|Year : 2015 | Volume
| Issue : 3 | Page : 215-218
Rhino-orbito-cerebral mucormycosis: Magnetic resonance imaging
Parveen A Lone1, Nisar A Wani2, Majid Jehangir2
1 Department of OMF Surgery, Indira Gandhi Government Dental College Jammu, Srinagar, Jammu and Kashmir, India
2 Deptartment of Radiodiagnosis and Imaging, Government Medical College, Srinagar, Jammu and Kashmir, India
|Date of Web Publication||17-Jul-2015|
Nisar A Wani
Department of Radiodiagnosis and Imaging, Government Medical College, Srinagar - 190 018, Jammu and Kashmir
Source of Support: None, Conflict of Interest: None
Rhino-orbito-cerebral mucormycosis (ROCM) is a potentially fatal fungal infection that commonly affects diabetic and other immunocompromised patients. Necrotizing and angioinvasive features of this class of pathogenic fungi facilitate spread from sinuses into orbit and brain with devastating consequences like cavernous sinus thrombosis. We describe magnetic resonance, including diffusion weighted imaging findings in a case of micobiologically documented ROCM in a 50-year-old diabetic man. Restricted diffusion was demonstrated in the distribution of infiltrating lesion right from soft issue facial component through left orbit and in the cavernous sinus. Favorable outcome was achieved with surgical debridement and prolonged amphotericin therapy.
Keywords: Magnetic resonance imaging, Mucormycosis, Rhino-orbito-cerebral
|How to cite this article:|
Lone PA, Wani NA, Jehangir M. Rhino-orbito-cerebral mucormycosis: Magnetic resonance imaging. Indian J Otol 2015;21:215-8
| Introduction|| |
Rhino-orbital-cerebral mucormycosis (ROCM) is an acute and uncommon aggressive fungal infection that occurs in immunocompromised patients including those with diabetes. Ketoacidosis in diabetes enhances susceptibility to ROCM. , The disease originates in the sinonasal mucosae and extends rapidly to neighboring structures, including orbit and sometimes brain. ROCM is characterized by a very high residual morbidity and mortality due to angioinvasive property of the fungus, which causes vascular occlusion resulting in extensive tissue necrosis. Early diagnosis and timely intervention is key to successful treatment. ,,, We present a case of ROCM to emphasize utility of magnetic resonance imaging (MRI) in diagnosis of this potentially fatal form of mucormycosis.
| Case Report|| |
A 50-year-old man presented with swelling of left upper eyelid, proptosis and loss of vision that began almost 25 days back and progressed gradually. He was diagnosed with type 2 diabetes mellitus 5 years before and put on oral hypoglycemic agents. On examination at presentation, patient was conscious and afebrile; pulse and blood pressure were normal. Cellulitis of left side of face was present from forehead up to left submandibular region. Palpebral and bulbar conjunctiva showed chemosis with proptosis of left eyeball. Left eye had reduced visual acuity with only hand movements perceptible; left pupil was sluggish reacting to light. Ophthalmoplegia in the form of weakness of all the left sided extra-ocular muscles was present. Laboratory evaluation showed hyperglycemia with random blood sugar level of 230 mg/dL; pH, bicarbonate and O 2 and CO 2 were within normal limits. Liver and kidney function tests were normal. Clinical suspicion of cavernous sinus thrombosis prompted an urgent MRI for further evaluation. Subcutaneous soft tissue edema/cellulitis was seen in the medial angle of left orbit extending into adjacent face; underlying left maxillary sinus showed significant mucosal thickening and left eyeball was displaced anterolaterally [Figure 1]. Axial MRI of the orbits showed diffusely infiltrating lesion, with hyperintense signal intensity on T2-weighted (T2-W) sequence, within the left orbit involving intraconal and extraconal spaces and continuous with subcutaneous lesion anteriorly. Posteriorly infiltrating orbital lesion was seen extending into the left cavernous sinus lateral to left internal carotid artery. Sinusitis was evident in frontal, ethmoid and sphenoid sinuses in the form of mucosal edema [Figure 2]. T1-weighted (T1-W) images showed isointense to hypointense signal intensity in the subcutaneous soft tissue and orbital infiltrating lesion; isointense signal intensity was seen in the left cavernous sinus along the lateral aspect of left internal carotid artery, which was narrowed [Figure 3]. Contrast enhanced T1-W images showed heterogenous enhancement of the left facial subcutaneous and intraorbital lesion; left cavernous sinus showed enlargement and discrete areas of heterogenous enhancement compatible with cavernous sinus thrombosis [Figure 4]. Diffusion weighted images (DWI) showed hyperintense signal intensity in the distribution of infiltrating lesion in subcutaneous soft tissue, orbit and left cavernous sinus [Figure 5]. Restricted diffusion was evident in the form of hypointense signal intensity in the corresponding distribution on apparent diffusion co-efficient (ADC) maps [Figure 6]. Restricted diffusion foci due to infarcts were seen in the bilateral cerebral hemispheres in the watershed distribution [Figure 7]. Imaging findings of sinusitis, infiltrating orbital inflammation and intracranial extension with cavernous sinus thrombosis in a diabetic patient was suggestive of ROCM. Nasal aspirate and soft tissue biopsy specimen revealed aseptate hyphae with right angle branching on KOH smear and culture, which confirmed microbiology as mucormycosis. Patient was treated with intravenous amphotericin and underwent surgical debridement after blood sugar was controlled with insulin therapy. Lateral rhinotomy, sinusectomy and orbital exenteration was performed and antifungal medication with plain amphotericin was continued for 10 weeks.
|Figure 1: T2-weighted coronal magnetic resonance imaging shows hyperintense signal intensity along peripheral left maxillary and frontal sinuses, left nasal turbinates are swollen. Left orbital hyperintense signal intensity lesion is seen medial to eyeball, displacing it laterally|
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|Figure 2: T2-weighted axial magnetic resonance imaging shows hyperintense left ethmoid cells. Soft tissue swelling is seen anterior to left eyeball. Left orbital hyperintense signal intensity lesion is seen extending along orbital apex into left cavernous sinus lateral to left internal carotid artery|
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|Figure 3: T1-weighted axial magnetic resonance imaging shows hypointense mucosal thickening of left ethmoid cells. Soft tissue swelling is seen anterior to left eyeball. Left orbital isointense signal intensity lesion is seen extending along orbital apex into left cavernous sinus lateral to left internal carotid artery which appears narrowed|
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|Figure 4: Postgadolinium enhanced T1-weighted axial magnetic resonance imaging shows heterogenous enhancement of preorbital soft tissue and intraorbital lesion. Patchy heterogenous enhancement is seen in left cavernous sinus|
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|Figure 5: Diffusion weighted (b = 1000) magnetic resonance imaging shows hyperintense signal intensity in the left orbit/orbital apex corresponding to the lesion seen on T1 and T2-weighted images|
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|Figure 6: Apparent diffusion co-efficient map showing hypointensity in left orbital/orbital apex lesion|
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|Figure 7: Diffusion weighted imaging (b = 1000) at the high parietal convexity shows small, watershed area infarcts as focal hyperintensities, more numerous on left side|
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| Discussion|| |
Fungal species causing ROCM (Rhizomucor, Rhizopus, Absidia and Mucor species) are opportunistic pathogens that only infect compromised subjects. The principal predisposing factors are diabetes mellitus (especially with ketoacidosis) and hematologic malignances with neutropenia. ,, In diabetes high blood glucose concentration enhances fungal growth. Serum of patient with ketoacidosis is not able to stop the growth of fungus. As neutrophils are responsible for defense against fungi, alteration in number or function of these white cells leads to an increased risk of infection. ,, Other identified risk factors are steroid therapy, organ transplantation, chemotherapy and chronic kidney disease. ,
Rhinocerebral mucormycosis arises from nasal and sinus mucosa and then spreads rapidly to nearby areas notably orbit and brain. The orbital extension occurs along the nasolacrimal duct, dehiscent medial orbital wall or the anterior and posterior ethmoid orifices. Spread to brain occurs through the orbital apex, traversing vessels or the cribiform plate of ethmoid bone. ,, The fungus adheres to the internal elastic lamina of the blood vessels causing thrombosis and results in ischemia and necrosis of tissues. Cavernous sinus thrombosis may also complicate mucormycosis. Cerebral injury in ROCM may result from direct extension of fungus or due to internal carotid artery ischemia. ,,,
Identification of the aforementioned changes on computed tomography (CT) and MRI can help in making an early diagnosis of ROCM. These changes are proportionate to the fungal invasion into the respective tissue. In the early stages CT shows mucosal thickening and absence of air-fluid level in the infected sinus. Later on destruction of medial orbital wall and invasion of rectus muscles, orbital apex and ipsilateral cavernous sinus may be seen. ,,,, Because of increased soft tissue resolution, MRI provides a better visualization of invasion/involvement of orbital soft tissue, infratemporal fossa, intracranial structures and perineural invasion and vascular obstruction than CT. MRI is also better choice than CT because of the coincident therapy with nephrotoxic drugs and possible compromised renal function may be made worse by potential nephrotoxicity of iodinated contrast use in CT. ,,,, MRI findings described in progressive spread of ROCM include a hyperintense sinus wall, T2-W hyperintense lesion extending from paranasal sinus along orbital apex into intracranial structures and narrowing or slow flow in the ipsilateral internal carotid artery in the vicinity of mucor invasion. ,,,, All these features were very well demonstrated by MRI in our case. We additionally noticed hyperintense signal intensity on DWI and corresponding hypointense signal on ADC maps in the lesion extending from orbit to cavernous sinus, compatible with restricted diffusion. DWI of brain also showed small infarcts in the watershed distribution in high parietal convexity. These small infarcts provided additional indirect evidence of tenuous blood supply at watershed territory due to narrowing of left internal carotid artery in cavernous sinus. Though restricted diffusion is a documented finding in sinus and cerebral fungal infections and resultant ischemia of optic nerve, there has not been any report of DWI of infiltrating lesion in ROCM to our knowledge. ,, Restricted diffusion in the path of mucor invasion in ROCM may be related to the tissue ischemia and necrosis resulting from angioinvasive nature of this fungal infection and ischemic and necrotic lesions in brain are very well-known to exhibit restricted diffusion. ,, DWI thus has potential to differentiate ROCM from other invasive lesions in this region notably carcinoma. Early diagnosis of ROCM is important so that timely surgical debridement is carried out and appropriate antifungal medication with amphotericin is started to reduce morbidity and mortality.
| Conclusion|| |
Magnetic resonance imaging is highly useful imaging modality for the diagnosis of ROCM and shows T2-W hyperintense signal intensity in sinonasal mucosa and infiltrating lesion in orbit. MRI determines the extent of invasion very well. Cavernous sinus thrombosis and internal carotid artery narrowing is well depicted by MRI. DWI may add specificity to the diagnosis by showing restricted diffusion in the path of fungal invasion.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]