Skull Base Condition (Acoustic Neuroma)

What is Acoustic Neuroma?

An acoustic neuroma is a benign, slow growing tumour. It is more correctly called the vestibular schwannoma, because of its origin on the vestibular nerve. Post mortem data shows that this tumour is under-diagnosed. An acoustic neuroma may be an incidental finding on MRI.
Acoustic neuromas account for 6% of all intracranial neoplasms, the majority of which are sporadic (95%). 5% are genetic-part of the inherited condition of NF2 (neurofibromatosis type 2) on chromosome 22.

Presentation

The patient may experience some of the following:
-Sudden SNHL or progressive high frequency SNHL
-Vertiginous episodes-but these are rare as the patient unknowingly compensates.
-Symptoms of raised intracranial pressure such as headache or visual disturbance.
-Brainstem compression-ataxia is a late symptom of this.

Investigations

-PTA.
-MRI scan with gadolinium contrast.
-Full otoneurological exam.
-Hitselbergers sign-postauricular numbness due to facial nerve compression.
-Reduced corneal reflex.
-Unterberger's test positive-patient marches on the spot with the eyes closed. A positive test is a rotation to one side or the other.

Management

Management options balance the risk of hearing loss, facial nerve palsy and surgical morbidity. There are several possibilities:
-Watchful waiting-with serial MRI scans for slow growing tumours.
-Retrosigmoid approach-preserves the hearing
-Translabyrnthine approach-destroys the hearing but is an easier approach. It is useful if there is little hearing to preserve.
-Middle fossa approach-is technically challenging as it involves opening the middle fossa. No driving for one year due to the risk of fitting.
-Intracapsular removal-useful to decompress large rumours in elderly patients with brainstem compression.
-Stereotactic radiosurgery-this multiplanar radiotherapy is useful in small tumours as it avoids surgery.

Complications

-Any intracranial procedure e.g. craniotomy-carries a 1% risk of mortality.
-Facial nerve palsy
-Total hearing loss