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Neurinoma of the auditory nerve
Last reviewed: 31.07.2022
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The diagnosis of the neurinoma of the auditory nerve (in other words, the vagibular nerve schwannoma) means that a tumor appeared in the myelin sheath of the pre-cochlear nerve (8th cranial nerve).
This primary intracranial neoplasm, formed by glial (Schwannian) cells, has a benign character. However, it can increase, which leads not only to hearing loss, but also to other negative consequences.
According to medical statistics, the neurin of the auditory nerve accounts for 5 to 10% of all cases of cranial neoplasm.
[Causes of neurinoma of the auditory nerve
The neurinoma of the auditory nerve is one- and two-sided, with almost 96% of cases being unilateral. To date, the causes of neurinoma of the auditory nerve, which occurs only on the one hand, have not been fully clarified. Although there is a version that this sporadic form of the disease is a consequence of increased radiation, which leads to the destruction of the myelin sheath of nerve fibers.
But the etiology of bilateral neurinoma is directly related to such a rare hereditary pathology as type II neurofibromatosis. In this disease, in cells of various parts of the nervous system, genetically determined mutations occur that lead to the growth of benign tumors (neurofibroma, meningiomas, gliomas, schwann). And bilateral neurinoma of the auditory nerve, which can be formed even in adolescents, is considered the main sign of Type II neurofibromatosis. According to experts, in patients with this diagnosis the probability of occurrence of a bilateral neurinoma of the auditory nerve is almost one hundred percent, and, as a rule, by 30 years they lose the opportunity to hear.
Symptoms of neurinoma of the auditory nerve
This benign tumor appears in the multilayered myelin sheath of the cranial nerve - the nervus acusticus (VIII pair), which is located in the internal auditory canal and combines two separate nerves - the auditory (nervus Cochlearis) and the vestibular (nervus Vestibularis). Neoplasm can capture one of them or both at the same time, but does not usually grow into the structure of other tissues, but only presses on closely adjacent surrounding nerve fibers, cerebellar vessels and brainstem structures.
The neurinomas of the auditory nerve develop rather slowly, so the onset of the pathological process proceeds asymptomatically. And all the symptoms of the neurinoma of the auditory nerve appear as the size of its size increases and are related to the areas in which the tumor begins to exert pressure and how intense it is.
As clinical practice shows, the earliest sign of this disease is ringing and noise in the ear (tinnitus) and a feeling of stuffiness. Over time, a person begins to hear worse with this ear, but the hearing decreases gradually. The consequences of neurinoma of the auditory nerve, when its size in diameter reaches 2.5-3 cm and continues to increase, is complete loss of hearing.
Depending on the size of the tumor and its location in the auditory canal, the following symptoms of neurinoma of the auditory nerve are noted:
- dizziness and impaired coordination of movements (loss of balance when sharp turns of the head and changing the position of the body) - are caused by tumor pressure on the vestibular part of the affected nerve;
- nystagmus (involuntary rhythmic movements of the eyeballs) - the result of neurinoma pressure on the brain stem;
- loss of sensation and numbness (paresthesia) of half of the face on the side of the affected nerve - caused by tumor pressure on the facial nerve, innervating all facial muscles;
- pain in the face (trigeminal prozopalgia) on the side of neurinoma - the result of tumor pressure on the trigeminal nerve;
- loss of taste on the front of the tongue and violation of salivation - caused by compression of the XII craniocerebral nerve;
- violation of swallowing and articulation - due to compression of the glossopharyngeal and vagus nerves;
- decreased sensitivity of the cornea of the pupil (change in the corneal reflex);
- double vision in the eyes (diplopia) is a consequence of the defeat of the oculomotor nerve;
- headache, bouts of nausea and vomiting - the result of increased intracranial pressure.
Increase in intracranial pressure occurs with large dimensions of the neurinoma of the auditory nerve, which begins to press on the internal cerebrospinal fluid spaces of the brain. As a result, the work of the ventricular system of the brain is disrupted, the excess of the cerebrospinal fluid accumulates in the ventricles of the brain and there is a dropsy of the brain (hydrocephalus). And this is a real threat of damage to the vital centers of the brain stem.
Diagnosis of neurinoma of the auditory nerve
The main methods of otoneurological examination for the diagnosis of neurinoma of the auditory nerve are X-ray of the temporal bones in the transverse projection (according to Stenvers), computed tomography (CT), magnetic resonance imaging (MRI), audiography (detection of hearing impairment) and electrostemagmography.
It should be noted that at a neurinoma size of up to 1.5 cm, a computer tomography of the presence of a tumor can not be detected, and an incorrect diagnosis is possible - neurosensory hearing loss, which has a similar clinical picture at the initial stages.
The most informative diagnostic method and standard for the diagnosis of neurinoma of the auditory nerve is magnetic resonance imaging of the brain in various projections.
MRI with neurinoma of the auditory nerve is performed absolutely for all patients who have this diagnosis or its assumption. The study is carried out using a contrast agent administered intravenously. Such a tomogram makes it possible to clearly determine the size of the neoplasia (it has an oval shape with clear, even contours), to reveal the tumor matrix (the place of its growth beginning), which in the majority of cases is located in the internal auditory canal (adjacent to the posterior surface of the pyramid of the temporal bone) or in the bridge of the bridge, which ends this passage.
Axial and frontal projections of MRI with neurinoma of the auditory nerve give an opportunity to see signs of an auditory canal widening, how deep the tumor has grown into the cranial cavity and what neurovascular structures have managed to affect.
What do need to examine?
Treatment of neurinoma of the auditory nerve
Treatment of neurinoma of the auditory nerve is carried out by surgical removal, by radiotherapy, and by radiosurgery. But in some cases, for example, with prolonged hearing impairment or low-symptomatic symptoms (especially in the elderly), only dynamic monitoring of the course of the disease with periodic control examinations is resorted.
Removal of the neurinoma of the auditory nerve by open surgical intervention is necessary if the tumor grows in patients of young and middle age and the disease progresses, or when relapses occur after the first operation for its removal. And irradiation or radiosurgery is resorted when the sizes of neurinoma are small, and the symptoms of the disease are not very pronounced.
Radiation therapy and radiosurgery
Treatment of the neurinoma of the auditory nerve with the help of its irradiation does not remove the neoplasm and is used to slow or stop its further growth. Radiation therapy - fractionated stereotactic radiotherapy - is carried out repeatedly in small doses. However, as noted by physicians, fractionated irradiation is used in the therapy of neurinomas of the auditory nerve at the very least - because of the risk of tumors in the trained brain tissues.
Radiosurgery is a more modern method of radiation therapy using a high dose of ionizing radiation. The gamma-ray flux using the Gamma-knife and Cyber-knife devices focuses precisely on the tumor - thanks to a stereoscopic X-ray navigation system. In addition to positive results, radiosurgery with neurinomas of the auditory nerve has other advantages.
First, healthy brain tissue is irradiated in minimal doses. Secondly, this treatment does not cause pain. Thirdly, radiosurgery refers to non-traumatic techniques, so the rehabilitation period for patients after such treatment is much shorter than after the usual surgical intervention.
Operation in neurinoma of the auditory nerve
The decision on direct surgical intervention is made on the basis of a comprehensive analysis of the clinical picture of the disease in a particular patient - taking into account its age, general condition, neoplasm size and hearing loss. The main goal, pursued by the operation with neurinoma of the auditory nerve - to remove the tumor and stop the pathological process. But to return the lost hearing with the help of a scalpel is impossible.
To get to neurinoma, the surgeon needs to get into the internal auditory canal - a bone channel 10-12 mm in length and a diameter of about 5 mm. The passage starts with a hole on the back surface of the pyramid of the temporal bone of the skull, crosses it and reaches the bridge of the cerebellum, which is located between the brain stem and the cerebellum.
In neurosurgery, three methods have been developed (surgical approaches) for the removal of the neurinoma of the auditory nerve: translabyrinth, suboccipital and through the middle cranial fossa.
With translabirinth access (through the outer wall of the labyrinth part of the middle ear), a skull opening (craniotomy) is performed behind the ear, a small segment of the middle ear is removed, and then the tumor itself. With this approach, one can see the nerve and remove all the neurin, but after the operation the patient irretrievably loses the ability to hear with this ear. In addition, in a large number of cases there is a persistent disruption of the functions of the vestibular nerve, which forms a pair with the auditory nerve.
Suboccipital (suboccipital) access is made by opening the skull in the area under the nape and is used to remove tumors of considerable size. After such an operation, the chances of maintaining the remaining hearing are much greater. According to statistics, with the removal of a neurinoma of the auditory nerve measuring 3 cm or more, the hearing can be saved in almost a quarter of operated patients.
If the removal of the neurinoma of the auditory nerve is decided to be performed through the middle cranial fossa (which lies between the large wings of the sphenoid bone, the Turkish saddle and the anterior surface of the temporal bone pyramid), then the size of the neurinoma does not exceed 1.5-2 cm in diameter, and hearing preservation is possible. According to some reports, the hearing remains in the range of 15-45% of such operations.
Postoperative period with neurinoma of the auditory nerve
Surgical operation with this pathology is performed under general anesthesia, with craniotomy (trepanation of the skull). Postoperative period with neurinoma of the auditory nerve is quite long. In addition, the possibility of damage during the operation of other nerves located in the zone interfering with the structure of the brain is not ruled out. It is because of these injuries that various complications can occur in operated patients.
So, with damage to the vestibular nerve, a disturbance of equilibrium is observed, which in time can pass. But the lack of coordination of different muscles (ataxia) threatens to be lifelong. And in general, as neurosurgeons say, after such an operation the vestibular nerve very rarely functions normally.
If the facial nerve was touched, there may be problems with eye closure (lagophthalmus) and peripheral paralysis of facial muscles (prooplegia). Violation of the trigeminal nerve (V pair) is expressed in violations of sensitivity on the face. Problems with swallowing after surgery indicate damage to such cranial nerves as glossopharyngeal, vagal and sublingual.
And when the neoplasm was removed from the brainstem, in the postoperative period with neurinoma of the auditory nerve (as well as all the rest of the time), patients can feel the numbness of the parts of the trunk from the opposite side of the affected nerve - contralateral paresthesia.
Prevention of neurinoma of the auditory nerve
To date, the emergence of any neoplasm - in particular, unidentified etiology - is virtually impossible. Therefore, the prevention of neurinoma of the auditory nerve consists only in the fact that with persistent noise in the ear and a decrease in hearing, a person needs to consult an otolaryngologist. Because if these are the first symptoms of a neurinoma of the auditory nerve, then timely adequate medical measures will help to get rid of the tumor and avoid damage to other cranial nerves.
Prognosis of neurinoma of the auditory nerve
You can predict the neurinoma of the auditory nerve. First of all, it depends on its "dimensions". With the help of radiosurgery, a small tumor in almost 95 cases out of 100 ceases to increase. However, after the usual surgical removal, almost every fifth tumor continues to grow ...
It is especially worth emphasizing that the neurinoma of the auditory nerve is extremely rarely malignant, that is, it degenerates into cancer. In addition, a spontaneous decrease in neurinoma is observed in almost 6% of cases.