Introduction:
Neoplasms of the orbit, called orbital schwannomas, are uncommon. Frequently, there are no clear-cut symptoms to report. To assist in diagnosing orbital schwannoma, classical imaging features visible on magnetic resonance imaging (MRI) and orbital ultrasonography can be helpful. Schwann cells found in the perineurium of peripheral nerves give rise to benign, slow-growing nerve sheath tumors called schwannomas. Adults are more likely to develop them than any other benign peripheral nerve tumor. Even though the precise cause of schwannomas is unknown, genetic abnormalities that cause Schwann cell hyperplasia, a condition related to neurofibromatosis syndromes, are considered to be to blame.
What Is Orbital Schwannoma?
The development of orbital schwannomas is complex. Most frequently, they manifest as a palpable mass in orbit, an ocular proptosis that is painless and non-pulsatile, or a globe displacement. There have been isolated cases of lid edema. It is sometimes difficult to pinpoint the precise nerve of origin because of the intricacy of the nerve fibers that traverse the orbit and the amount of orbital fat. On the other hand, supraorbital and supratrochlear nerves are often where orbital schwannomas develop.
They are, therefore, mostly located in the supraorbital area. Consequently, extraocular movement or visual problems are rarely brought on by orbital schwannomas. The optic nerve may be compressed if the tumor is near the orbital apex and big enough to do so, resulting in decreased visual acuity or compressive symptoms such as scotomas, dyschromatopsia, and decreased contrast sensitivity. Although they can develop at any age, orbital schwannomas commonly manifest in people during their third and sixth decades of life. They are not biased toward any particular eye color or gender.
What Pathophysiology Is Associated With Orbital Schwannomas?
Orbital schwannomas are distinguished from neurofibromas, which impact the nerve fibers directly because they are visible as encapsulated growths inside a sympathetic or peripheral nerve. They are benign tumors, and malignant transformation is infrequently linked to them. They often happen in the muscular cone of the orbit's superior temporal area, pulling the eyeball lower and forward.
The histologic elements of the ocular schwannomas that aid in a pathologic diagnosis are as follows:
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Antoni A type - Solid regions made up mostly of tumor cells that make up the tumor.
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Antoni B type - has free cystic spaces but no axons.
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The Verocay Body - It represents the palisading of tumor nuclei in acellular tumor zones.
Verocay bodies can be used as a marker for orbital schwannoma when they are present. S-100 histochemical staining might result in a favorable result.
What Are the Signs and Symptoms Associated With Orbital Schwannomas?
The early signs include:
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Hearing loss that deteriorates with time.
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Facial pain, numbness, or weakness.
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Chronic headaches.
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Dizziness.
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Arms or legs that are weak.
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Balance problems, especially while walking at night or on uneven terrain.
A patient with an orbital schwannoma typically exhibits the following symptoms:
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Proptosis.
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Painless bulging of the eyeball.
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Inflammation of the eyelids.
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Eyeball dystopia.
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Low ocular motility.
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Vision problems, such as blindness.
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Changes in the optic disc, including choroidal striae, in those with hyperopia.
What Is the Clinical Presentation Of Orbital Schwannomas?
Occasionally, lid swelling and a slow, non-pulsating proptosis are sneaky symptoms of orbital schwannomas. Most tumors invade the superior quadrant, producing frank hypogeous or inferiorly displaced proptosis. Patients who appear late may have diplopia, restricted eye movement, decreased visual acuity, and signs of optic nerve compression such as scotomas, dyschromatopsia, and reduced contrast sensitivity. Depending on which nerve is impacted, patients may experience pain or paresthesias along the damaged nerve's distribution. In extreme instances, the orbital mass could be noticeable. Bilateral orbital involvement in schwannomas is uncommon.
What Are the Diagnostic Procedures to Diagnose Orbital Schwannomas?
Many imaging techniques are available for the assessment and follow-up of orbital schwannoma. Magnetic resonance imaging (MRI) is best for identifying tumors and their connection with surrounding soft tissue structures, whereas computed tomography (CT) is best for determining bone erosions and planning surgery.
CT Scan - On a CT scan, orbital schwannomas are homogeneous, smooth, spherical, elongated lesions with a density resembling extraocular muscle. CT can also show calcification in primary tumors. They are smooth, well-defined tumors that will develop along the axis of the orbit and will conform to the shape of the hollow. Compared to other PNSTs, orbital schwannomas are more oval or spindle-shaped.
MRI - Typically, schwannomas show hypointense signaling on T1 and hyperintense signaling on T2. MRI can show the histology and morphology of tumors with homogeneous or heterogeneous enhancement. While Antoni A areas have intermediate T1 and T2 intensities, Antoni B areas exhibit hypointensity on T1 and hyperintensity on T2. In roughly 41 percent of schwannomas, there may be cystic degeneration but no contrast enhancement; these areas may correspond to Antoni B regions. Because lymphomas have intermediate T2 and mold around nearby structures, whereas schwannomas intrude and distort the area, MRI may be able to discriminate between them.
Ultrasound - Rapid examination, follow-up, or advancement of schwannomas can be accomplished with B-scan ultrasonography. They appear on ultrasonography as solid, spherical, well-defined lesions with a reflecting surface.
What Are the Treatment Modalities That Are Used to Diagnose Orbital Schwannomas?
The preferred course of therapy is total surgical resection. Even if the capsule is extremely thin, particularly in tumors with cystic degeneration, the recurrence rate is almost negligible without a capsule breach. Surgical technique, tumor location, degree of dissection, ongoing reduced vision, and limited eye movement have all been documented. A repeat MRI after a long period of time is advised to check for recurrence.
Conclusion:
Approximately 1 to 2 percent of all cancers in the orbit are schwannomas. They are well-defined, encapsulated, and slowly growing tumors that develop in the peripheral nervous system. For the tumor to be completely removed, the normal anatomy to be preserved, and the restoration of visual acuity and ocular movements to occur, it is crucial to make an early diagnosis and a precise assessment of the schwannoma's extent.
The best evaluation technique for individuals with suspected orbital schwannomas is magnetic resonance imaging (MRI). The preferred course of treatment for orbital schwannoma is complete surgical excision. It can be readily removed since it is well-encapsulated. There is, nevertheless, a very minimal chance of recurrence. Malignant transformation is hardly ever a concern. To know more, consult the doctor online.
