|Year : 1983 | Volume
| Issue : 4 | Page : 347-352
Impact of computrised axial tomography on orbital diagnosis
Sushma Vashisht, RK Goulatia, Y Dayal, Sneh Bhargava
Dr. Rajendra Prasad Ophthalmic Sciences & Department Of Radiology, All India Institute of Medical Sciences, New Delhi, India
Section of Radiology, Dr. Rajendra Prasad Centre for Ophthalmic Science All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Vashisht S, Goulatia R K, Dayal Y, Bhargava S. Impact of computrised axial tomography on orbital diagnosis. Indian J Ophthalmol 1983;31:347-52
|How to cite this URL:|
Vashisht S, Goulatia R K, Dayal Y, Bhargava S. Impact of computrised axial tomography on orbital diagnosis. Indian J Ophthalmol [serial online] 1983 [cited 2020 Jul 4];31:347-52. Available from: http://www.ijo.in/text.asp?1983/31/4/347/27551
CT is approximately 86% to 91 accurate in detecting orbital lesions and therefore is one of the most effective detection systems utilised to day in radiology. It is highly useful not only in permitting localisation but often yielding definite information about its nature. It has replaced orbitography, to some extent orbital venography and to a great extent arteriography. Retrobulbar fat being of low density provides good contrast to accentuate the relatively higher density of the muscle cone, optic nerve and most of the orbital pathological lesions which are always of high attenuation.
This paper aims at firstly to document the impact of CT in localising and determining the extent of an intra-orbital mass lesion and to predict its nature. Secondly it aims to differentiate the medical versus the surgical causes of exophthalmos i.e. psuedo-tumour & grave's disease from space occupying surgical lesions.
| MATERIAL & METHODS|| |
Orbital CT scans of 100 patients with clinically suspected orbital mass lesions were analysed. Scans were obtained parallel to Reid's base line with EMI head scanner CT 1010 using the 160 x 160 matrix and a 10 m.m. collimation. Examination was performed in the majority of patients without contrast medium, in a few cases contrast was used and enhanced scans obtained. Serial orbital scans were obtained in some patients wherever indicated. The different lesions encountered are summarised in [Table - 1][Table - 2].
| Observations and discussion|| |
Lesions of the orbit are divided into intraconal or extraconal ones. Many lesions however will occupy both the intra & extra conal compartments, therefore this classification should be considered flexible.
| Intraconal lesions|| |
These include primary lesions arising from the globe, optic nerve and from the structures adjacent to the optic nerve.
| Retinoblastomma|| |
CT reveals the exact size of the intra-occulat lesion & extent of spread in the retrobulbar space, the optic nerve, the optic chiasma, to the other eye ball and intracranially. Calcification is also documented in more cases on CT as compared to plain x-rays. In the 30 cases under review 15 were pre-operative & 15 post operative cases.
Pre-operative-Cases :-The effected eyeball was larger then its counterpart in 7 cases [Figure - 1], a retrobulbar mass was recorded in 4 cases, one of which revealed an extension of growth upto the supraseller region. Multiple increased attenuating lesions in the brain parenchyma suggestive of secondary deposits were seen in another case of retinoblastoma. CT scan revealed calcification [Figure - 1] in double the no. of cases (12 cases) as compared to plain x-rays (6 cases). In 4 cases of this lesion eye-balls were of normal size.
Post-Operative-Cases In 15 cases CT scan was done post operatively i.e. after enucleation of the eye to exclude any recurrences. The scan revealed a retrobulbar mass in 4 cases and optic nerve thickening in one case.
Neoplasms of Optic Nerve : (7 cases)
These include gliomas & meningiomas. These tumours cause thickening, enlargment and/or irregularity of the optic nerve. CT provided the best radiographic means of demonstrating orbital portion of the nerve. Of the 7 cases seen, smooth thickening of the optic nerve was seen in 6 cases [Figure - 2] & in I case irregular thickening was seen.
In one case of meningioma of optic nerve (O.N) sheath, smooth thickening of the nerve was seen which was indistinguishable from optic nerve glioma.
Haemangioma :- (4 cases)
All 4 cases of haemangioma in this series in unehanced scan were seen as sharply outlined, round, uniformly , high attenuating lesions inside the muscle cone [Figure - 3].
Haeniangiopericytonuz :- (3 cases)
May arise inside or outside the muscle cone. Out of 3 cases I was intraconal & 2 extraconal. The case with intraconal lesion demonstrated mass in the intraconal retrobulbar region with no characteristic features. Two cases of extraconal lesions demonstrated mass lesion involving whole of the orbit with areas of calification and ossification seen in one case.
Pseudo-Tumour :- (12 cases)
Althouoh CT findings varied in these patients but were distinct from those observed in Grave's Ophthalmopathy. In psuedotumour the changes are characterised by abnormal soft tissue densities within the orbit varying considerably in size, shape and location. These abnormal densities may be attached to the globe posteriorly to extraocular muscles or to the optic nerve. They may be multifocal & involve several orbital structures separated by normal appearing fat or may present an irregular mass lesions obliterating the retro-bulbar fat.
Grave's Disease : (4 cases)
The most common CT finding in Grave's disease are proptosis, muscle swelling, thickening of optic nerve & anterior prolapse of the septum. The changes vary depending upon the degree & severity of the disease. [Figure - 5]
Extraconal Lesions of the Orbit
May arise extraorbitally from structures adjacent to the orbits e.g. paranasal sinuses & nasopharynx and invade the orbit secondarily or they may arise within the extraconal compartment but still within the orbital cavity.
Lacrinal Gland Tumour :-(4 cases)
These are recognised by their characteristic location in the upper & outer quadrant of the orbit. They are isodense with the orbital muscles.
(2 cases) :
| Dermoid cyst|| |
Because of their fat content it is considered that they appear as low attenuating lesions on CT & may not be visualised owing to lack of effective contrast. But dermoids have also been recorded as round smoothly contoured high density lesions. Characteristic defect in the bone could clinch the diagnosis pre-operatively.
Meningioma (3 cases)
Orbital meningioma can be divided in 2 categories.
I. Intraorbital from the sheath of the optic nerve. (already discussed).
2. Extension of intracranial meningioma from the sphenoid, olfactory groove or tuberculum sella.
Of the two cases of meningiomas extending into the orbit thickening & sclerosis of greater wing of sphenoid with a high attenuating orbital mase was seen in one [Figure - 6] & recurrence of intra-orbital & intra cranial high attenuating mass was seen in the 2nd case.
Fibrous Dysplasia :
In all 3 cases expansion of the bone which extended to occupy the whole of the orbit was seen. In one case areas of increased attenuation alternating with areas of decreased attenuation representing bone & fibrous tissue were seen. None of the three cases showed any soft tissue component. Being an exclusively osseous lesion CT does not give any additional information compared to plain x-rays but depicts the extension of osseous lesion in the axial projection in an overlap free manner not possible by conventional radiography.
Plexiform Neurofibromatosis :- (3 cases)
May occur inside or outside the muscle cone usually associated with anomalies of orbital wall such as dysplasia of greater wing of sphenoid & raised lesser wing of sphenoid. Enlargment of the optic canal may ocour with or without the presence cf a glioma of optic nerve.
Rhabdomyosarcoma : (4 cases)
Is the most common orbital malignancy in children, the patients present with rapidly progressive exophthalmos. In ail cases the tumour mass was present outside & inside the muscle cone, it was isodense with orbital muscles.
Lymphoma : (3 cases)
As there in lack of Lymphoid tissue behind the anterior orbital septum, Lymphomas are seen to arise in front of the orbital septum and outside the muscle cone. All 3 cases showed a mass extending from anteromedial compartment to retro-bulbar region displacing the eyeball laterally & outwards. The mass is elongated & isodense with the orbital muscles.
Neuroblastorna & Lukaemia :- (3 cases)
In children neuroblastoma and Leukaemia are the most frequent causes of secondery deposists in the orbit. In 1 case of neuroblastonia CT depicted bilateral orbital mass lesions & in Leukaemia irreguler shaped masses were seen but there were no distinctive features.
Orbital Metastasis : -
Metastatic deposists to orbit were seen in the retrobulbar soft tissues both in the extraconal & intraconal spaces in a patient of bronchogenic carcinoma of Squamous cell type. Similar multiple high attenuating lesions were also seen intracranially consistent with metastatic disease.
| Masses of Paranasal Sinuses & Nasopharyngeal Lesions invading orbit|| |
These masses penetrate the orbit and produce proptosis of the eye-ball. In this series one case of mucocele of ethmoid sinus extended into the orbit and the maxillary sinus. CT revealed a round sharply outlined isodense mass occupying the ethmoid, maxillary sinuses & medial part of the orbit [Figure - 7]. In other 2 cases of carcinoma of ethmoid sinus and one case of nasopharyngeal carcinoma extension of mass from ethmoid & nasopharynx respectively was seen into the orbit.
Aneurysm of infraclinoid part of internal carotid artery
Angiography is the best way to visualise intracranial aneurysms. An aneurysm of the internal carotid artery was seen as an area of increased attenuation in the paraseller region. Carotid angiography demonstrated a big aneurysm of infraclinoid part of internal carotid artery.
Caroto-cavernous fistula with retrograde filling of both Ophthalmic Veins was seen on carotid angiography. On CT, dilated & tortous Superior Ophthalmic Vein was seen.
In one case on CT poorly defined structure was seen adjacent to the eyeball. On carotid angiography faint visualisation of arteriovenous malformation in the orbit & multiple supratentorial A.V. malformations were seen. Orbital phlebography demonstrated abnormal venous channels throughout the orbit. In another case of A.V. malformation in the orbit and over the face, CT was normal. On angiography A.V. malformation could be demonstrated. The necessary detail to outline feeding arteries & draining veins is best achieved by angiography.
| Summary|| |
This analysis of 100 cases of orbital lesions shows that the presence the shape and the location of a mass lesion as depicted by CT can make a correct pre-operative diagnosis in majority of cases. Vascular lesions like haemengiomas are high attenuating while most others are isodense with the muscle cone. Pseudo-tumours can be correctly assessed if followad serially. Similarly in cases of endocrine exophthalmos where other investigations were not informative correct diagnosis could be made by CT. In cases of retinoblastoma recurrence of tumour & its extension could be delineated accurately. This is of great value for the management of a case. Similarly for diagnosis & follow up of cases of O.N. glioma and for the demonstration of intracranial spread CT is the investigation of choice.
| References|| |
Llyod. G.A.S., Ambrose. J.A.E., An evaluation of CAT in the diagnosis of orbital tumours, Escat seminar, London.
Moseley, I.F., Bull, J.W.D., Computrised axial tomography, carotid angiography and orbital phlehography in the diagnosis of space occupying lesions of the orbit., 1975, Advances in cerebral angiography, ed. G. Salmon, Berlin, Heidelberg, New York, 361.
Enzmann, D., Donaldson, S.S., CT in orbital pseudo, umour, 1976, Radiology, 120: 597.
Hilal, S.K., Trokel, S.L., CT of the orbit using thin sections., 1977, seminars in reentgenology, 12 : 137.
Enzmann, D„ Mashalls, W.H., Rosenthali., A.R., Kriss. J.P : Computed tomography in graves ophthalmopathy., 1976, Radiology, 118 : 615
Weisberg, L.A., Nice, C., Katz, M.. 1978 cerebral computed tomography, a text atlas. W.B. Saunders Co. Philadelphi London Toronto. 02. 3
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7]
[Table - 1], [Table - 2]