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 Table of Contents  
COMMISSIONED ARTICLE
Year : 2013  |  Volume : 1  |  Issue : 2  |  Page : 101-106

Interpretation of magnetic resonance imaging of orbit: Simplified for ophthalmologists (Part II)


1 Department of Ophthalmology, P D Hinduja National Hospital and MRC, Mumbai, India
2 Department of Radiodiagnosis, P D Hinduja National Hospital and MRC, Mumbai, India
3 Department of Radiodiagnosis, R P Centre for Ophthalmology Sciences, AIIMS, New Delhi, India

Date of Submission18-Mar-2013
Date of Acceptance19-Mar-2013
Date of Web Publication20-May-2013

Correspondence Address:
Barun K Nayak
Department of Ophthalmology, P D Hinduja National Hospital and MRC, Mumbai
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2320-3897.112178

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  Abstract 

The basics of orbital magnetic resonance imaging (MRI) has been discussed in the previous issue. This article is in continuation of the previous article, and deals with the systematic approach towards the diagnosis of various orbital pathological lesions. It starts with the concept of various compartments in the orbit with their boundaries, followed by the mention of different lesions occurring in those compartments. The representative pictures of MRI orbit is also being provided with their main features on MRI of some commonly occurring pathologies of orbit. The purpose of this article is to impart the skill amongst ophthalmologists of interpreting orbital MRI.

Keywords: Magnetic resonance imaging (MRI), MRI orbit, orbital compartments, orbital pathologies


How to cite this article:
Nayak BK, Desai S, Maheshwari S, Singh D, Sharma S. Interpretation of magnetic resonance imaging of orbit: Simplified for ophthalmologists (Part II). J Clin Ophthalmol Res 2013;1:101-6

How to cite this URL:
Nayak BK, Desai S, Maheshwari S, Singh D, Sharma S. Interpretation of magnetic resonance imaging of orbit: Simplified for ophthalmologists (Part II). J Clin Ophthalmol Res [serial online] 2013 [cited 2019 Oct 22];1:101-6. Available from: http://www.jcor.in/text.asp?2013/1/2/101/112178

In the previous issue, we have described the basics of orbital magnetic resonance imaging (MRI) and the appearance of normal anatomical structures on orbital MRI. [1] A proper, understanding of orbital pathology is essential for diagnosing various lesions on the basis of orbital MRI. The purpose of this presentation is to outline a systematic approach while interpreting the orbital MRI films, to be followed by providing the MRI images of some of the common lesions of orbit.

Any mass lesion in orbit can produce two types of effects as described by Rootman J. The functional effects, which can be in the form of the motor disturbances, sensory disturbances, and the secretory disturbance of orbital structure. These are mainly responsible for the clinical presentation. Secondly, the mass effects, which can be in the form of either shifting of structures (positive effect) or enlargement of space as a result of pressure or cicatrization (negative effect). This can also produce symptoms sometimes. However, the MRI will always highlight the mass effect accurately apart from the nature and characteristics of the mass itself. Hence, the final conclusion should be drawn only after correlating the MRI findings with the clinical picture.


  Lesions of orbit Top


The lesions can start de novo in orbit and periorbital tissue or may be a reflection of systemic disease or secondary's from the tumor of the other parts of the body. The various pathologies of orbit can fall in one of the five broad categories mentioned below: [2]

  1. Inflammatory
  2. Neoplastic
  3. Structural abnormality (acquired or congenital)
  4. Vascular
  5. Degenerations and depositions



  Inflammatory Top


This constitutes about 3/5 th of all the orbital pathologies out of which about 85% is due to the thyroid ophthalmopathy. Inflammatory condition can be divided into acute, subacute or chronic. The examples of acute conditions are infective cellullitis, non-specific idiopathic inflammation (pseudotumor), acute ocular inflammation (uveitis, keratitis, scleritis), sudden event in pre-existing lesion (hemorrhage in lymphangioma), and fulminant neoplasm (chloroma, rhabdomyosarcoma, metaplasia). The subacute category includes thyroid orbitopathy, infective cellulitis (fungal), specific or non-specific idiopathic orbital inflammation (granuloma), primary ocular inflammation (scleritis, uveitis), collagen vascular disease, rapidly developing (fulminant) malignancies. The chronic inflammatory conditions can be due to primary and secondary neoplasia, thyroid, lymphoproliferative disorders, collagen vascular disease, idiopathic sclerosing inflammation, and rare diseases like amyloidosis.


  Neoplastic Top


This constitutes about 1/5 th of all orbital lesions. These can be benign or malignant.


  Structural Top


It can be congenital (eg., Crouzon's disease, craniofacial dysostosis, maxillary hypoplasia, facial asymmetry) or acquired (Post-traumatic: Direct physical, thermal, chemical, radiation induced). Some other lesions can be in the form of cysts (dermoid, implantations, lacrimal, mucocoele) and ectopias.


  Vascular Top


Character of flow (hemodynamics) will vary based on the type of lesion. Non-obstructive vascular lesion on the arterial side can have high or low flow (such as tumors, malformations and shunts). Venous malformation can be either distensible or non-distensible. There may be arterio-venous abnormalities (dural fistula, arterio-venous malformations), venous lymphatic (lymphangioma), arterio capillaries (Sturge Weber, hereditary hemorrhagic telangiectasia). Furthermore, there may be purely obstructive arterial or venous lesions. Infantile capillary hemangiomas are high-flow tumors on the arterial side. Cavernous hemangioma is a lesion with low arterial flow. Congenital arterio venous (AV) malformation and acquired AV fistulas may be high or low flow based on the large or small shunt vessels.


  Degeneration and depositions Top


These can be atrophy, cicatrization, or depositions (progressive myopathy, amyloid deposition, and linear scleroderma).


  Compartments of orbit Top


For proper diagnosis of pathologies on MRI, we must have proper knowledge of various compartments in the orbit. Each compartment can have a limited type of lesions due to the presence of different types of tissue in each compartment. However, sometimes the lesion may extend in more than one compartment or may be even diffuse involving multiple compartments.

The various compartments for this purpose can be divided as follows: [3]

  • Intraconal space
  • Extra ocular muscles
  • Extraconal space
  • Subperiosteal space
  • Lacrimal gland
  • Ocular
  • Preseptal space


We will describe the boundaries of various spaces and the common lesions found in that space. Although axial, coronal and sagittal cuts are always used for studying proper orientation of various lesions in orbit, we will also mention the most suited cuts for a particular compartment.


  Intraconal space Top


This is the space inside the four recti muscles and their connections (muscle cone). A very important structure, which lies inside this space, is the optic nerve and its sheath. This can be considered as a separate compartment as its lesions are different than the rest of the intraconal space. Optic nerve sheath is the extension of meninges and has the same characteristics. The space between optic nerve and the sheath is the subarachnoid space. The optic nerve has S shaped course in the sagittal plane and parasagittal planes are used to study the optic nerve. However, the diameter of the optic nerve and surrounding subarachnoid space is best studied in the coronal planes. The common lesions here are optic neuritis, fracture of orbital apex with bleeding, perineuritis and optic glioma. Other conditions are optic nerve sheath meningioma, metastases, and sarcoidosis.

The rest of the intraconal space can be best studied in the coronal plane. Common lesions are cavernous hemangioma, inflammatory pseudotumor, and varix. Other lesions include lymphangioma, neurofibromatosis, enlarged vein in AV fistulae and metastases. Rarely, lymphoma and capillary hemangioma may also occur in this space.


  Extraocular eye muscles Top


Primary evaluation is performed in the coronal sections and both side should be studied together to know the enlargement of the muscles. However, the axial or parasagittal cuts depict the muscles in the longitudinal extent and it is essential to establish the involvement of tendon and muscle belly together or only the muscle belly. Thyroid myopathy involves only the muscle belly and spares the tendon. Common conditions affecting muscles are thyroid orbitopathy, myositis and lesions with the pseudotumors. Other rare lesions are lymphoma, rhabdomyosarcoma, AV fistula, and trauma.


  Extraconal space Top


It is the space between the muscle cone and the periosteum of the orbital wall and anteriorly limited by orbital septum. The best plane to visualize this space is coronal sections. Lymphoma and capillary hemangioma are common lesions whereas rhabdomyosarcoma, neurofibroma and metastases are rare lesions of this space.


  Subperiosteal space Top


This is the space between the periosteum and the bony wall of the orbit. All cuts are important based on the location of the lesion. This space can be affected by lesions originating from the surrounding structures, as well. Common lesions are mucocoele, orbital fractures, subperiosteal abscess, and tumors of paranasal sinuses, dermoids, metastases, osteomas, epidermoids, and meningiomas. Other rare lesions can be fibrous dysplasia, plasmacytoma, Wegener's granulomatosis, cholesterol cysts, and Paget's disease. Soft-tissue damage can be assessed in traumatic cases.


  Lacrimal gland Top


The coronal sections provide the best assessment of lacrimal gland, which is situated in upper outer quadrant of orbit. Epithelial lesions can be benign (pleomorphic adenoma) or malignant (pleomorphic adenocarcinoma). Non-epithelial tumors are lymphomas and inflammatory pseudotumors.


  Ocular Top


Most of the lesions of the globe can be diagnosed by direct examination or other investigations such as ultrasound. MRI is useful in diagnosis of uveal melanoma, hemangioma, metastases, and infantile retinoblastoma.


  Preseptal space Top


This is the space in front of orbital septum in the upper and lower lids. MRI is rarely ordered for diagnosis of lesions of this space, but it can depict the extent and infiltration of orbital septum. The common conditions are inflammatory, xanthelasma, tumors of limited malignant potential. Rare conditions are lymphomas, capillary hemangioma, and metastases.


  Steps for Reading an MRI film Top


  • Place the MRI film in a viewing box
  • What is the abnormality and characteristics of lesion in T1 weighted images?
  • What is the abnormality and characteristics of lesion in T2 weighted images?
  • What is the location (compartment) of the lesion?
  • What is the extent of the lesion?
  • What are the morphologic characteristics (such as well-circumscribed or diffuse, mottled or uniform, fluid space etc.)?
  • Review special sequences such as FLAIR, STIR [1]
  • Is contrast done - if yes what is the nature of the lesion post contrast?
  • Correlate clinically so as to be able to have differential diagnosis.


We will now be describing MRI of some of the pathological conditions [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19] that we encounter frequently. Understanding and interpreting these images has been kept very simple, as only the selected relevant cuts are provided here with pointers. However, we encourage the readers to note and analyze the findings themselves before reading the legends provided with the images.
Figure 1: MR images showing fl uid (*) within the left sphenoid sinus extending into the adjacent left orbit. It is intermediate in signal on axial T1WI (A) and hyperintense on T2WI (B) Sagittal T2WI (C) showing fluid contents in intraconal compartment of left orbit and sphenoid sinus. Post-contrast sagittal T1WI (D) showing hypointense intraconal lesion with rim enhancement (arrow) consistent with an intraorbital abscess
Features are suggestive of Sinusitis complicated by left intraorbital abscess


Click here to view
Figure 2: Axial T1W magnetic resonance imaging (A) showing oval isointense intraconal mass (*) in the right orbit, which is hyperintense on T2WI (B). It is showing marked homogeneous enhancement following
contrast administration (C). Diagnosis: Cavernous hemangioma in the right orbit


Click here to view
Figure 3: Coronal T1W (A) and T2W (B) magnetic resonance imaging showing a well-defi ned hyperintense intraorbital mass (*) in the superior quadrant. It shows suppression (**) of its bright signal on sagittal T2W
fat-suppressed image (C) consistent with the presence of fat. Diagnosis: Right Orbital dermoid


Click here to view
Figure 4: Axial magnetic resonance imaging showing a multiloculated trans-compartmental lesion within the right orbit, which is hyperintense on both T1W (A) and T2W (B) weighted images. It does not show
suppression of signal on T2W fat suppressed image (B) suggestive of recent hemorrhage within it. A blood-fl uid level (arrow) is seen in the anterior portion of the mass. This was a previously normal child presenting with sudden onset proptosis. Features are suggestive of right orbital Lymphangioma


Click here to view
Figure 5: Axial MRI showing a lobulated T1 hyperintense (A) mass(Black *) within the left globe with extraocular extension. The bright signal persists in T1W fat-suppressed image (B) denoting absence of intra-lesional fat. The mass is hypointense (Black*) on T2WI (C) consistent with presence of melanin (White*). Diagnosis: Right Choroidal melanoma

Click here to view
Figure 6: Magnetic resonance imaging of a child showing a T1 isointense (A) and T2 hyperintense (B) mass within the right orbit causing abaxial proptosis and buckling of the optic nerve. Another mass lesion (*) is seen in the suprasellar cistern suggestive of metastatic deposit. Multiple expansile masses (arrows) also seen involving the calvarium in the axial (C) and sagittal (D) T2WI. Features are consistent with Metastatic neuroblastoma right orbit

Click here to view
Figure 7: Magnetic resonance imaging showing fusiform enlargement of the right optic nerve which is intermediate in signal intensity on T1WI (a) and slightly hyperintense on T2WI (b). Diagnosis: Right side
Optic nerve glioma


Click here to view
Figure 8: Coronal MRI showing a cystic lesion within the belly of right superior rectus muscle (*) in the T2WI (a). A tiny eccentric nodule at 6 o' clock position (white arrow) in T1WI (b) represents a scolex. Diagnosis: Myocysticercus in right superior rectus

Click here to view
Figure 9: Axial T1W (a) and T2W (b) magnetic resonance imaging (MRI) showing an ill-defi ned diffuse enlargement of the left lateral rectus muscle including its tendinous insertion and causing proptosis.
The enlarged muscle is mildly hyperintense on T2W (b) MRI. Patient presented with a painful proptosis, dysmotiity and acute congestion. Diagnosis: Left Orbital pseudotumor


Click here to view
Figure 10: Axial MRI showing a left intraocular mass * with retrobulbar extension. It is intermediate in signal on T1WI (A). The mass and optic nerve show mild heterogeneous enhancement on post contrast T1W
MRI (B). The T2WI (C) shows a hypointense focus(white *) within the mass which corresponds to calcifi cation (Black*) on axial CT image (D). Diagnosis: Left sided Retinoblastoma with extra-ocular extension


Click here to view
Figure 11: Bilateral intra-orbital hematomas in a child with scurvy. Axial T1W fat suppressed magnetic resonance imaging showing hyperintense collections within bilateral upper orbits consistent with hematomas

Click here to view
Figure 12 : (A) Axial T1W MRI showing a lobulated hyperintense mass (White*) within the right globe along the ciliochoroidal region extending into the vitreous cavity arising from the choroid. (B) The coronal T1W
MRI shows the similar hyperintense lesion medially (Black*). (C) The mass is hypointense on T2W image (White*) and is consistent with presence of melanin. Diagnosis: Right Ciliochoroidal Melanoma


Click here to view
Figure 13: (A) Orbital Wegener's Granulomatosis A1 and A2. T2W fat suppressed axial images show swollen hyperintense bilateral lateral rectus muscle (black asterisk *) with involvement of the muscle insertion. Bilateral lacrimal glands are swollen. Hyperintense soft-tissue is seen involving upper lid of the right eye. (B) T1W coronal images show swollen lateral recti muscles appearing isointense and swelling of right superior rectus (White Asterisk *). Note is made of pansinusitis

Click here to view
Figure 14: (a) Retrobulbar cyst with microphthalmos left side: (a) Axial T1W magnetic resonance imaging shows a hypointense multiloculated retrobulbar cyst with microphthalmos. (b) Coronal T2W images, cyst
appears hyperintense with thin septum within causing fl attening of the posteromedial wall of the eyeball. The eyeball is displaced by this lesion. There is no communication between the globe and the cyst


Click here to view
Figure 15: Left Eyelid Arteriovenous malformation: (a) Coronal T1W magnetic resonance imaging shows a focal soft-tissue lesion in the left upper eyelid laterally (White asterisk *). It appears to be isointense with fat interspersed within it. (b) Axial T2W Fat suppressed images, it appears hyperintense. Multiple fl ow voids are visualized within it suggestive of vessels (white arrow). Posteriorly the lesion is seen to abut the left lacrimal gland, which is normal. These features are suggestive of a hemangioma or a low fl ow Arterio venous malformation (AVM)

Click here to view
Figure 16: Right enucleated socket follow-up: Axial TIW (a) and Coronal T2W magnetic resonance imaging (b) show that the right eyeball is not visualized; however, the extraocular muscles are seen and the right optic nerve appears atrophic. Enucleation without an implant was carried out following an advanced extraocular Retinoblastoma. The patient later underwent a dermis fat graft in the same socket

Click here to view
Figure 17: (A) Axial T1W image there is a large exophytic hypointense, tumour admixed with moderate amount of subretinal hemorrhage present in the right eyeball(white asterisk *). (B) Axial and Sagittal T2W
image the lesion appears hypointense with tumour invasion spreading along the right optic nerve(white arrow) with complete distortion of the perineural sheath(White arrow). Diagnosis: Right Retinoblastoma with optic nerve involvement


Click here to view
Figure 18: Axial and Coronal T1W images show a hypointense round silicone implant in the left orbit. It is surrounded by a crescent shaped hypointense region which is suggestive of the prosthesis. This was a case of Left advanced Retinoblastoma which underwent enucleation with an implant. Diagnosis: Left Orbital non integrated silicone implant with prosthesis (White*)

Click here to view
Figure 19: Axial T2 weighted MRI images of a patient presenting with left pulsatile proptosis after history of trauma show (a) enlarged flow void of the left cavernous sinus (arrow). (b) The dilated and tortuous left superior ophthalmic vein (*) is seen in the left orbit. Diagnosis: Left carotico-cavernous fistula.

Click here to view


A detailed discussion on the images is out of the scope of this article. Interested readers are advised to consult radiology books with an interest in orbital imaging for further understanding. A simple way to improve your skill will be, to study all the MRI films of the patient in concern. Note down your own findings in detail after studying the films. Thereafter, take out the report provided by the radiologists, review the full report including the conclusion. Compare your own noted findings with the radiologists report and mark the discrepancies between the two reports This will help to improve your own analytical skill and confidence. After a couple of months you will become an expert in reading the MRI of the orbit. The purpose of this write up is to initiate the interest toward the interpretation of orbital MRI amongst the ophthalmologists, and hope it serves the purpose.

 
  References Top

1.Nayak BK, Desai S, Maheshwari S. Interpretation of magnetic resonance imaging of orbit: Simplified for ophthalmologists (Part I). J Clin Ophthalmol Res 2013;1:29-35.  Back to cited text no. 1
    
2.Rootman J. Disease of Orbit: A Multidisciplinary Approach. Philadelphia: Lippincott Williams & Wilkins; 2003. p. 35-52.  Back to cited text no. 2
    
3.AJ, Kazi I, Felix R. Magnetic resonance imaging of orbital tumors. Eur Radiol 2006;16:2207-19.  Back to cited text no. 3
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19]



 

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  In this article
Abstract
Lesions of orbit
Inflammatory
Neoplastic
Structural
Vascular
Degeneration and...
Compartments of ...
Intraconal space
Extraocular eye ...
Extraconal space
Subperiosteal space
Lacrimal gland
Ocular
Preseptal space
Steps for Readin...
References
Article Figures

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