X-ray signs of skull and brain tumors

Clinical diagnostics of brain tumors is associated with great difficulties. Depending on the localization and nature of growth, the tumor can cause both general cerebral symptoms (headache, dizziness, impaired consciousness, personality changes, etc.) and focal neurological disorders (impaired vision, hearing, speech, motor skills, etc.). Moreover, the same tumor at different periods of development is sometimes completely "silent", sometimes causes severe disorders up to loss of consciousness.

Currently, doctors have a set of radiation methods that detect brain tumors in almost 100% of cases. The recognized leaders among radiation diagnostic methods are CT and MRI. The main tasks facing a specialist in the field of radiation diagnostics when examining patients with brain tumors:

1. identify a tumor;
2. determine its topography;
3. establish its macrostructure (solid or cystic nature, presence of necrosis or calcification);
4. determine the relationship of the tumor with surrounding brain structures (presence of hydrocephalus, mass effect).

Computer and magnetic resonance tomograms show direct and indirect signs of a tumor. A direct sign is a direct image of the tumor itself. Visualization of a tumor on magnetic resonance tomograms is associated with different proton density and magnetic relaxation time of normal and tumor tissue. On computer tomograms, the image appears due to the fact that tumor tissue differs from the surrounding brain tissue in the coefficient of absorption of X-rays. With low absorption of X-rays, the tumor appears as an area of reduced density (hypodension area). Its shape, size and outlines can be used to some extent to judge the size and nature of the growth of the neoplasm. We will only note that there may be a hypodensity zone of edema around it, somewhat "concealing" the true size of the tumor. A brain cyst has some similarity with a tumor, especially with its irregular configuration, but the contents of the cyst are close to water in the amount of absorbed X-rays.

Tumors originating from the arachnoid membrane - arachnoid endotheliomas (meningiomas) often have a fairly high density and are distinguished on tomograms as rounded hyperdense formations. Most of these tumors are well supplied with blood, so after the introduction of a radiocontrast agent, their density on tomograms increases. A direct image of the tumor can be obtained with a radionuclide study. A number of radiopharmaceuticals, for example, 99mTc-pertechnetate, accumulate in increased quantities in the neoplasm due to a violation of the blood-brain barrier. On scintigrams and especially on emission tomograms, an area of increased concentration of the radionuclide - a "hot" focus - is determined.

Indirect signs of a brain tumor include:

1. mixing of surrounding parts of the brain, including midline structures;
2. deformation of the ventricles and disturbances of cerebrospinal fluid circulation up to the development of occlusive hydrocephalus;
3. various manifestations of brain tissue edema, varying in duration and severity;
4. lime deposits in the tumor;
5. destructive and reactive changes in the adjacent bones of the skull.

The role of angiography in the diagnosis of brain tumors is small. Its main purpose is to determine the nature of vascularization if surgical treatment is planned, or to perform preoperative embolization. Naturally, it is always preferable to perform DSA.

Tumors of the skull bones are diagnosed using conventional X-rays and tomograms. The most obvious image is that of osteoma, as it consists of bone tissue and stands out well on images. In most cases, osteoma is localized in the area of the frontal sinus. The picture of hemangioma is quite indicative. It causes a rounded defect of bone tissue with finely scalloped compacted edges. Sometimes, against the background of such a defect, one can notice radially diverging fine bone rafters or a cellular structure.

However, specialists in the field of radiation diagnostics often encounter single or multiple destructive foci in the skull bones that are round or irregular in shape. The number of foci varies from one to several dozen. Their size varies widely. The contours of the destructive foci are smooth but unclear, and there are no sequesters in them. Such foci are either metastases of a malignant tumor originating from a tumor of the lung, mammary gland, stomach, kidney, etc., or a manifestation of myeloma disease. It is almost impossible to distinguish myeloma nodes and cancer metastases from radiographs. Differential diagnostics is based on the results of plasma protein electrophoresis and urine tests. Detection of paraprotein indicates myeloma disease. In addition, scintigraphy in patients with metastases reveals hyperfixation of the radiopharmaceutical in areas of bone tissue destruction, whereas such hyperfixation is usually absent in myelomas.

Tumors in the sella turcica area occupy a special place in clinical oncology. The reasons for this are varied. Firstly, anatomical factors are important. The sella turcica houses such an important endocrine organ as the pituitary gland. The carotid arteries, venous sinuses, and the basilar venous plexus are adjacent to the sella. The optic chiasm is located approximately 0.5 cm above the sella turcica, so visual disturbances often occur when this area is affected. Secondly, pituitary tumors disrupt the hormonal status, since many types of pituitary adenomas are capable of producing and releasing potent substances into the blood that cause endocrine syndromes.

Of the pituitary tumors, the most common is the chromophobe adenoma, which grows from the chromophobe cells of the anterior lobe of the gland. Clinically, it manifests itself as adiposogenital dystrophy syndrome (obesity, weakening of sexual function, decreased basal metabolism). The second most common tumor is the eosinophilic adenoma, which also develops from the cells of the anterior pituitary gland, but causes a completely different syndrome - acromegaly. In addition to a number of general symptoms, this disease is characterized by increased bone growth. In particular, skull X-rays show thickening of the vault bones, enlargement of the superciliary arches and frontal sinuses, enlargement of the lower jaw and external occipital protrusion. Basophilic and mixed adenomas also originate in the anterior pituitary gland. The first of them causes a syndrome known in endocrinology as Itsenko-Cushing syndrome (moon face, obesity, sexual dysfunction, high blood pressure, systemic osteoporosis).

The assumption of a pituitary tumor is based on clinical and anamnestic data, but the exact diagnosis is established taking into account the results of radiation studies. The role of the radiologist is very important, since pituitary adenomas are subject to surgical or radiation treatment. In the latter case, impeccable aiming of the radiation beam (for example, a proton beam) at the pathological focus is required to exclude damage to adjacent brain tissue.

The possibilities and methods of radiological diagnostics depend on the size of the adenoma. Small tumors (microadenomas) are not recognized on radiographs; CT or MRI are required to detect them. On computer tomograms, an adenoma, if it is well enough delimited, immersed in the parenchyma of the gland and not too small (at least 0.2-0.4 cm), appears as a rounded focus of increased density.

Recognition of large adenomas is usually not difficult even when analyzing plain X-ray images of the skull, since they cause changes in the bones that form the sella turcica. The sella increases in size, its bottom deepens, the walls become thinner, the anterior sphenoid processes of the lesser wings of the sphenoid bone rise. The entrance to the sella turcica widens. Its back straightens and lengthens.

The normal dimensions of the sella turcica depend on the gender, age, and body type of the person, so special tables have been created by which specialists in the field of radiation diagnostics determine the proper dimensions.

Craniopharyngiomas have already been mentioned above - embryonic tumors originating from the remnants of the pituitary tract (Rathke's pouch). Craniopharyngioma can grow in the sella turcica and then manifests itself with typical symptoms of an endosellar tumor, as well as an adenoma. However, in the vast majority of cases, it develops above the sella, quickly leading to visual disturbances, increased intracranial pressure and hydrocephalus. Then the entrance to the sella widens, atrophy and destruction of the top of the back of the sella develop. Diagnosis is facilitated by identifying various calcareous inclusions in the form of numerous grains of sand, larger lumps or ring-shaped or arcuate shadows, which are often contained in the craniopharyngioma.