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

Complications of ear surgery

There are risks with all surgical procedures. The degree of risk is related to both the specific procedure and to the underlying pathology. The patient should be given an indication of the likely risk in a sensitive way, so that they are not frightened into abandoning surgery.
A full explanation of the underlying condition will highlight the risks of leaving an ear disease untreated. Risks should be documented in the case notes and on the consent form.
The list of complications for CSOM is similar to that of the operation-the untreated disease carries similar risks as the operation.

These are:
-Hearing loss-temporary and permanent. Always obtain an audiogram at least within 3 months
of surgery, but preferably nearer to surgery and perform pre-op tuning fork tests and
document your findings
-Tinnitus-temporary and permanent.
-Vertigo and unsteadiness-temporary and permanent
-Facial nerve palsy-temporary and permanent
-Wound infection
-Need for further surgery
-Formation of mastoid cavity
-Need for ongoing care e.g. aural toilet for mastoid cavities

Inter-operative considerations
These can be avoided by taking precautions, e.g. always setting up and checking items such as facial nerve monitors yourself. The precaution undertaken in theatre, such as the use of a facial nerve monitor, should be recorded on the operation note. An inter-operative unusual finding or complications shold be witnessed and recorded by a senior colleague if available.

Immediate post-operative period
Check for facial nerve palsy in recovery.

Post-operative ward review
Facial nerve function should be checked, along with the eye movements for nystagmus. Webber's tuning fork test should be done. The patient should localise to the operated ear.

Inner Ear Condition (Benign Paroxysmal Positional Vertigo(BPPV))

What is Benign Paroxysmal Positional Vertigo?

BPPV is the most common cause of vertigo (80%) in patients who present in a dizzy clinic. Its pathogenesis is the displacement of otoliths from the macula of the utricle. Otoliths are calcium cabonate-containing particles that that migrate by the force of gravity towards the semicircular canals depending on the head position of the patient. The most common semicircular involved is the posterior one (95%). The aetiology can be idiopathic (50%), from infection (20%) and from head trauma (30%).

Symptoms and Signs

Typically, the patient complains of spinning vertigo when the head is placed in a particular position. Usually, this involves lying down, lifting the head looking upwards or bending down and looking upwards. The vertigo generally lasts 10 to 30 seconds. It becomes less intense with repeated manoeuvres (fatiguability). Hearing is not affected. The condition is self-limiting and resolves spontaneously in the majority of patients over a few weeks to months but can persist up to two years. It can recur, especially in the elderly.
The pathognomonic sign is seen on the Dix-Hallpike manoeuvre. This involves placing the supine patient on a couch and tilting the head backwards over the edge of the couch such that the neck is extended 30 degrees and rotated 45 degrees to one side. In this position, the ampulla of the posterior semicircular canal, which contains the end organ, is most dependent. When positive, nystagmus will be noted after a latency period of a few seconds. The nystagmus will last for up to 30 seconds and will become less noticeable with repeated manoeuvres. On sitting up, some patients demonstrate a reversal of nystagmus. This feature of reversal is not required to make the diagnosis.

Investigations

No investigations are essential but as this is an inner ear condition some routinely do an audiogram.

Management

Medications are of little benefit as the spells are episodic and short-lasting. As the condition is self-limiting, patients may experience total resolution of symptoms over time. However, in 1992, John Epley demonstrated the particle repositioning manoeuvre (PRM) which aims at returning the displaced otoliths to the utricle. The success rate is quoted at 80% after one treatment and up to 95% after repeated manoeuvres.
If conservation methods fail, occlusion of the posterior canal can be performed via a transmastoid approach with good success. It comes with a 4 to 5% risk of hearing. Fortunately, with the high success rate of PRM, surgery is rarely performed nowadays.