What is Acoustic Neuroma?
Acoustic neuromas, also called vestibular schwannomas, are noncancerous growths that impact the nerves responsible for hearing and balance. As they grow, they can pose dangers by putting pressure on the brain area that controls the flow of spinal fluid.
The tumour forms on your 8th cranial nerve, also known as the vestibulocochlear nerve. This nerve is crucial because it sends signals from your inner ear to your brain, helping you hear and stay balanced.
Despite its rarity, understanding its symptoms, diagnosis, and treatment options is crucial for individuals potentially impacted by this condition.
Symptoms of Acoustic Neuroma
Acoustic neuromas typically grow slowly, leading to a gradual progression of symptoms. Initially, individuals may experience mild hearing loss, followed by the onset of tinnitus—a persistent ringing in the ear.
As the tumour advances, it can irritate the trigeminal nerve, resulting in weakness on the same side of the tumour due to its proximity to the facial nerve.
Subsequently, as the tumour grows, it can compress the brainstem, leading to weakness in the limbs as the nerves from the cerebral cortex to the feet, legs, abdomen, thorax, and hands pass through the brainstem.
This proximity to the brainstem can cause further complications, such as increased pressure in the brain, ultimately leading to vision loss in both eyes. This gradual progression underscores the importance of early detection and intervention in managing acoustic neuromas effectively.
The Cause of Acoustic Neuroma
Acoustic neuromas can be associated with a gene issue on chromosome 22. This gene usually makes a protein that helps control the growth of Schwann cells covering the nerves.
It is still not clear what triggers this gene problem and the root cause of this condition is unknown. This gene change is inherited in people with a rare disorder called neurofibromatosis type 2. People with this disorder often develop tumours on both sides of their head’s hearing and balance nerves. These tumours are called bilateral vestibular schwannomas.
The Diagnosis
In the diagnostic phase, it’s crucial to clinically assess the extent of nerve involvement. If hearing loss is present, it indicates involvement of the vestibular nerves. Acoustic neuromas originate from the acoustic nerve, which is responsible for hearing. Therefore, understanding which nerves are affected helps in accurately diagnosing acoustic neuromas, explains Dr. Sampangi Raghu Ram Raj, a Neurosurgeon.
Next, we examine whether the facial nerve is affected by assessing for any weakness in facial muscles. Additionally, we investigate if there’s involvement of other nearby structures or nerves, such as weakness in the limbs or loss of vision. This clinical assessment helps in understanding the full scope of the condition and guiding further diagnostic and treatment decisions.
Also, conducting an MRI of the brain with contrast is essential to visualize the acoustic neuroma. Additionally, to evaluate hearing loss, audiometry is performed. This test helps determine the precise degree of hearing loss by measuring decibel levels. The audiogram, generated from audiometry, provides detailed information about the extent of hearing impairment, aiding in accurate diagnosis and treatment planning.
He also further added that when preparing for surgery, it’s crucial to determine whether the tumour has invaded the surrounding bone. To assess bone involvement, a CT scan of the temporal bone is necessary. This imaging procedure provides specific details about the extent to which the tumour has grown into the bone, guiding surgical planning and ensuring appropriate treatment measures are taken.
If vision loss is present, it’s important to undergo an ophthalmological examination to assess for any potential permanent damage to the eyes and to ensure appropriate management.
What surgical approaches do you recommend?
Dr. Sampangi Raghu Ram Raj emphasizes that the treatment depends on the size of the tumour. If the tumour is incidentally discovered during another scan, it may be monitored over time. In such cases, patients can schedule yearly appointments with a neurosurgeon for follow-up. If there is any indication of growth, the neurosurgeon may request an MRI to assess changes in tumour size.
If the tumour is causing symptoms such as hearing loss, and facial nerve weakness, or if symptoms are progressively worsening, removal of the tumour becomes necessary. This can be achieved through either open or endoscopic approaches. Stereotactic radiosurgery is another option, although the most commonly chosen procedure is an open craniotomy for tumour excision.
Do you anticipate total tumour removal with a single operation? If not, what are the follow-up procedures?
Yes. 99.9% of the tumour would be removed in a single sitting.
One crucial aspect to consider is family history. If a close family member such as a parent, sibling, or even a second-degree relative has been diagnosed with acoustic neuroma, seeking a neurosurgeon’s opinion and undergoing a thorough assessment is advisable. The neurosurgeon can determine the individual’s risk of developing acoustic neuroma and decide whether further evaluation or monitoring is necessary during subsequent visits.