Glioma is a common primary cranial brain tumor arising from cancerous brain glial cells, with an annual incidence of about 3-8 per 100,000 population. It accounts for 40-50% of cranial brain tumors and is the most common intracranial malignant tumor. Gliomas are caused by the interaction of congenital genetic risk factors and environmental carcinogenic factors. Some known genetic disorders, such as neurofibromatosis (type I) and tuberous sclerosis, are genetic susceptibility factors for glioma. Some environmental factors may be associated with the development of glioma. For example, electromagnetic radiation, macrophage virus infection, etc. However, there is no conclusive evidence that these factors can lead to tumor development.
I. According to pathomorphology, they can be classified as
1. astrocytoma, which is the most common type of glioma. It is most commonly seen in the cerebral hemispheres in adults and in the cerebellum in children. It can be divided into the following types.
(1) Benign astrocytomas
(1) Fibrous astrocytoma.
(2) Protoplasmic astrocytoma.
(3) Fibroblastic astrocytoma.
(2) Mesenchymal (malignant) astrocytoma is the malignant type of astrocytoma.
(3) Glioblastoma is the most malignant type of astrocytoma.
(4) Multiplex yellow astrocytoma is a solid type of tumor located superficially in the brain.
(5) Subventricular giant cell astrocytoma is often associated with tuberous sclerosis.
(6) Hairy cell astrocytoma can be distributed in cerebral hemisphere, hypothalamus area, anterior visual pathway, brainstem and cerebellum.
(2) Oligodendroglioma: It can be divided into two grades: oligodendroglioma and mesenchymal (malignant) oligodendroglioma.
3.Ventricular meningioma and mesenchymal (malignant) ventricular meningioma are tumors that occur from the ventricular epithelium.
4.Mixed glioma is a glioma that contains two glial cell components.
5.Choroid plexus tumor is divided into two types: choroid plexus papilloma and choroid plexus carcinoma.
6.Neuroepithelioma of uncertain origin includes three kinds of lesions: astroblastoma, polar glioblastoma, and cerebral gliomatosis.
7.Mixed neuronal and neuronal glial tumors, including ganglioneuroblastoma, ganglioneuroglioma, pro-connective tissue infantile ganglioglioma, embryonic dysplastic neuroepithelioma, and central neuroblastoma.
8.Pineal parenchymal tumor can be divided into pineal cell tumor and pinealoblastoma, mixed/transitional pineal cell tumor, both of which are less common.
9.Embryonic tumors belong to embryonic brain tumors, including medullary ependymoma, neuroblastoma, ventriculoblastoma, primitive neuroectodermal tumor, and medulloblastoma.
10.Neuroblastoma tumor
Based on the pathological malignancy of tumor cells, they can be classified as
1.Low-grade glioma (WHO grade 1-2), which is a well-differentiated glioma; although it is not a benign tumor, the prognosis of patients is relatively good.
2. High-grade glioma (WHO grade 3-4), which is a poorly differentiated glioma; it is a veritable malignant tumor with a poor prognosis for patients. Low-grade glioma may “accumulate” new mutations during the cell proliferation process, thus transforming it to high-grade glioma (malignancy).
Four common symptoms of glioma
1.Headache: It is mainly caused by the increase of intracranial pressure. The growth of tumor and edema around the tumor lead to the gradual increase of intracranial pressure, which compresses and pulls the pain-sensitive structures in the skull. It can also be caused by tumor stimulation of meninges, headache is mostly seen on the affected side, headache is intermittent at the beginning, light in the morning and heavy in the evening, with the progress of tumor, headache will gradually increase and last longer.
2. Vomiting: It is mostly caused by the increase of intracranial pressure and stimulation of the medullary vomiting center or vagus nerve, which can be without nausea, but often jet vomiting. In young children, the headache may not be significant because of the separation of cranial suture, but the vomiting is more obvious because tumors in the posterior cranial fossa are common.
3.Increased intracranial pressure: It can cause optic papillary edema and finally lead to optic nerve atrophy and vision loss. When the tumor compresses the optic nerve, it causes primary optic nerve atrophy and vision loss. The abducent nerve is easily squeezed, resulting in abducent nerve palsy and diplopia.
4.Epilepsy: the incidence is about 30%. Most of them are caused by direct stimulation or compression of tumor. Most of the seizure types are limited type, but there are also grand mal seizures. The symptoms during seizures are related to the location and nature of the tumor, and the incidence is high for tumors in and around the motor area. The incidence of glioblastoma, astrocytoma and oligodendroglioma is higher.
III. Examination of glioma
CT, MRI and electroencephalography are the main examinations for glioma, and CT is superior in detecting the presence of intra-tumor hemorrhage and calcification.
MRI is superior to CT examination in showing the location and nature of the tumor. MRI has various examination methods, such as MR magnetic resonance spectroscopy to determine the nature of the tumor and functional MRI to clarify the relationship between the lesion and the function of the surrounding brain tissue. The more advanced PET-MRI has more advantages than PET-CT in the systemic diagnosis of tumors.
IV. Treatment of glioma
Different treatment strategies should be adopted for patients with different stages of glioma. Glioblastoma is characterized by infiltrative growth, with unclear boundaries with normal brain tissue, often beyond one lobe, growing toward normal brain tissue, finger-like deep destruction of brain tissue, proliferative growth, and cut longer and longer like a beard. Glioma is like a tree root, which means that only the main trunk of the root can be removed during surgery, while its small hairy roots remain buried in the soil and continue to grow. The brain tissue, which is the commanding part of the body, cannot be removed as much as other tumors, so it is theoretically impossible to remove them completely. In contrast, tumors in the brain stem, medulla oblongata, anterior and posterior central gyri and other important parts of the body are not operable at all, so the treatment objectives of surgery are
1. to obtain pathological diagnosis, especially the immunohistochemical results are meaningful for the subsequent treatment.
2.To remove the tumor completely or reduce the tumor volume to decrease the number of tumor cells.
3.To relieve the symptoms of intracranial hypertension.
4.Prolong life and create time for other subsequent comprehensive treatment.
5.Obtain detailed genetic information of tumor cells to provide a basis for finding effective treatment.
Early stage gliomas, huge tumors in non-functional areas, should be surgically removed as early as possible. In practice, about 50% of gliomas cannot be fully resected. In order to avoid functional damage after surgery, even for total resection, there will still be tumor remnants in the primary site, so it is difficult to eradicate and the recurrence rate is high. Glioma grade 3 or 4 recurrence can be as fast as one month or as slow as six months. At present, the application of neuronavigation, intraoperative electrophysiological monitoring, multimodal neuroimaging fusion techniques combined with microneurosurgery techniques can significantly improve the surgical total resection rate and reduce surgical complications, especially the tumor surgery in functional areas can preserve the neurological function to the greatest extent.
Patients with mid- to late-stage glioma or those who are weak and close to the possibility of surgical resection can be treated with radiotherapy and Chinese medicine, but since all other types of glioma are insensitive to radiotherapy except medulloblastoma, which is highly sensitive to radiotherapy, and ventricular meningioma, which is moderately sensitive, some literature reports that radiotherapy has the same prognosis as non-radiotherapy patients. In addition, radiation can cause radiation necrosis of surrounding normal brain tissue, which in turn can cause worsening of symptoms. Therefore, irradiation intensity, irradiation range, and irradiation duration need to be selected according to the patient’s systemic condition, and currently stereotactic radiotherapy is widely recommended.