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Meningioma is a typical tumor developed from outside of the brain, and it takes 20% of entire brain tumor.
Tumor grows massively from the attachment of dura mater, and apply pressure to surrounding brain tissues. On the other hand, there is a case where it takes plate-like shape so called as meningioma enpalque. Meningioma is grouped, as shown below, subtype 9 of Grade I, subtype 3 of Grade II, and subtype 3 of Grade III.
More than 90% of grade I are benign tumors, but there exist malignant anaplastic meningioma. Treatment is primarily surgical removal, and in case when it is unable to remove, stereotactic radiosurgery is selected. At the surgery, Simpson grade is commonly used to indicate the relationship between removal degree and reappearance. This expresses removal degree in 5 stages and indicate reappearance rate in 5 to 20 years after surgery.
It develops from spider-membrane chorionic cells covers brain surface and grows up in receiving alimentation from nearby dura mater mainly. This part is referrd as attachment of meningioma, and there are many cases where reactive bone thickening is recognized.
Meningioma is a disease develops from outside of brain, so that it mainly receives alimentation from external carotid artery, and at fundus region, attached part is extracted nutrient artery extended from external carotid artery and radiated tumor shadow as sun ray appearance image in the early image of cerebrovascular photography.
In convexity meningioma, tail-shaped by contrast agent enhancement effect is often seen on dura mater outside of attachment part of tumor. This is called as infiltration part of tumor and called as tail sign. Therefore, it is said that the surgery operation may cut all circumference 2.0cm broader further from attached part. Most of the Brain after surgical removal remains depressed even after the removal, since it has been compressed and concaved for long time.
There is a certain meningioma which can be diagnosed by simple X-Ray photography. They are psammomatous type meningioma, so that in case when it is diagnosed, at walk-in clinic, by simple X-ray photography before Ct or MRI is taken, we may receive great compliment or be called as clip-artist, either one of these.
Meningioma is easy to be complicated with Neurofibromatosis (NF) – type II for which the cause is thought by the variation of 22nd chromosome. Depend on the part tumor is developed, there are cerebral falx, parasagittal, fundus, tuberculum sellae, olfactory pit, sphenoidal limbus, Cerebellar Vault region, cerebellopontine angle, macropore, petroclival, intraventricular (lateral cerebral ventricle, 3rd intraventricular), Cerebellar tentorium, pineal region, sylvian fissure, middle cranial fossa, Meckel Cavity, vagina nervi optici, cavernous sinus, and spinal cord. They are called by development part name.
They are different by region, but in front side, anterior falx artery out from top end of the ocular artery becomes a nutrient vessel, and in middle part, this artery and middle meningeal artery become nutrient vessel. At the rear side, it receives the alimentation from meningeal branch of occipital artery of the external carotid branch.
Whether this tumor can completely be removed is depends on how neatly brainstem side of large tumor can be peeled off. Also, enough craniotomy at temporal region is necessary.
When this tumor is removed, it can be said that it is desirable. First coagulate nutrient vessel of posterior ethomoid artery and cut tumor of the anterior skull base off in certain level, then goes into sylvian fissure. Also, in case of large size tumor, enough craniotomy at temporal region is necessary.
As for the removal of this tumor, in case if interhemispheric approach is taken, bridging vein to superior sagittal sinus need to be sacrificed, thus causing high risk of venous infarction. It is preferable to take pterional approach for the removal.
Tumor developed in this region gradually causes obstruction at not only superior sagittal cavity but also sinus rectus. This tumor’s characteristics is to cause a growth of persistent falcial vein, i.e. persistent embryonic Dural venous channel, shown in Fig.24 as a result.(Nakagawa H., et al: Surg Neurol 32:219-24,1989.)
This type of tumor is said that it is developed by the abnormity of capillary blood, such as epidemical anemia, multi-cloned Gamma globulin. In fact, origin of this tumor is unknown so that it may be close to inflammatory mass rather than common and typical meningioma. The case shown here is female case, and generally speaking, they are common among female.
This is extremely rare tumor, but few reports exist. The generation base of this tumor is:
Above three are considered as the generation base. The last one has no pathological proof, thus considering that this is just a speculation, this case has no relations with falx or cerebellar tentorium so that the writer considers this is developed from velum interpositum.
Fundamentally, tumor at Meckel cavity (trigeminal schwannoma) is surgically removed completely, and cancellous vein sinusoidal tumor only remains. However, tumor which is strongly conglutinated with first branch of the trigeminal nerve should be left remains. Surgical method for removal is transpetrosal approach. This surgical method is; firstly, perform skin incision with having long skin flap toward the direction of broader sagittal cavity to prevent spinal fluid leakage, then create the closure in the style of implanting into dura mater defect part using galea or temporal muscle. For the remaining tumors, stereotactic radiotherapy (Gamma knife, Cyber knife, I-MRT) is performed.
Basically, above mentioned stereotactic radiotherapy is performed. When mass becomes larger, there I a case where tumor is cut off purposing to decrease tumor capacity.。
Basically, this is a Cerebrospinal tumors in the dura mater, but as shown in Fig.29, there is an exception where tumor has occupied intermedullary.
Infratemporal approach is taken place for the tumor advanced from cranial fossa to infratemporal fossa. This method uses the curved skin incision from front side of tragal to lower end of mandible bone angle at rear side. Zygomatic arch is cut and remove temporal bone. This method is a variation of zygomatic approach, and able to remove upper and lower dumbbell tumor.
Intracranial metastasis of benign meningioma is extremely rare case. It is reported with 0.76%. Malignant meningioma is getting higher to 20 to 40%. Lung is the most common, liver follows. Primary lesion is side sagittal sinus meningioma, and its cause is infiltration to venous cavity. In the tissue type, meningotheliomatous type is the most common one, and this example is the same one.
Pathologically speaking, meningioma is grouped into 3 types, meningotheliomatous type, transitional type, and mixed type at first pathological classification, but merely there are psammomatous type, angiomatous type, microcystic type, metaplastic meningioma, and secretary type exist. As aforementioned and in psammomatous type, there is a case where meningioma is draws up by simple cephalic CT.
In general, complete removal is possible by craniotomy procedure, but in deep brain case and the case where damage on nerve is possible, there might select radiation therapy to suppress the growth. In case if it is pathologically malignant case (many fission images can be seen, 4% of entire meningioma), even if the removal is done macroscopically, radiation therapy is still necessary. Growth speed is unexpectedly fast till it is reappeared to the same size of early stage removal. Even if it is not malignant case, there is a case where tumor is developed in island shape since tumor infiltrate and advance in dura mater.
Other than the above, there is papillary meningioma which is a special meningioma. Its increment or advancement is extremely fast, and intraspinal dissemination might be developed in many cases. Also, in pathologically, lymphoplasmacyte-rich meningioma can rarely be recognized. Since meningioma will infiltrate into dura mater, in case when it advances to venous cavity, there is the one which takes special advance pattern, i.e.it may form the transitional nest in lung. Else, the case is known where estrogen and progesterone (luteal hormone) receptor are appeared in meningioma, but regarding the appearance frequency, progesterone is higher than estrogen. These are their characteristic which progesterone or estrogen developing type has higher probability of reappearance.
As for the approach of after tumor removal operation, transpetroal approach for Meckel Cavity meningioma, Occipital interhemispheric transtentorial approach for Pineal body region, and for lateral ventricle triangular section, transcortical intraventricular approach which is the method via cortical structure from the back of the parietal perception field or method via cortical structure from temporal cortex to reach tumor in triangular section, is used. In case if it is in the dominant hemisphere, former method is safer.
At the Surgical operation in Cranial Nerve Surgery, it is important to pay attention to vein rather than artery, so that even at the removal of meningioma, important issue is to pay attention to the vein. That is to say, whether feeder treatment is properly done for the sacrificed vein which becomes a drainage of tumor blood vessel or take care of the process stage when most of the tumor is removed. Especially for large sized olfactory fossa meningioma, performing the method of reaching the hemispherical cleft has a possibility of causing broader area venous infarction, so that it is better to removal using all cases pterional approach. It is important to reduce the influences to the surrounding tissue by shrinking the volume of tumor mass with using loop coagulator or ultrasonic vacuum equipment CUSOR.
