OVERVIEW

Where is the auditory nerve located, in the ear or in the head?

The auditory nerve is located within the skull on both sides of the human head, extending from the medulla oblongata (the part connecting the spinal cord and the brain) to the internal auditory canal. In other words, the auditory nerve is present both deep in the ear and inside the cranial cavity.

What is the function of the auditory nerve?

The auditory nerve is responsible for transmitting auditory signals on one hand and balance-related signals on the other. Damage to the auditory nerve can lead to deafness and balance disorders.

What is an acoustic neuroma?

Acoustic neuroma is the most common type of intracranial nerve tumor, accounting for 7%–12% of intracranial tumors. It originates from the outer layer (the nerve sheath) of the auditory nerve.

Cranial nerves are like electrical wires: the core of the nerve is equivalent to the metal wire inside, while the nerve sheath is like the insulating outer covering. Acoustic neuroma is a tumor that arises from the nerve sheath and should more accurately be called a vestibular schwannoma. It mainly occurs in the intracranial segment of the auditory nerve.

Is the incidence of acoustic neuroma high?

Acoustic neuroma accounts for 6% of brain tumors and can occur in any ethnic group. The incidence is slightly higher in women than in men.

Is acoustic neuroma malignant or benign?

Malignant transformation of acoustic neuroma is extremely rare. Almost all patients can undergo complete tumor resection, and recurrence after total removal is very rare, if it occurs at all.

SYMPTOMS

What are the clinical manifestations of acoustic neuroma?

• Tinnitus: Unilateral, varying in pitch, progressively worsening, often occurring simultaneously with hearing loss, or may be the only early symptom.

• Hearing loss: Unilateral progressive deafness, often initially presenting as difficulty understanding speech despite hearing sounds, eventually leading to complete deafness.

• Vertigo: A minority experience brief rotational vertigo, accompanied by ear pressure, nausea, and vomiting, similar to symptoms of endolymphatic hydrops. However, most report unsteadiness or a spinning sensation. Due to the tumor's slow growth, vestibular compensation gradually occurs, leading to the disappearance of vertigo.

• Patients may experience pain deep in the ear or mastoid region, along with numbness in the posterior wall of the external auditory canal.

What are the consequences of acoustic neuroma?

• Persistent hearing decline may lead to complete hearing loss.

• Facial nerve dysfunction typically occurs in the late stages, manifesting as facial muscle twitching and paralysis.

• If the trigeminal nerve is affected, trigeminal neuralgia may occur.

• In the terminal stage, patients may experience dysfunction of the brainstem's vital centers and cerebellar tonsillar herniation, leading to death.

CAUSES

What causes acoustic neuroma?

• Genetic factors: Both unilateral sporadic and bilateral acoustic neuromas are caused by the same NF-2 gene, located on human chromosome 22. The classic type 1 neurofibromatosis (NF-1), found on chromosome 17, can also develop into bilateral acoustic neuromas.

• Other physical, chemical, or biological factors may also play a role.

Who is more likely to develop acoustic neuroma?

It is more common in adults aged 30–60, with a higher incidence in women. The female-to-male ratio is approximately 3:2.

Under what conditions does acoustic neuroma grow faster?

Pregnancy in female NF-2 patients can accelerate symptom onset and tumor growth. This suggests that hormones may trigger rapid growth of acoustic neuromas.

DIAGNOSIS

What tests are needed for acoustic neuroma?

Hearing tests; Vestibular nerve function tests; X-ray examination; Cerebral angiography; CT and MRI scans; Brainstem auditory evoked response testing.

Why are these tests performed for acoustic neuroma? What are their purposes?

• Hearing tests: Can differentiate whether hearing impairment originates from the conduction system, cochlea, or auditory nerve.

• Vestibular nerve function tests: Since most acoustic neuromas originate from the vestibular portion of the auditory nerve, this test is a common diagnostic method.

• X-ray examination: Detects abnormalities such as internal auditory canal enlargement or petrous bone tomography indicators to diagnose acoustic neuroma.

• Cerebral angiography: Evaluates tumor blood supply and facilitates preoperative embolization to reduce intraoperative bleeding.

• CT and MRI scans: These two tests complement each other. While CT can confirm the presence of a tumor, MRI provides details about whether the tumor is compressing the fourth ventricle. When CT is inconclusive, MRI can aid in differential diagnosis.

• Brainstem auditory evoked response testing: Over 95% of acoustic neuromas exhibit abnormalities in this test, making it widely used for early diagnosis.

Which diseases are easily confused with acoustic neuroma?

Acoustic neuroma should be differentiated from facial nerve tumors, meningiomas, epidermoid cysts, gliomas, trigeminal schwannomas, and arachnoid cysts. Specific differentiation should be performed by a specialist.

TREATMENT

Which department should I visit for acoustic neuroma?

Neurology, Neurosurgery.

What are the treatment principles for acoustic neuroma?

Early diagnosis and early treatment. For larger tumors accompanied by headaches, nausea, or vomiting, prompt surgery with complete tumor removal is the treatment principle.

Does acoustic neuroma always require surgery?

Not necessarily.

It mainly depends on the tumor size, the patient's physical condition, their preferences, and the medical facility's capabilities.

• For tumors >3cm in diameter or those causing intracranial hypertension (excessive brain pressure leading to headaches, severe vomiting, etc.), radiation therapy alone is generally not advisable. Due to significant compression, especially on the brainstem, surgical removal is the only option.

• For tumors <3cm in diameter, gamma knife or X-knife radiotherapy may be considered.

What are the risks of acoustic neuroma surgery?

• The most common complications are hearing loss and facial paralysis, manifesting as inability to close the eyes, mouth deviation, or leakage while drinking.

• Severe cases may affect the brainstem, leading to respiratory or cardiac arrest and death.

What is the approximate hospitalization cost for acoustic neuroma?

Around 50,000 RMB, though the final cost depends on tumor size, complications, and local economic conditions, possibly higher.

How long is the typical hospitalization period for acoustic neuroma?

Generally 2–3 weeks.

Is follow-up required after discharge for acoustic neuroma treatment?

Yes. The first follow-up should be 1 month after discharge, then 3 months, followed by 6 months and 1 year, with gradually extended intervals.

What tests are needed for acoustic neuroma follow-up?

The most important is a cranial MRI.

How long can a patient with acoustic neuroma live?

This depends on how early the tumor is detected and the extent of surgical removal. Acoustic neuroma is benign, and complete resection allows long-term survival.

Is medication required after discharge for acoustic neuroma treatment?

If complications occur, corresponding medications may be prescribed. There are no specific drugs for acoustic neuroma itself.

Does surgery or hearing aids help with deafness caused by acoustic neuroma?

Deafness caused by acoustic neuroma is sensorineural hearing loss. Neither surgery nor hearing aids can restore hearing.

DIET & LIFESTYLE

What should patients with acoustic neuroma pay attention to in daily life?

• Strictly follow the doctor's instructions, take medication on time and in the correct dosage, and do not stop medication without authorization;

• Schedule regular follow-up examinations and imaging tests;

• Patients should learn about acoustic neuroma and seek immediate medical attention if symptoms of recurrence occur;

• Avoid air travel and diving within three months;

• Keep the wound area clean and dry, prevent water from entering the ear canal, and avoid infection.

PREVENTION

How to Prevent Acoustic Neuroma?

Given that the cause of acoustic neuroma is not very clear, and it is known to be related to DNA issues, the only approach is early detection and prompt surgical treatment. The most crucial prevention lies in post-surgery care, where active measures should be taken to prevent complications such as intracranial infections, lung infections, and others.