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What is Acoustic Neuroma, Causes and Treament

  By posted Jul 29th 2013
Healthy Living

 

What is Acoustic Neuroma, Causes and Treament  Healthy living

 

 

 

Acoustic Neuroma is a slow growing, benign tumour, which arises from the hearing nerve (VIIIth cranial nerve).  The hearing nerve has two parts

 1) Conveying hearing, theacoustic nerve 

2) Maintaining balance, the vestibular nerve. 

 

Acoustic neuroma is a misnomer as this tumour arises from vestibular component (95%) and better termed ‘vestibular schwannoma’. Each nerve is like a wire, nerve and inside it is a string and a protecting wrap made up of ‘schwann cells’. These tumours arise from Schwann cell hence termed ‘schwannoma’.

 

Incidence of acoustic neuroma varies from region to region. Average incidence is 0.7 to 1 per lac population. The incidence has apparently increased due to early detection, secondary to advancement and easy availability of imaging modalities like Magnetic resonance imaging (MRI). 

 

Exact cause of solitary (single) tumour is not known. However, there is a familial disorder known as Neurofibromatosis-2 (NF-2), where due to abnormality in chromosome no. 22, close family members suffer from bilateral acoustic neuromas. 

 

Presentation of Acoustic Neuroma

Acoustic neuromas can present with varied symptoms depending on their size and rate of growth. Symptoms range from subtle minor complaints like simple persistent headache to a critical, diminution of vision. A relatively small tumour can present as ringing in the ear (tinnitus) and gradual worsening deafness. While a larger tumour produce mass effect and can present as imbalance, giddiness, altered speech, and even visual blurring (due to high pressure on visual nerve). They can produce obstruction to the flow of water in the brain (CSF) termed ‘hydrocephalus’. 

 

Due to its critical position in cerebello-pontine angle (CPA) these tumours present a great challenge to the neurosurgeons. CPA is a space situated between small brain (cerebellum), pons (brain stem) and petrous bone. It provides space for all major cranial nerves like trigeminal (V N), abducent (VI), facial (VII), hearing (VIII) and swallowing nerves (IX to XI Ns). There are other important vessels running through this region.

Clinical examination of patients with these symptoms is of immense importance. Tests required to establish the diagnosis are MRI (Plain and following contrast injection) and audiometry (quantification of hearing).

 

Treatment of Acoustic Neuroma

The treatment depends on the size of the tumour and whether it is  unilateral or bilateral.

 

Presentation of Acoustic Neuroma

 

Options 

1) Microsurgery 

2) Radiation therapy 

3) Watchful observation

 

Treatment of Acoustic Neuroma

Microsurgery: It has been the main type of  treatment in most acoustic neuromas. The facial nerve (VII) remains in close proximity to the tumour and preservation of this is the goal. Neurosurgeons having been operating these tumours for approximately a century. Initially, saving the life of the patient was the main goal. However, as neurosurgery advances, they can now save the facial nerve and even the hearing. The introduction of the microscope, CUSA (Cavetronic ultrasonic suction aspirator) and intra-operative electric monitoring (electromyography) have made tumour excision easy and relatively safer. Microsurgical training and the experience of the neurosurgeon has also played an important role in improving tumour excision. Patients with hydrocephalus may need a separate operation, where a tube is inserted into the cavities of brain (ventricles), which shunts the obstructed CSF to the tummy or elsewhere (ventriculo-peritonial shunt surgery).

 

Treatment of Acoustic Neuroma

Radiation therapy: This is usually effective for small tumours (<2cm) or small residual/ recurrences after initial surgical excision. It can be accomplished either by using gamma knife (γ-rays) or X-ray knife (Linear accelerator). This helps arrest growth of the tumour and sometimes can even shrink it. This treatment is mostly useful when the hearing needs to be saved like in cases of bilateral acoustic neuromas in one patient (NF-2). It also reduces the chances of facial disfigurement, which is otherwise a known complication of surgical intervention (either temporary or permanent).

 

Treatment of Acoustic Neuroma

Watchful observation- In selected patients where the growth rate of the tumour is slow, it is demonstrated on serial MRI scans.

 

*Data Courtesy: Dr Shashank Joshi, Consultant in Neurosurgery, MS, MCH (Neurosurgery),Sevenhills Hospital *Image courtesy: © Thinkstock photos/ Getty images and
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