Discussion
Head and Neck NF has a high morbidity, as highlighted by our results which correlates with previous literature. NF of the face and neck in particular has a reported mortality rate of up to 25%, with 65% of cases having evidence of mediastinal extension5. Type 2 diabetic patients have a mortality rate of 30.3% when presenting with head and neck NF6.
NF of the head and neck is divided into two subgroups. Firstly, the eyelids/scalp and secondly, face/neck. Minor trauma is the usual cause of the first subgroup with odontogenic infections and pharyngeal/tonsillar infections the usual causative factors of the second subgroup5.
The presentation of head and neck NF is variable but 5/8 patients identified in this series and admitted under the ENT team presented with features consistent with peri-orbital cellulitis. One patient had evidence of parapharyngeal abscess formation with another patient having evidence of peri-tonsillar abscess. One patient developed NF as a result of a Varicella Zoster lesion which may have provided a route of entry for bacterial spread.
Peri-orbital or peri-ocular necrotising fasciitis is a rare entity but can have longstanding functional, cosmetic and psychological consequences as highlighted by one of the cases where the patient required enucleation of the left eye and subsequent reconstructive surgery.
NF can be very difficult to distinguish from severe cellulitis clinically. Misdiagnosis is common, especially amongst children7. Diagnosis of peri-ocular NF can be even more challenging due to the difficulty differentiating pre-septal from post-septal orbital cellulitis particularly in the paediatric population. Necrosis of the eyelid can become apparent quickly due to a reduction in subcutaneous fat6. Bilateral peri-ocular NF can occur as infection spreads across the nasal bridge, and is limited posteriorly by the highly vascularised orbicularis oculi muscle as demonstrated in 2 of the cases studied7. Left untreated, progression to blindness, intra-cranial disorders and death have been reported8.
Immediate aggressive debridement of necrotic tissue down to viable tissue is important as NF spreads along avascular tissues planes, with limited antibiotic penetration. Anti-microbial therapy can have little effect on the cytotoxins which mediate the pathological process3. Re-exploration procedures are important to ensure any nidus of infection has been removed and to facilitate subsequent reconstructive surgery.
A systematic review by Lazzeri et al showed 28% of peri-ocular NF had no cause identified, 22% of cases were caused by penetrating injuries and 17% caused by local blunt trauma8. Localised eyelid swelling, pain and non-specific erythema were the most common presenting features8.
Rajak et al. looked at 29 cases of peri-ocular NF with an age range of 21-95 years2. Fourteen percent of patients suffered unilateral visual loss, with 41% of patients requiring soft tissue reconstruction of the eyelid2.
Fifty percent of patients with peri-ocular NF had subsequent morbidity, with a reduction in visual acuity noted over a 2-year period in the United Kingdom9.This was consolidated by Amrithet al. in 2003 who looked at 95 patients, and reported that morbidity was related to loss of vision10. Visual loss in these patients was caused by orbital spread of the infection, central retinal artery occlusion and corneal perforation10.
Gas formation on cross sectional imaging is non-specific and usually seen in type 1 necrotising fasciitis. This emphasises that imaging should not delay surgical intervention if there is clinical concern. If imaging is undertaken, MRI is most sensitive and specific, with a 100% sensitivity, compared to CT scanning with an 80% sensitivity.
Mortality of peri-ocular NF increases with late diagnosis and delay in treatment. This can be accounted for by the rarity of the condition and a lack of awareness10.
The necessity for the ENT surgeon to have a high index of suspicion is imperative, particularly with elevated inflammatory markers and a history of rapidly progressing erythema/ecchymosis. The need to recognise this clinical entity is vitally important, especially amongst the paediatric population.