Acoustic Neuroma

Introduction

Following cell differentiation and proliferation, cell division is the process through which cells are multiplied. Tissues are groups of cells, and the abnormal growth of tissue in an organism is referred to as a tumour. Tumours typically originate as a result of certain disruptions in cell development and the generation of new cells. When a tumour’s growth is restricted, it is benign (non-cancerous), but when it spreads to the body’s key organs, it is malignant (cancerous).

What is Acoustic Neuroma?

Acoustic neuroma is a non-malignant and rare tumour that is also called a Vestibular schwannoma. It is produced by the Schwann cells that surround and support the nerves. The vestibular and auditory nerves, which control balance and hearing, respectively, compose the branches of cranial nerve VIII, commonly known as the vestibulocochlear nerve, where tumours have grown. A critical instance develops when the tumour grows rapidly and continuously.

Causes of Acoustic Neuromas

• Some people have a rare genetic condition called neurofibromatosis type 2, which is characterized by the formation of tumours on the nerves. Acoustic neuroma is a result of this condition. 
• Acoustic neuromas are reported in only 5% of patients with neurofibromatosis type 2 (NF2 patients). 
• In the majority of cases, the exact aetiology of auditory neuroma is unknown. However, some risk variables, including family history, radiation exposure, age, and loud noise exposure, are still thought to be the root cause.

Symptoms of Acoustic Neuroma

Along with other difficulties, the growth of tumours in the vestibulocochlear nerve might affect balance. The following are the symptoms of such tumorous growth:

• Impaired hearing: Acoustic neuromas 90% of the time accompany some degree of hearing loss. The tumour’s pressure on the nerve or the discharge of compounds harmful to hearing can both cause hearing loss. 
• Tinnitus: Patients with tinnitus experience a high-pitched hissing or buzzing sound in their ears. Tinnitus can occasionally become persistent. Hearing loss may or may not be present in tinnitus patients.
• Vertigo and loss of balance: Vertigo, a sudden sensation of the head tilting and spinning, is caused by the growth of a tumour on the balance and auditory nerve. Because of this patient can become unsteady and lurch. 
• The fullness of the ear: Acoustic neuroma patients may experience full ears as if water is trapped in the ear canal. Hearing loss is frequently to blame for this.
• Other signs and symptoms of an acoustic neuroma include facial numbness, headaches, nausea, changes in taste, and difficulty swallowing.

Diagnosis of Acoustic Neuroma

The examination of the ear is typically the first step in the diagnosis of an acoustic neuroma, which is then followed by evaluations of the patient’s medical history, imaging, and hearing capacity. Tumours in the brain may be detected with MRI or CT scans using magnetic resonance imaging (MRI) or computerized tomography (CT). The following tests are crucial for determining the presence of an acoustic neuroma: 

• Audiometry: An audiometer uses a painless hearing test to quantify one’s hearing depending on how loud sounds are and how quickly they vibrate. 
• Pure Tone Average (PTA): it is a measurement used to assess hearing impairment for speech comprehension. A higher rating denotes a hearing impairment.
• Speech Reception Threshold (SPT):  The patient can hear speech at this volume at least 50% of the time. A higher score, similar to PTA, denotes hearing impairment.
• Discrimination in speech (SD): It is a test of the patient’s capacity to distinguish between speech in quiet and noisy settings. Hearing loss is indicated by the lower score.

Treatment for Acoustic Neuroma

The course of treatment for an acoustic neuroma might vary; it is typically determined by the patient’s general health, the size and progression of the tumour, and its symptoms. Three treatment methods are available:

• Monitoring: Adults who have primary slow-growing tumours may not exhibit any symptoms, making patient surveillance a valuable alternative for follow-up care. The ideal situation for a monitor is when the tumours are up to 1.5 cm in size. Before the tumour grows to a dangerous size, surgery must be performed to remove it.
• Surgery: Acoustic neuromas can potentially be treated surgically. The surgical procedure’s main goals are to eliminate the tumour and avoid facial paralysis. Complete excision, however, may not always be possible due to the tumour’s proximity to vital brain regions. This procedure carries the potential for several side effects, including hearing loss, tinnitus, cerebrospinal fluid leakage via the nasal route, face numbness, etc.
• Radiation therapy: It is a non-surgical option; stereotactic radiosurgery, which is most frequently used, can stop the growth of the tumour and lessen the death of neighbouring cells. With this technique, the gamma rays are directed precisely to the tumour without damaging nearby cells. For patients with big tumours, this treatment is not advised.

Summary

Tumours typically originate as a result of certain disruptions in cell development and the generation of new cells. Acoustic neuroma is a non-malignant and rare tumour that is also called a schwannoma. Acoustic neuromas are reported in only 5% of patients with neurofibromatosis type 2 (NF2 patients). Along with other difficulties, the growth of tumours in the vestibulocochlear nerve might affect balance. Tumours in the brain may be detected with MRI or CT scans using magnetic resonance imaging (MRI) or computerized tomography (CT).

 Frequently Asked Questions

1. How does Stereotactic Radiosurgery Work?
Ans. With the help of a 3D coordinate system, stereotactic surgery may find small targets inside the body and carry out a variety of minimally invasive surgical procedures on them, including biopsy, ablation, lesion, stimulation, injection, implantation, and radiosurgery, etc.

2. Define Audiometry?
Ans. A diagnostic hearing test is called audiometry. The loudness of the tone and the speed of the sound determine one’s capacity to hear it. For the detection of hearing impairment, it is crucial.

3. What is the Speech Reception Threshold?
Ans. The speech reception threshold is the lowest degree of speech hearing at which a person can recognize 50% of spoken words. Each ear has reached its speech reception threshold. It serves as a reference point for supra-threshold tests and serves to validate the thresholds discovered using PTA.

4. What is Tinnitus?
Ans. Patients with tinnitus experience a high-pitched hissing or buzzing sound in their ears. Tinnitus can occasionally become persistent. Hearing loss may or may not be present in tinnitus patients.