Acoustic Neuroma

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Clinically Relevant Anatomy

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Mechanism of Injury / Pathological Process

Acoustic Neuroma is a benign, slow growing brain tumour, originating from the Schwann cells in the myelin sheath of the vestibular portion of the 8th Cranial Nerve, the Vestibulococholear or Acoustic Nerve.

Acoustic Neuroma AKA Vestibular Schwannoma

Should it be referred to as Acoustic Neuroma or Vestibular Schwannoma?

As the tumour does not grow on the acoustic (or cochlear) portion of the vestibulocochlear nerve, and as it is not a true Neuroma (= Nerve Tumour) but is a Schwannoma (= Nerve Sheath Tumour) there can be no argument that Vestibular Schwannoma is the more accurate name.
This tumour is also sometimes named Cerebellopontine Angle Tumour.

Generally, the tumour grows slowly, and can stay in the bony ear canal for decades. If it is (still) completely inside its position it is called intrameatal.

If it has grown larger and there is not enough space in the ear canal after pushing and suppressing the nerves and vessels passing through, the acoustic neuroma grows out of the ear canal and into the cerebellopontine angle, in one of the divided spaces left and right of the extended spinal cord, into the brainstem. In these cases the tumour is called a Cerebellopontine Angle Tumour.

Clinical Presentation

Early Signs:

The most frequent and common first symptom is a decrease in hearing on one side. In most cases the loss of hearing occurs slowly and subtly. Those affected often notice the hearing problem very late or by chance, for example when telephoning or during a routine examination. Above all, high-frequency hearing difficulties are noticed - suddenly one can no longer hear the birdsong or it has changed.

The increasing hearing difficulties are often accompanied by ear noise, or tinnitus; tinnitus may even be the first symptom, without the person affected having or experiencing hearing loss. Like hearing loss, tinnitus is also present mostly in the high-frequency range.

Although acoustic neuromas mostly originate from the upper part of the balance nerve, vertigo and impaired balance rank only in third place as a symptom of an acoustic neuroma. They appear as swaying dizziness, and seldom as vertigo and unstable walking. Often only after being asked directly do acoustic neuroma sufferers admit to experiencing an occasional vague feeling of instability, mostly in the dark and with sudden head and body movements.

Later Signs:

An acoustic neuroma growing towards the skull base can interfere with the functions of other cranial nerves and vessels, which supply the brain and lead into the brain through the openings in the skull base.

If the 7th cranial nerve (Facial Nerve) is impaired this leads to motor failures in the face, as this nerve is responsible for facial muscles, amongst other things. Facial paralysis or facial palsy are referred to here. With severe damage, the production of tear fluid and secretions from the nose and palate are affected. Eventually, the sense of taste in two thirds of the tongue will also suffer.

If the 5th cranial nerve (Trigeminal Nerve) is impaired this leads to sensation problems or facial pain, ie.trigeminal neuralgia. These symptoms occur less frequently because this cranial nerve passes further away from the cerebellopontine angle.

It is similar with the 9th cranial nerve ( Glossopharyngeal Nerve) and 10th cranial nerve (Vagal Nerve). Impairments to these nerves lead to problems swallowing, painful swallowing and taste disorders in the rear third of the tongue, amongst other problems.

Diagnostic Procedures

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Outcome Measures

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Management / Interventions

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Differential Diagnosis

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Key Evidence

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Resources

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