The acoustic neuroma is a term coined decades ago when it was thought that the tumor had its origin in the hearing nerve or cochlear nerve. Today we know that the tumor of the sheath of Schwann cells, specifically the superior division of the vestibular nerve. Both nerves, cochlear and vestibular constitute a common nerve trunk, called vestibulocochlear nerve. Although the term acoustic neuroma is wrong, in the scientific literature still known by this name and also the vestibular schwannoma.
It is a tumor begins to grow within the internal auditory canal and as is taking size extends the cerebellopontine angle in the posterior cranial fossa. This is an area of great importance in coexisting nerve and vascular structures extreme consideration, such as extrusion, which is a part of the brainstem, or cerebellum and cranial nerves or arteries that supply the brain stem and cerebellum. Any damage to this area can cause death of the patient or leave some irreparable consequences.
Causes of acoustic neuroma
The acoustic neuroma is one of the most common intracranial tumors, comprising 8-10% of all. This is a benign tumor that appears as a result of the loss of a tumor suppressor gene on the long arm of chromosome 22.
The incidence of this tumor is considerably increased in cases of neurofibromatosis, and the onset of a tumor in each of the internal auditory canals that have pathognomonic neurofibromatosis type 2.
Symptoms of acoustic neuroma
The most common symptoms include hearing loss, ear noises or tinnitus and balance disorders. There may be other symptoms such as headache, numbness or paralysis of the face.
If the tumor continues to grow, gradually symptoms of compression of the cerebellum and brainstem may appear. If it were to reach an important (4 cm or more) size could produce an obstructive hydrocephalus with all that entails clinic.
Diagnosis of acoustic neuroma
First, and as should always be done to reach a diagnosis, we will build on the clinic that the patient, followed by an audiometric evaluation. If this is consistent with this type of tumor, we ask a computed tomography (CT) with contrast and magnetic resonance imaging (MRI), also with contrast, which will give us information on the location of the tumor and its characteristics, such as the shape, size, behavior with the contrast, or the relationship with neighboring structures vital aforementioned
How these tumors handled?
We have three ways to act in these processes:
- expectantly. If the tumor is small you can make regular monitoring of the lesion with serial MRIs. If it stays stable conservative treatment will be followed, and if growth will be seen to intervene.
- radiosurgery. Stereotactic radiation comprises administering to the tumor can be shaped stereotactic radiosurgery, in a single dose, or as stereotactic radiotherapy, fractionated multisession. This approach is intended to stop tumor growth, having some cases progressively smaller and others that still progressing tumor growth. If the latter is confirmed, it will be necessary to intervene surgically.
- Microsurgery. Used by ear specialists and neurosurgeons, either, or together as we do at our hospital. Using this technique in most cases we managed to remove the tumor completely and we no longer have to worry over its growth potential.
There are three possible approaches to these tumors:
- retrosigmoid. It is the most used by most neurosurgeons. If we want to preserve hearing will be the technique of choice. The biggest drawback is the necessary retraction of the cerebellum to reach the tumor.
- translabyrinthine. With the mere realization of this approach the patient automatically loses hearing, which will be done in all those processes in which the size or location is discarded, input, preservation of that function. The surgical field is smaller than in the previous approach, but it has the advantage that it is not necessary to retract the cerebellum.
- middle fossa. It is used in tumors in which we want to keep hearing and those that are small in size. It is the least used surgical technique.
Removal of acoustic neuroma
The tumor should be resected always, but in those cases where the facial nerve is very thin and leaves us only a small sheet of tumor attached to it, it is lawful and accepted in major surgical series of relevance not risk facial paralysis patient and let the little remaining tumor, on the other hand, usually show no or little growth over time.
What are the risks the removal of acoustic neuroma?
The removal of an acoustic neuroma requires great anatomical knowledge of the area and a great technical skill. The whole procedure must be done with the help of a surgical microscope to provide us with good lighting in the depth of field and magnification adequate for the proper handling of nerve structures.
One of the most common problems that occur after the removal of an acoustic neuroma, in addition to hearing loss, facial paralysis is. The cochlear nerve responsible for hearing can be preserved only in those small tumors which do not amount to occupy the bottom of the internal auditory canal.
Avoid facial paralysis is one of the biggest challenges we have surgeons who take care of the excision of these tumors. A complete facial paralysis is very disfiguring and causes serious problems of coexistence and behavior in affected individuals.
In our hospital, we are in the set neurosurgeons and otolaryngologists team, we have achieved an anatomical preservation of the facial nerve in 93% of cases and a functional conservation of the same by 78%. In patients facial paralysis is final we can make nerve anastomosis techniques, that can recover the function of the facial nerve. In this sense, we have achieved very favorable results, thanks to the Unit Facial Paralysis of our center, which are integrated the following specialties: neurosurgery, otolaryngology, maxillofacial surgery, rehabilitation, ophthalmology, neurology, neurophysiology and neuroradiology. Thanks to the joint and coordinated participation of all these specialists the results are very good