2. VESTIBULAR SCHWANNOMA/ ACOUSTIC NEUROMA
It’s the most common intracranial schwannoma constituting 80
% of all cerebellopontine angle tumors.
It’s benign encapsulated , extremely slow-growing tumor either
solid or cystic which arises from the Schwann-cells (transition
zone) of the vestibular nerve within the internal auditory canal
are histologically composed of alternating regions of Antony type
A and B areas. It can extend into the cerebellopontine angle.
The number of newly diagnosed cases per year is around 13 per
one million individuals.
Bilateral AC is diagnostic of neurofibromatosis type 2.

3. ANATOMY OF CEREBELLOPONTINE ANGLE
It’s a triangular area and bounded by:
1- Laterally: medial portion of posterior surface of temporal
bone.
2- Medially: Edge of pons.
3- Posteriorly: cerebellar hemisphere and flocculus.
4- Superiorly: trigeminal nerve.
CONTENTS:
1- Anterior inferior cerebellar artery. 2- 7th and
8th Cranial nerves.

4. FEATURES:

5. CLINICAL SYMPTOMS
1- Most common ; Progressive Unilateral SNHL (retrocochlear)
present in 95% of cases and often accompanied by tinnitus
which is present in 65% of cases.
2- Marked difficulty in understanding speech out of proportion
to the pure tone hearing loss.
3- May present with sudden hearing loss.
4- True vertigo is seldom seen.
5- Earliest cranial nerve involved is 5th CN.
6- 4th , 6th, 9th , 10th , 11th and 12th can also be involved.
7- Rare presentations include facial numbness or pain,
earache or facial weakness, cerebellar ataxia or symptoms
of hydrocephalus (headache, visual disturbance, mental
status change, nausea, and vomiting).

6. SIGNS
 Ear: normal otoscopy.
 Cranial nerves:
1- 5th CN: Earliest sign is impaired corneal reflex.
Motor functions are affected rarely.
2- 7th CN: Sensory first; loss of sensation in the
postero-superior aspect of EAC called Hitselberger
sign.
3- 9th and 1oth pulsy: palatal, pharyngeal and
laryngeal paralysis.
4- Eyes: Nystagmus.
5- Cerebellar signs present.

7. CLASSIFICATION OF AN ACCORDING TO SIZE
Intameatal Extrameatal size Mm
Grade 1 Small 1-10
Grade 2 Medium 11-20
Grade 3 Moderately large 21-30
Grade 4 Large 31-40
Grade 5 Giant More than 40

8. INVESTIGATIONS
1- Audiological tests: show features of retrocochlear hearing loss
(high frequency SNHL) ; recruitment negative, poor speech
discrimination score and presence of roll-over phenomenon.
 2- Acoustic reflex: stapedial reflex decay or missing in up to 70%
of patients.
 3- Caloric test: diminished or absent normal test finding does not
eliminate the diagnosis.
 4- Plain x-ray: best view perorbital view ; difference of 1 mm in the
vertical height of internal acoustic meatus is significant.
 5- CT-scan; can not detect intermeatal tumors.
 6- MRI; MRI with gadolinium enhancement is is gold standard.

10. Conservative Treatment
• Since especially in the elderly vestibular schwannomas are slowly
growing tumours, a wait and see strategy should be considered
at least in the short term (6–12 months) for patients with a small
vestibular schwannoma (in older patients and individuals in poor
health).
• Radiotherapy: Stereotactic radiosurgery (gamma knife) may stop
vestibular schwannoma growth mainly in small intracanalicular
and extracanalicular lesions. Radiosurgery as the first therapeutic
option is recommended in bilateral vestibular schwannomas (e. g.
morbus Recklinghausen) but only when the tumours are small.
• Annual imaging is recommended for all patients being managed
conservatively for the rest of their life or until vestibular
schwannoma growth is seen to a certain
limit.

11. Surgical Treatment
 Translabyrinthine approach in patients with medium sized
and large tumours and in patients with small tumours with poor
hearing .
 Middle fossa approach in patients with intracanalicular or
small tumours with good hearing as an attempt to preserve
residual hearing.
 Retrolabyrinthine or retrosigmoidal approaches in
patients with large extracanalicular vestibular schwannomas
Additional Useful Surgical Procedures
• Intraoperative facial nerve monitoring.
• Intraoperative hearing monitoring: may be useful in

12. Differential Diagnosis
• Meningioma is, in most cases, recognized on radiologic
features (tumour usually extrinsic to internal auditory
canal, sessile with peritumoral dural enhancement and
intratumoral calcifications). An enhanced “dural tail” is a
distinguishing feature.
• Other cerebellopontine angle lesions
(cholesteatoma, arachnoid cyst, lipoma, haemangioma,
glomus tumour, facial neuroma) can in most cases be
recognized by their radiologic aspects and MRI
characteristics

13. Prognosis
Conservative Therapy With radiotherapy tumour control is
around 96%, tumour regression 35%, lesion of the trigeminal
nerve less than 5.6%, facial weakness 2%, and hearing loss 32%.
There is no CSF leak and no mortality.
If irradiation cannot stop tumour growth (in about 4%
of cases), surgery is technically sometimes extremely difficult.
Malignant transformation after radiotherapy is also valid for
neuromas.