PATHOGENESIS OF UNILATERAL PROPTOSIS

A C T A O P H T H A L M O L O G I C A V O L . 5 5 1 9 7 7

Department of Neurological Surgery {Heads: W. M . Nichols and R. J . A . Fraser),

Aberdeen Royal Infirmary, Aberdeen, Scotland

PATHOGENESIS OF UNILATERAL PROPTOSIS

BY

A. R. CHOUDHURY

A series of 34 patients presenting with unilateral proptosis has been studied in order to evaluate the mechanism of proptosis. It is observed that symmetrical (axial) proptosis is usually the result of generalised increase in intraorbital contents and occurs in thyroid disease and with intracranial lesions lying remote from the orbit. Rarely, in myasthenia gravis, it may be caused by myogenic paralysis of the extraocular muscles. Asymmetrical proptosis is the result of localised increase in intraorbital contents, and this occurs with expanding lesions of the orbit and in lesions arising from neighbouring structures and enroaching the orbit.

Key words: unilateral proptosis - exophthalmos - space occupation - venous stasis - extraocular muscle weakness - pathogenesis.

When an eye is proptosed the direction of proptosis may be directly forward and this is called symmetrical (axial) proptosis, or it may deviate up or down, o r to either side, and this is called asymmetrical proptosis. This condition has long been recognised as a manifestation of various underlying conditions, the frequency of which has varied according to the interest of the authors and has been described by O’Brien & Leinfelder (1954), Dixon (1941), Drecher & Bene- dict (1950), Van Buren et al. (1957), Bullock & Reeves (1959), Schultz et al. (1961), Pohjola (1964), Zakharia et al. (1972), Choudhury (1973) and many others.

~~

Received November 3, 1976.

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A . R. Choudhury

The investigation and management of patients with unilateral proptosis are mainly the responsibility of the ophthalmic surgeon but commonly require the close co-operation of various other specialties. Neurosurgeons are involved in the treatment of those lesions which spread from, or are liable to spread into the cranial cavity. Surgical exploration of the orbit for tumour may call for simultaneous exploration of the anterior or middle cranial fossae. Not infre- quently the causative lesion lies intracranially in a site remote from the orbit and in such a situation intracranial exploration is necessary.

Despite the presence of extensive literature on th eaetiology and pathology of this condition, there are relatively few references as regards its pathogenesis. For this reason a careful review of 34 consecutive cases of unilateral proptosis has been undertaken in order to establish the pathogenesis.

Clinical Material and Methods

From April, 1971 to July, 1973, 34 patients with unilateral proptosis were studied in the Department of Neurosurgery at the Aberdeen Royal Infirmary. Careful history taking, thorough general medical and detail ophthalmological examinations of the patients, and correlation with the findings of routine and special investigations, operative findings and autopsy findings in fatal cases, form the basis of this study, the object of which is to evaluate the pathogenesis of unilateral proptosis. For this reason only cases with an exophthalmometric reading in excess of 2 mm were included, the non-effected eye having been considered normal. All measurements were made by the Hertel Exophthalmo- meter. Cases with bilateral involvement, even if they manifested such an exophthalmometric difference, were not considered. The ophthalmological examinations comprise inspection of the eyes, palpation including resistance of the globes to pressure, movements of the extraocular muscles, measurements of the proptosis and intraocular tension, and fundoscopy. Forced-duction test was not done. Photographs of the eye, haematological examination including full blood count, ESR, WR and serum calcium, Mantoux test and plain radiographs of the orbit, skull, paranasal sinuses and chest, were the routine investigations. Photographs, including postoperative ones, were essential to form a base line and for future reference. Plain radiographs were the most valuable investigations in diagnosing the nasal lesions and were helpful in others. Other special investigations were selected on the merit of the individual case, and thyroid function studies were done in suspected cases of endocrine proptosis. Carotid angiography was the most commonly performed and useful investigation in most cases other than traumatic orbital lesion and endocrine proptosis. Orbital

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Unilateral Proptosis

venography was done in orbital lesions and orbital pneumography in lesions suspected of arising from optic nerve and at times for extraconal lesions. Brain scan was done for intracranial lesions and myodil ventriculography in cerebellar lesions. Histopathological examinations of the tissue removed at operation and autopsy findings in fatal cases, established the final diagnosis in neoplastic lesions. Ultrasonography of the orbits and computerized axial tonography of the orbits or brain were not done. B-scan ultrasonography is available in spe- cialised eye hospitals only. It is invaluable in the investigation of orbital soft tissue masses, their detection and differentiation. EM1 scanning is now available in larger neurosurgical centres. I t has proved promising in the investigation of intracranial and orbital disease. It compliments the existing non-inva- sive procedures and orbital venography in the investigation of orbital disease

Table I. Analysis of 34 cases of unilateral proptosis studied.

Site of lesion No. of cases Type of lesion

Orbital

Nasal

Orbito-cranial

Cranial

9 Metastatic tumour (4) Retrobulbar haematoma associated with fracture of roof of orbit (3) Optic nerve glioma (1) Ocular myasthenia (1)

4

12

6

Empyema of ethmoid (1) Nasopharyngeal carcinoma (1) Carcinoma of maxillary antrum (1) Sarcoma of maxilla (1)

Carotid-cavernous fistula (4) Intracavernous carotid aneurysm (3) Posterior communicating aneurysm (I) Cavernous sinus thrombosis (1) Pituitary adenoma (1) Sarcoma of pituitary fossa (1) Sphenoidal ridge meningioma (1)

Subarachnoid haemorrhage (4) Subdural haematoma (1 ) Medulloblastoma (1)

Endocrine 3 Thyroid disease (3)

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(Wright et al. 1975). Wider availability and use of EM1 scanning may eli- minate the need for orbital pneumography and pneumo-encephalography which are not only unpleasant but also not without risks.

Analysis of the Series

The patients were divided into categories according to the site of the lesions. Table I shows the groups and the type of lesion in each group. Sites of the lesions for a table of this sort are defined essentially on the basis of causation of proptosis and are arranged as follows: (1) orbital - those lesions that arise from the structures in the orbit including its bony walls, Neoplastic lesions may arise primarily in the orbit or may extend into the orbit either by invasion from the surrounding structures or as a metastatic deposit. Trauma to the orbit can produce retrobulbar haematoma which may or may not be associated with fracture of the roof of the orbit. Myogenic paralysis of the external ocular muscles of the eyeball also falls into this group. (2) nasal - these lesions

Fig. 1. Schematic drawing of six sagittal sections of orbit showing variation in the degree and direction of proptosis in lower sections in comparison to the normal upper sections. Lower sections (A) showing mild degree of proptosis and displacement of the eyeball directly forwards by generalised increase in intra-orbital contents and diffuse space occupation; (B) showing mild degree of proptosis and the displacement of the eyeball downwards by an anteriorly placed localised space occupying lesion; and (C) showing marked degree of proptosis and displacement of the eyeball downwards by a posteriorly

placed localised space occupying lesion.

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Fig. 2 . Left sided proptosis due an empyema of the left ethmoid. (A) photograph of the eyes, showing displacement of the left eyeball temporally; (B) tomogram of the paranasal sinuses, showing lesion extending from the left ethmoid into the orbit and encroaching on the left nasal cavity and left frontal sinus; (C) A. P. view of the orbital venogram, showing displacement upwards and outwards of the first and second segments of the venous parallelogram on the left: and (D) orbital pneumogram, showing outward dis-

placement of the eyeball, by expansion of the left ethmoid into the orbit.

comprise those of the nasal cavity, nasopharynx and the paranasal sinuses. (3) orbito-cranial - those lesions that arise in or about the cavernous sinus and sphenoidal ridge. (4) cranial - those intracranial lesions that a re remote from the orbit. ( 5 ) endocrine - this is grouped separately because the proptosis here is the localised manifestation of a generalised disorder.

There were three patients in this group, all due to thyroid diseases. They were referred to us for excluding other underlying pathology because their thyroid function tests were normal.

24 1 Acta ophthal. 53, 2 16

A. R. Choudhury

Discussion

Proptosis is the forward displacement of the eyeball in relation to the skull. It may occur due to space occupation in the orbit from lesions arising in the orbit or lesions encroaching from the neighbouring structures. Such space occupation may result from a localised or from a generalised expanding lesion. Secondary venous stasis in the orbit may produce oedema and congestion of the orbital tissues which may displace the eyeball forward. Lastly, instability of the eyeball may occur from weakness of the external ocular muscles and this may lead to proptosis.

Space occupation

A localised expanding lesion in the orbit may arise from its walls, from the intraobital contents or as an invasion from the neighbouring structures. The effect of such a lesion will depend upon its site and size. An anteriorly placed lesion (Fig. 1 B) displaces the eyeball up or down or to either side, and produces a mild to moderate degree of proptosis. Fig. 2 illustrates such a case

Fig. 3. Left sided proptosis due to a left sphenoidal ridge meningioma. (A) photograph on the eyes, showing displacement of the left eyeball temporally and downwards. (B) photograph of the eyes, showing marked ptosis on the left side; and (C) plain radiograph of the orbit, showing increased bone density of the sphenoidal bone on the left side

and widening of the left superor orbital fissure.

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Fig . 4. A. P. views of orbital venograms. (A) early phase, showing displacement of the superior ophthalmic vein medially and upwards in the left orbit, and (B) late phase of the venogram, showing delayed emptying of the superior ophthalmic vein on the left compared to the right, indicating obstruction of the posterior venous drainage of the orbit due to sphenoidal ridge meningioma. (C) A. P. view of the left carotid angiogram, showing upward and inward displacement of the middle cerebral group of arteries, and (D) lateral view, showing upward displacement of the middle cerebral group and enlargement of the ophthalmic artery, indicating a sphenoidal ridge

meningioma with its extension into the orbit.

caused by an empyema of the left ethmoid extending into the orbit. It produced a left-sided proptosis of 1 1 mm and displacement of the eyeball temporally (Fig. 2 A). Fig. 2 B, C and D show the expansion of the ethmoid.

A posteriorly placed orbital lesion (Fig. 1 C) also displaces the eyeball away from its axis and produces a greater degree of proptosis. This is due to contributory additional factors such as venous stasis in the orbit and extraocular muscle weakness due to pressure on the 3rd, 4th and 6th cranial nerves at the superior orbital fissure. Figs. 3 and 4 illustrate such a case caused by an orbito- cranial meningioma arising from the left sphenoidal ridge. It produced a left- sided proptosis of 15 mm and displacement of the eyeball temporally and

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A . R. Choudhury

downwards (Fig. 3 A), and marked ptosis (Fig. 3 B). Figs. 3 C and 4 A, B, C, D show the presence of a left-sided orbito-cranial mass lesion.

Intraconal expanding lesions lying immediately behind the eyeball have been reported to cause symmetrical proptosis (Dixon 1941 ; Wright 1970). In our experience, these lesions displace the eyeball either vertically or horizon- tally because of their origin from one or the other side of the optic nerve. Fig. 5 illustrates such a case caused by a right intraorbital optic nerve glioma. It produced a right-sided proptosis of 5 mm and showed displacement of the eyeball temporally (Fig. 5 A).

Fig. 5 B shows the retrobulbar mass lesion and Fig. 5 C confirms the diagnosis.

Diffuse space occupation may occur in the orbits in thyroid disease, and this is the commonest cause of both unilateral and bilateral proptosis (Smith 1967; Wright 1970). Here the globe is displaced directly forward (Fig. 1 A) because of the generalised deposition of hydrophilic mucopolysaccharide throughout the orbital tissue, hence the proptosis is often symmetrical. The unilateral nature of the proptosis depends upon the relative increase in intraorbital content in one or the other orbit. A highly selected group of these cases are referred for

Fig. 5. Right sided proptosis due to right intraorbital optic nerve glioma. (A) photograph of the eyes, showing displacement of the right eyeball temporally; (B) orbital pneumogram, showing the dumbell shaped enlargement of the optic nerve, and (C) photo-

micrograph, showing a well differentiated fibrillary astrocytoma.

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Unilateral Prohtosis

Fig. 6. Left carotid angiogram, A. P. view, showing a large subdural haematoma with displacement of the anterior cerebral artery to the right side and calcification in the falx

cerebri in the midline.

special investigation in order to exclude any underlying localised space occupying lesion. These cases comprise those who are clinically euthyroid and in whom thyroid function tests are either normal or non-contributory. Three such cases were encountered in the present series. In them, the diagnosis was established because of the symmetrical nature of the proptosis ,absence of difference in exophthalmometric readings taken in sitting and supine positions - Hauer’s sign - and a normal orbital venogram.

Venous stasis

Unilateral proptosis, when it is caused by venous stasis alone, is the result of relative increase in intraorbital contents and is found in intracranial lesions lying remote from the orbit. Such lesions may cause intracranial hypertension which, in turn, produce increased intracranial venous pressure. This is trans- mitted from the cranial cavity to the orbital veins, resulting in orbital venous

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A . R. Choudhury

stasis; consequent venous congestion and oedema of the orbital tissue produce an increase in orbital contents and proptosis. The unilateral nature of the proptosis is very dependent upon the pattern of the venous drainage from the cavernous sinus, which forms the final common pathway for antegrade and retrograde venous flow from and to the orbit respectively. The venous system is remarkably variable. The cavernous sinue may fail to develop on one side or the other (Hamby 1966) or the venous drainage of one sinus may predominant- ly be into the other side (Pool & Potts 1965). The side of dominance of venous drainage from the cavernous sinus probably determines the side of the proptosis, but proptosis tends to be symmetrical in this type of case (Fig. I A).

Davidoff & Dyke (1938) and Pfeiffer (1943) described cases of unilateral exophthalmos from relapsing, juvenile, chronic subdural haematomas. The proptosis was due to deformity of the lateral orbital wall, with its convexity inwards and thus compromising the orbit. Gardner (1948) described a case of unilateral exophthalmos which was due to raised intracranial pressure occur- ring in a haemangiomatous cyst of the cerebellum; in this case the exophthalmos was caused by an encephalocele in the orbit through its roof which had been absorbed following a previous fracture.

F i g . 7. Right sided proptosis due to right carotid cavernous fistula. (A) photograph of the eyes, showing congested and oedematous eyelids and complete ptosis. (B) lateral view and (C) A.P. view of right carotid angiogram, showing the early filling of the

cavernous sinus and distended ophthalmic veins.

, 246


Fig. 8. Right sided proptosis due to an unruptured right posterior communicating aneurysm. (A) photograph of the eyes, showing mild degree of right sided proptosis. (B) photograph of the eyes, showing complete ptosis on the right side. (C) lateral view, and (D) A. P. view of right carotid angiogram, showing the posterior communicating

aneurysm. It also shows an internal carotid bifurcation aneurysm.

Two such cases were encountered in the present series. Chronic subdural haematoma in one and a cerebellar tumour in the other were the causes of unilateral proptosis. There was no mechanical defect in the walls of the orbit. Venous stasis in the orbit consequent to raised intracranial pressure was presumably the factor responsible for the causation of proptosis. Fig. 6 shows a left chronic subdural haematoma which caused a symmetrical proptosis of 7 mm on the left side.

Proptosis of sudden onset may occur in acute intracranial hypertension as a result of orbital venous stasis (Duke-Elder & Scott 1971; Choudhury 1975). As a rule the proptosis is bilateral in this condition. During this study four of the 88 cases of spontaneous subarachnoid haemorrhage had unilateral proptosis. Association of haemorrhage into the extraocular orbital tissues and optic nerve sheath has been reported in such cases (Walsh & Hedges 1951; Muller & Deck 1974) and may be a contributory factor.

Venous stasis, unassociated with intracranial hypertension is the dominant

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A . R. Chouclhury

factor in the genesis of proptosis in lesions situated medially in the orbito- cranial junction. In these conditions, neurogenic weakness of the extraocular muscles acts as a contributory factor and here the proptosis is usually asymmetrical. Retrograde venous flow in the orbit with consequent stasis occurs in cavernous sinus lesions. Fig. 7 illustrates such a case caused by a right carotid- cavernous fistula. This produced a right-sided proptosis of 11 mm, complete ptosis and gave rise to congested and oedematous eyelids (Fig. 7 A). Fig. 7 B and C show the fistula and the orbital venous stasis. Pituitary adenomas may produce exophthalmos due to venous stasis (Dixon 1941; Meadows 1944) and intracranial carotid aneurysms may produce similar changes, presumably by venous stasis (Jefferson 1937). Fig. 8 illustrates such a case caused by an unruptured right posterior communicating aneurysm. It produced a right-sided proptosis of 3 mm (Fig. 8 A), complete ptosis (Fig. 8 B) and displaced the eyeball temporally. Fig. 8 C and D show the aneurysm. Other tumours in the pituitary fossa may produce proptosis due to venous stasis. Figs. 9 and 10 illustrate such a case caused by a sarcoma arising from the pituitary fossa. It produced a left-sided proptosis of 4 mm (Fig. 9 A), complete ptosis (Fig. 9 B) and nasal displacement of the eyeball (Fig. 9 C). Fig. 10 shows the mass lesion of the pituitary fossa.

Fig. 9. Left sided proptosis due to a sarcoma of the pituitary fossa. Photographs of the eyes. (A) showing mild degree of left sided proptosis. (B) showing complete ptosis on the left side, and (C) showing dilatation of the pupil and displacement of the eyeball

nasally on the left side.

248


Fig. 10. (A) plain radiograph of the skull, lateral view, showing complete destruction of the pituitary fossa. (B) Tomogram of the pituitary fossa, showing complete destruction of the pituitary fossa with extention into the sphenoidal bone. (C) Lateral view of the left carotid angiogram, showing pronounced upward stretching of the carotid syphon, and (D) lateral view of the right carotid angiogram, showing slight upward stretching

of the carotid syphon, indicating a destructive mass lesion in the pituitary region.

Eyeball instability

This occurs with paralysis of the external ocular muscles. Neurogenic paralysis or weakness is a common occurrence and contributes to the other factors, i. e. space occupation and venous stasis, in the causation of proptosis. Rarely myogenic paralysis of the muscles alone may lead to proptosis. This is seen in some cases of myasthenia gravis - though as a rule proptosis in this condition is bilateral. Unilateral proptosis in this condition had been reported (Dixon 1941). In his series there were three cases of ophthalmoplegia which showed unilateral exophthalmos. Here the flaccidity of the ocular muscles allows orbital fat to push the eyeball forward and the proptosis, as a rule, is symmetrical. Fig. 11 illustrates such a case with a right-sided symmetrical proptosis of 3 mm and bilateral partial ptosis (Fig. 1 1 A). There was improvement in ptosis (Fig. 11 B) and movement of the eyeball (Fig. 11 C and D), after the injection of a test dose of Tensilon.

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A . R. Choudhury

Fig. 11. Right sided proptosis due to ocular myasthenia. Photograph of the eyes. (A) showing bilateral partial ptosis and after injection of a test dose of Tendon, showing (B) improvement in ptosis, (C) movement of the eyeballs towards the left, and (D) movement

of the eyeballs towards the right.

Acknowledgments

I wish to thank Mr. W. M. Nichols, Mr. R. J. A. Fraser and Dr. A. W. Downie under whose care these patients have been treated, Dr. A. F. MacDonald for help in radio- logical investigations, Mr. J. C. Taylor for help in reviewing the manuscript, the staff of the Departments of Medical Illustration, University of Aberdeen and Derbyshire Royal Infirmary for assistance in preparations of illustrations and Miss Barbara Smith for secretaral assistance.

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Author’s address: Abdur R. Choudhury, M. S., F. R. C. S., Department of Neurosurgery, Derbyshire Royal Infirmary, Derby, England.

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PATHOGENESIS OF UNILATERAL PROPTOSIS

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