Have you noticed that your hearing is worse in one ear than the other? Perhaps you have persistent ringing in one ear, feel slightly off balance when walking, or have noticed that your balance just isn’t what it used to be.
There are many common causes for these symptoms. However, one condition that doctors may sometimes need to rule out is an Acoustic Neuroma, more accurately known as a Vestibular Schwannoma.
Vestibular Schwannomas are benign, usually slow-growing tumours that develop on the nerve connecting the inner ear to the brain. This nerve carries important information about both hearing and balance.
Interestingly, Vestibular Schwannoma doesn’t always cause dramatic attacks of spinning vertigo. In many people, the first clue is actually a gradual change in hearing in one ear, persistent one-sided tinnitus or a subtle deterioration in balance.
What is a Vestibular Schwannoma?
The inner ear communicates with the brain through a nerve called the vestibulocochlear nerve, also known as the eighth cranial nerve.
This nerve has two important jobs:
- Carrying hearing information from the inner ear to the brain
- Carrying information about balance and head movement from the inner ear to the brain
A Vestibular Schwannoma develops from the Schwann cells that surround this nerve.
Vestibular Schwannomas are benign and usually slow-growing tumours. Some remain small and stable for many years, while others gradually increase in size.
Because of where the tumour grows, it can affect hearing and balance. If it becomes larger, it can also place pressure on nearby nerves and structures.
Acoustic Neuroma or Vestibular Schwannoma – what’s the difference?
They refer to the same condition.
Acoustic Neuroma is the older and more commonly recognised term.
Vestibular Schwannoma is considered the more accurate medical name because these tumours usually arise from Schwann cells surrounding the vestibular portion of the nerve.
What are the symptoms of a Vestibular Schwannoma?
Symptoms vary considerably between people.
Common symptoms can include:
- Hearing loss in one ear
- One ear hearing noticeably worse than the other
- Persistent tinnitus in one ear
- Difficulty understanding speech
- Difficulty hearing conversations in background noise
- A feeling of fullness in one ear
- Dizziness
- Disequilibrium
- Feeling off balance when walking
- Veering while walking
- Reduced balance in the dark
- Difficulty on uneven ground
- Occasionally vertigo
Larger tumours can sometimes cause:
- Facial numbness
- Tingling or altered sensation on one side of the face
- Facial weakness
- More significant balance problems
- Coordination difficulties
- Headaches
Having one or more of these symptoms does not mean that you have a Vestibular Schwannoma.
Hearing loss, tinnitus and dizziness are extremely common and have many other possible causes.
It is the combination and pattern of symptoms that helps determine whether further investigation is appropriate.
Hearing loss in one ear
One of the most common symptoms of Vestibular Schwannoma is sensorineural hearing loss that is worse in one ear than the other.
This can develop very gradually.
You might notice:
“I always put the phone to my right ear because I can’t hear as well through my left.”
or:
“I can hear that someone is speaking, but I can’t understand the words properly through one ear.”
Some people don’t realise there is a significant difference until they have a formal hearing test.
This is known as asymmetric sensorineural hearing loss.
Unexplained asymmetrical hearing loss is one of the reasons an Audiologist, ENT specialist or doctor may recommend further investigation.
What about tinnitus in one ear?
Tinnitus is the perception of a sound that isn’t coming from an external source.
It may sound like:
- Ringing
- Buzzing
- Hissing
- Whistling
- A high-pitched tone
Tinnitus is extremely common, and most people with tinnitus do not have an Acoustic Neuroma.
However, persistent tinnitus that predominantly affects one ear—particularly when accompanied by hearing loss in the same ear—may warrant further assessment.
Does a Vestibular Schwannoma cause vertigo?
It can, but this is where Vestibular Schwannoma can be surprising.
You might assume that a tumour affecting the balance nerve would cause severe spinning vertigo.
Often it doesn’t.
Because most Vestibular Schwannomas grow slowly, vestibular function may also change slowly. This gives the brain time to gradually adjust to the altered information coming from one inner ear.
Instead of dramatic vertigo, a person might simply notice:
“I don’t feel as steady as I used to.”
They may experience:
- Mild chronic disequilibrium
- Reduced confidence walking
- Difficulty on uneven ground
- Difficulty with quick head movements
- Increased unsteadiness at night
- A tendency to veer while walking
Some people may barely notice their balance impairment.
Why might my balance be worse in the dark?
Your brain uses information from three major systems to maintain balance:
- Your vestibular system in your inner ears
- Your vision
- Sensory information from your muscles and joints, called proprioception
If one vestibular system becomes weaker, your brain may compensate by relying more heavily on vision.
During the day, this can work extremely well.
When you walk in darkness, however, that visual information is suddenly reduced.
This can expose the underlying vestibular weakness.
Someone may therefore say:
“I’m completely fine during the day, but I feel really unsteady walking to the bathroom at night.”
This can be an important clue during a vestibular assessment.
Can a Vestibular Schwannoma cause facial numbness?
Larger Vestibular Schwannomas can sometimes place pressure on nearby nerves.
One of these is the trigeminal nerve, which carries sensation from the face.
This can potentially cause:
- Facial numbness
- Tingling
- Altered sensation on one side of the face
New facial numbness should always be medically investigated.
What about facial weakness?
The facial nerve also travels close to the hearing and balance nerves.
Facial weakness is not usually the first symptom of a small Vestibular Schwannoma, but it can occur with larger tumours or sometimes following treatment.
New facial weakness should be medically assessed promptly.
What about headaches?
Small Vestibular Schwannomas generally don’t cause significant headaches.
Larger tumours can extend towards the brainstem and cerebellum and place pressure on surrounding structures.
In more advanced cases, symptoms may include significant balance problems, coordination difficulties or headaches.
Fortunately, access to modern hearing tests and MRI means many Vestibular Schwannomas can be identified when they are much smaller.
What might a Vestibular Physiotherapist find?
A Vestibular Physiotherapist cannot diagnose a Vestibular Schwannoma simply by examining you in the clinic.
However, vestibular assessment can identify whether one side of the balance system appears weaker than the other.
It can also help identify whether another, more common vestibular condition is responsible for the dizziness.
A Vestibular Physiotherapy assessment may include:
- Eye movement testing
- Bedside Head Impulse Testing
- Positional testing
- Balance testing
- Walking assessment
- Head-movement testing
- Assessment with the eyes open and closed
Eye movement testing
The vestibular system and eyes work very closely together.
A Vestibular Physiotherapist may assess how well your eyes:
- Follow a moving target
- Move quickly between targets
- Remain steady when looking in different directions
The clinician will also look for involuntary eye movements known as nystagmus.
These tests provide information about how the vestibular and neurological systems are functioning.
A person with a small Vestibular Schwannoma may still have completely normal eye movement testing.
What is the Head Impulse Test?
The Head Impulse Test is a simple bedside test used to assess an important reflex called the Vestibulo-Ocular Reflex, or VOR.
The VOR allows you to keep your vision clear while your head is moving.
During the test, you look at a stationary target while the clinician makes small, quick movements of your head.
Normally, your eyes remain locked on the target.
If one vestibular system isn’t working as effectively, your eyes may briefly move away from the target and then make a quick corrective movement back.
This is called a corrective saccade.
An abnormal Head Impulse Test can therefore indicate weakness of the vestibular system on one side.
However:
A normal Head Impulse Test does not rule out a Vestibular Schwannoma.
What is a Video Head Impulse Test?
A more detailed version of the Head Impulse Test is called Video Head Impulse Testing, or vHIT.
The patient wears specialised goggles that accurately measure eye movements while the head is moved.
This can provide more detailed information about the function of the semicircular canals and the Vestibulo-Ocular Reflex.
Again, vHIT can identify vestibular weakness, but it does not tell us why the weakness exists.
It cannot diagnose an Acoustic Neuroma by itself.
Why do we still test for BPPV?
Someone with a Vestibular Schwannoma can still develop completely unrelated vestibular conditions.
One of the most common is Benign Paroxysmal Positional Vertigo (BPPV).
BPPV typically causes brief episodes of spinning vertigo when:
- Rolling over in bed
- Getting into or out of bed
- Looking upward
- Bending down
Tests such as the Dix-Hallpike Test and Supine Roll Test can help identify BPPV.
This is important because not every episode of dizziness in someone with an Acoustic Neuroma is necessarily being caused by the tumour.
If BPPV is present, it can often be treated using a canalith repositioning manoeuvre such as the Epley manoeuvre.
How is balance tested?
A Vestibular Physiotherapist may assess your balance under several different conditions.
For example, you may be asked to stand:
- With your feet together
- Heel-to-toe
- On one leg
- With your eyes open
- With your eyes closed
- On a firm surface
- On a foam surface
- While moving your head
Some tests deliberately reduce the amount of useful information coming from your vision or feet.
This places more demand on the vestibular system.
If your balance deteriorates significantly when your eyes are closed or you stand on an unstable surface, it can provide useful information about how your brain is using vestibular information.
How is walking assessed?
Walking may also be tested while:
- Turning your head from side to side
- Looking up and down
- Changing direction
- Walking with your eyes closed
- Walking heel-to-toe
- Negotiating obstacles
These tests help identify difficulties that might not be obvious when you are simply sitting or standing still.
What hearing tests are performed?
A formal hearing assessment is particularly important when Vestibular Schwannoma is being considered.
An audiogram can determine:
- How well each ear hears different pitches
- Whether one ear is worse than the other
- Whether the hearing loss is coming from the inner ear
- How well each ear understands speech
The key finding that may prompt further investigation is unexplained asymmetric sensorineural hearing loss.
What is speech discrimination testing?
Speech discrimination or word recognition testing looks at how clearly each ear understands spoken words.
Some patients can hear that a sound is present but have difficulty making out exactly what is being said.
If one ear performs unexpectedly poorly compared with the other, this can be another reason to investigate the auditory nerve.
What is an Auditory Brainstem Response test?
An Auditory Brainstem Response, or ABR, measures electrical responses produced by the hearing pathway.
Small electrodes are placed on the head while sounds are played through headphones.
ABR testing can sometimes identify abnormalities in how auditory information travels along the hearing nerve.
Historically, it was commonly used when Acoustic Neuroma was suspected.
Today, MRI is much better at detecting small Vestibular Schwannomas.
What scan is used to diagnose a Vestibular Schwannoma?
The most important imaging investigation is an MRI.
MRI allows doctors to look closely at the:
- Internal auditory canals
- Hearing and balance nerves
- Cerebellopontine angle
- Brainstem and surrounding structures
MRI can determine:
- Whether a Vestibular Schwannoma is present
- Which side it is on
- How large it is
- Whether it extends outside the internal auditory canal
- Whether it is affecting nearby structures
- Whether it changes in size over time
MRI is therefore used both to diagnose and monitor Vestibular Schwannomas.
Does everyone with dizziness need an MRI?
No.
Vestibular Schwannoma is an uncommon cause of dizziness, and the vast majority of people experiencing dizziness will have another explanation.
Further investigation becomes more important when symptoms or examination findings include:
- Unexplained hearing loss affecting one ear more than the other
- Persistent unilateral tinnitus
- Progressive unilateral hearing symptoms
- Unexplained vestibular weakness affecting one side
- Facial numbness
- Facial weakness
- Other neurological abnormalities
Your doctor, Audiologist or ENT specialist can determine whether imaging is appropriate.
When should I seek medical assessment?
Most tinnitus, hearing loss and dizziness are not caused by an Acoustic Neuroma.
However, further investigation may be appropriate if you experience:
- Progressive hearing loss affecting one ear
- Unexplained differences in hearing between the ears
- Persistent tinnitus predominantly affecting one ear
- Unexplained vestibular weakness on one side
- Persistent balance problems accompanied by one-sided hearing symptoms
- Facial numbness
- Facial weakness
- Other new neurological symptoms
Sudden hearing loss should be assessed urgently.
You should also seek prompt medical attention for new facial weakness, severe new balance problems, double vision, weakness or numbness affecting the limbs, difficulty speaking or other sudden neurological symptoms.
The key message
An Acoustic Neuroma, or Vestibular Schwannoma, is a benign, usually slow-growing tumour affecting the nerve responsible for hearing and balance.
It does not always cause dramatic vertigo.
In fact, one of the most common clues is gradual hearing loss affecting one ear more than the other, often accompanied by persistent unilateral tinnitus.
Bedside vestibular testing can identify whether one balance system appears weaker, but MRI is the key imaging investigation used to diagnose a Vestibular Schwannoma.
For people who experience dizziness or imbalance because of altered vestibular function, Vestibular Physiotherapy can help the brain adapt through vestibular compensation.
An individualised rehabilitation program may include gaze-stability exercises, balance retraining, walking exercises, habituation, visual-motion rehabilitation and a gradual return to normal activities. Current evidence suggests that this multimodal approach is the most promising physiotherapy strategy for people with Vestibular Schwannoma.
The Vertigo Co
If you are experiencing persistent dizziness, imbalance or unexplained vestibular symptoms, or you have been diagnosed with an Acoustic Neuroma and are struggling with your balance, consider booking a comprehensive Vestibular Physiotherapy assessment with The Vertigo Co.
This article provides general educational information only and is not a substitute for individual medical assessment. Sudden hearing loss, new facial weakness or numbness, severe new balance disturbance or other new neurological symptoms require prompt medical assessment.
