acoustic neuroma

1. ROLL NO. :25

2. OUTLINE
•Clinical features
•Investigations
•Management

3. ACOUSTIC NEUROMA
Tumor of VIIIth cranial nerve
Acoustic Neuroma also known as
VESTIBULAR
SCHWANNOMA,
NEURILEMMOMA Or VIIIth
NERVE TUMOUR
Incidence: It constitutes of around
80% of cerebellopontine angle
tumours and 20% of all brain.

5. PATHOLOGY
Gross: Benign,
encapsulated, slow
growing tumour of the
VIIIth cranial nerve.
Microscopy:
Elongated spindle
cells.
Rod shaped nuclei
lying in rows or
palisades

6. ORIGIN AND GROWTH
Origin:
• The tumour almost always arises from the schwann cells of the
vestibular.
• Rarely from the cochlea division of VIIIth nerve within the external
auditory canal.
Growth:
• Causes widening and erosion of the canal and then appears in
cerebellopontine angle.

7. CEREBELLOPONTINE ANGLE
Triangular space in the posterior cranial fossa.
ANATOMY
Bounded by: Tentorium- Superiorly
Brainstem- Posteromedially
Petrous part of temporal bone- Posteriorly laterally
It is important landmark anatomically and clinically as it is occupied
by CPA cistern, which houses the C.N. Vth , VIth , VIIth , VIIIth

8. • It grows: Antero-superiorly - to involve Vth nerve
Inferiorly – to involve IXth , XIth nerve
• In later stages it causes displacement of the brain stem pressure on
cerebellum and raised intracranial lesion.

9. CLASSIFICATION
ACOUSTIC NEUROMA
Intracanalicular
(confined to
internal
auditory canal)
Small size
(up to 1.5cm)
Medium size
(1.5-4cm)
Large size
(over 4cm)

10. CLINICAL FEATURES
• Age and sex : - Mostly seen in age group of 40 to 60 years.
- Both sexes are equally affected.
• COCHLEOVESTIBULAR SYMPTOMS:
-Earliest symptoms when tumour is still intracanalicular.
-Caused by pressure on cochlear or vestibular nerve
fibres or on the internal auditory artery.
-Progressive unilateral sensorineural hearing loss
- Tinnitus

11. Mark difficulty in
understanding speech:
• Imbalance / unsteadiness-
Vestibular symptoms
• Vertigo
• Sudden hearing loss
• Fullness in the ear

12. CRANIAL NERVE INVOLVEMENT
1. 5th Nerve: Earliest nerve to be involved.
Reduced corneal sensitivity
Numbness or paraesthesia of face.
Involvement indicates – Tumour size = 2.5 cm and occupies the
cerebellopontine angle
2. 9th and 10th nerve –
Dysphagia and Hoarseness-Due to palatal, pharyngeal and laryngeal
paralysis
3. Other cranial nerves : XIth , XIIth, IIIth IVth and VIth are affected when tumours
are very large

13. 4. Facial nerve
• Sensory fibres are
affected early.
• Hitzelberger’s sign:
Hypoaesthesia of
posterior meatal wall.
• Loss of taste (Tested by-
Electrogustometry)
• Schirmer test: Reduced
lacrimation.
• Motor fibres: Affected
late
• Delayed blink reflex

14. BRAINSTEM INVOLVEMENT
• Ataxia
• Weakness & Numbness of arms and legs
• Exaggerated tendons reflexes
RAISED INTRA-CRANIAL TENSION
• Headache
• Nausea
• Vomiting
• Diplopia (VIth)
• Papillo-edema with blurring of vision.

15. CEREBELLAR INVOLVEMENT
• Pressure symptoms on cerebellum are seen in large tumors.
Revealed by:
Finger nose test
Knee-heel test
Dysdiadochokinesia (Inability to perform rapid alternative muscles
movement)
Ataxic gait
Inability to walk along a straight line (tendency to fall on the affected side)

16. INVESTIGATIONS
FOR
ACOUSTIC NEUROMA
ROLL NO. 26

17. AUDIOLOGICAL TESTS
A) PURE TONE AUDIOMETRY :
 PTA with AC and BC will show sensorineural hearing
loss, more marked in high frequencies.
B) SPEECH AUDIOMETRY
 It shows poor speech discrimination and this is
proportionate to pure tone hearing loss.
 Roll-over phenomenon : Reduction of discrimination
score when loudness is increased beyond a particular
limit is most commonly observed.

18. NOTE : SISI and Threshold Tone Decay are not sensitive
or specific and have been abandoned in favour of
imaging techniques.

19. VESTIBULAR TEST
A) CALORIC TEST :
• Diminshed or absent response in 96% of patients.
• May be normal, when tumour is small.

20. BERA
• BRAINSTEM-EVOKED RESPONSE AUDIOMETRY
• Useful in the diagnosis of retrocochlear lesions.
• In the presence of the VIIIth nerve tumour, a delay of
>0.2 ms in wave V between two ears is significant.

22. IMAGING STUDIES
1) MRI with Gadolinium contrast :
 GOLD STANDARD
More sensitive and specific.
Non-invasive and free of radiation hazards to the
patient.
Can detect even intracanalicular tumours of few
millimetres.

24. 2) Computed Topography (CT) Scan :
 Can show any erosion of the temporal bone.
3) Plain X-rays :
 Different views :
• Transorbital
• Stenver’s
• Towne’s
• Submentovertical

25. 4) Vertebral angiography :
 Helps to differentiate acoustic neuroma from other
tumours of cerebellopontine angle.

26. CSF EXAMINATION
 Protein level is raised.
 Lumbar puncture is usually avoided.

27. IMPORTANT TESTS FOR AN WORK-UP
• PTA
• Speech discrimination curve
• Roll-over curve
• Evoked response audiometry
• Imaging studies

28. DIFFERENTIAL DIAGNOSIS
• Acoustic Neuroma
• Meningioma
• Epidermoid (cholesteatoma)
• Arachnoid cyst
• Schwannoma of other cranial nerves
• Aneurysm
• Glomus tumour
• Metastasis

29. Management Of
Acoustic Neuroma
Chinmay Sharma 19027

30. Management By:
•Surgery
•Radiotherapy

31. Surgery:
• Treatment of choice
• Various approaches are:
1) Middle cranial fossa approach
2) Translabyrinthine approach
3) Suboccipital (retrosigmoid) approach
4) Combined translabyrinthine-suboccipital
approach

32. 1)Middle cranial fossa approach:
• Ultimate goal of this approach is to expose the Internal
Auditory Canal (IAC) from the roof of the petrous temporal
bone.
• Smaller tumours are removed that are typically confined to
internal auditory canal.
• Only procedure that fully exposes the lateral third of the
internal auditory canal without sacrificing hearing.
• Adequately exposes the facial and superior vestibular nerves
within the IAC.
• Hearing is preserved.

33. Middle cranial fossa approach

34. Translabyrinthine approach:
• Indicated in:
Tumours >2.5 cm
Poor preoperative hearing
• Provides the best view of the lateral brain stem and CPA facing
the acoustic tumor.
• Hearing sacrifice is complete and unavoidable.
• Allows early identification of facial nerve and its preservation
• A C-shaped incision is planned behind the ear as needed to
expose the mastoid tip, sigmoid sinus and transverse-sigmoid
junction.

35. • In this approach
(1) Tumour size is not a limiting factor;
(2) It allows early identification of facial nerve in the IAM and its
preservation;
(3) Cerebellar retraction is not required.
Incision in
Translabyrinthine
approach

36. Translabyrinthine approach

37. Suboccipital (retrosigmoid) approach
• Posterolateral neurosurgical technique to access various
posterior fossa structures and even extends into the middle
fossa
• A surgical approach to the cerebellopontine angle through the
occipital bone posterior to the sigmoid sinus.
• Least extensive soft tissue dissection and bony removal.
• Hearing-sparing technique
• Can be applied to all acoustic tumors
• Destruction of the labyrinth is not required

38. • May require cerebellar retraction or resection. provides
opportunities for CSF leak and postoperative edema, hematoma,
infarction, and bleeding.
• skin incisions:
1)Linear,
2)Lazy S-shaped,
3)C-shaped, and
4)Curvilinear inverted U-shaped
incisions

39. Retrosigmoid approach

40. Combined translabyrinthine-suboccipital approach
• In translabyrinthine approach, separation of tumours adherent to brain
stem and exposure of vital arteries and cranial nerves may be compromised;
total removal may not be possible
• In suboccipital approach, it is often difficult to preserve facial nerve and
remove the portion of tumour in the petrous bone.
• In combined approach:
Translabyrinthine approach- Facial nerve preservation
Retrosigmoid approach- tumour removal.

41. Comparision

42. Approach will depend on:
•Size
•Location
•Quality of preoperative hearing
•Hearing preservation

43. Size
• Opportunities for hearing conservation decrease as
tumors become larger.
• It is much more difficult to conserve when tumors are
>2.5cm in diameter.
• Surgeons limit hearing conservation surgery to smaller
tumors
• Prefer translabyrinthine approach to maximize the
chance of facial nerve conservation for larger tumors.

44. Location
•Lies within the lateral portions of the internal auditory
canal- Middle cranial fossa approach
•Significant volume medial to the plane of the Internal
acoustic meatus- Retrosigmoid approach

45. Quality of preoperative hearing
•If the patient has no useful hearing, either the
translabyrinthine or the retrosigmoid approach is
selected.

46. Hearing preservation
• Hearing completely preserved: Middle cranial fossa approach
• Hearing preservation depends on size of tumour: Retrosigmoid
approach
• Hearing loss unavoidable: Translabyrinthine approach

47. Radiotherapy
•X-knife or Gamma knife surgery
•Cyber knife

48. X-knife surgery
• Form of stereotactic radiotherapy
• Radiation energy converged on the tumour
• Minimal effect on the surrounding normal tissue
• Cause arrest of growth and reduction in size
• Indication:1)Patient who refuse surgery
2) Surgery is contraindicated
3) Residual tumour left after surgery

49. Cyber knife
•Improved form of X-knife surgery
•Without skull frame for stereotactic localization
•More accurate
•Uses real-time image guidance technology.