MRSA has also been reported as an increasingly common pathogen in orbital cellulitis [11]. However, little is known about CA-MRSA infections of the eye and orbit [1, 25, 27, 32, 40, 42, 43, 50, 56, 57]. Most of what we know is limited to case reports, and the majority of these CA-MRSA infections involved the USA300 clone. In almost all community-acquired cases described in the current literature, this disease quickly assumes a downhill clinical course. In some cases, even with appropriate antibiotic treatment and surgical debridement, some patients are left with significant morbidity from extensive tissue necrosis, including blindness or the need for enucleation.

Our personal experience at the Wills Eye Institute initially was derived from ten consecutive cases of postseptal MRSA identified from March 2006 through February 2008, with more and more cases presenting after the analysis. This initial cohort represents cases seen at several hospitals in the Philadelphia area as well as cases seen in an outpatient o ce setting. The average age of this initial cohort was 28.9 years, with a bimodal distribution ranging from 6 weeks to 61 years.

Patients were diagnosed and monitored with both clinical examination and CT scanning. The younger cohort of patients had focal, superficial abscesses with surrounding cellulitis that were drained and treated with oral antibiotics. These patients all required just one surgical intervention. The exception to this was a 6-week- old infant who was transferred to Children’s Hospital of Philadelphia with a significant orbital cellulitis that appeared to arise from a local wound to the lower eyelid and spread into the subperiosteal space. She required prolonged intravenous antibiotics and two trips to the operating room, but eventually settled without sequelae.

The adult patients had more aggressive infections that spread along tissue planes with multiple microabscesses and a true tissue cellulitis (Fig. 10.4a, b). These more aggressive infections required hospitalization, intravenous antibiotics, and often multiple surgeries to debride the infections. On average, each of these older patients had two surgical debridements to bring the infections under control. Because of the more severe nature of some of these infections, their slow responses to antibiotics, and the inflammatory e ects of surgery, steroids were added in three of five adult cases. In these cases, corticosteroids noticeably helped patients improve and recover.

Inpatient management included vancomycin in all our patients, typically in conjunction with a second drug. These combinations were always chosen and managed by the infectious disease team, which was invaluable. In addition, most of these patients were sent home with prolonged 2- to 4-week courses of intravenous vancomycin via a peripherally inserted central catheter. All ten patients returned to baseline, although some with residual scarring. Two of the adult patients had residual ptosis, one of which was treated, and the other is still being followed.

10.6Evaluation of Orbital Cellulitis

The evaluation of orbital cellulitis has evolved over the past several decades. At the heart of this debate is the fact that periorbital cellulitis ranges from a relatively benign condition with no lasting side e ects that may be treated with oral antibiotics to a debilitating, progressive infection requiring surgical and intravenous intervention that

potentially leads to optic nerve dysfunction, central nervous system damage, and even death. Complicating this devastating range of infectious manifestations is the potentially rapid rate of orbital expansion that can occur, leading to the aforementioned consequences.

After completing a thorough physical exam, dedicated orbital CT scan is the investigation of choice for preseptal and orbital cellulitis [8, 24]. However, not every patient warrants radiological evaluation. On initial presentation, CT can assess the sinuses and extent of periorbital infection if edema is excessive and the clinician is unsure that the infection is solely preseptal. Patients with clear clinical pictures and no signs of postseptal or optic nerve involvement do not need CT evaluation. On the other hand, patients with worsening clinical presentation, proptosis, ophthalmoplegia, worsening visual acuity, declining color vision, bilateral symptomotology, or signs of central nervous system complications require immediate CT scan, especially if surgery is planned because of orbital compression or if there is no clinical response to treatment after 48 h [8, 24, 43, 53].

The use of CT must be tempered with the knowledge that radiologic improvement will lag behind the clinical picture by a number of days [24]. CT scans are helpful in aiding the initial evaluation of orbital cellulitis, the location of the primary infection, and the risk of spread to surrounding areas. Yet, the clinical examination and fol- low-up, not CT scans, should drive therapy, and CT scans should not be repeated regularly once obtained. Once orbital cellulitis is diagnosed, the clinical exam and culture results will dictate appropriate management with specific antibiotics and possible surgery. If rapid visual decline occurs on clinical exam, operative intervention will take place well before a follow-up CT scan documents progression. Repeat CT scan may be useful in fol- low-up to rule out frontal lobe abscesses if the clinical exam dictates.

Summary for the Clinician

■MRSA has also been reported as an increasingly common pathogen in orbital cellulitis.

■The evaluation of orbital cellulitis has evolved over the past several decades.

■Dedicated orbital CT scan is the investigation of choice for preseptal and orbital cellulitis.

■The use of CT must be tempered with the knowledge that radiologic improvement will lag behind the clinical picture by a number of days.

10.7Medical Treatment of Orbital Cellulitis

Medical therapy of periorbital cellulitis obviously requires the use of antibiotics, but which one is the typical question. Preseptal infection is typically treated with oral antibiotics. Orbital infections require immediate intravenous antibiotic therapy, targeting the most likely pathogens. In the early twenty-first century, broad-spectrum antibiotics that cover gram-positive organisms, including MRSA, are the best place to start for preseptal infections. Choices of oral antibiotics may include doxycycline, trimethoprimsulfamethoxazole, clindamycin, or fluoroquiolones.

In orbital cellulitis, anaerobes will potentially be involved, in addition to gram-positive cocci and MRSA. In these typically polymicrobial infections, the use of two agents with broad coverage is often required until culture results are obtained. Intravenous antibiotic choices would include vancomycin, clindamycin, ampicillin sulbactam, secondor third-generation cephalosporins, aminoglycosides, and fluoroquinolones. Transition to oral antibiotics may occur once improvement is documented and sustained [4, 45, 53]. Interestingly, data showed that oral ciprofloxacin and clindamycin may be equally e ective and safe as initial intravenous therapy for advanced cases [4]. This is not standard of care, however.

Targeting specific pathogens initially may be di cult as most studies agreed that routine local culture or blood cultures are typically negative and thus unhelpful. The yield is quite low on all pathogenic studies. Further, what data do exist in favor of culture are often biased; historically, the treatment-refractory and most severe cases are those that have been cultured surgically, yielding poorly universal data pointing toward highly aggressive polymicrobial etiologies of infection [37].

If surgery is performed and microbiology obtained, antibiotics can be changed pending sensitivities. If specimens are not obtained, clinical suspicion and broadspectrum antibiotics geared toward the aforementioned common pathogens remain the gold standard. Further, one must remember the changing spectrum of orbital cellulitis pathogens and the currently growing level of resistance. If suspicion for MRSA is high or broad-spectrum treatment ine ective, appropriate therapy must be redirected.

Fortunately, there are still multiple antibiotics that work against CA-MRSA. These include sulfonamides such as trimethoprim-sulfamethoxazole, quinolones, aminoglycosides,tetracyclines,clindamycin,and rifampin; all o er potential aid in curing the infection. Clindamycin or trimethoprim-sulfamethoxazole should be used in children with MRSA as fluoroquinolones and tetracyclines cannot be utilized in this age group. Vancomycin,

linezolid, and amikacin are e ective as well, although usually reserved for aggressive infections and multiresistant hospital-acquired MRSA [17, 49, 55].

Many infectious disease doctors rightfully worry 10 about Clostridium di cile from prolonged clindamycin use. This should be taken into consideration when prescribing antibiotics, especially since drug-resistant C. di cile is now being reported. In addition, more clin- damycin-resistant cases of MRSA continue to occur, and

it is becoming less of a first-line agent.

Nasal decongestants used in the short term will open sinus passages and may augment antibiotic treatment by reducing sinus swelling and improving drainage [24]. Also, the use of corticosteroids in the setting of infection is certainly controversial [58]. Many otolaryngologists manage acute sinusitis with the combination of antibiotics and steroids since steroids diminish the mucosal edema that prevents the sinuses from opening and draining. This is true even in cases that have secondary orbital cellulitis. No doubt, the orbit is a small space, and its

Summary for the Clinician

■Preseptal infection is typically treated with oral antibiotics.

■Orbital infections require immediate intravenous antibiotic therapy.

■Choices of oral antibiotics may include doxycycline, trimethoprim-sulfamethoxazole, clindamycin, or fluoroquiolones.

■In orbital cellulitis, anaerobes will potentially be involved in addition to gram-positive cocci and MRSA.

■The use of two agents with broad coverage is often required until culture results are obtained.

■Intravenous antibiotic choices include vancomycin, clindamycin, ampicillin sulbactam, secondor third-generation cephalosporins, aminoglycosides, and fluoroquinolones.

■Transition to oral antibiotics may occur once improvement is documented and sustained.

■Nasal decongestants used in the short term will open sinus passages and may augment antibiotic treatment by reducing sinus swelling and improving drainage.

■Many otolaryngologists manage acute sinusitis with the combination of antibiotics and steroids since steroids diminish the mucosal edema that prevents the sinuses from opening and draining.

structures are at risk for compression during an acute process like orbital cellulitis. If bactericidal antibiotics are utilized to destroy the bacteria, then reducing the inflammation within the orbit may reduce the risk for a compartment syndrome. In our anecdotal experience, steroids do seem to help these patients and are typically started with antibiotic therapy if significant swelling and compression are present.

10.8Surgical Treatment of Orbital Cellulitis

While the advent of CT in the evaluation of orbital cellulitis has become critical for diagnostic purposes, debates regarding antibiotic regimen, use of corticosteroids, and surgical drainage have persisted ever since. Management is therefore another point of contention within the recent literature. Fundamentally, when progressing and extending below the periosteum, orbital cellulitis subsists in a largely avascular area with relatively decreased mucosal blood flow. This, coupled with the fact that increasing age usually coincides with mixed infections and microbial synergy, may augment antibiotic resistance [21]. Thus, intravenous antibiotics that are e ective against orbital pathogens in vitro may be ine ective in the clinical treatment of advanced orbital cellulitis. Management of orbital cellulitis may therefore be quite di cult.

Treatment regimens and management styles have, and often remain, largely driven by individual experiences and physician preferences. Many doctors treat with only antibiotics, having positive personal experiences with such regimens. These physicians are often of the mindset that surgery may seed adjacent areas and reserve such invasive interventions for antibiotic-refractory cases as a result [53]. Further, some reports have shown that early drainage actually prolongs hospitalization. Contradicting this, other cases portend that early surgical intervention may shorten hospital courses; to wait too long for surgical drainage may lead to infection that does not sterilize even with abscess drainage [21].

Harris revolutionized this argument in 1994 by making age a large factor in the management of orbital cellulitis [21]. His review confirmed the tendency to culture-negative or single-isolate infections in children younger than 9 years that responded to antibiotic therapy alone. Ten of his 12 patients younger than 9 years old required no surgical intervention; the remaining 2 cleared their infection promptly after intervention. Four of the 16 patients between 9 and 14 years of age cleared without drainage, while a di erent 25% in this transitional age range had refractory and multiorganism infections. Polymicrobial illnesses were the norm in the nine adults,

and on average they had five di erent bacteria isolated from each culture.

Experience gleaned from these studies divided need for surgical intervention into emergent, urgent, and expectant groups. Keep in mind that most cases of orbital cellulitis arise primarily from acute sinusitis. Thus, sinus surgery is the key component in the surgical treatment of orbital cellulitis arising from the sinus infection. As a result, otolaryngology involvement up front is a very important part of managing these patients. Emergency drainage was deemed appropriate for cases of optic nerve or retinal compromise secondary to induced mass e ect. This is true for all ages. Urgent drainage is described in this review as drainage within 24 h of presentation. Categorized therein are large subperiosteal abscesses and abscesses that have extended away from the sinuses of origin or atypical infections not arising from the sinus (Fig. 10.5a,b). Frontal sinusitis should be urgently drained for pathogen identification and evaluation as central nervous system penetration of the infection is more likely and can be quite devastating. Also, since virtually all patients older than 14 years will have a complex, polymicrobial infection, these infections should be drained more urgently as antibiotics are less likely to be e ective.

Patients younger than 9 years may be observed, given the predilection toward simple infections in this population and the typical response to antibiotics alone. Expectant management may also be used for patients with no visual compromise, small medial subperiosteal abscesses and e usions, and cases with no frontal sinus or intracranial involvement. However, while hospitalized and on intravenous antibiotics, these patients must be clinically monitored on a regular basis for progression

and development of an a erent pupillary defect, visual decline, fevers that do not defervesce within 36 h, or 3 days without clinical improvement.

In a more recent publication, Harris further summarized criteria necessary for the initiation of nonsurgical intervention [18]. The following needed to be absent: age of 9 years or older, frontal sinusitis, nonmedial or large subperiosteal abscess, gas within abscess on CT or other suspicion of anaerobic infection, recurrence after prior surgical intervention, radiologic evidence of chronic sinusitis, acute optic nerve or retinal compromise, or dental etiology of infection predisposing to anaerobic infiltration. Importantly, it was noted that clinical judgment is of utmost importance in all cases. Patients even without these signs may warrant surgery if clinically deteriorating, so these patients should have clinical exams regularly. Conversely, even patients with these signs may be treated medically if clinically stable.

Most studies agreed that surgery is warranted in the circumstances mentioned. However, several more recent studies supported that surgical drainage is justified in all abscesses obvious on CT scan, regardless of patient age or clinical presentation [24]. Still, other reports in the twentyfirst century argued that immediate intravenous antibiotics are the treatment of choice for subperiosteal abscesses as well as retrobulbar loculations [4, 45, 53]. Certain pediatric textbooks written in the last 10–12 years argue those very facts, some of which entertain immediate surgical drainage and watch-and-wait protocols in the same chapter [53]. It seems that the only universal rule within the current literature is that the decision to treat must rest on the physician’s opinion, clinical judgment, and knowledge of the potential course of orbital cellulitis.