|Year : 2015 | Volume
| Issue : 2 | Page : 66-70
Computed tomographic evaluation of proptosis in a Southern Nigerian tertiary hospital
Ehimwenma Ogbeide1, Akhigbe Oriazo Theophilus2
1 Department of Radiology, University of Benin Teaching Hospital, Benin City, Edo State, Nigeria
2 Department of Radiology, Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria
|Date of Web Publication||14-Jul-2015|
Dr. Ehimwenma Ogbeide
Department of Radiology, University of Benin Teaching Hospital, Benin City, Edo State
Objective: To describe the pattern of computed tomographic findings in patients presenting with proptosis at our institution. Methods: A retrospective review of patients with proptosis who were referred to the Radiology Department for cranial Computed Tomography (CT) scan at the University of Benin Teaching Hospital, Benin City, Nigeria from January 2010 to September 2013 was undertaken. SPSS version 16 software was used for data analysis. Results: The request forms, CT images and reports of 33 patients which comprised 15 males and 18 females were reviewed. The mean age of the patients was 28.83 ± 17.43 years (age range 2 to 63 years). The disease presentation was unilateral in 29 patients and bilateral in 4 patients. Computed Tomographic diagnosis of tumor in 27 patients was the commonest finding. Conclusion: Computed tomography is a valuable tool in the management of patients with proptosis providing useful information regarding possible etiology and extent of causative lesion.
Keywords: Computed tomography, orbit, proptosis, tumor
|How to cite this article:|
Ogbeide E, Theophilus AO. Computed tomographic evaluation of proptosis in a Southern Nigerian tertiary hospital. Sahel Med J 2015;18:66-70
| Introduction|| |
Proptosis refers to forward protrusion of the eye globe. It may be unilateral or bilateral, acquired or congenital. Proptosis is always significant and may indicate orbital or systemic disease.  There are many causes of proptosis, which can be broadly classified as infective, inflammatory, tumors, vascular anomalies and bony abnormalities.  The lesions may originate primarily in the orbit or secondarily extend into the orbit from adjacent structures such as the paranasal sinuses or nasal cavity. The condition presents a diagnostic challenge requiring deliberate and thoughtful investigation.  Clinical findings may provide clues to possible etiology with radiological imaging playing a pivotal role in arriving at a diagnosis and histology providing the definitive diagnosis in relevant cases.
Cross-sectional imaging with computed tomography (CT) and magnetic resonance imaging (MRI) is of value in imaging the orbits and its contents. MRI has many advantages, including high soft tissue contrast and multiplanar imaging capability, but major drawbacks of this technology are poor bone imaging, comparatively high cost, longer image acquisition times and less availability. CT scanning has revolutionized evaluation and surgery of orbital and periorbital pathology. In the orbits, structures with varied attenuation coefficients within a confined space make CT very useful.  Although MRI is gaining more acceptance overall, the use of CT is preferred over MRI in certain cases such as detection of calcification as in suspected retinoblastoma.  Bony lesions causing proptosis are also better evaluated by CT and thus lesions arising from the orbital walls or extending into it can be interrogated to good effect with CT. The extraocular muscles are also well demonstrated as they are surrounded by the low-density fat. On CT axial scans taken at the level of the eye lens the anterior part of the globe should normally not exceed a distance of 21 mm anterior to the interzygomatic line. The difference between the two sides should not exceed 2 mm.
The purpose of this study is to evaluate retrospective data on CT findings in patients presenting with proptosis at the University of Benin Teaching Hospital (UBTH), Benin City, Nigeria.
| Materials and Methods|| |
A retrospective review of 33 patients aged 2-63 years with proptosis who presented for CT scan from January 2010 to September 2013 was undertaken. The study setting was the Radiology Department of the UBTH a tertiary health facility which serves as a referral center. Most of the patients were referred from the Departments of Ophthalmology and Ear, Nose and Throat Surgery of the hospital. Data reviewed were from the request forms, CT reports and CT films of the patients and included age, sex, indication for the CT scan and the CT findings. The CT machine used for the scans was either a Siemens 1998 Somatom ART or a General Electric Bright Speed 2007 machine. A lateral scanogram was obtained and in the majority of the patients; slice thicknesses of 5 mm was used while in other patients slice thickness of 3 mm or 2.5 mm was employed. In all patients, standard cranial CT protocol was utilized with gantry angulation of not <10° for any given patient. The patients were scanned in the supine position prior to and after intravenous injection of contrast medium that was either 60 ml of 76% urograffin or 50 ml of iopamidol. Where necessary coronal slices were obtained with the patient in the prone position. The images were evaluated on soft tissue and bone window settings. The data were analyzed using SPSS version 16.0. Chicago, SPSS Inc software program.
| Results|| |
Thirty-three patients were included in the study that comprised 15 males and 18 females (male to female ratio 1-1.2) as shown in [Figure 1]. The mean age of the patients was 28.83 ± 17.43 years with age range 2-63 years [Table 1]. Patients below the age of 30 formed 51.5% of the study population. As shown in [Table 2], the presentation of the disease was unilateral in 29 patients (87.9%) and bilateral in 4 patients (12.1%). The most common side affected was the right in 17 (51.5%) of all patients while the left side was affected in 12 (36.4%) of the patients [Table 2].
The various lesions causing proptosis are shown in [Table 3]. CT finding of tumor was the commonest abnormality in 27 (81.8%) patients. The other causes included trauma in 4 patients (12.1%), infective and inflammatory conditions in 3.0% of patients each. Of the 27 cases that had tumors, the females were more commonly affected comprising 17 cases. The four cases of bilateral proptosis were caused by tumors with three occurring in adults and one in a child. The tumors were further classified into those that were primarily intraorbital and those that secondarily extended into the orbit from adjacent structures such as the paranasal sinuses and the nose. [Figure 2] and [Figure 3] show the axial pre and postcontrast CT images respectively of a patient with right sided proptosis due to a primarily intraorbital tumor. [Figure 4] shows the unenhanced coronal CT scan of a patient with sinonasal tumor extending into the orbit. The primarily extraorbital tumors were more in number comprising 70.4% of all tumors while primarily intraorbital masses were found in 29.6% of cases. The 23 cases that had unilateral tumors were right sided in 13 patients (56.5%) and left-sided in 10 patients (44.5%).
|Figure 2: Unenhanced axial computed tomography scan showing intraorbital mass with right proptosis. The mass appears homogenous and there is evidence of bony destruction|
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|Figure 3: Post contrast axial computed tomography scan showing non homogenous enhancement of the right intraorbital mass|
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|Figure 4: Unenhanced coronal computed tomography scan showing sinonasal tumor with extension into the orbit. The affected globe is not visualized due to marked proptosis|
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Overall, females were more commonly affected (54.5%) than their male counterparts (45.5%) as shown in [Table 4] although this relationship was not statistically significant. As shown in [Table 4] there was 1 case of inflammation and 1 infective cause of proptosis, both males. 3 of the 4 cases of trauma leading to proptosis were males (75%) [Table 4].
| Discussion|| |
The most common cause of proptosis in our present study was tumor in 81.8% of patients. Several authors have documented tumors as a common cause of proptosis. ,, Sabharwal et al., reported tumors (46%) to be the most common lesions causing proptosis in their study.  Similarly, Masud et al., reported neoplasms (33%) as the most common cause of proptosis in both pediatric and adult age groups.  Sharma et al., found inflammation the commonest cause of proptosis, in 47% followed by tumor in 37% which the authors opined could be due the small sample size in their study or the referral of tumor patients to the cancer hospital.  The patients with tumors were however much more in our study and majority (70.4%) of all tumors were from adjacent structures with secondary involvement of the orbit as compared to the primarily intraorbital neoplasms which constituted 29.6%. Komolafe et al., in a study of the pattern and indications for ophthalmic referrals of patients with otorhinolaryngology problems found that 53.8% of the consults were sent on account of proptosis and sinonasal tumors were the cause in 46.2% of the patients.  In this study, sinonasal tumors were responsible for the majority of the paraorbital lesions. CT findings revealed the location of the lesions with demonstration of extensions into the orbit and in some cases intracranially. In addition, CT evidence of bony destruction and contrast enhancement pattern as demonstrated in some of our patients may be of value in distinguishing malignant from benign sinonasal tumors. Some authors advocate the judicious use of CT scans in all cases and MRI in selected cases of sinonasal tumors for better tumor-free resections and improved survival.  However, CT combined with MRI may offer greater accuracy in evaluating the status of the bony structures. 
Orbital tumors usually present with gradual proptosis although rhabdomyosarcoma is well known to present acutely, mimicking orbital cellulitis.  Boparai and Dash reported orbital rhabdomyosarcomas in 9.4% of 148 cases of unilateral proptosis of neoplastic origin.  In 2 patients in this study a male and a female both 10 years of age, the primary consideration was rhabdomyosarcoma with the periorbital one presenting with bilateral proptosis and the other presenting with left sided proptosis. Orbital rhabdomyosarcoma is a highly malignant lesion of childhood that presents as rapidly progressive proptosis. The orbit is the commonest site of head and neck rhabdomyosarcoma and on CT scanning they are isodense or hyperdense with uniform contrast enhancement, distortion of the globe and in about half of cases show bone destruction. 
Optic nerve glioma was the primary consideration in two patients in this study, with one of them showing destruction of the adjacent bone [Figure 2] and [Figure 3]. Optic nerve glioma, an uncommon tumor typically presents in childhood although the two cases in our series were adults. There is enlargement of the optic nerve which may be uniform and diffuse or fusiform. On CT, the mass is commonly of homogenous density with mild uniform enhancement. The adult variety is rare, is usually of the higher grade and extends from a primary lesion involving the optic chiasm.
Metastases are mostly extraconal with encroachment of the intraconal compartment and associated bone destruction. They may be isodense or hyperdense with evidence of enhancement following contrast administration. Pseudotumor is the most common cause of intraorbital mass lesions in adulthood. On CT, it may appear as subtle hyperdensity of intra-orbital fat, and attenuation changes on two-phase helical CT and delayed coronal CT may be helpful in differentiating between orbital lymphoma and pseudotumor.
In the present study, there was a history of trauma in 4 patients (3 males and 1 female) with resulting proptosis that was corroborated by the CT findings. The percentage of trauma related proptosis in our study was 12.1% and this was higher than that of Sharma et al.,  a retrospective review of 30 patients in which trauma was the causative factor in one patient. Considerable orbital injury usually occurs before proptosis results and in 2 of 3 cases in this study, road traffic accidents were the mechanism of injury and in one of the patients there were multiple facial fractures and traumatic laceration of the globe. In the other patient, there was mild proptosis with fracture of the skull base.
Sharma et al., found meningioma as a cause of proptosis in 6.7% of cases.  In 1 patient, a 21-year-old female that presented with left sided proptosis, meningioma was the primary differential and the lesion appeared as a an avidly enhancing, predominantly left-sided hyperdense mass in the skull base with extension into the orbits worse on the left side.
Bony lesions in our present study were found in 2 cases (6.1%), one involved the sphenoid bone and the other right orbital roof.
In 1 patient in this study, the CT impression was sinonasal infection although culture result was available. Onyekonwu and Chika-Okosa recognized the need for ophthalmologists to rule out sino-orbital aspergillosis in every patient presenting to them with proptosis in this era of HIV/AIDS pandemic. 
Several studies have reported high accuracy of CT in the evaluation of proptosis. ,, Sabharwal et al., had diagnostic accuracy of 82%. Sharma et al., obtained a value of 86.6% while Mahsud and Bano in their study of a pediatric population had 80% diagnostic accuracy. To the best of our knowledge, this is the first study considering CT findings in patients with proptosis in this environment. Unfortunately, further characterization of the lesions in our study was not possible as histology was unavailable in most patients. The number of patients in our study is relatively few considering the number of years under review. Some patients were excluded due to incomplete data, while others may have been referred for CT scans but due to financial constraints could not undergo the procedure. Our report is thus based on a limited experience, and it is our recommendation that future studies on a larger number of patients, within addition histologic correlation be undertaken in this environment.
| Conclusion|| |
Computerized tomography is an established, important tool in the management of proptosis as it serves to evaluate the extent and possible etiology of the condition.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]