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Acoustic Neuroma

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Acoustic neuroma is a rather common tumor of the brain. In the majority of the cases, it originates from the vestibular nerve which with the cochlear nerve form the acoustic nerve. It is a benign tumor. Some rare malignant cases are mentioned in bibliography and they usually have to do with patients with genetic predisposition and multiple neuromas.

Despite its almost given benign nature, acoustic neuroma, as it grows, causes serious complications with paralysis of cranial nerves and symptoms due to the pressure it exercises on the brain. These complications are dangerous for the life of the patient and for this reason they require prompt diagnosis and treatment of the tumor.

The patients symptoms usually escalate as the tumor increases in size and gradually affects the cranial nerves. In the early stages, the typical picture is the case of a patient who mentions unilateral humming, tinnitus in the one ear, that is. From the clinical examination we do not usually detect any pathological findings and the same is true for the audiological checkup. Any damage in hearing has to do initially with high frequencies and, thus, it may be non-detectable.

For each patient, approaching the third decade in his/her life, with unilateral tinnitus, a doctor should suspect acoustic neuroma. The neuroma which will be diagnosed at such an early stage may easily be treated surgically or alternatively with gamma-knife, having no or minor consequences for the function of hearing or the facial nerve which is in contact with the acoustic nerve. A chosen examination for such cases is the MRI, although sometimes less costly examinations may be done, like a CT and the auditory brainstem response.

As the tumor increases in size, the effects on hearing start to become more obvious. The patient visits the doctor, because in addition to humming he has also noticed that hearing in one of his ears has deteriorated. In more advanced cases, he notices hypoesthesia in the same side of the face, with more characteristic the one of the cornea in the eye. The patient may mention incidents of vertigo and loss of balance, incidents of ear staffing or even suffer acute deafness. If in the clinical examination we find evidence of paresis in the face muscles, then we must suspect that the tumor has become very large or that we deal with neuroma of the facial nerve, without excluding the possibility of a malignant disease.

The sooner we diagnose the acoustic neuroma the greater choice we will have. In general, the method of treatment or the kind of surgical access for the removal of the neuroma depends on its size. And we say in general, because in addition to size, there are other parameters which need to be taken into account. These have to do with the general state of the patients health, the level of hearing, the spreading of the tumor into the internal auditory meatus, the pneumatosis and other anatomic parameters of the mastoid.

The prompt visit of the patient to the doctor and the doctors increased alertness in diagnosing the acoustic neuroma, in combination with the progress in imaging techniques, have contributed in diagnosing neuromas at an early stage, having a diameter up to one centimeter. For such sizes, one choice is that of observation. The neuroma develops at a pace of about 3 to 4 millimeters per annum, while it can remain unchanged for a long period of time. We can, therefore, recommend the repetition of MRI after six months or maximum a year. If the neuroma exceeds the size of one centimeter we may lose the advantage of using gamma-knife, or it may become impossible to practice transtemporal access to which we will refer below. Thus, the method of observation is recommended for patients with easy access to medical services and a high level of awareness of the problem and compliance to medical advice.

For tumor up to one centimeter, another way of treatment is gamma-knife, focused radiation that is. Radiation has the ability to freeze the development of the tumor for a long period of time. Rarely, however, does it manage to obliterate it. The patient may be relieved from the general consequences or the complications of an operation, but not the local consequences on both hearing and the function of the facial nerve. What is more, the patient is not relieved from the need for regular medical observation by MRI.

The most realistic and radical treatment for tumors with a diameter of up to one centimeter is the surgical removal with transtemporal approach. This access allows the removal of the tumor by preserving hearing and the functions of the facial nerve. As more and more neuromas will be diagnosed at an early stage, we believe that transtemporal approach will gain more and more value.

If the neuroma is diagnosed having a diameter larger than one centimeter, transtemporal approach cannot be practiced and the gamma-knife loses its effectiveness. For such tumors we recommend surgical removal with access depending on the level of hearing. If hearing ability is of a satisfactory level, then suboccipital access is recommended. Using this access we prevent the damage of the hearing organ in revealing the tumor and, thus, there are the conditions for the partial preservation of hearing with careful removal of the tumor. And we mention partial preservation of hearing, because, even with this type of access, hearing worsens and, in some cases, the sounds which are received by the operated ear are rather annoying. This danger becomes even greater in cases where the tumor develops into the internal auditory meatus.

If hearing ability is low before the operation, or of such level that we do not anticipate the preservation of any functional hearing ability with the suboccipital approach, then the translabyrinthine approach is selected. This access presupposes the damage of the hearing organ in order to reveal the tumor, it is, however, the best tolerated method by the patient and with the most chances of saving the facial nerve. What is more, the translabyrinthine approach with its extensions allows the removal of neuromas of a quite large size.

Surgery of the acoustic neuroma is rather demanding. It is necessary for the patient to be thoroughly examined by the anesthetist before surgery, as well as his/her hospitalization in the intensive care unit for one to two days after the surgery. Our scientific team cooperates with specialized neurosurgeons, in order to guarantee the successful outcome of any operations on our patients.