Brain tumors are heterogeneous group of various intracranial tumors, benign or malignant, arising from the abnormal uncontrolled division of cells, which in the past were a normal part of the the brain matter (neurons, glial cells, astrocytes, oligodendrocytes, ependymal cells), lymphatic tissue, blood vessels of brain, cranial nerves, meninges, skull, glandular formations of brain (pituitary and pineal gland) or arising from the metastasis of the primary tumor located in another organ. Tumor type is determined by the cells forming it. Depending on the location and histologic variant the disease symptoms are formed. Brain tumors are relatively rare and make about 1.5% of all types of tumors.
Patients with brain tumors account for about 4% of patients with organic lesions of the nervous system. Brain Tumors occur at any age but most often, they are discovered in adolescence. The origin of brain tumors has not yet been elucidated. They are thought to develop from cells that were delayed in the early stages of their transformation into a mature form. Rarer, tumors arise from adult cells. In the development of brain tumors, a number of endogenous and exogenous factors (hormonal influence, infection, injury, etc.) have important meaning.
Classificationof Brain Tumors
Brain tumors are classified into:
- primary and secondary (metastatic);
- benign and malignant;
- single and multiple
Depending on the location of tumors in relation to the brain substance, we distinguish between:
Intracerebral tumors occur one and a half times more often than extracerebral ones (Park, Kim, Sade, & Lee, 2009). Extracerebral tumors originate not from the substance of the brain, but from the surrounding tissues (lining of the brain, blood vessels, bones of the skull).
By histological structure, brain tumors are classified into:
- gliomas, derived from glia;
- neuromas – tumors of the cranial nerves;
- meningiomas or arahnoidendoteliomas – tumors of the meninges;
- pituitary adenoma
- metastatic tumors (cancer, sarcoma);
- other rarer tumors.
Impact of tumors on brain varies. Some of them directly compress the brain, causing destruction (meningioma, osteoma, etc.). Other tumors destroy brain substance, replacing it with its own tissue (gliomas, metastatic cancer). Destruction of brain tissue causes the appearance of focal symptoms. Along with the impaired function of the brain at the location of tumor, the functions of both closely located sections of the brain, and remote ones are disturbed as well. The cause of these functional disorders is a disturbance of blood and cerebrospinal fluid flows, caused by a tumor, shift of parts of the brain, and the effects of tumor’s pathological exchange products on the brain tissue. Significant role in the disturbance of brain function the increased intracranial pressureplays (Herholz, Langen, Schiepers, & Mountz, 2012). The increased intracranial pressure is caused by the following factors: an increase in brain size due to the tumor mass, edema and swelling of the brain (edema is fluid accumulation in vascular and cell spaces; swelling of the brain is the colloid-chemical binding of water with the cells of the brain); excessive accumulation of fluid in the ventricles of the brain; stagnation of blood in the venous system of the brain. The intensity of intracranial pressure increase depends on many factors, including the location (proximity to cerebrospinal fluid circulation channels), size, histostructure of tumor.
Tumorsof the Frontal Lobes
Because of tumors of the frontal lobes, mental disorders occur. Especially characteristic is inertia, mental processes lethargy. Patients become less spontaneous, acquire lack of initiative, lose criticism to their condition, and become untidy. When the tumor is located in the lower part, the phenomena of disinhibition, aggression, a tendency to flat jokes, moria are observed. Inertness of mental processes is combined in patients with motor inertia; frontal or premotor apraxia appears. For tumors of the frontal lobes, seizures are typical. Seizures often begin with a combined rotation of the head and eyes to the side opposite the tumor. If the localization of the process is in the left hemisphere, motor aphasia and agraphia is observed. On the side opposite to the tumor, frontal ataxia may develop. Paresis of the extremities appears at the location of tumors in the posterior part of the frontal lobe. Abnormal reflexes of oral automatism, grasping phenomena are typical. At basal tumor localization, sense of smell is disturbed; Foster-Kennedy syndrome is observed (Brennan, 2008).
Precentral Gyrus Tumors
Precentral gyrus tumors begin with Jacksonian seizures. Initially, cramps are limited to a small group of muscles, corresponding to the tumor’s location. Gradually, cramps acquire a tendency to spread to adjacent muscles, and then seizures, beginning with focal, become generalized. With the growth of the tumor, seizures get accompanied with muscle weakness. Initially, paresis has transient nature, then become persistent and gradually transform into paralysis.
They are characterized by sensory Jacksonian seizures, which gradually turn into persistent disorder of sensitivity on the side opposite to the tumor.
This type is characterized by sensory disorders. They mainly affect complex kinds of sensitivity (topognosia, discrimination, two-dimensional spatial sense stereognosis). Patients lose their orientation in their own parts of the body (violation of the body schema). When parietal apraxia occurs, patients lose the ability to perform routine activities. If the tumor affects the parietal lobe of the left hemisphere, reading, writing, arithmetic suffers, while oral speech is preserved.
Temporal Lobes Tumors
These tumors are characterized by seizures. Sometimes, they are accompanied by olfactory, gustatory, or auditory hallucinations or aura. Often a temporal ataxia occurs. If the tumor affects the left temporal lobe, the speech (sensory, semantic aphasia) is damaged as well as reading and writing associated with it. Due to the impact of the tumor on adjacent parts of the brain, stem symptoms (Weber syndrome) can appear as well as signs of basal ganglia (Parkinsonism).
Occipital Lobes Tumors
They are accompanied by central homonymous hemianopsia. During stimulation of the cortex photopsias (feeling flickering sparks, stains, etc., before the eyes) are observed. Formed visual hallucinations are rare. There may be metamorfopsia and visual agnosia.
This type of tumors causes sensitivity disorders, hyperpathia and thalamic pain. Owing to the proximity of the internal capsule to the pathways, the functions of all the analyzers are frequently disturbed, and pyramidal disorders occur.
Brain Stem Tumors
These tumors affect cranial nerves. Typical are the alternating syndromes that gradually progress with the tumor’s growth.
Usually, they are neuromas of acoustic nerve or meningiomas. The first symptom of the tumor is the noise in the ear, which is accompanied by hearing impairment. Acoustic nerve damage is followed by the paresis of the facial muscles, impaired sensitivity to the corresponding side of the face. Nystagmus and dizziness can be observed. As the tumor grows, cerebellar symptoms appear on the corresponding side of the face and pyramid symptoms appear on the opposite side (Echevarría, Fangusaro, & Goldman, 2008).
For this type of tumor, the main focal symptom is ataxia, dismetriya, adiadochocinesia, decreased muscle tone. All of these symptoms at cerebellar hemisphere tumors are expressed on the affected side of face. Cerebellum tumors are accompanied with especially severe disorders of balance and gait. Pyramidal pathology is usually weak.
Pituitary adenomas are characterized by early appearance of bitemporal hemianopsia, primary optic atrophy and enlargement of the sella, which can be completely destroyed with large tumors. Often there is a violation of carbohydrate and water exchange (polydipsia, polyuria). Eosinophilic adenoma is characterized with acromegaly, chromophobe is characterized with hypophyseal syndrome, basophilic with Cushing's syndrome.
The clinical picture of brain tumors includes three groups of symptoms:
- general or cerebral;
- distant symptoms (secondary focal),
Complex of cerebral symptoms that occur at tumors due to the increased intracranial pressure is called hypertensive syndrome. The symptoms of the increased intracranial pressure include: headache, vomiting, dizziness, changes in the heart rate, mental disorders, seizures, cranial nerves damage, changes of the skull bones and spaces containing cerebrospinal fluid, as well as changes in the fundus.
Headache is the most common symptom of a brain tumor. Local headaches felt in a particular part of head, may be due to irritation by the tumor of the cranial nerves (branches of the trigeminal, glossopharyngeal, vagus nerve), the walls of the venous sinuses, adjacent shells, large shell and cerebral vessels. In addition to local, there may be common headache. Pathogenesis of common headaches is associated with the increased intracranial pressure. General headache is deep, tearing, bursting, very intense. Headache at brain tumors is rarely permanent and progressively increasing, most often it occurs in separate attacks. Especially characteristic is the appearance of headache in the morning, it often appears at excitements, and especially with physical exertion (coughing, sneezing, lifting weights, etc.). Headache may depend on the position of the head and body in space.
Forced position of the head at tumors arises reflexively due to stimulation of the cranial nerves and the upper cervical roots, because of the influence of the tumor on the movement of cerebrospinal fluid and irritation of the labyrinth.
Vomiting usually occurs quickly and unexpectedly, without anticipatory nausea, morning vomiting that, occurring on an empty stomach, is frequently observed. Vomiting is often triggered by a change of head position. Vomiting occurs mostly at an altitude headache. Pathogenetically, vomiting at brain tumors is associated with the increased intracranial pressure, but it can also be a focal symptom, if the tumor is localized subtentorially.
Dizziness is manifested as an apparent rotation of yourself or the surrounding objects in a certain direction ("system" dizziness), as well as a sense of instability, shaking, nausea, sudden weakness, blackouts, loss of balance. Dizziness is often accompanied by nausea, vomiting, and is usually not constant, but periodic. Dizziness is most common at tumors affecting the vestibular part of the eighth pair or its way in the brain stem and cerebellum. At hemispheric tumors, it is less common.
Changes in the fundus and visual acuity are one of the most important objective symptoms of a brain tumor. Changes in the fundus appear as stagnation and atrophy of optic disks, and hemorrhages in the retina circumdisk departments. The appearance of stagnant disks at brain tumors is associated with mechanical compression of the optic nerve and blood vessels due to the increased intracranial pressure. Because of venous blood stagnation, swelling and protrusion of the optic disc and the surrounding retina is observed. Apparently, intoxication also plays its role. Stagnant disks are characterized by a color change, they become gray-red, their boundaries disappear, edematous retina surrounding the disks becomes cyanotic, expanded veins are lost in it, the disc increases in size and protrudes forward. Along the vessels, hemorrhage appears. The final stage of stagnant disks is their secondary (white) atrophy. Stagnant disks are usually bilateral, but sometimes asymmetry is observed. Subjective symptoms accompanying stagnant discs are short-term eyesight weakening in the form of fog or feeling veil before the eyes. At incipient atrophy of the optic nerve, consistent reduction of the eyesight appears (Neville, Corpron, Blakely, & Andrassy, 2003).
Mental changes often accompany the brain tumors and can be observed at tumors of any location. The pathogenesis of mental disorders at brain tumors is very complex. In some cases, mental disorders are caused by hypertensive syndrome, in some cases, they are the focal symptom. The most common mental disorders at brain tumors include disorders of consciousness. They can occur paroxysmally, in the form of attacks, but often develop gradually, when stun goes into stupor, and then into a coma, from which the patient cannot be withdrawn. Disorders of consciousness, such as stun, are observed in the later stages of the disease, due to hypertensive syndrome. Patients cannot keep track of the flow of conversation, speak slowly, with pauses, they are sluggish, apathetic, silent, no longer respond to speech addressed to them.
Seizures. Hypertensive syndrome at brain tumors is expressed by seizures. They can occur at tumors of various locations (mostly tumors of the temporal and frontal lobe). Focal, Jackson seizures have diagnostic value.
Changes in the heart rate and breathing are observed in the later stages of tumors. They appear in the bradycardia and tachycardia, often interchanging each other. Typical is bradycardia accompanying headache and vomiting. In the terminal stages of the disease, tachycardia is observed. The emergence of persistent tachycardia, especially after the bradycardia, is an unfavorable prognostic sign. Changes in breathing, as well as heart rate, can manifest themselves in deceleration, acceleration, rhythm disturbances. Shortness of breath, especially the slowdown, indicates a dangerously serious condition of a patient.
Change in cerebrospinal fluid. Pressure of the cerebrospinal fluid is most often high, but at tumors, breaking communication between the ventricles and subarachnoid space, it may be low. Changing the composition of the cerebrospinal fluid is expressed in increasing protein, usually 2-3 times in comparison with the norm. Sometimes, the content of cellular elements at the expense of lymphocytes is increased. The tumor cells are found rarely.
Changes in the skull bones caused by the increased intracranial pressure, are expressed in the general thinning of the flat bones of the skull, in deepening digital impressions, in dehiscence. In addition, some scull sections, especially sensitive to the increased intracranial pressure – dorsum sellae, wedge-shaped spines, the small wing of the main bone holes, through which the cranial nerve exits, change (Neville, Corpron, Blakely, Andrassy, 2003).
Change in spaces containing brain cerebrospinal fluid. With an increase in intracranial pressure, the size and position of the ventricles and subarachnoid spaces change. These changes depend on the accumulation of cerebrospinal fluid in the ventricles, the mass and location of the tumor. With tumors in the posterior fossa, cerebrospinal fluid accumulates in the lateral and third ventricles. Changes in ventricular at intraventricular tumors depend on the location of the latter. With the rise in intracranial pressure, ubarachnoid space disappears and cerebral cisterns are reduced.