Neuroma, a benign nerve tumor
Acoustic neuroma is a benign nerve tumor developed at the expense of cells of the Schwann sheath, which coats the auditory nerve, in particular its vestibular branch, which makes it prefer the exact term of vestibular schwannoma.
The nerves of the peripheral nervous system are surrounded by Schwann cells that twist around themselves along the nerve, enveloping it in its entirety, forming a stack of membranes, called the myelin sheath. It is thanks to this sheath that the message transmitted can travel very quickly along the nerve and over great distances, isolating the nerve from electrical leaks that would otherwise occur. This speed of reception of messages is a privilege of certain vertebrates, including humans.
Rare, even very rare a few decades ago since an ENT specialist was supposed to diagnose 3 to 5 of them in the course of a career, we discover many more nowadays (up to several tens in the course of a career). The modern means of investigation (auditory evoked potential, scanner, magnetic resonance imaging) are certainly responsible for the increase in this figure, but probably not only.
The auditory evoked potential records the electrical activity of the auditory pathways after the emission of sound clicks. The electrical impulse, generated by the hair cells in the inner ear (hearing cells) is carried by the auditory nerve to the central nervous system (brain).
Certain changes in the latency of the auditory waves are characteristic of schwannoma. The role of cell phones is still relevant in the increase of this pathology where the temperature rise on the cells of the peri-auricular region, triggered by the microwaves of the phones (limit the listening time/hands-free kit) is incriminated. It is known that any repeated modification, in particular of temperature, on cells can induce irreversible cellular mutations and develop tumors. Ionizing rays (all radiation in excessive doses) are also incriminated.
The signs of call
Rarely balance disorders, although this tumor, which grows more or less quickly, develops on the periphery of the vestibular nerve compressing it little by little. Its growth is variable (from fast to very slow) and can change from one form to another. Tinnitus can be a revealing sign. It is often hearing problems that motivate the consultation. The audiogram performed reveals a unilateral sensorineural deafness (i.e. a deafness of the inner ear) in a subject in his fifties, which will require other examinations and particularly a magnetic resonance imaging (MRI) that will confirm the diagnosis and especially visualize and appreciate the size of the schwannoma. The treatment will be based on its evolution (variable), the age of the patient, and also taking into account the patient’s wishes.
• The surgery is delicate, at the border between ENT surgery and neurosurgery. It sacrifices hearing most of the time and can sacrifice a cranial nerve very close to the tumor if it is important enough: the facial nerve, motor nerve of the face.
• Therapeutic abstention is justified if the patient’s age is important or the tumor is not very or not at all progressive.
• Gamma Knife which, as its name indicates, is a very targeted radiotherapy (gamma ionizing radiation), acts like a scalpel in a sometimes inaccessible area of the skull and lasts only a few hours maximum. In the best cases, the tumor is destroyed but a fibrosis remains.
Genetic factors involved
Vestibular schwannoma occurs sporadically, with no genetic or familial cause found.
However, as we have seen, there are probably predisposing factors (telephone/ionizing radiation). It is therefore essential to avoid prolonged listening to the telephone. The hands-free kit keeps away the heat sources produced by the micro waves and it is preferable to use it.
Finally, a nerve disorder, neurofibromatosis type 2, can lead to vestibular schwannomas which are diagnosed much earlier (adolescence or before) and which are of genetic origin.
Vestibular schwannoma is more than ever a topical issue. The possibility of a predisposing factor that would constitute in particular the cell phone has pushed researchers and scientists to carry out meta-analyses to know the reality of such assertions. But the necessary hindsight to confirm or deny the role of microwaves in this kind of tumors requires years of investigations and a sufficient number of significant results. It is surprising, however, that no conclusive tests have been performed by the manufacturers before a worldwide distribution (due to the generalized craze).
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