Acoustic neuroma is an intracranial tumor arising from 8th cranial nerve known as vestibulocochlear nerve present in internal acoustic meatus or cerebellopontine angle located at a petrous part of the temporal bone in the posterior cranial fossa. It arises from the myelin sheath of the nerve formed of the cells. It waits from the vestibular part of the 8th cranial nerve.
Acoustic neuroma is classified on the basis of size. Small tumors are referred to as the size of less than 1.5 cm. Schwann tumors belong to the size group of 1.5 to 2.5 cm. Large acoustic neuroma is of size greater than 2.5 cm.[1]
What Is The Average Size Of An Acoustic Neuroma?
The average size of acoustic neuroma is usually less than 1.5 centimeters and belongs to an incomplete small size classification group. This is because acoustic neuroma is a slow-growing tumor and mostly found as a fast-growing incidental finding on various brain investigations and postmortem.
There was three growth patterns seen in the acoustic neuroma. The first pattern is no growth or very slow growth of the tumor. The second pattern is slow-growing tumors with a growing rate of <0.2cm/ year. The third pattern is fast-growing tumors with a rate of above>1cm/ year.[2]
The first-line treatment for acoustic neuroma is to wait and watch. Continuous follow up is required to monitor the growth rate and spread of the tumor. Surgical treatment is also available and successful incomplete treatment. Various different approaches are used to reach the site of the tumor because of a difficult location. The approaches commonly used are the translabyrinthine approach, the rectosigmoid approach, and the middle cranial fossa approach.
Does Hearing Return After The Surgery?
Hearing ability depends upon various factors involved in the acoustic neuroma first-line it depends on the size of the tumor, large tumors are usually associated with loss of hearing ability. Surgical treatment may or may not be able to restore the ability to hear. Various surgical approaches have different prognosis for hearing ability postoperatively.
The most commonly used approach that is the translabyrinthine approach is associated with loss of hearing ability in most of the cases because it respects the whole of the tumor which can also take away the auditory nerve with it. Usually was before using this approach, hearing ability is already lost. The effort to reduce the hearing loss could be done in borderline size of tumors.
The rectosigmoid approach has the poorest prognosis in terms of return of hearing ability. There is slow-growing dissection done in this approach with the significant damage to the vestibulocochlear nerve first which is generally responsible for the loss of hearing ability postoperatively.
The middle cranial fossa approach for the treatment of acoustic neuroma is the best approach to save the hearing ability of the patient. It implies minimal dissection of the surrounding tissues and precise removal of the tumor which can help in saving the hearing ability. Also, this approach is used for small tumors which also have an impact on hearing due to less involvement of the associated nerve. This approach usually compromises the resection of the tumor if followed for large size tumors and some of the tumor tissue could be left behind. The use of any of the given approaches depends upon the requirement of the patient and the expertise of the surgeon performing.
Conclusion
Acoustic neuroma is usually a small-sized tumor with a slow growth rate and minimal symptoms. Surgical resection can be done if the size has exceeded the other treatment modalities and if the patient opts for this choice. The various approaches used for the treatment of acoustic neuroma are also dependent upon the available technology at the hospital and on the expertise of the surgeon. The hearing ability could be saved in small size tumors and can be supported by the use of hearing aids after the operation but the resection of the tumor is much more important than saving the hearing ability of one side of the ear.
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