Cerebellar tumor is a benign or malignant neoplasm localized in the cerebellum. It can be primary and secondary (metastatic) in nature. Cerebellar tumor is manifested by variable symptoms, which belong to 3 main groups: cerebral, cerebellar and stem. Diagnosis is based on the results of magnetic resonance imaging of cerebral structures. The final verification of the diagnosis is carried out only according to the histological examination of tumor tissues. Surgical treatment consists in the most radical removal of the formation, restoration of circulation of cerebrospinal fluid and elimination of compression of the brain stem.
General information
Neoplasms of the cerebellum account for approximately 30% of all cerebral tumors. Modern histological analysis has made it possible to identify more than 100 morphological species of these formations. However, generalized data collected by practitioners specializing in neurology, neurosurgery and oncology suggest that in 70% of cases, a glioma is a tumor of the cerebellum.
Tumor formation of the cerebellum can occur at any age. Some types of neoplasms (for example, medulloblastoma) occur mainly in children, others (hemangioblastomas, astrocytomas) — in middle—aged people, and others (glioblastomas, metastatic tumors) – in the elderly. Belonging to the male sex and the Caucasian race increases the risk of cerebellar oncopathology.
Causes and pathogenesis
Etiological factors provoking the growth of tumor formations are not known for certain. It was noted that in about a tenth of the patients, the cerebellar tumor is hereditarily determined and is included in the Recklinghausen neurofibromatosis clinic. An important role in the initiation of the tumor process is assigned to radioactive radiation, the effects of oncogenic viruses (some types of adenoviruses, herpes viruses, human papillomavirus, etc.) and the effect of carcinogenic chemicals on the body. The risk of neoplasms increases in immunocompromised individuals (HIV-infected, receiving immunosuppressive therapy, etc.).
Pathogenetic mechanisms accompanying a cerebellar tumor are implemented in three main directions.
- Firstly, there is damage to the cerebellar tissues associated with their compression by growing tumor formation and death. Clinically, this is manifested by focal cerebellar symptoms.
- Secondly, a tumor of the cerebellum in the process of its growth fills the cavity of the IV ventricle and begins to squeeze the brain stem, which is manifested by stem symptoms and a disorder of the function of the cranial nerves (CN).
- The third mechanism causes the development of cerebral symptoms, it is associated with increasing hydrocephalus and increased intracranial pressure. A sharp increase in pressure in the posterior cranial fossa leads to the lowering of the tonsils of the cerebellum and their infringement in the large occipital foramen. At the same time, the lower part of the medulla oblongata is squeezed between the cerebellum and the bone of the occipital foramen, compression of the structures localized in it leads to severe bulbar disorders, cardiac and respiratory disorders.
Classification
Like neoplasms of other localizations, tumor processes of the cerebellum are divided into benign and malignant. Of the benign formations in the cerebellum, locally growing hemangioblastomas and astrocytomas with infiltrative growth are most often observed. Often these tumors give a cystic transformation and are a small node with a large cystic cavity located nearby. The most common malignant tumor of the cerebellum in children is medulloblastoma, characterized by particularly intense growth and spread across subarachnoid spaces. The second place in prevalence belongs to cerebellar sarcoma.
It should be noted that clinically classifying a cerebellar tumor into benign and malignant can be somewhat conditional. The limited space of the posterior cranial fossa causes the danger of compression of the brainstem in any type of neoplasm.
In accordance with the genesis of cerebellar neoplasms, they are divided into 2 large groups — primary and secondary tumors. The primary tumor of the cerebellum originates directly from its cells, being the result of their tumor metaplasia. The secondary tumor of the cerebellum has a metastatic origin, can be observed in breast cancer, malignant lung tumors, thyroid cancer, gastrointestinal malignancies. Primary tumors can have both benign and malignant character. Secondary tumors are always malignant.
Symptoms
The clinic of tumor processes of the cerebellum consists of general cerebral and cerebellar symptoms, as well as signs of damage to the brain stem. Often the symptoms of these 3 groups occur simultaneously. In some cases, the disease manifests itself by the appearance of symptoms of only one group. For example, a tumor of the cerebellum localized in its worm usually begins to manifest with general cerebral symptoms, and damage to the cerebellar tissue can be compensated for a long time and not give any clinical manifestations. Sometimes the first symptoms are signs of compression of the trunk or damage to any cranial nerve.
The general cerebral symptoms accompanying a cerebellar tumor do not differ from similar symptoms in tumors of the cerebral hemispheres. Patients complain of a constant or paroxysmally increasing headache, more often occurring in the morning, having a diffuse character (less often localized in the back of the head). Cephalgia is accompanied by nausea, independent of food. Vomiting at the height of headache, dizziness, cortical disorders (drowsiness, deafness, increased exhaustion, in some cases — olfactory, auditory or light hallucinations) are possible. If a growing tumor of the cerebellum blocks the outflow of cerebrospinal fluid, then the symptoms increase: the patient takes a forced position — they tilt their head back or forward, take a knee-elbow position with their head lowered, nausea and vomiting attacks become more frequent. With a sharp blockage, often associated with a rapid change in the position of the head, a hypertensive-hydrocephalic crisis is observed.
The actual cerebellar (focal) symptoms vary depending on the location of the neoplasm. The main clinical syndrome is cerebellar ataxia. When the worm is affected, it is manifested by gait disorder and instability. The patient walks, staggering and stumbling, spreads his legs wide or balances with his hands so as not to fall, he can “drift” on turns. Typically, the presence of nystagmus — involuntary movements of the eyeballs. It is possible to develop cerebellar dysarthria — a speech disorder characterized by its interruption, division into syllables (“chanting speech”). When the cerebellar hemisphere is affected homolaterally (on the side of the lesion), coordination and proportionality of movements are disrupted. There is a miss when performing finger-nasal and knee-heel tests, dysmetry, intentional tremor, a change in handwriting to large and sweeping.
As the cerebellar tumor grows, it penetrates from one hemisphere to another, from the worm to the hemispheres and vice versa. Clinically, this is accompanied by a mixture of signs of damage to these structures, a bilateral coordination disorder.
Damage to the brain stem can manifest itself as signs of its compression, as well as violations on the part of individual CN. There may be trigeminal neuralgia, strabismus, central neuritis of the facial nerve, hearing loss, taste perception disorder, dysphagia, paresis of the soft palate. Vomiting, which has no connection with headache, is typical for stem syndrome. It is caused by irritation of the receptors of the posterior cranial fossa and can be provoked by sudden movements or a change of position. Progressive compression of the trunk is accompanied by motor restlessness, tachycardia or bradycardia, diplopia, increased nystagmus and oculomotor disorders (paresis of the gaze, divergent strabismus, mydriasis, ptosis); vegetative disorders, arrhythmia, tonic convulsions are possible. There are respiratory disorders, up to its complete stop, which can cause the death of the patient.
Diagnostics
A neurologist’s examination of the patient does not always suggest a tumor of the cerebellum, since specific cerebellar signs may be absent. The presence of pronounced cerebral symptoms is a reason for referring a patient to an ophthalmologist’s consultation with an ophthalmoscopy. The detection of a pattern of “stagnant” optic nerve discs on the fundus indicates hydrocephalus. Further diagnostic search requires the connection of neuroimaging methods: CT or MRI of the brain. They allow not only to identify neoplasms, but also to determine its size and location, which is necessary for planning surgical treatment. In some cases, in particular, if the vascular nature of the tumor is suspected, cerebral magnetic resonance angiography is additionally performed.
It is necessary to differentiate a cerebellar tumor from a cerebellar cyst, cerebral vascular aneurysm, brain abscess, intracerebral hematoma, ischemic stroke in the vertebrobasilar basin.
Treatment
The main method of treatment is surgical. The question of the expediency and scope of surgical intervention is decided by a neurosurgeon. Radical removal of the tumor is optimal. However, this is not always possible due to the germination of the formation into complex anatomical structures, the IV ventricle. In such cases, the purpose of the operation is to remove as much tumor tissue as possible and restore normal cerebrospinal fluid circulation. To eliminate compression of the brainstem, partial resection of the opening of the occipital bone and the 1st cervical vertebra can be performed. In some cases, bypass surgery is used to reduce hydrocephalus. With a sharp development of hydrocephalus with an increase in stem symptoms, puncture of the ventricles of the brain and external ventricular drainage are indicated.
Removal of the tumor is always accompanied by a histological analysis of its tissues. Determining the degree of malignancy of a neoplasm is crucial for subsequent treatment tactics. Surgical treatment of malignant tumors is usually combined with radiation and chemotherapy. In parallel with surgery, symptomatic treatment is carried out — painkillers, antiemetics, diuretics, sedatives, etc.
Forecast
The results of treatment of cerebellar neoplasms depend on their size, prevalence and malignancy. In cases of benign nature of the tumor and its complete removal, the prognosis is favorable. Without treatment, with a progressive increase in the size of the formation, the patient dies from compression of the stem structures responsible for respiration and cardiovascular activity. With incomplete removal, benign tumors of the cerebellum recur and after a few years a second operation is required. Malignant tumors are prognostically unfavorable. The survival rate of patients after surgical treatment in combination with adjuvant therapy ranges from 1 to 5 years.
