What Is an Astrocytoma?

Astrocytoma refers to tumors formed by astrocytes. According to the literature, astrocytomas account for 13% to 26% of intracranial tumors and 21.2% to 51.6% of gliomas. There are more men than women. Stellate cell tumors can occur in any part of the central nervous system. Generally, they are more common in the adult hemisphere and subthalamic region of the thalamus, and more common in children under the scene. Those on the screen are more common in the frontal and temporal lobes, followed by the parietal lobes, and the occipital lobes are the least. It can also be found near the optic nerve, thalamus, and third ventricle; those under the curtain are mostly located in the cerebellar hemisphere and the fourth ventricle, and can also be found in the cerebellar vermis and brain stem.

Basic Information

English name

astrocytoma

Visiting department

Oncology

Multiple groups

male

Common locations

Cerebral hemisphere

Contagious

no

Causes of astrocytoma

Astrocytoma

The tumor is mainly located in the white matter, showing infiltrative growth. There is no obvious boundary in the solid. Most of the tumors are not limited to one brain lobe. The outward growth can invade the cortex and the inward can destroy the deep structure. Tumors with cystic changes can be called "cysts inside the tumor". Astrocytoma in the cerebellum is usually a large sac with tumor nodules on the sac wall. The sac wall is composed of fibrous connective tissue and glial fibers. Therefore, only the tumor nodules can be removed to achieve the goal of tumor eradication. This kind of tumor is called "tumor in the sac". A small number of cerebellar astrocytomas are substantial, show invasive growth, have no obvious boundaries, and have a worse prognosis than cystic ones.

2. Anaplastic or malignant astrocytoma

It is mainly found in the brain, and the tumor is large, sometimes invading several lobes or invading the contralateral cerebral hemisphere across the midline. The tumor tissue is gray-red, soft in texture, and grows invasively in the brain, with a certain boundary with surrounding brain tissue. Tumor cells can infiltrate into the cortex, forming a "satellite phenomenon" around the periphery of neurons. There are cystic changes and small focal hemorrhagic necrosis.

3. Hair cell type astrocytoma

Hair cell astrocytoma grows slowly and originates from a tumor of the neuroepithelial tissue. Tumors occur in the white matter and cerebellar hemispheres of the midline structure. The most typical are tumors that occur in the funnel, sometimes called funnel tumors; the optic nerves are called optic gliomas, which occur in the anterior optic pathway, hypothalamus and brain stem The tumor boundary was poorly defined, mostly parenchymal and abundant in blood supply.

Clinical manifestations of astrocytoma

Clinical symptoms include general symptoms and local symptoms, the former mainly depends on the increase of intracranial pressure, while the latter depends on the location of the lesion and the pathological type and biological characteristics of the tumor.

General symptoms

The continuous growth of tumors occupies the intracranial space. The tumor blocks the cerebrospinal fluid circulation pathway and causes hydrocephalus and / or cerebral edema. Cerebrospinal fluid reabsorption disorders can cause increased intracranial pressure, such as headache and vomiting.

2. Clinical manifestations of tumors of different nature

(1) Astrocytoma grows slowly, and the course of disease often lasts several years, with an average of 3.5 years. Most patients develop slowly and progressively. Epilepsy is usually the first symptom. Epilepsy begins in 50% of patients. Most patients have headaches and psychomotor activities. Sexual muscle weakness, vomiting and significant disturbance of consciousness may occur. Neurological examination Most patients have optic disc edema and neurological disorders. Nearly half of the patients develop limb muscle weakness, while a few suffer from speech difficulties, sensory disturbances, and vision changes.

(2) Anaplastic astrocytoma The duration of disease is shorter than that of astrocytoma by an average of 6 to 24 months. The main clinical symptoms of cerebral hemisphere lesions are headache, psychiatric symptoms, limb weakness, vomiting, speech difficulties, vision changes, and lethargy. Nervous system examination can find hemiplegia, optic disc edema, manifestations of neurological damage to the brain, blindness, and loss of body sensation. The onset of the disease is progressive, some of which may be suddenly worsening. Early intracranial pressure may be manifested in the early stage of hematopoietic, neurological weakness, memory loss, confusion, epilepsy and endocrine disorders.

(3) Hair cell astrocytoma generally has a long course, and those with anterior visual pathway tumors in the orbit are mainly visually impaired with painless exophthalmos, and may have different types of hemianopia, strabismus, and optic atrophy Those with tumors located at the intersection of the eyes are mostly affected by bilateral vision, including optic disc edema, strabismus, optic nerve atrophy, and headache. Hypothalamic tumors often have endocrine disorders, mesencephalic syndrome, and precocity. Tumors larger than 2cm in diameter can cause hydrocephalus.

Astrocytoma examination

Neuroelectrophysiology examination

EEG is helpful to those with epilepsy as the first symptom. It is mainly manifested by focal low amplitude slow waves, and some of them are extensive moderate or severe abnormalities. Visual evoked potential (VEP) examination is for optic glioma. Temporal occipital tumors are helpful, and brainstem auditory evoked potentials (BAEP) are helpful for the diagnosis of tumors in the brainstem, cerebellum and other parts.

2.X-ray inspection

In most patients, plain radiographs of the skull showed increased intracranial pressure. Partial or circular calcification was seen. Optic nerve tumors show that the enlargement of the foramen of the optic nerve can lead to deformation of the anterior bed process and saddle nodules to form a "pear shaped saddle."

3.CT inspection

The fibrous and protoplasmic astrocytomas have low density and relatively uniform CT, with no obvious space occupying effect, no bleeding or necrosis in the tumor, and no obvious edema around the tumor. Except for a few cases, the contrast injection is generally not enhanced or slightly enhanced. Anaplastic astrocytoma showed low density or heterogeneous low density and high density mixed lesions on CT.

4.MRI examination

Astrocytoma has a low T ₁ W signal and a high T ₂ W signal on MRI. MRI can clearly show the extent of tumor infiltration of brain tissue. After enhancement, astrocytomas are generally not enhanced, and a few tumors have peripherally spotted, slightly enhanced shadows. Benign astrocytoma showed low signal on T ₁ weighted image and high signal on T ₂ weighted image. The signal intensity was uniform, the peritumoral edema was slight, and the enhancement of Gd-DTPA was not obvious. Malignant astrocytoma shows mixed signals on the T ₁ weighted phase, with low signals as the main, and occasionally lower or high signals, which reflects necrosis or bleeding in the tumor.

On MRI of anaplastic astrocytoma, the tumor T ₁ W is low signal and T ₂ W is high signal. Glioblastoma with more morphology is slightly uniform, without necrosis or bleeding. After enhancement, 80% to 90% of the tumors were enhanced. The tumor enhancement manifestations are different, and can be annular nodules, irregular, etc., and some tumor enhancement is uniform.

Astrocytoma diagnosis

Diagnosis can usually be made based on the patient's clinical manifestations and auxiliary examinations.

Lumbar puncture should be considered contraindicated in patients with markedly increased intracranial pressure. Generally, astrocytomas show increased intracranial pressure to varying degrees. Most of the white blood cells in the cerebrospinal fluid examination are normal and the protein content is increased. This is particularly obvious when the tumor is close to the ventricle or subarachnoid space. However, normal cerebrospinal fluid protein content cannot rule out the existence of the tumor .

Differential diagnosis of astrocytoma

Astrocytoma is difficult to distinguish from the acute phase of cerebral infarction and the acute phase of demyelinating disease, and can only be distinguished by intensive follow-up. After 5-10 days and 3-6 weeks of acute cerebral infarction and demyelinating disease respectively, typical changes in lesions will appear on CT and MRI of the skull, while astrocytomas will not change in imaging in the short term. MRI of hypothalamic hair cell astrocytoma can be significantly enhanced due to the uniform tumor signal, which is often difficult to distinguish from solid craniopharyngioma and germ cell tumor on the saddle.

Astrocytoma treatment

At present, astrocytoma mostly advocates: strive for surgery as much as possible, and adjuvant radiotherapy and / or chemotherapy as appropriate; those who cannot operate can take stereotactic radiation therapy and / or chemotherapy.

Stereotactic radiation therapy (SRT) can be divided into single or single high-dose irradiation to control astrocytoma, mainly including -knife and X-knife, among which -knife treatment is more accurate. The following situations may be considered:

1. For small solid solid gliomas located in the deep part of the brain and / or important functional areas (such as the brainstem and thalamus) with clear boundaries, SRT can be used simply to reduce radiation damage to normal brain tissue.

2. Some high-grade gliomas with poor radiotherapy sensitivity (such as anaplastic astrocytoma, glioblastoma, etc.) can be supplemented or boosted with SRS / SRT after routine general radiotherapy after surgery. Increasing the radiation dose of tumor tissue and improving the local control rate.

3. For low- / high-grade gliomas that recur after surgery and radiotherapy and are smaller in size, SRS / SRT treatment alone may be considered.

Astrocytoma prognosis

After surgery and / or radiotherapy, the prognosis of astrocytoma is still good. It is generally believed that the pathological type of the tumor, the degree of surgical resection, the age of onset, the course of disease, and clinical manifestations can determine the prognosis of the patient. The 5-year survival rate of patients with complete tumor resection can reach 80%, while the 5-year survival rate of patients with partially resected tumor or tumor biopsy is only 45% -50%. For patients over 40 years of age with subtotal tumor resection, radiotherapy can achieve satisfactory results. The prognosis of tumor recurrence is not good. About half of the tumors recur after malignant transformation. Nearly one third of the tumors recur into glioblastoma.