Necrotizing fasciitis (NF), although relatively uncommon, was first recognized by Hippocrates in the fifth century BC.  This disease is a severe infection characterized by a rapid and devasting progression involving the superficial fascia leading to skin necrosis. NF commonly affects the abdomen, extremities and perineum. It is associated with a high mortality rate of 25 – 30%. NF has many names including: hospital gangrene, necrotizing erysipelas, flesh eating bacterial infection, and progressive bacterial synergistic gangrene. Periorbital NF, albeit uncommon due to its relatively uncompromised and robust blood supply, has a reported mortality of 8-15% and a rate of vision loss of 13.8%.
The incidence of NF in general is 3 per 100,000 with 10,000 new cases annually in the US. In a 2-year British prospective study, the incidence of periorbital NF was reported to be 0.24 per million per annum. Periorbital NF is rare in adults and even more so in children as the mean age of diagnosis reported by Lazzeri et al is 50.18 years. While some publications have suggested a female predominance (of 54%) others have suggested nearly equal incidence amongst ghe sexes. 
Common triggers for periorbital NF include trauma and surgery. Amrith et al reported unidentifiable triggers in approximately 27% of cases.Known risk factors for the development of periorbital NF include: advanced age, chronic renal failure, peripheral vascular disease, drug abuse, diabetes mellitus, alcoholism, rheumatologic disease, systemic malignancy and immunosuppression. The incidence of NF increases with use of immunomodulating agents such as steroids and chemotherapeutic agents.
NF can be categorized by the causative microorganisms cultured from the wounds: Type 1 is a polymicrobial infection, primarily affecting immunocompromised individuals, consisting of mixed anaerobes, gram-negative bacilli and enterococci. Type 2 NF consists of infections with group A Streptococcus (Streptococcus pyogenes) with or without a coexisting Staphylococcal infection. The rate of mortality for Type 1 and Type 2 are 20% and 30-35% respectively. The British Ophthalmology Surveillance Unit 2-year prospective study described a mortality rate of 10%. In addition, NF with cervical involvement demonstrated a mortality rate of 20%. Mortality rate increases for NF that involves the lower part of the face and cervical area, areas closer to the mediastinum, chest and carotid sheath which may result in pulmonary complications.
Clinical Course and Features
NF is characterized by the acute onset of a painful non-specific erythematous rash with edema around the affected region. Early on the presentation may resemble erysipelas or preseptal cellulitis. There is fever and severe pain as the infection spreads subcutaneously along the fascial planes. Patients may present with tachycardia disproportionate to the fever. Ocular involvement initially may be limited to keratitis, uveitis, or chorioretinitis. Within 48 hours, the lid skin develops a violaceous discoloration which may progress to the appearance of fluid-filled bullae. Thrombosis of dermal and subdermal perforating vessels lead to black necrotic patches. Within 4-5 days, frank cutaneous gangrene develops; within 8-10 days the skin sloughs and becomes gangrenous due to underlying suppuration.
NF behaves differently in the orbit relative to other regions of the body. The orbit has a rich vascular supply, thin eyelid skin and lack of subcutaneous fat between the skin and the muscle, as such the skin infection becomes noticeable earlier and the necrosis of the thin eyelids occurs rapidly – thus, the symptoms to treatment are typically shorter. The marginal lid is often spared because its extensive blood supply from marginal arterial arcade.
Diagnosis still is primarily clinical based on symptoms and disease progression. According to the IDSA guidelines for NF, features that may help differentiate cellulitis from NF are (1) severe pain that seems disproportional to clinical findings; (2) failure to respond to initial antibiotic therapy; (3) hard, wooden feeling of the subcutaneous tissue, extending beyond the area of apparent skin involvement; (4) systemic toxicity; (5) edema or tenderness extending beyond the cutaneous erythema; (6) crepitus; (7) bullous lesions; and (8) skin necrosis or ecchymosis.  Diagnosis is confirmed with a deep tissue biopsy with gram stain and culture.
While imaging is not necessary to make a diagnosis, CT and MRI do play a role in identifying the extent of the infection and aid in the planning of surgery. CT is the modality of choice because it can offer fast and easy localization of the initial site of infection, extent of disease, presence of gas and fluid-filled bullae and anatomical information. In addition, through CT and MRI imaging – NF can be excluded when no fascial subcutaneous or deeper cutaneous layer involvement is shown.
Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score uses values of C-Reactive protein, white blood cells, hemoglobin, sodium, creatinine, and glucose to help distinguish NF from other soft tissue infections. A LRINEC score of greater than 6 warrants further investigation. High LRINEC scores (>5) can be seen in other musculoskeletal infections. 
The mainstay of treatment for NF is surgical intervention with serial debridement coupled with aggressive antibiotic therapy, fluid resuscitation, and blood pressure support. Early recognition and initiation of treatment help to decrease morbidity and mortality. There are only a handful of cases of periorbital NF that have successfully been treated with medical intervention alone . Antimicrobial coverage includes aerobes (including MRSA), and anaerobes. Combinations may include vancomycin plus one of the following (1) piperacillin-tazobactam, (2) a carbapenem, (3) ceftriaxone plus metronidazole, (4) fluoroquinolone metronidazole. Clindamycin should be added as it suppresses streptococcal toxin and cytokine production.
As mentioned earlier, surgical intervention is the mainstay component of treatment for NF and periorbital NF. In cases of periorbital NF, a computer-tomographic (CT) – guided approach to surgical debridement has been used to minimize the loss of healthy tissue by providing information regarding the extent of disease, confirming the presence/absence of gas, localizing the initial site of infection, and can providing anatomic information to guide surgical debridement. Preserving healthy tissue facilitates later reconstruction.
The efficacy of intravenous immunoglobulin (IVIG) has not been well established in the treatment of streptococcus toxic shock syndrome and it’s role in NF. Extracellular streptococcal toxin plays a role in organ failure and tissue necrosis, therefore neutralizing it theoretically would improve patient outcomes. However, because of the batch variability IVIG it is difficult to study effects of this treatment option on outcome.
Hyperbaric oxygen (HBO) therapy may also play a role in the treatment of NF and orbital NF. HBO therapy has been show to reduce mortality and improve tissue viability. This is likely achieved by HBO therapy’s role in inhibition of exotoxin production, leucocyte function, and attaining sufficient tissue oxygen levels to kill strict anaerobes.   However, the mainstay treatment includes surgical debridement, which should not be delayed to facilitate HBO therapy, and it should be employed cautiously because of it’s own associated morbidity and mortality.
After the initial infection is controlled and surgical debridement completed, there can be large areas left to heal. Survivors of NF and periorbital NF can have substantial cosmetic and functional defects. Negative-pressure wound therapy (NPWT) is currently being employed to facilitate debridement, to promote wound healing and granulation tissue development, and to act as a bridge allowing temporary wound closure. There is some reluctance to adopt this technique for periorbital NF as NPWT may increase intraocular pressure, worsening glaucomatous changes, or could lead to central retinal vein occlusion – causing decreased vision or at worst blindness. A case report of periorbital NF and NPWT demonstrated positive results with preserved visual acuity and a fair cosmetic outcome, suggesting that this may be an appropriate method in some cases.
The key to the successful treatment of NF is early and aggressive diagnosis and treatment.
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