An acoustic neuroma, also known as a vestibular schwannoma, is a non-cancerous growth that develops on the main nerve connecting the inner ear to the brain. This nerve, called the vestibulocochlear nerve (cranial nerve VIII), plays a role in both hearing and balance. This benign tumor can lead to various symptoms, including tinnitus.
What is an Acoustic Neuroma?
An acoustic neuroma originates from Schwann cells, which are specialized cells that normally provide support and insulation to nerve fibers. These tumors grow slowly over many years. They commonly affect adults between 30 and 60 years old, with most cases occurring spontaneously without a clear cause.
The tumor develops on the vestibulocochlear nerve. As it expands, it can press on these delicate nerves. Although benign, their growth can affect nearby nerves and brain structures, potentially leading to symptoms.
How Acoustic Neuroma Leads to Tinnitus
An acoustic neuroma causes tinnitus by interfering with the auditory nerve. As the tumor grows, it can compress or irritate the cochlear nerve, disrupting the electrical impulses sent along the nerve.
This disruption of nerve signals can lead to misfiring or abnormal electrical activity within the auditory system. This creates the perception of sound even when no external sound is present. Additionally, the tumor’s presence can alter blood flow to the inner ear, contributing to the dysfunction of the auditory system and the generation of internal sounds.
Specific Characteristics of Acoustic Neuroma Tinnitus
Tinnitus associated with an acoustic neuroma has specific characteristics. A distinguishing feature is its unilateral nature, occurring in only one ear.
The sounds reported vary, but commonly include ringing, buzzing, roaring, or hissing. This tinnitus can be continuous or intermittent, and its intensity can range from a soft whisper to an overwhelmingly loud noise. While pulsatile tinnitus (a rhythmic sound synchronized with a heartbeat) is less common with acoustic neuromas than with vascular conditions, the unilateral and persistent nature of the sounds warrant medical evaluation.
Diagnosis and Treatment Approaches
Diagnosing an acoustic neuroma involves specialized tests. An audiometry test, conducted by an audiologist, assesses hearing in each ear, often revealing asymmetric hearing loss. Auditory brainstem response (ABR) testing measures brain wave activity in response to sounds, helping identify abnormalities in the auditory pathway.
The definitive diagnostic tool is magnetic resonance imaging (MRI) with contrast dye. An MRI can detect tumors as small as 1 to 2 millimeters, providing detailed images of the brain and surrounding structures. If an MRI is not feasible, a CT scan might be used, though it is less sensitive for detecting small tumors.
Management strategies for acoustic neuromas and associated tinnitus are tailored based on tumor size, growth rate, overall health, and symptoms. One approach is observation, also known as “wait and scan,” which involves regular imaging and hearing tests every 6 to 12 months, particularly for small, slow-growing, or asymptomatic tumors. If the tumor grows or symptoms worsen, active intervention may be considered.
Microsurgery involves the surgical removal of the tumor. Another approach is radiation therapy, specifically stereotactic radiosurgery, which uses precisely targeted radiation to stop tumor growth without requiring an incision. This is often used for smaller tumors, generally less than 2.5 centimeters, or for patients not suitable for surgery. While these treatments aim to manage the tumor, tinnitus can sometimes persist even after intervention, and additional therapies like sound therapy or counseling may be used to manage the ongoing symptom.