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.