Acoustic Neuroma

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Clinically Relevant Anatomy
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Mechanism of Injury / Pathological Process
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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[edit | edit source]

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[edit | edit source]

Early Signs:[edit | edit source]


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:[edit | edit source]

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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Imaging[edit | edit source]

Magnetic Resonance Imaging (MRI) is the main method for imaging Acoustic Neuromas[1].

Computer Tomography (CT) is the second examination procedure of choice[2]. It is used:
- when patients cannot be examined with an MRI ( e.g. magnetisable metallic implants, pacemakers and other active (electronic/magnetic) control devices, claustrophobia, etc.)

Audiometry[edit | edit source]

 A test of hearing function, which measures how well the patient hears sounds and speech, is usually the first test performed to diagnose acoustic neuroma. The patient listens to sounds and speech while wearing earphones attached to a machine that records responses and measures hearing function. The audiogram may show increased "pure tone average" (PTA), increased "speech reception threshold" (SRT) and decreased "speech discrimination" (SD).



Outcome Measures[edit | edit source]

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Management / Interventions
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Differential Diagnosis
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The differential diagnosis includes:
Meningeoma, facialis neurinoma, lipoma, lymphoma, hamartoma, hemangioma, AV malformation, bleeding, arachnoiditis, Ramsey Hunt syndrome, labyrinthitis, neuritis, cochlear otospongiosis, neurovascular compression syndrome.

Key Evidence[edit | edit source]

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Resources
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Case Studies[edit | edit source]

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Recent Related Research (from Pubmed)[edit | edit source]

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References[edit | edit source]

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  1. Neuroradiology. 1992;34(2):144-9.fckLRMagnetic resonance imaging of acoustic neuromas: pitfalls and differential diagnosis.fckLRLhuillier FM, Doyon DL, Halimi PM, Sigal RC, Sterkers JM.
  2. AJNR Am J Neuroradiol. 1986 Jul-Aug;7(4):645-50.fckLRCT in diagnosis of acoustic neuromas.fckLRWu EH, Tang YS, Zhang YT, Bai RJ.