Zygomaticomaxillary Osteomyelitis due to COVID-19 Associated Mucormycosis (CAM): A Case Series of 10 Patients

Osteomyelitis of bones in the middle third of the face is rare. A review of the literature shows that the mandible is the most commonly involved facial bone. Osteomyelitis of the maxilla is extremely rare. [3]

Osteomyelitis occurring due to fungal infection was rare and occurs in an indolent manner. Osteomyelitis is more commonly seen in males (80.36%) than in females (19.64%), with a peak incidence in 30–39 years of age [4]. The maxilla is the most common jaw bone being affected by fungal osteomyelitis and is more commonly associated with diabetes mellitus. Among fungal osteomyelitis, Candida is the most commonly encountered followed by Aspergillosis and Mucormycosis. These organisms are from an original infection that has not been treated properly, commonly from dental extraction [5]. Niranjan et al., in their ten-year study reported that 52% of all the osteomyelitis cases were that of fungal osteomyelitis, whereas 48% belonged to the nonfungal category [6].

Adekeye et al. published a review of 141 cases of osteomyelitis of the jaws and reported the incidence of malar bone osteomyelitis to be only 1.42% [3]. The incidence of zygomatic bone osteomyelitis reported in our study of cases with CAM is 8.6%.

There are no other existing literature reviews or systematic reviews found in the existing pool of knowledge highlighting the incidence, causes and mode of spread of zygomatic bone osteomyelitis. There have been however isolated case reports and case series of zygomatic bone osteomyelitis. Most of these cases are due to tuberculosis and fungal causes (candidiasis, cryptococcus and aspergillosis). The majority of tuberculous cases of zygomatic osteomyelitis are due to hematologic spread of pulmonary tuberculosis by seeding of bacilli or by direct spread from neighboring structures [7]. There have been rare cases reported caused due to trauma and also idiopathic osteomyelitis of zygoma. An analysis of mode of spread of infection to zygomatic bone in a few rare cases reported in the literature is presented in Table 2.

Table 2 Review of literature describing zygomatic bone osteomyelitis with etiology, clinical features, mode of spread and treatment

Mucormycosis is an invasive fungal disease caused primarily by fungi belonging to the order Mucorales. This fungus usually acts as an opportunistic pathogen, seen in soil, decaying organic debris and frequently occurs in the patients with a compromised immune system. The leading predisposing factors for mucormycosis are uncontrolled diabetes mellitus, lymphomas, leukemias, renal failures, organ transplant, long-term intake of corticosteroids, immunosuppressive therapy and AIDS. Iron plays an important role in the growth of mucormycosis. Fungal hyphae produce ‘rhizoferrin,’ which binds iron fervently. This iron–Rhizoferrin complex is then taken up by the fungus and becomes available for its vital functions. In the cases of diabetic ketoacidosis, the patients are at high risk of developing mucormycosis, due to an elevation in the available serum iron [15]. Pertaining to the cases reporting to our institution is of special significance to note that all the 10 patients described exhibited poor glycemic control which was a predisposing factor for the opportunistic infection.

The infection develops after inhalation of fungal sporangiospores into the paranasal sinuses. The infection may then rapidly extend into adjacent tissues. Upon germination, the invading fungus may spread inferiorly to invade the palate, posteriorly to invade the sphenoid sinus, laterally into the cavernous sinus to involve the orbits, or cranially to invade the brain. The fungus invades the cranium through either the orbital apex or cribriform plate of the ethmoid bone and ultimately kills the host. Occasionally, cerebral vascular invasion can lead to hematogenous dissemination of the infection with or without development of mycotic aneurysms [16]. Upon visual inspection, infected tissue may appear normal during the earliest stages of spread of the fungus. Infected tissue then progresses through an erythematous phase, with or without edema, before onset of a violaceous appearance, and finally the development of a black, necrotic eschar as the blood vessels become thrombosed and tissue infarction occurs. Infection can sometimes extend from the sinuses into the mouth and produce painful, necrotic ulcerations of the hard palate [2]

In the present case series, the authors are of the opinion that the fungal spores enter via the nasal cavities and then spread to the paranasal sinuses. The maxillary sinus is thus invariably involved. The fungus erodes through the posterior aspect of the maxillary sinus gaining access to the infratemporal fossa. From the infratemporal fossa the infection directly invades into the body of the zygoma from the posterior aspect and in some cases also the arch of the zygoma. This has been deduced by the characteristic pattern observed in the CT imaging of each case which shows erosion of the posterolateral wall of the maxillary sinus with obvious haziness in the area of the infratemporal fossa. Retrospectively to co-relate with this clinically, at time of maxillectomy the posterior aspect of the maxilla and the pterygoid bone i.e., the infratemporal fossa and the structures therein were invariably diseased and required thorough debridement in all of the cases. This does indicate that spread to the zygoma from the maxilla could well be by way of the ipsilateral infratemporal fossa. According to the existing literature the zygomatic bone can be approached for resection intra-orally or extra-orally. For the cases in this series an open approach was preferred via Weber Ferguson incision to provide unhindered access to this posterior aspect and to be able to thoroughly debride the involved tissues of the infratemporal fossa. Although theoretically access to the zygoma can be achieved intraorally as well, it was deemed prudent by the surgical team to approach extra-orally for a more thorough, aggressive and definitive resection. The pathway of spread is elucidated by the flowchart in Fig. 11.

Fig. 11figure 11

The incidence of zygomatic osteomyelitis in the literature is rare. Although a definitive cause for this has not been empirically stated in any of the past studies it can be speculated that it is due to the fact that the bone has a rich vascular supply and that there are no direct potential sources of infection such as teeth present in the bone. Additionally, the bone is not in any direct contact with the oral microflora nor is it in communication with the environment, it being a solid, non-pneumatized bone, not bearing a sinus. With this in consideration an open approach was preferred via Weber Ferguson incision to provide unhindered access to this posterior aspect and to be able to thoroughly debride the involved tissues of the infratemporal fossa.

This case series attempts to highlight the unique nature of the mode of zygomatic involvement of the patients affected with CAM as compared to case reports and series presented in the past such as those due to tuberculosis, other fungi, trauma, etc. In our experience with cases of zygomatic bone osteomyelitis due to CAM, an aggressive surgical resection of bone and thorough debridement of diseased tissues combined with a dual antifungal drug therapy was the key to successful recovery. The authors recommend this treatment regimen for similar cases encountered.

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