Causes of Eye Protrusion
When orbital lesions increase the volume of orbital contents or reduce the size of the orbital cavity, the position of the eye can be shifted forward and eye protrusion can occur; in addition, the size of the orbital cavity also plays an important role, and secondary enlargement of the orbital cavity can alleviate eye protrusion to some extent.
The diseases that cause protrusion of the eyeball are broadly divided into the following categories, namely, protrusion of the eyeball due to tumor, endocrine protrusion of the eyeball, inflammatory protrusion of the eyeball, traumatic protrusion of the eyeball, protrusion of the eyeball due to genetic and developmental diseases, and protrusion of the eyeball due to other diseases.
I. Eye protrusion caused by tumor
1, sinus-related tumors: sinuses are air-containing bone cavities around the nasal cavity, hidden in some facial skull and brain skull, there are 4 pairs, namely maxillary sinus, septal sinus, frontal sinus and butterfly sinus. There are anatomical reasons for the high incidence of rhinogenic proptosis, as the nose, sinuses and orbit have a subtle and complex anatomical relationship, and more than 2/3 of the orbital wall is separated from the sinuses by thin bone plates. Sinus tumors may not have any ocular symptoms in early stage, but when they invade the orbit, they may squeeze the eye and show ocular symptoms and signs. Tumors originating from the maxillary sinus tend to cause the eyeball to protrude upward with bulbar conjunctival edema; tumors originating from the septal sinus tend to displace the eyeball inferiorly or superiorly; while tumors originating from the frontal sinus tend to displace the eyeball inferiorly. Careful observation of the direction of eye protrusion can help determine the primary site of the tumor.
Orbital tumors are closely related to the skull base. The orbital roof is part of the skull base, which separates the orbital content from the anterior cranial fossa and frontal sinus. In the posterior part of the orbital apex, the orbit communicates with the skull through the optic nerve foramen and supraorbital fissure. Therefore, intracranial lesions invading the orbit can result in protrusion of the eye, most commonly seen in meningiomas. Meningiomas of the pterygoid crest, saddle node, and optic nerve sheath are relatively common. In addition, meningioma of the middle and anterior cranial sulcus, glioma, pearl retinal cyst, Galen’s vein tumor, metastatic carcinoma, chordoma, etc. can cause eye protrusion.
3.Other tumors: intraorbital vascular tumors, cavernous sinus cavernous hemangioma, neurogenic tumors, inflammatory pseudotumors, dermatomal cysts, lacrimal gland tumors, eosinophilic granuloma and other metastatic malignant tumors, malignant lymphoma, etc. can cause eye protrusion. Among them, vascular tumors, neurogenic tumors, lacrimal gland tumors and inflammatory pseudotumors are the more common causes of proptosis.
Endocrine proptosis
Endocrine proptosis is a common cause of eye protrusion, which can be divided into thyrotropic proptosis and thyrotropic proptosis. The former is caused by hyperthyroidism, while the latter is a significant protrusion of the eye due to excessive secretion of thyrotropin by the pituitary gland. It is most often seen in thyroid-related eye disease.
Anti-thyroid medications, surgery and 131 I are all used to treat hyperthyroidism combined with proptosis, the key being to keep the thyroid gland functioning normally. Simple proptosis requires no special treatment and most of it disappears when thyroid function returns to normal. Follow-up is recommended for patients with mild infiltrative proptosis, as the natural course of TAO has a tendency to be self-limiting. Patients with moderately or severely active infiltrative proptosis can be treated with methylprednisolone shock therapy and orbital radiotherapy, and if necessary, with analogues of growth inhibitors or other immunosuppressive agents.
C. Inflammatory proptosis
One type of inflammatory proptosis is caused by acute inflammation of the orbit, such as orbital fasciitis, orbital cellulitis, cavernous sinus thrombophlebitis, etc. The other type of proptosis is caused by chronic inflammation of the orbit. The other is caused by chronic inflammation of the orbit such as infiltration of inflammatory cells, proliferation of fibrous tissue, etc. The clinical manifestation is similar to that of a tumor, so it is called pseudotumor.
In addition, periorbital infections can also lead to protrusion of the eye, such as septal and frontal sinus abscesses. Due to the thin orbital wall, it is easy to destroy the bone wall under the action of trauma, and the orbit is connected to the sinus, forming a closed cavity where sinus secretions accumulate for a long time, resulting in chronic inflammation and orbital pressure increase, which leads to eye protrusion, optic nerve compression and eye symptoms. This can manifest as eye displacement, limited movement, diplopia, and optic neuritis or abscess compression of the optic nerve due to inflammation spreading to the orbit, which can lead to vision loss. It is important to note that chronic sinusitis does not always have obvious nasal symptoms, but only ocular symptoms such as protrusion of the eyeball and decreased vision, which are often misdiagnosed as retrobulbar optic neuritis or orbital tumor, and should be differentiated and routinely consulted by ENT. If the inflammation of the optic nerve is mild and short-lived, the vision can be restored after anti-inflammation and decongestion; if long-term optic neuritis and optic nerve compression cause atrophy and degeneration of the optic nerve, it is difficult to restore the vision after surgery. Therefore, early diagnosis and treatment should be carried out to remove the lesion as early as possible.
IV. Traumatic proptosis
Traumatic proptosis is commonly caused by post-traumatic intraorbital hemorrhage, intraorbital emphysema or traumatic cavernous sinus fistula.
1. Intraorbital hemorrhage: trauma or foreign body entering the orbit and damaging the blood vessels can cause hemorrhage or form a hematoma in the orbit, which is a common comorbidity of orbital trauma. Due to the increase of intraorbital pressure and hematoma compression, it can cause eye pain, vomiting, heart rate slowdown, eye movement disorder or diplopia, and also moderate or severe eye protrusion, subcutaneous petechiae on eyelids, vision loss, and even blindness. Protrusion of the eye occurs suddenly and is difficult to recover. When the protrusion is severe, the cornea is exposed and the eye is endangered.
2. Orbital emphysema: The accumulation of air in the eyelid or orbital tissue is called orbital emphysema. It is mostly seen in trauma and occasionally in surgical trauma. In a small number of patients, there is no history of trauma and it is called spontaneous orbital emphysema. Orbital emphysema is most often seen as a result of a fracture of the bony orbital wall behind the orbital septum, which is intact. Most fractures occur in the orbital floor or the intraorbital wall and affect the fragile cardboard, with orbital tissue communicating with the septal sinus and sometimes the pterygoid sinus; a few orbital apex fractures result in orbital tissue communicating with the frontal sinus. Accumulation of gas in the orbital fat or muscle cones and increased intraorbital tension result in protrusion of the eye, limitation of motion, diplopia, widening of the lid fissure and eyelid tension, and characteristic tonicity between the superior margin of the upper lid plate and the superior orbital rim. Compression of the eyeball through the eyelid can reduce the degree of protrusion with a characteristic twisting pronation or grip snow sensation.
3. Traumatic carotid cavernous sinus fistula: Carotid cavernous sinus fistula is a group of clinical syndromes caused by the formation of abnormal arterial and venous traffic between the carotid artery and its branches and the cavernous sinus. It is divided into traumatic, spontaneous and congenital. The cavernous sinus is a plexus of veins between the two dural layers of the saddle, into which the superior ophthalmic vein, inferior ophthalmic vein, parietal pterygoid vein, lateral fissure vein and basilar vein converge, and the internal carotid artery passes through with the superior ophthalmic nerve, the talocrural nerve, the trigeminal nerve and the abducens nerve. When the wall of internal carotid artery ruptures for any reason, the arterial blood directly converges into the cavernous sinus, which is formed by the traffic between carotid artery and cavernous sinus. After the inflow of carotid artery, the pressure in the cavernous sinus increases and flows backward into the superior ophthalmic vein, causing its reverse filling, obvious thickening, expansion and obstruction of reflux, resulting in protrusion of the eyeball, restriction of eye movement, congestion of the bulbar conjunctiva, and long term vision loss or even blindness.
4. Eye prolapse: Trauma can also lead to eye prolapse and optic nerve dissection. Such patients should reset the eye in the shortest possible time. Treatment mainly includes local pressure bandaging, reducing intraorbital pressure, hemostasis, anti-inflammation, hormone and nerve nutrition, etc. If necessary, CT-guided surgery can be performed to drain the blood in the orbit or perform orbital decompression, and then reset the eye to reduce the occurrence of retinal necrosis and optic nerve atrophy and maximize the recovery of visual function.
V. Protrusion of the eye caused by genetic and developmental diseases
1, Crouzon syndrome: rare, autosomal dominant inheritance, the degree of performance varies greatly, about 1/ 3-1/ 4 of the clinical cases by a new mutation. In recent years, the gene is located on 10q25-26, due to the abnormal fibroblast growth factor receptor 2 gene, which is a series of head and facial deformities due to premature closure of cranial suture and craniofacial bone dysplasia. Some cases may have headache, vomiting and mental retardation due to increased cranial pressure and brain injury caused by premature closure of the cranial suture. The incidence of Crouzou syndrome in newborns is 1/50,000, and prenatal molecular diagnosis to block the transmission of the disease gene can prevent the birth of affected children.
2, orbital meningoencephalic bulge: is a disease in which part of the brain parenchyma and meninges protrude into the orbit through a congenital orbital wall defect, a dominant cranial cleft malformation, generally in children and young people, the incidence of brain bulge is 1/ 35000, orbital meningoencephalic bulge is more rare. It is clinically divided into anterior and posterior meningoencephalic bulges. The clinical manifestations of anterior meningoencephalomegaly are bilateral symmetry, widening of the nasal dorsum and anterior bulging, some patients may have facial deformities, and pulsating masses may be found in the medial orbital area and nasal root. The clinical manifestations of posterior meningoencephalomegaly are protrusion of the eye on one or both sides, often displaced inferiorly with pulsation, and a pulsating mass may be palpable in the deep orbital region, with occasional loss of vision, primary optic nerve atrophy and limited eye movement, and trigeminal neuralgia. The pulsatile ophthalmoplegia of meningocephalic bulge is characterized by consistent pulsation, absence of vascular murmur, and compression of the ipsilateral carotid pulsation that does not disappear, which can be differentiated from carotid-cavernous sinus fistula, arteriovenous hemangioma, and other orbital tumors with abundant blood supply. In addition, meningocephalic bulges have pulsations synchronized with the heartbeat on ultrasound, and the density of CT is the same and homogeneous as the brain tissue, which can be used to differentiate them from dermatomal cysts and teratomas. Treatment should be surgical in cooperation with neurosurgery.
VI. Eye protrusion caused by other diseases
1. Cranial fibrous dysplasia: It is a thickened and deformed lesion of the skull caused by the replacement of bone by fibrous connective tissue, and its etiology is still unclear. It occurs in the frontal and pterygoid bones, especially at the base of the skull. Involvement of the orbital bone may cause protrusion of the eye. It is generally believed that most patients do not have neurological deficits and do not require treatment. However, in adolescent patients with ocular protrusion, prompt surgical treatment is recommended.
2. Erdheim-Chester disease: This disease is a rare systemic histiocytosis of unknown origin, which involves the skeletal system mainly as symmetrical long bone sclerosis. Lesions occurring in the orbital region are rarely reported and include bilateral retrobulbar infiltrates, ocular protrusion, diplopia, optic nerve compression and yellow tumors of the eyelids.
3. Nodular febrile nonsuppurative lipofuscinosis: Also known as Weber-Christian syndrome, this is an inflammatory disease that originates in the fatty layer and has an acute or subacute course, mostly in young and middle-aged women. It can cause inflammation of the orbital fat and protrusion of the eye. Inflammation of the adipose layer can occur in the subcutaneous, visceral, peritoneal and greater omentum, with clinical symptoms of multi-organ damage, a systemic disorder of unknown etiology, and effective glucocorticoid therapy.
4, abnormal bone fiber hyperplasia: is a skeletal system disease characterized by bone fiber degeneration, abnormal proliferation of normal and immature bone scattered in the fiber tissue. CT is a better choice for the diagnosis and follow-up of this disease. MRI can differentiate it from meningioma, bone tumor and mucous cyst, especially for the involvement of central nervous system structures, and can help determine the extent of soft tissue. The pathological changes of abnormal bone fiber hyperplasia are proliferating fibroblasts and woven bone trabeculae instead of normal bone structure, with a large number of collagen fibers and woven bone trabeculae between the proliferating fibroblasts. Mucinous degeneration, cystic degeneration, hemorrhage and necrosis may occur in the lesion area. Bone fiber abnormal proliferation sign is a benign lesion and the treatment plan needs to be chosen according to the clinical presentation of the patient. It invades the orbit and causes manifestations such as diplopia and ophthalmoplegia, and surgery aims to relieve diplopia or ophthalmoplegia.
5. Parasitic larvae cause protrusion of the eyeball: The parasitic larvae of the Mannheimer’s larvae can cause larvae disease in humans. Surgical removal of the larvae can cure the disease. It is important to pay attention to living and eating habits and not to eat raw frogs and raw water to prevent this disease.
6. Spontaneous intraorbital hematoma leading to protrusion of the eye: it can occur at any age and is likely to occur in patients with bleeding tendency and no other orbital or systemic pathology. It can be treated surgically when it affects visual function. Intraorbital hemorrhage associated with the superior rectus muscle has also been reported as an acute onset of unilateral ocular proptosis and diplopia, with spontaneous resolution of symptoms after a few days or weeks, and orbital imaging showing complete resolution or moderate persistent thickening of the ocular muscle without significant symptoms.
In addition, cavernous sinus thrombosis, sympathetic nerve stimulation, and axial myopia can present with ocular protrusion; hematologic disorders, such as retrobulbar infiltration of leukemia cells can lead to ocular protrusion and pain, which may improve after chemotherapy; drug allergy and severe acute pancreatitis complicating ocular protrusion and visual impairment have also been reported, with the exact cause of onset unknown.