Orbital schwannoma

Introduction to orbital schwannoma Neurilemmoma is a benign tumor that occurs in axon sheath cells and is more common in the cranial nerves and peripheral nerve roots, limbs, and head and neck. Orbital schwannomas are one of them. basic knowledge The proportion of illness: 0.008% Susceptible people: no specific population Mode of infection: non-infectious Complications: schwannomas

Causes of orbital schwannoma

(1) Causes of the disease

The cause is unknown.

(two) pathogenesis

Schwannoma is a tumor formed by the proliferation of nerve sheath cells. The nerve sheath cells are derived from the embryonic neural crest and are covered by the cranial nerves (except for the olfactory and optic nerves), peripheral nerves and autonomous axons. It is rich in nerve tissue. The axons of these nerves are covered with sheath cells, so schwannomas can occur. It is difficult to determine which nerve is actually present on the clinical and operating table, but because this tumor is located in The upper part suggests that the supraorbital nerve and the superior nerve of the trochlear and its branches are more common. The optic nerve belongs to the central nervous system and does not contain nerve sheath cells. There is no schwannomas in the optic nerve fibers, but the meninges of the optic nerve sheath contain sympathetic components. This tumor occurred, Freedman et al, Graham, McDonald and Liao Zhiqiang reported sphincter tumors in the eye, anterior sclera, lacrimal gland and cornea, respectively.

Orbital schwannoma prevention

Radiation therapy can be tried for tumors with tight optic nerves and good vision.

Orbital schwannoma complications Complications

According to Schatx, 1.5% to 18% of patients with neurofibromatosis also have schwannomas.

Symptoms of orbital schwannomas Common symptoms Nasal edema Double eyeball prominent palsy

Due to the slow growth of the tumor, the initial lack of obvious symptoms and signs, eyeball protrusion is a common clinical manifestation, the tumor can reach this diameter after reaching 1cm in diameter, except for the tumor that occurs on the side of the orbital side of the eye, chronic progressive eyeball protrusion is The main reason for the diagnosis is that the eyeball has a minimum protrusion of 3mm and a maximum of 30mm or more. The eyelids are enlarged and thinned, and the protruding eyeballs are surrounded. Most of the cases are moderately eyeballs. Because the tumors occur mostly in the muscle cone and the upper part of the eyelids, they are represented by the axis. The eyeball is prominent, or accompanied by a downward shift of the eyeball. The tumor that occurs in the infraorbital nerve branch is located in the lower part of the eyelid, which drives the eyeball to shift upward. The tumor originates in the anterior or posterior iliac crest, and the iliac crest can be swollen and swollen. , the surface is smooth, medium hardness, solid or sac sexy, can move, originating from the sensory nerve can be tender, ophthalmoscopy can often find the original optic disc atrophy or optic disc edema, due to oppression of the eye, choroid-retina wrinkles Pleated or edema, diplopia and ocular dyskinesia are more common in tumors occurring in II, IV, VI cranial nerves or cases with obvious ocular protrusions. Compression of the motor nerve of the eye, causing extraocular muscle paralysis or mechanical resistance caused by the tumor occupying a certain position, rather than motor nerve disorder, because the tumor is located on one side of the nerve trunk, tumor neurological dysfunction is rare, occurs in Branches of the ocular nerve, oppression, and irritation may have spontaneous pain and tenderness during percussion. 1/3 to 1/2 patients may have this symptom.

Intraorbital schwannomas compress the wall, bone absorption, spread to the sinus or intracranial, can cause nasal congestion, headache and other related symptoms.

Both schwannomas and neurofibromas are peripheral nerve tumors, and sometimes both tumors can occur in the same individual.

Examination of orbital schwannomas

Pathological examination: The giant sphincter tumor is round, elliptical or conical, grayish white, surrounded by a complete and thin capsule, with a smooth surface, which is easily torn by tissue forceps during surgery. One or one side of the tumor Sometimes the thickened and distorted nerve trunk is visible. The inside of the capsule is grayish white and tender and tender. It is relatively brittle and soft. There is a yellow softening zone between them. It can be cut off with a curette. Occasionally, the tumor cystic changes, only the thin layer tumor tissue in the tumor envelope. The inside is a slurry. If the tumor contains more fibers, the tumor is harder and the cyst is thicker. The deep part of the sac is always associated with the optic nerve, tendon or sacral wall, and the relationship with the primary nerve. The nerve trunk membrane, which is attached to the primary nerve, grows in the small nerves along the fibers to the distal end, thickening, until the formation of tumors.

Microscopic observation, according to the arrangement of tumor cells can be divided into two types: Antoni A and Antoni B. The former tumor cells are fusiform, the membrane is unclear, the cytoplasm is eosin stained, the nucleus is rod-shaped, and the cells are arranged in a tight bundle. The nucleus of the same cell is arranged neatly in a row, in the form of a fence or a military parade. Sometimes the tumor cells are arranged in a swirl or tactile body, and there are abundant collagen fibers outside the tumor cells. Antoni B tumor cells are like type A. Loosely scattered in the mucus matrix, there are many small sacs between the cells.

Special staining and immunohistochemical techniques are useful for the differential diagnosis of schwannomas and neurofibromas and other neurogenic tumors. The reticular fibers stain the scattered fibers parallel to the long axis of the tumor cells in the Antoni B muctoid matrix. Alcian was negative, while neurofibromatosis was characteristically positive. S-100 protein and Bodian axon staining were usually positive. Electron microscopy showed that Schwann cells had long cell processes and tiny reticular fibers in the cytoplasm.

1. Ultrasound exploration A super-display shows that the tumor is in a regular, low internal reflection; if there is liquefaction in the lesion, it shows multiple low-reflection peaks between multiple high reflections, B-ultrasound shows that the tumor is mainly located in the muscle cone, and the lesion is round or Oval shape, clear boundary, less internal echo, some tumors may have circular or irregular liquid dark areas (liquefaction chamber), less sound attenuation, mild compressibility, CDI shows that the lesion is often rich Blood flow signal.

2. CT scan of typical schwannomas on CT scans, tumors occur mostly in the upper and inner side of the iliac crest, and the tumor often shows a fusiform tumor consistent with the long axis of the eyelid. The boundary is clear and smooth, and it can be sausage-like, round, and divided. Leaf-shaped or multiple tumors, sometimes showing thickened nerves at the back end of the tumor. Some tumors combined with liquefaction chambers have lower density on CT, and rare tumors may have calcification. Late tumors can spread through the supraorbital fissure to the brain. CT shows enlargement of the supracondylar fissure. After enhancement, the intracranial tumor spreads. Enhanced medium density on CT.

The tendency of tumors to spread through the supracondylar to the intracranial is a feature of orbital schwannomas, which should cause clinical attention.

3. Compared with other tumors of the orbit, MRI is characterized by the judgment of schwannomas. On MRI, the schwannomas are clearly defined, elliptical or oblong-shaped, and the long axis of the lesion is usually consistent with the anterior-posterior direction of the eyelid. Such an elliptical or fusiform tumor shape is often suspected to be a peripheral nerve tumor. More commonly, the tumor is outside the cone, especially in the upper part of the palate. When the parietal bone is missing, the signal between the tumor and the brain is lost, suggesting that the dome is thinned or destroyed. According to the histological characteristics of the tumor, the tumor showed homogenous or heterogeneous signals. On the T1WI image, the tumor showed a medium signal compared with the extraocular muscle, and showed a low signal compared with the sputum fat. The tumor showed different high, medium and low signals on the T2WI image. The mucus component, B-type schwannomas, is stronger on the T2WI image than the A-type signal. The more cellular components of the tumor, the lower the signal on T2WI; the more mucus components, the higher the T2WI signal, the more obvious the enhancement. Many clinical schwannomas may be complicated by intratumoral components. MRI signals, especially T2WI, are mostly heterogeneous signals, that is, low signal, medium signal and high signal.

After enhancement, depending on the histological characteristics of the tumor, the degree of enhancement is different, and the mucus part is more enhanced than the tumor cell part, which is helpful for surgical resection. If the mucus component of the tumor is too much like the water signal, the tumor may not be significantly enhanced. It is an MRI signal that has not been seen in other tumors.

Tumor cystic changes are one of the characteristics of MRI in the diagnosis of schwannomas. The cystic changes are low-like on water on T1WI, high on T2WI, and no enhancement after enhancement, but not so if there is water in the mucus When the content is high, the tumor signal is the same, and it is actually a solid tumor.

Another feature of orbital schwannomas is that the tumor is very easy to spread through the supracondylar to the intracranial, but dumbbell-shaped or peanut-shaped, so any suspected schwannomas, especially when the tumor has spread to the tip of the sac, the sacral fissure expands or Recurrent tumors should be carefully examined by MRI to exclude intracranial spread.

Diagnosis and differentiation of orbital schwannomas

The disease is mostly in middle-aged patients, progressive ocular protrusion; ultrasound shows hypoechoic, especially in the presence of liquefaction cavity; CT and MRI show that the tumor is long oval, combined with intratumoral cystic changes, located in the upper part of the sac, when the tumor spreads into the intracranial Schwannomas should be suspected in the form of dumbbells.

Similar to schwannomas, cavernous hemangioma, but the latter A is mostly high-intensity reflex, CDI shows no significant blood flow in the lesion.

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