Generality
Acoustic neuroma is a benign form of brain tumor. The lives of those who are carriers of it are therefore not at risk, but the symptoms (above all, loss of hearing and lack of balance), especially if severe, affect most of the daily activities. In most cases, the triggering causes remain unknown.
The diagnosis is not easy, as, in addition to an accurate neurological control, it also requires considerable intuition on the part of the doctor.
The choice of the most appropriate therapy is made on the basis of different assessments, which concern both the characteristics of the tumor and those of the patient.
Figure: acoustic neuroma or vestibular Schwannoma. It can be seen that the tumor grows at the level of the vestibulocochlear cranial nerve, but also in the vicinity of the facial one. From the site: //baptisthealth.net/
What's a brain tumor
A brain tumor is a mass of cells that forms and expands in a completely anomalous way inside the brain, due to a genetic mutation .
Depending on the characteristics with which it occurs, a brain tumor can be defined in various ways:
- Benign or malignant . Brain tumors characterized by slow growth of the abnormal cell mass are considered benign. Brain neoplasms with fast growth are instead considered malignant.
- Primary or secondary . Primary brain tumors are those that originate directly in the brain or in parts adjacent to it (for example, the meninges or the pituitary gland). Secondary brain tumors, on the other hand, are the result of a process of metastasis, in which the cells of a neoplasm arisen elsewhere (for example, in the lung) have moved and invaded the? ™ brain.
Furthermore, there is a third, more general, classification criterion that distinguishes brain tumors depending on the degree of severity . The degrees are four, from I to IV: in the first two (I and II), slow-growing neoplasms are localized in a precise zone; tumors in rapid and expansive growth are included in the III and IV. However, it is not excluded that an I or II degree tumor mass evolves and becomes grade III or IV.
What is acoustic neuroma?
The acoustic neuroma - also known as vestibular Schwannoma - is a benign brain tumor that affects the Schwann cells (hence, the second name) of the? VIII cranial nerve (or vestibulocochlear nerve ).
WHAT ARE SCHWANN CELLS?
Those of Schwann are particular cells, which envelop the prolongations of neurons (axons) several times and produce myelin, an insulating substance that increases the speed of conduction of the nervous signal. To get an idea of what is a Schwann cell, think of wrapping a slightly puffy balloon (the Schwann cell) around a pencil (the axon of the neuron) many times.
Schwann cells are glia cells and are part of the peripheral nervous system . In general, glia cells are responsible for providing support and stability to neurons.
THE VIII CRANIAL NERVE
The cranial nerves are twelve and are identified with Roman numerals, from I to XII.
? VIII, the so-called vestibulocochlear nerve, is a sensory nerve that controls hearing and balance. It originates in a region of the brain called the encephalic trunk and, like all cranial nerves, is formed by a bundle of several neurons, whose extensions are wrapped in many points by Schwann cells.
Epidemiology
In general, brain tumors are quite rare. According to English statistics, the acoustic neuroma strikes, annually, about 13 people per million inhabitants; it is more common in women (the reason for this has not yet been clarified) and among individuals aged 40 and over; it is rather rare among children and young people.
Although in most cases a precise cause cannot be recognized, 5 cases out of 100 are linked to a particular congenital condition, known as type 2 neurofibromatosis .
Causes
Except for those individuals suffering from type 2 neurofibromatosis, in all other cases the precise causes of origin, which cause the acoustic neuroma, have not yet been fully clarified.
However, being a form of brain tumor, the researchers believe that at the origin there is a genetic mutation of the Schwann cells of the ™ VIII cranial nerve.
What this mutation is is still under study.
TYPE 2 NEUROPHYBROMATOSIS
Neurofibromatosis type 2 is a benign tumor affecting the nervous system, in particular the cranial and spinal nerves. It is caused by a mutation of the NF2 gene (chromosome 22, protein produced: merlina or schwannomina), which can be transmitted by parents or arise spontaneously after the formation of the embryo.
The symptoms of neurofibromatosis type 2 consist of bilateral acoustic problems, cataracts, skin plaques, peripheral neuropathies, meningiomas and ependymomas.
Symptoms and Complications
To learn more: Symptoms Neurinoma of acoustics
The symptoms that characterize the acoustic neuroma appear gradually, as the mass of tumor cells grows slowly and discontinuously. In fact, the growth rate of the tumor is 1-2 mm per year. All this clearly complicates the diagnosis, which, in many cases, is not easy to establish.
The main symptoms of acoustic neuroma are acoustic and balance problems ; the secondary ones, much rarer than the previous ones, are, instead:
- Headache
- Numbness, tingling and / or pain on one side of the face
- Visual problems (blurred vision)
- Loss of muscle coordination on one side of the body (ataxia)
- Difficulty in swallowing and changes in tone of voice
NB: the slow growth rate characterizes most cases of acoustic neuroma; however, there may be cases where the tumor expands faster.
ACOUSTIC AND BALANCE PROBLEMS
Tumor growth, at the level of the Schwann cells of the ™ VIII cranial nerve, compromises the control of auditory and balance functions. This explains why individuals suffering from acoustic neuroma suffer from hearing loss, tinnitus and vertigo .
The acoustic problems are almost always felt on one side only (the one governed by the affected nerve), but they can occur on both sides if there is a type 2 neurofibromatosis at the origin of the neoplasm.
COMPLICATIONS
The main complication of an acoustic neuroma is the fact that, if neglected, it can expand more and more, to the point of radically influencing everyday life: hearing loss, dizziness, tinnitus, etc., in fact, make any daily activity difficult (above all, social interaction and work).
The second complication, on the other hand, concerns the possibility that a very serious condition is established, known as hydrocephalus . In these situations, if the treatments are not timely, there is a real risk that the brain will suffer irreparable damage.
Diagnosis
Figure: nuclear magnetic resonance of an acoustic neuroma (white arrow). From the site: www.bimjonline.com
Since symptoms appear slowly and resemble those of other pathologies (such as, for example, Ménière's syndrome), it is not easy to identify an acoustic neuroma.
In order to make a correct diagnosis, not only neurological checks are needed, but also considerable intuition on the part of the doctor, who must consider the hypothesis on the basis of the signs and symptoms reported by the patient.
A late diagnosis allows the neoplasia to expand, although the rate of growth is not high.
THE NEUROLIGIC CONTROLS
When an acoustic neuroma is being researched, neurological controls are targeted and consist of:
- Audiometric tests, to assess the patient's acoustic abilities. It analyzes what kind of sounds are warned and which ones are not perceived.
- Nuclear magnetic resonance ( NMR ), to identify the location and size of the tumor. It is, perhaps, the most appropriate test to identify acoustic neuroma, as it is reliable and not at all invasive.
- Computerized axial tomography ( TAC ), to have an image not only of the brain, but also of the other internal organs. If there is an acoustic neuroma, this is visible, however it must be remembered that the CT scan uses harmful ionizing radiation.
IMPORTANCE OF PRECISE DIAGNOSIS
Delineating the characteristics of an acoustic neuroma by means of an accurate diagnosis is essential for setting the most appropriate therapy.
Treatment
The acoustic neuroma can be treated in different ways; before choosing how to act, we must assess the size and location of the tumor, as well as the patient's age and health status. In fact, the removal procedure is quite delicate and, if the risks associated with it are greater than the benefits that can be derived from it, then it is better to opt for alternative treatments or wait for any developments.
WHEN TO BE LIMITED TO MONITORING?
If the acoustic neuroma is small and has a very slow growth rate, immediate action is not required. The only countermeasure (if it is to be defined as such) adopted in these cases is the periodic monitoring of the tumor, using nuclear magnetic resonance.
This choice is even more justified if the patient is elderly or in not perfect health condition; in such circumstances, in fact, the intervention could represent a greater danger than the tumor itself.
According to a statistical survey, the ¾ of acoustic neuromas have a very slow growth rate and are simply kept under control.
THE TUMOR REMOVAL OPERATION
The removal of the acoustic neuroma consists in a microsurgery operation, to be performed under general anesthesia and after craniotomy (ie the incision and the opening of the skull, at the point where the tumor is located).
Usually, tumors that are not large in size are eliminated completely and without problems; those of large dimensions, on the other hand, hide various pitfalls, therefore their removal is partial and is completed, at a later time, by radiosurgery.
The operation requires a hospitalization of at least a week; the return to working life occurs after about two months.
Risks, complications and precautions of surgery
The main risk during surgery is that of injuring the cranial facial nerve (VII cranial nerve), adjacent to the vestibulocochlear nerve. If the acoustic neuroma is large, the probability of this happening is very high: it is for this reason that the surgeon, in such situations, limits himself to a partial removal of the tumor. From a statistical survey, it emerged that as many as 3 out of 10 people, with a large neuroma, suffer damage to the facial nerve during the operation.
The other major complication of the surgery is the loss of much of your hearing. The patient must be informed of this possibility and of the possible need to use auditory support to compensate for the acoustic deficit.
THE INTERVENTION OF RADIO SURGERY
Radiosurgery is a particular intervention, which makes use of sophisticated instrumentation and can be put into practice both individually and after microsurgery.
Briefly, radiosurgery consists in striking, with a very intense beam of ionizing radiation, the area occupied by the tumor or what remains of it (if it has already been partially removed).
Turned under local anesthesia, therefore with the alert patient, radiosurgery is particularly indicated for those neurinomas located in delicate positions and difficult to access through surgery.
Risks of radiosurgery
Radiosurgery can also damage the cranial nerves or healthy parts of the brain. If this happens, the effects appear after several weeks, if not months, and consist of numbness and facial paralysis (one in 100 people) and loss of hearing (one third of the operations).
HOW MUCH IS A SERIOUS APPLICATION?
The reappearance of the acoustic neuroma, after the surgery, is a rare but possible event. It occurs in 5 cases per 100. To notice a possible relapse, it is good to undergo periodic diagnostic checks.
Prognosis
The prognosis of an acoustic neurinoma varies from patient to patient. It depends not only on the same factors that affect the therapeutic choice, but also on the experience of the medical team to which one relies for treatment.
The factors for a positive prognosis are:
- Reduced size and slow rate of growth of acoustic neuroma: in these cases the surgery is not a priority.
- Good health status of the patient, which allows him to endure an invasive operation such as tumor removal.
- Experience and preparation of the medical team that follows the patient: this guarantees the choice of the most appropriate intervention for the acoustic neuroma in question, as well as its best resolution.
