Acoustic neuroma MRI

Acoustic Neuroma (Vestibular Schwannoma) is a non-cancerous (benign) tumor that develops on the vestibulocochlear nerve, which connects the inner ear to the brain. This nerve is responsible for transmitting sound and balance information. Acoustic neuromas are slow-growing tumors that typically arise from Schwann cells, which produce the myelin sheath covering the nerve.

Causes of Acoustic Neuroma

The exact cause of most acoustic neuromas is unknown, but some cases are linked to a genetic disorder called neurofibromatosis type II (NF2). People with NF2 tend to develop benign tumors on multiple nerves, including both sides of the vestibulocochlear nerve.

Most acoustic neuromas occur sporadically, meaning they are not inherited or linked to a specific cause.

Symptoms of Acoustic Neuroma

Symptoms of acoustic neuroma can vary depending on the size and location of the tumor, but they typically develop slowly as the tumor grows. Common symptoms include:

• Hearing Loss: Gradual hearing loss in one ear is the most common symptom. This may be accompanied by a sensation of fullness or ringing in the ear (tinnitus).
• Tinnitus: Persistent ringing, buzzing, or hissing sound in the affected ear.
• Balance Problems: As the tumor affects the vestibular part of the nerve, dizziness, unsteadiness, and a sense of vertigo may occur.
• Facial Numbness or Weakness: In larger tumors, nearby facial nerves can be affected, leading to numbness, tingling, or muscle weakness in the face.
• Headaches: Pressure on nearby tissues or nerves may cause headaches.
• Ear Fullness: A feeling of fullness in the affected ear, without any infection.

Diagnosis of Acoustic Neuroma

Diagnosing acoustic neuroma typically involves a combination of clinical examination and imaging studies:

• Hearing Test (Audiometry): A detailed hearing test is often the first step in evaluating hearing loss and can help identify the specific type of hearing loss associated with acoustic neuroma.

• MRI Scan: Magnetic Resonance Imaging (MRI) with contrast is the gold standard for diagnosing acoustic neuroma. It allows for detailed imaging of the brain and inner ear structures, helping to detect even small tumors.

• CT Scan: Although less sensitive than MRI, a computed tomography (CT) scan may be used if MRI is not an option.

• Electronystagmography (ENG): This test may be used to evaluate balance and detect vestibular dysfunction, although it is not always necessary.

• Brainstem Auditory Evoked Response (BAER): This test evaluates the hearing pathways in the brainstem and may show abnormalities when the tumor affects the auditory nerve.

Treatment of Acoustic Neuroma

Treatment depends on the size and growth of the tumor, symptoms, and overall health of the patient. Options include:

1. Observation (Watchful Waiting): Small, slow-growing tumors that are not causing significant symptoms may be monitored with regular MRI scans to track growth. This is often the approach for elderly patients or those for whom surgery carries high risks.

2. Surgery: There are several types of surgical approaches to remove the tumor, depending on its size and location. Surgery aims to remove as much of the tumor as possible while preserving hearing and facial nerve function. However, complete removal may sometimes damage nearby structures, leading to complications like hearing loss or facial nerve weakness.

   • Translabyrinthine approach: Used for larger tumors or when hearing preservation is not possible.
   • Retrosigmoid/suboccipital approach: Allows for the possibility of hearing preservation.
   • Middle fossa approach: Used for smaller tumors, with the aim of preserving hearing.

3. Radiation Therapy: Stereotactic radiosurgery (such as Gamma Knife or CyberKnife) can deliver targeted radiation to shrink or stop the growth of the tumor. This option is often used for smaller tumors or for patients who are not candidates for surgery.