Mucormycosis

The nose is the portal of entry for rhinocerebral mucormycosis, a treacherous and often fatal disease. Hope for a cure rests in early recognition and aggressive therapy. Ninety per cent of such mycotic infections occur in the clinical setting of poorly controlled diabetes mellitus with ketoacidosis. They may also occur in association with other debilitating diseases. These organisms have a special affinity for vascular walls and produce thrombosis that results in ischemic necrosis of involved tissues.

Dark gangrenous nasal mucosa is the classic clinical sign of mucormycosis. This finding is associated with a purulosanguinous exudate and an unpleasant odor. Nasal septal perforation and necrosis of the turbinates are commonly seen. Orbital involvement is indicated by the presence of proptosis, ophthalmoplegia, and even blindness due to thrombosis of the ophthalmic artery. Extension of the infection posteriorly through the superior orbital fissure and optic canal leads to intracranial involvement. A more common pathway for intracranial spread of these infections is through the cribriform plates along the path of small penetrating arteries and veins. Complications of intracranial involvement are many and include increased intracranial pressure, arterial thrombosis and infarction, cerebral abscesses, and occasionally mycotic aneurysm formation.

On plain films mucormycosis is radiographically featured by focal destruction of the bony walls of the nasal cavity, associated with soft-tissue densities in the nasal cavity and adjacent ethmoid and maxillary sinuses. On CT and MRI the inflammatory mass has a homogeneous appearance. Fungal infections are often hypointense on both T1 and T2-weighted images due to the solid components of the fungal growth, high protein concentration, and the presence of manganese, which is paramagnetic. Early orbital involvement may be indicated by lateral displacement and thickening of the medial rectus muscle. Further infiltration of the retrobulbar space results in increased density in the orbital apex and thickening of the optic nerve. Coronal imaging is essential for evaluating the cribriform plate region. The radiographic findings of mucormycosis are not always specific, and the process may simulate closely an aggressive tumor. Whenever a nasal mass is found in a patient who has poorly controlled diabetes or other chronic debilitating disease, mucormycosis must be seriously considered.