chronic suppurative otitis media

2 OTOLARYNGOLOGY
progressive brain stem displacement and cerebellar involvement. Diplopia due to pressure on the VIth
cranial nerve, and hoarseness with dysphagia due to involvement of the IXth and Xth nerves is rare.
5. Terminal symptoms. The raised CSF pressure causes failing vision due to papilloedema, headache,
alteration in conscious level and eventually coma.
In the otological phase, general examination will usually reveal no abnormalities. The patient may have a
unilateral neural hearing loss. Hypaesthesia of the posterior external ear canal on the side of the hearing loss
should raise the index of suspicion (Hitselberger sign). Loss of the corneal reflex is an early sign of
trigeminal nerve impairment. Nystagmus when present may be of the vestibular or cerebellar type. Facial
nerve impairment is usually of the sensory element and can be elicited as a lack of taste on
electrogustometry or loss of lacrimation on Schirmer’s test. Slight facial weakness may show as a delay in
the blink reflex. Later the patient may have evidence of ataxia. Neurological signs of the other cranial nerve
palsies will eventually become apparent.
Investigations
1. Radiological investigations. The most accurate means of identifying small intracanalicular tumours is
magnetic resonance imaging (MRI) with gadolinium enhancement. This is therefore the investigation of
choice and is used for screening. Computerized tomography (CT) scanning with high definition and
enhancement techniques will accurately diagnose and delineate most tumours, but should only be used
when MRI is unavailable.
2. Audiometry. A unilateral or asymmetrical sensorineural hearing loss can usually be demonstrated by a
pure tone audiogram. The hearing loss is classically a neural lesion with no loudness recruitment,
abnormally rapid adaptation and disproportionately poor speech discrimination. Stapedial reflex decay can
be measured using impedance audiometry, and this gives a low-false negative rate of around 5%. Brainstem
electric response audiometry has only a 3% false-negative rate. It demonstrates a retrocochlear lesion by an
increased latency between N1 and N5 waves. If the pure tone threshold hearing loss is greater than 70 dB,
the accuracy of audiometric testing is poor.
3. Vestibular investigations. Caloric responses are usually reduced in or absent from the affected side, but
there is no abnormality in some patients with small tumours. Special audiometric and vestibular testing are
now rarely, if ever, used for the diagnosis of an acoustic neuroma.
Differential diagnosis of a tumour at the cerebellopontine angle
1. Acoustic neuromas (constitute 80% of cerebellopontine angle tumours).
2. Meningioma.
3. Neuroma of the VIIth nerve.
4. Congenital cholesteatoma.
5. Aneurysm of the basilar or vertebral arteries.
6. Cholesterol granuloma of the petrous apex.
7. Cerebellar tumour.
Management
The ideal management is a single stage total removal of the lesion, with preservation of all neural function
and with minimal morbidity and mortality. However, this ideal is not always possible. Each case must be