium, onset of contralateral eyelid oedema and skin discoloration, contralateral ophthalmoplegia and extraocular muscle paresis and proptosis. MRI is indicated to confirm the diagnosis of cavernous sinus thrombosis. Absence of flow or luminal narrowing on T2-weighted and gadolinium-enhanced images will confirm the diagnosis.
Orbital cellulitis is an ophthalmic emergency, and management needs hospitalisation and treatment with intravenous antibiotics with close monitoring to identify and treat any complication at the earliest. Initial empirical antibiotic chosen should cover a broad spectrum of bacteria including Staphylococcus, Streptococcus and anaerobes. Third-generation cephalosporins or ampicillin-sulbactam combinations are initial antibiotics of choice. If anaerobic infection is suspected, metronidazole or clindamycin can be added. The antibiotic can be changed based on the sensitivity report if a specific positive culture is available and a specific organism is isolated. The optimal duration of antibiotic treatment is variable with 14–21 days being the minimal suggested duration as with other severe infections like meningitis [5]. Imaging modality like CT scan is indicated to rule out orbital abscess, sinusitis or orbital foreign body in the setting of trauma. The patient is sent for the imaging after giving the initial dose of antibiotic. Subperiosteal orbital abscess associated with sinusitis needs surgical drainage if signs of compressive optic neuropathy are present or no improvement in signs and symptoms is noted after 24–48 hours of antibiotic therapy. Young patients with small medial subperiosteal abscess without any signs of complication can be managed medically, while large abscess needs drainage [27]. Abscess along the medial orbital wall can be drained either by endonasal or orbital route. Endonasal route is preferred if associated ethmoid sinus collection also needs drainage [28]. Orbital route is preferred for drainage along the other orbital walls. Though the decision to drain subperiosteal abscess is ultimately guided by the clinical course, the volume of the abscess material as determined on CT scan has been found to correlate with the need for drainage with subperiosteal abscess more than 1,250 mm requiring drainage in a study by Todman and Enzer [29]. Orbital abscess with collection of pus within intra- or extraconal space needs immediate drainage as the inflammatory and infectious collections release mediators which are toxic to orbital tissues. Orbital cellulitis associated with retained wooden or vegetative foreign body in post-trauma cases requires orbital surgery for foreign body removal.
1.3 Fungal Orbital Infection
Fungal infections of the orbit are relatively rare and can mimic other infectious, inflammatory and neoplastic conditions of the orbit, thereby delaying the diagnosis in some cases. Though a variety of fungus can invade the orbit, the main aetiologic organisms causing invasive orbital infection include Rhizopus, Mucor, Absidia and Aspergillus species [30]. Because of the proximity of the orbit to the paranasal sinuses, fungal orbital infections are usually acquired by extension of paranasal sinus disease [31]. Direct implantation of the organism to the orbit can occur following trauma. Infection can also spread to the orbit from a distant site by haematogenous route.
1.3.1 Mucormycosis
Mucormycosis or zygomycosis is an acute fulminant fungal infection caused by the Rhizopus, Mucor and Absidia species. It is usually found in immunocompromised patients with diabetic ketoacidosis being the most important risk factor [32]. Other risk factors include immunosuppression in cases of bone marrow transplantation intravenous drug use, long-term corticosteroid therapy, desferrioxamine therapy and neutropenia [30, 33]. Mucormycosis is rarely reported in immunocompetent patients. The infection is usually acquired by colonisation of the nasal and oral mucosa by the fungal spores which spread to the paranasal sinus and orbit.
The clinical presentation is usually acute with fever, periorbital pain and inflammation, epistaxis, ptosis, ophthalmoplegia, proptosis, loss of corneal sensation and decreased vision (Fig. 1.3). The extent of cranial nerve paresis is usually out of proportion to the amount of inflammation which provides a clue to the diagnosis. The organism has the propensity for angioinvasion which can cause vascular occlusion and ischemic tissue necrosis which adds to the area of the septic necrosis caused by the fungus. Tissue infarction and necrosis also cause the typical black-coloured eschar over the palate, nasal septum and facial skin which are usually the late manifestations of the infection. Invasion and occlusion of the central retinal artery or choroidal vasculature is responsible for the early and severe visual loss.
Fig. 1.3
Orbital mucormycosis presenting as total ophthalmoplegia with orbital inflammation (a) and with associated eyelid skin fistulae (b) in patients with uncontrolled diabetes. CT scan showing opacification near the orbital apex and associated extraocular muscle thickening (c) and diffuse orbital and ethmoid sinus involvement (d)
Extension of the disease can occur from the sinus to the orbit and to the brain through orbital apex, cribriform plate or via blood vessels [34]. Rhino-orbital-cerebral mucormycosis can be a fatal disease if not treated, and early diagnosis and prompt management are imperative to reduce the mortality and morbidity associated with the disease. Imaging the orbit and paranasal sinuses with CT or MRI is indicated in uncontrolled diabetic or immunocompromised patients with acute onset of ophthalmoplegia, proptosis and decreased vision to rule out mucormycosis. CT scan reveals opacification of the sinus by the mass, bone erosion and extension to the orbit. Early CT findings are thickening of the extraocular muscles adjacent to the involved sinus [35]. Diagnosis is confirmed by KOH mount, Gomori’s methenamine silver stain and culture of the biopsy material obtained from the eschar material or paranasal sinus or orbital mass. The fungus is seen as large, right angle branching, nonseptate hyphae on smear.
The management approach for orbital mucormycosis includes an early diagnosis and prompt institution of systemic antifungal therapy. Polyene antifungal amphotericin B administered intravenously is the drug of choice. The drug is potentially nephrotoxic and hence needs dose titration and monitoring of the renal functions. Liposomal amphotericin B has less nephrotoxicity with good tissue penetration and is an alternative to amphotericin B [30, 35]. However, the preparation is more expensive compared to amphotericin B. A newer antifungal like posaconazole is better tolerated than amphotericin B and can be an alternative in patients not tolerating or responding to amphotericin B [36]. Extensive surgical debridement is needed in most patients to remove the necrosed tissue and allow for the penetration of antifungal medications. Surgical procedure can range from drainage and aeration of the involved sinuses to radical orbital exenteration. Local irrigation with amphotericin B following surgical debridement is also advocated in few studies [37]. Urgent neurosurgical consultation is needed in patients with CNS involvement. Hyperbaric oxygen therapy is also shown to be effective in the treatment of mucormycosis as it decreases the local acidosis which promotes fungal growth [38].Control of the underlying condition like diabetic ketoacidosis or systemic immunosuppression is of utmost importance for controlling the infection.
1.3.2 Orbital Aspergillosis
Aspergillus infection of the orbit can occur in two different clinical forms, invasive and non-invasive orbital infection [39]. Invasive orbital aspergillosis usually occurs in immunocompromised patients, and the predisposing factors are similar to that of mucormycosis infection. The presentation can be acute with clinical picture resembling orbital cellulitis with proptosis, ptosis, ophthalmoplegia and visual loss (Fig. 1.4). Vascular invasion can cause tissue ischemia, and the black eschar characteristic of mucormycosis can also be seen in the late stages of Aspergillus infection [39]. Aspergillus have propensity to involve the sphenoid sinus more commonly probably due to the hypoxic environment, and this can present as optic neuropathy without other signs of orbital involvement [30]. A non-invasive form of orbital aspergillosis occurs usually in immunocompetent patients as an extension from the sinus disease, commonly maxillary sinus disease. The disease is commonly caused by Aspergillus fumigatus and starts with colonisation and expansion of the sinus cavity. Breakdown of the anatomical barrier causes orbital extension of the disease. The symptoms are primarily due to pressure effect by orbital mass and present as slowly progressive proptosis with globe displacement.
Fig. 1.4
Pre- (a) and postoperative (b) photographs of a young adult with recurrent invasive sino-orbital aspergillosis status post debridement managed by orbital exenteration, partial maxillectomy and systemic voriconazole. CT scan shows extensive sino-orbital mass filling the maxillary sinus and orbit and extending to the orbital apex (c, d)
CT scan is the diagnostic investigation of choice if sino-orbital aspergillosis is suspected. The infection appears as heterogeneous opacification of the sinus with the presence of calcification which is highly suggestive of Aspergillus infection. Focal areas of bone destruction can be seen on CT. In early stages of the disease, severe unilateral thickening of the nasal mucosa on CT scan is found to be a consistent finding and should raise suspicion of invasive fungal infection [40]. Diagnosis is confirmed by endoscopic biopsy and microscopy and culture of the involved sinus tissue or orbital mass. Microscopy of the KOH-mounted tissue can provide a rapid diagnosis about the type of fungus but cannot provide information about tissue invasion. It is important to take superficial and deep biopsies and send the material for histopathology and special staining with Gomori’s methenamine silver and periodic acid-Schiff to avoid false negative results and to detect invasive disease which will help in deciding about the management option [41].
Non-invasive sino-orbital aspergillosis is usually treated by surgical debridement of the orbital mass and the involved sinuses. Antifungal therapy is usually not indicated, and prognosis remains good in these cases. Invasive sino-orbital aspergillosis is a potentially fatal disease, and urgent treatment is indicated with a combination of surgical debridement and systemic antifungal therapy (Fig. 1.5). The involved sinus and orbital tissues are debrided and aerated. Orbital exenteration might be needed in cases with extensive orbital involvement; especially with involvement of the orbital apex to prevent intracerebral spread of the infection [41]. Intravenous amphotericin B is the mainstay medical treatment. Liposomal amphotericin B is better tolerated and more effective and with lower renal toxicity compared to amphotericin B. Irrigation of the sinus and orbital cavity can be done with amphotericin B during the time of debridement. Recently, a new azole group of drug, voriconazole, has been approved by FDA as the first-line treatment for invasive sino-orbital aspergillosis. This drug is well tolerated with minimal side effects like visual disturbance and skin rash [42]. In immunocompromised patients, particular attention should be paid to reverse the predisposing factor. Complication includes involvement of the cavernous sinus and cerebrum involvement which is the cause of mortality in these patients.
Fig. 1.5
Sino-orbital aspergillosis in immunocompetent patients. Proptosis with superior globe displacement (a) caused by maxillary sinus aspergillosis causing orbital floor destruction and extending to the orbit (b). Ethmoid sinus aspergillosis extending to medial orbit causing lateral globe displacement (c). In addition to the ethmoid sinus mass, note thickening of the ipsilateral nasal mucosa on CT scan (d)
1.4 Parasitic Orbital Infections
Parasitic infection of the orbit is uncommon compared to the bacterial and fungal infections. The common parasites causing orbital infection are cysticercosis and echinococcosis. Orbital diclofilariasis and myasis have also been reported rarely.
1.4.1 Orbital Cysticercosis
Orbital cysticercosis is caused by the Cysticercus cellulosae, the larval form of Taenia solium. In cysticercosis, the human being acts as the intermediate host, and the disease is acquired in humans by ingestion of the eggs through contaminated food, water or through autoinfection. Neurocysticercosis is the most common form of infection, and ocular involvement has been reported in 12.8–40 % cases [43, 44]. Intraocular cysticercosis has been thought to be the most common form of ocular involvement. However, recent studies have reported an increased incidence of adnexal and orbital disease, probably attributed to the increased awareness about the various clinical manifestations and availability of various imaging modalities like ultrasound B scan and CT scan which can detect the parasitic involvement of the various ocular structures [45]. Orbital cysticercosis is a disease of young adults and children with the median age reported as 13 years [46]. Males and females are affected equally.
Ocular motility restriction and proptosis are the most common clinical manifestations of the disease. Diplopia due to ocular movement restriction, pain and redness is the common presenting complaint. Other presentations include ptosis and eyelid and subconjunctival nodules. The clinical presentation can mimic orbital inflammatory disease or oculomotor nerve paresis [47, 48]. The anterior orbit is involved more commonly than the posterior orbit, and the cyst is found in relation to the extraocular muscle in 80 % cases. The medial rectus muscle is involved most commonly [49]. The toxin released by the dying parasite can induce an inflammatory response and can manifest as eyelid oedema and orbital cellulitis. Rarely, the bony orbit or subperiosteal space can be the primary site of involvement [50, 51]. Optic nerve involvement can present as primary optic neuritis or disc oedema causing diminished vision. The lacrimal gland can be involved rarely manifesting as dacryoadenitis [52].
Diagnosis of orbital cysticercosis is made based on the clinical features and imaging findings. History of recurrent orbital inflammation with remissions or acquired ptosis and proptosis with extraocular motility restriction in a young adult, especially in endemic areas, should raise a suspicion of orbital cysticercosis (Figs. 1.6 and 1.7). Blood investigations can reveal eosinophilia and serological test like ELISA for cysticercosis have a reported sensitivity of 65–98 % and specificity of 70–100 % [53]. Hence results of serological tests should be interpreted in the context of the clinical picture. Orbital imaging with ultrasound or CT scan is the most definitive diagnostic modality. On B scan ultrasound, a live cyst appears as sonolucent cavity with well-defined margins. The scolex within the cyst appears as a highly reflective spot within the cyst [54]. The response to the therapy and various stages of degradation of the cyst can be detected on ultrasound as regression in the size of the cyst, loss of the scolex, collapse of the walls and decrease in the muscle thickness [45]. On CT scan, the cyst appears isodense with the vitreous. Inflammatory response in case of a dying cyst can appear as contrast enhancement of the tissues around the cyst. B scan ultrasound is comparable to CT scan in detecting the cyst [45]. B scan has been reported to have a better ability to detect the scolex within the cyst as compared to CT scan. B scan can be the imaging modality of choice for serial imaging during the course of treatment as it is less expansive and avoids radiation exposure to the patient. However, during initial diagnosis, CT scan might be indicated to rule out any concurrent neurocysticercosis.
Fig. 1.6
Orbital cysticercosis presenting as sudden onset proptosis, strabismus and ocular motility restriction in a child (a, b). Resolution of proptosis and strabismus and improvement of ocular motility (c, d) following 4-week course of albendazole and oral steroid. Anterior extension of the cysticercus cyst is visible subconjunctivally (e) and responded well to medical management (f)
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