Discussion
Only a handful of case reports have described about the frontal sinus
osteomyelitis following mucormycosis8–11.
Mucormycosis usually affects the nose and paranasal sinuses; the disease
can spread via direct extension or by hematogenous spread. Hossieni and
colleagues12 initially have described about the routes
of spread of mucormycosis. We hypothesize the following pathway for the
spread of mucormycosis into the frontal sinus –
- Via the ethmoidal air cells by direct extension, leading to frontal
outflow tract obstruction.
- By erosion of frontal sinus floor from superior part of the orbit.
- Perineural spread along the supraorbital or supratrochlear nerves.
- Along the anterior ethmoidal arteries.
- Direct spread to the brain through the roof of the ethmoid and
cribriform plate to skull base/frontal bone to Basi frontal lobe.
- Disease tracking along the Orbital apex.
In acute osteomyelitis, the patient is toxic with tender swelling over
the bone involved, called Pott’s puffy tumour. The Pott’s puffy tumour
was initially described as complication of acute bacterial frontal
sinusitis. The successful management of frontal bone osteomyelitis
entails removal of the entire sequestrum and debriding the involucrum
till the normal bony architecture is reached. Frontal sinus obliteration
with the fat, muscle and alloplastic materials have been tried with
varying success. In the setting of mucormycosis, it is utmost important
to clear all the disease till the fresh bleeding is observed. The main
crux of frontal sinus cranialization or obliteration in the mucormycosis
setting is to ensure complete elimination of disease and dead space,
formation of a protective barrier for the intracranial spread and with
the ability to reassess clincoradiologically for disease recurrence. The
use of alloplastic materials is usually not recommended in the settings
of severe infection13.
The disease is more susceptible to complete endoscopic surgical
resection along with bony debridement if detected
early14. Because antifungal medication alone will not
suffice, all grossly diseased tissue must be excised. Debridement should
be repeated until a healthy tissue margin is found, and it should be
done at regular intervals, if necessary. Sinus surgery, wide resection
of necrotic soft tissue and bone, and exenteration of the orbit, if
necessary, are examples of more comprehensive surgical treatments15,16. According to the available literature, patients
with intracranial extension are less likely to react to radical surgery,
and their prognosis is poor17. However, if surgery is
done early on, the chances of survival increase significantly14. It is well established that the management of
comorbid conditions is crucial in the successful management of
mucormycosis. It is also the single most crucial factor determining the
overall prognosis of the patient18.
As per the AMBILOAD trial19, higher dose preparations
of amphotericin B does not improve the overall outcome compared to the
conventional dosing. Before amphotericin B dosage, factors such as
existing diabetic and hypertension-induced nephropathy must be kept in
mind. There is no strict consensus on the duration and the target dosage
of amphotericin B therapy20, especially in the
recurrent setting. Based on our institutional expert multidisciplinary
team recommendations, we have titrated the target dose based on the
extent of the disease, comorbidities, and response to therapy.
The overall better outcomes in this study can be attributed to the early
detection, prompt surgical debridement, prolonged amphotericin B and
strict management of comorbidities, In a recent systematic review, 80%
mortality was seen with CNS involvement21; Among the
patients who have survived the CNS, debridement has the minimal or early
invasion of the dura and brain.
Long term outcomes of fungal osteomyelitis of frontal bone are not well
established.