|EXPEDITED PUBLICATION - REVIEW BRIEF
|Year : 2021 | Volume
| Issue : 3 | Page : 250-253
Indications for exenteration and role of imaging in rhino-orbital-cerebral mucormycosis: An ophthalmologist's perspective
Jayashree Bakthavatchalam1, Viji Rangarajan2, Veena Noronha3
1 Department of Orbit and Oculoplasty, Aravind Eye Hospital, Chennai, Tamil Nadu, India
2 Consultant and HOD, Orbit and Oculoplasty Clinic, Aravind Eye Hospital, Coimbatore, Tamil Nadu, India
3 Consultant Radiologist, VRR Scans, Chennai, Tamil Nadu, India
|Date of Submission||11-Aug-2021|
|Date of Acceptance||11-Aug-2021|
|Date of Web Publication||09-Sep-2021|
Dr. Jayashree Bakthavatchalam
Department of Orbit and Oculoplasty, Aravind Eye Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bakthavatchalam J, Rangarajan V, Noronha V. Indications for exenteration and role of imaging in rhino-orbital-cerebral mucormycosis: An ophthalmologist's perspective. TNOA J Ophthalmic Sci Res 2021;59:250-3
|How to cite this URL:|
Bakthavatchalam J, Rangarajan V, Noronha V. Indications for exenteration and role of imaging in rhino-orbital-cerebral mucormycosis: An ophthalmologist's perspective. TNOA J Ophthalmic Sci Res [serial online] 2021 [cited 2021 Sep 21];59:250-3. Available from: https://www.tnoajosr.com/text.asp?2021/59/3/250/325720
| Introduction|| |
Coronavirus-associated rhino-orbital-cerebral mucormycosis (ROCM) is a well-known clinical entity for the medical fraternity at present. Early diagnosis may be sight saving as well as lifesaving. This needs a multispeciality approach with radiological imaging playing a vital role in diagnosis and management of this potentially fatal infection. The main modality of surgical treatment is endoscopic sinus surgery, transcutaneous retrobulbar amphotericin B injection, and exenteration of the involved eye. Exenteration being a destructive procedure could cause psychological impact to the patients, their family, and at times to the surgeon as well. Imaging at the early presentation can help us to prevent exenteration and thereby to keep the clinicians' morale high in treating these patients.
| Exenteration Procedure and Its Indications|| |
Orbital exenteration presents a challenge to the reconstructive surgeon. In our personal experience, orbital exenteration was most commonly performed for malignancies which included squamous cell carcinoma, sebaceous gland carcinoma, eyelid malignant melanoma, choroidal melanoma with orbital involvement, and for orbital mucormycosis with disease progression despite antifungal therapy and sinus debridement. In most of these cases, an eyelid sparing exenteration can be used to achieve more rapid healing. Some of the defects were lined with split-thickness skin graft or allowed to granulate [Figure 1] by secondary intention. The most common complication encountered in orbital excenteration procedure is intraoperative bleeding. This can be avoided by careful attention to hemostasis by packing the orbit with gauze soaked with adrenalin, cauterizing the bleeding vessels, and using bone wax. Once performed, cosmetic rehabilitation is long with multiple postoperative visits, independent of the method used to close the defect. Orbital mucormycosis had the highest mortality rate and was associated with diabetes and immunosuppression.
Principle of exenteration
Exenteration involves removal of the soft-tissue contents of the orbit including the eye, extraocular muscles, periorbita, and part or all of the eyelids.
Types of exenteration
Exenteration can be classified as:
Total exenteration: All of the soft tissues of the orbital and periocular adnexa are removed.
Subtotal exenteration: The soft tissue contents of orbit are removed with preservation of eyelid skin.
Extended exentration: It involves resection of adjacent structures, for example, the paranasal sinuses for the management of a sino-orbital malignant tumor. The extent of the surgical resection is dictated by the extent of the disease process.
This mutilating procedure is used for the management of a number of benign as well as malignant conditions which are not amenable to other treatment modalities.
Considerations for exentration
Exenteration can be done for some benign and malignant conditions and also in life-threatening infections like sino-orbital mucormycosis not responding to antifungal therapy and postsinus debridement.
The preoperative evaluation comprises:
- A review of paraffin fixed histological sections
- A thorough ophthalmic examination of both eyes
- A general physical examination of the patient
- A review of radiological imaging.
| Patient Preparation|| |
The patient must be prepared for the loss of the eye and for the cosmetic deformity that results from orbital exenteration. Hypoesthesia of the forehead and cheek owing to removal of branches of the fifth nerve during exenteration should be anticipated. Furthermore, the patient should be aware of the possibility of tumor recurrence or metastatic spread despite surgical intervention. Discussing the options for cosmetic rehabilitation preoperatively, with the use of photographs to demonstrate the postsurgical appearance with an orbital prosthesis, may be beneficial in gaining acceptance of the planned procedure.
Surgical procedure of orbital exenteration
Orbital exenteration is done under general anesthesia
- Mark an incision line around the orbit just inside the orbital rim. Cut through the skin and muscle with a scalpel blade or cautery needle. If the eyelid skin is to be preserved, the initial incision is made adjacent to lashes, a myocutaneous flap is elevated anterior to the orbital septum until the orbital rim is reached
- Dissect beneath the orbicularis muscle to the orbital rim. Incise periosteum along the rim. At the medial and lateral rims, disinsert the canthal ligaments from their attachments to bone
- Separate periorbita from the orbital walls with a freer elevator
Firm attachment will be encountered at the trochlea and along the superior and inferior orbital fissures. Transect the lacrimal duct as it enters the lacrimal canal just inside the inferomedial orbital rim. If there is involvement of the lacrimal sac and duct, remove the anterior wall of the canal with rongeurs and transect the duct as its entrance into the nose.
- Pass enucleation scissors medially around the orbital tissues to the apex
Transect the tissues and remove the specimen. Alternatively, a wire snare allows clean separtion of the orbital contents closer to the apex.
- Pack the orbit with gauze sponges soaked with epinephrine and applies pressure for 10 min
Remove the sponges and cauterize any residual bleeding vessels. Perforating vessels through the orbital bones are controlled with bone wax.
- Harvest a spilt-thickness skin graft from the upper, outer quadrant of the thigh with a dermatome
Place the graft in the orbit and trim excess skin from the wound margins. If the graft was not meshed, excise the dog-ear flaps that develop when the graft is folded into the orbital concavity.
- Suture the graft to skin at the orbital rim with interrupted and running 6-0 Vicryl stiches
- Lay multiple 2-inch strips of Telfa or nonadherent gauze to cover the graft and overlap the orbital rim.
Press the cotton into the cavity to mold into the crevices. Cover the wound with a firm dressing.
| Postoperative Care|| |
The patient is placed on a regimen of broad-spectrum antibiotics postoperatively. After 5–7 days, the orbital packing can be removed. The orbital cavity is irrigated daily with a dilute solution of hydrogen peroxide and povidone–iodine and crusts are debrided with a forceps. The orbit is usually well epithelialized within 3–4 months. An oculofacial prosthesis may be fitted after 3 months [Figure 2].
| Potential Complications|| |
Graft failure or delayed healing
This results from bleeding beneath the graft caused by inadequate hemostasis, low-grade infection, or poor approximation of the graft to the orbital walls. If small areas of the graft become necrotic, these areas are debrided. If the graft does not survive, it can be removed and the socket irrigated daily with 50% hydrogen peroxide and antibiotic ointment until it heals by spontaneous granulation.
Numbness of the forehead is inevitable because the frontal and supratrochlear nerves are excised with the orbital contents.
Openings in the lamina papyracea of the ethmoid bone may be present from tumor involvement or from spontaneous dehiscence, or from iatrogenic perforation during surgery. If the sinus mucosa is breached or has been biopsied, it may grow into the orbit beneath the skin graft, resulting in failure. A graft should not be placed over the opening. The fistula can be closed later by marsupialization.
| Imaging in Rhino-Orbital-Cerebral Mucormycosis|| |
Imaging helps to reduce morbidity and mortality, helps in surgical planning, and also to determine the prognosis and posttreatment follow-up.
The imaging modality of choice in mucormycosis is magnetic resonance imaging (MRI) with contrast. The protocol should include plain and contrast in three orthogonal planes (axial, coronal, and oblique sagittal planes) with the following sequences – T1 and T2 images with and without fat suppression, diffusion-weighted imaging (DWI) for diagnosing orbital abscess, optic nerve, and brain infarction, and magnetic resonance (MR) angiogram to look for vascular occlusions.
Computed tomography (CT) scan can be done when the disease is confined to the paranasal sinus and for endoscopic sinus surgery planning or it can be combined with the MRI. CT can be done for follow-up of the patients for localized sinus disease. CT protocol includes both plain and contrast in axial and coronal planes from the mandible to the brain in bone and soft tissue windows.
Imaging findings in ROCM can be subdivided into paranasal sinus, orbit, and cerebral and skull base. The radiologist and treating physicians should be aware of these findings for early detection and treatment.
MRI should be done to look for the spread of the disease in orbit, brain and the skull base.
Nasal cavity and paranasal sinuses
Black turbinate sign is seen in nasal mucormycosis. It is seen as dark T2 soft tissue in the involved turbinate against a background of edematous mucosa. Postcontrast shows no enhancement in the dark necrotic tissue, whereas the inflamed mucosa shows bright enhancement [Figure 3].
|Figure 3: Coronal section of magnetic resonance imaging in T2-weighted image showing black turbinate sign with involvement of maxillary sinus in the left side|
Click here to view
Paranasal sinuses commonly involved are ethmoid, sphenoid, and maxillary sinuses.
Computed tomography scan
In CT scan one must look for sinus opacification, erosion of the wall of the sinuses, soft tissue in the orbit, erosion of the floor of the anterior cranial fossa or the roof of the ethmoid bone and the spread of the disease to brain. CT scan cannot diagnose mucormycosis just based on the opacification of the paranasal sinuses. The presence of bony erosion and spread to the adjacent structures may be an indicator of mucormycosis in a setting of COVID-19 infection.
Magnetic resonance imaging
The sinuses display isointense signal in T1-weighted image (T1-WI) and mixed signal in T2-WI. The presence of T2 hypointense signal in the background of hyperintense mucosal/fluid signal is highly suggestive of mucormycosis. The T2 hypointense signal is due to paramagnetic elements like iron and manganese in the fungal hyphae. Normal viable mucosa enhances and necrotic dead tissue shows a lack of enhancement.
This fatal disease can spread to the orbit, brain, infratemporal fossa, and skull base. All orbital tissues can be involved including orbital fat, extraocular muscles, optic nerve, nasolacrimal canal, superior orbital fissure, and orbital apex.
Computed tomography/magnetic resonance imaging
- Fat – Early sign of orbital extension is fat stranding, mainly the fat adjacent to the involved sinus. It is best appreciated in T2 fat sat or STIR images as hyperintense signal against a background of dark signal from the normal suppressed fat. CT will show increased attenuation. It enhances postgadolinium
- Extraocular muscles – Initially, the muscles adjacent to the sinus are enlarged, but as the disease progresses, all the muscles get involved. The edematous muscles display hyperintense signal in T2-WI and enhance postcontrast. Once ischemia sets in, no enhancement is seen in the extraocular muscles
- Optic nerve – Vision loss can result from direct involvement of the optic nerve by the fungus or ischemia due to arterial occlusion or compression by the fungal soft tissue. MRI can easily differentiate these entities. Direct involvement will be seen as thickened optic nerve sheath complex with T2 hyperintense signal and enhancement of the thickened optic nerve sheath. Ischemia is readily identified on DWI, seen as a bright signal with reduced apparent diffusion coefficient (ADC) and lack of enhancement. In compression of the optic nerve, the optic nerve will be engulfed by the enhancing or nonenhancing necrotic tissue
- Nasolacrimal canal – Hypointense lesion is seen in the canal as a direct extension from the adjacent sinuses [Figure 4]
- Superior orbital fissure and orbital apex – Spread of disease to the apex from the sinuses or pterygopalatine fossa should be looked for as the disease can then spread rapidly to the cavernous sinus. The soft displays a similar signal as the rest of the fungal tissue. It enhances with contrast. Once necrosis sets in there will be no enhancement.
|Figure 4: Axial section in T2-weighted image and diffusion weighted imaging showing optic nerve infarction on the left optic nerve|
Click here to view
Imaging in the other areas of spread in mucormycosis
Mucormycosis can spread to the infratemporal fossa which is seen as edema of the temporalis and pterygoid muscles, best appreciated in fat-suppressed T2-WI as a bright signal. Identifying involvement of the pterygopalatine fossa is very important as it is an important gateway for spread of infection to the skull base, orbit, and brain if they are not already involved.
Early intracranial spread is best appreciated in contrast-enhanced MRI. Enhancement is seen in the thickened dura. Brain abscess is seen as ring-enhancing lesions with edema. Acute infarcts are seen in the vascular territory as areas of bright signal on DWI and reduced ADC suggestive of diffusion restriction.
Cavernous sinus thrombosis (CST) – Contrast-enhanced MRI is the modality of choice to diagnose CST. Filling defects or areas of nonenhancement will be seen in the cavernous sinus.
MR angiogram should be done as a part of the protocol for vascular occlusion.
| Conclusion|| |
Mucormycosis is a potentially fatal infection, and therefore, early diagnosis both clinical and radiological is most important. Exenteration is the last resort to save the life of the patient not responding to other modes of management and imaging both CT and MRI have a very important role in the diagnosis and management of these patients in saving sight and life!
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]