Presented by Dr Myo Mg Mg (ORL HNS) at NSU, MGH

1. CEREBELLOPONTINE ANGLE
TUMORS
Dr. Myo Maung Maung
ORL-HNS
29.4.19
1

2. OUTLINES
• INTRODUCTION
• HISTORY OF CP ANGLE TUMORS SURGERY
• APPLY ANATOMY
• TYPES OF CP ANGLE TUMORS
• ETIOLOGY
• CLINICAL FEATURES
• DIAGNOSIS
• MANAGEMENT
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3. INTRODUCTION
• The most common neoplasms in the posterior fossa
• About 5-10% of all intracranial tumors
• Most are benign
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4. HISTORY OF CP ANGLE TUMOR SURGERY
• As most of the CP angle tumors are benign, their complete removal
leads to excellent long-term outcomes.
• But still early 20th century, CP angle lesions were very difficult to
diagnosed and rarely completely excised. (mortality rate surgery ~
50%)
4

5. • With advancement of neuroradiological imaging and surgical
technique, they became uniformly treatable with acceptable
morbidity and very low rate of mortality.
5

6. • 1st successful removal – Sir Charles Balance in 1894
• 1st intracapsular tumor removal – H. Cushing in 1917 (high recurrence
rate)
• To prevent recurrence, W. Dandy introduced total tumor removal
concept in 1925
• W. House advocate translabrynthine approach and middle cranial
fossa approach in 1960s.
• In 1967, Oivecrona can preserve the facial nerve for the 1st time.
• In 1980, Leksell introduced Gamma-knife as non-surgical treatment.
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7. APPLY ANATOMY
• Comprehensive knowledge of complex anatomy of the CP angle is a
pre-requisite for achieving good surgical results.
• Whatever the tumor size and extension, the anatomical relationships
of the cranial nerves in the area of fundus of IAC and brainstem zone
are constant.
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8. 1. Sensory roots of CN 5
2. Pons
3. Vestibulocochlear nerve
4. Facial nerve
5. Abducent nerve
6. Medulla Oblongata
7. Motor roots of CN 5
8. Basilar sulcus
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9. 9

10. 10

11. 11

12. • It is a potential space in the posterior fossa of the brain.
• Boundaries
• Anterior – Posterior surface of the temporal bone
• Posterior – anterior surface of the cerebellum
• Medial – lateral surface of brainstem
• Lateral – Petrous bone
• Superior – inferior border of pons and cerebellar peduncle
• Inferior – cerebellar tonsil
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13. Contents / Neurovascular relationship
• Cranial Nerves
• CN V, VI, VII, VIII
• Vessles
• Superior Cerebellar Artery
• Anterior Inferior Cerebellar Artery
• Variable numbers of draining veins
• Foramen of Lushcka
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14. 14

15. TYPES OF CP ANGLE TUMORS
• Most of these are Vestibular Schwannoma which comprised 80-85%
of all CP angle lesions
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16. • Other tumors include
• Meningiomas
• Epidermoids
• Facial and lower cranial nerves schwannomas
• Arcachnoid cysts
• Lipomas
• Vascular tumors
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17. Vestibular Schwannoma
• Previously called Acoustic Neuroma (misnomer)
• Vestibular schwannoma is more accurate term
• Slow growing Benign tumor, usually unilateral
• Arise from abnormally proliferative schwann cells which envelops
lateral portion of vestibular nerve in IAC.
• Equal frequency on superior and inferior vestibular nerves
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18. Etiology
• Precise etiology is not known
• Defect in chromosome 22q
• In bilateral cases, association with Neurofibromatosis type 2
18

19. PATHOGENESIS
• It compresses rather then invades the nerve on which it arose, this
leaves a plane between tumor and nerve fibers. This features
facilitate the dissection during surgery.
• As it grows, fills the IAC and eventually protrudes out of the canal as
extra-meatal expansion.
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20. • Extra-meatal expansion causes stretching and displacement of
• VII and VIII nerve in anterior aspect of tumor
• AICA in inferior aspect of the tumor
• Further growth and expansion sufficient enough to touch and
compress the cerebellum, foramen Lushcka and trigeminal nerve.
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21. • Slow progressive process of active bone resorption is also seen in VS
d/t increased vascularization, fibrosis and adhesion in tumor area and
pressure effect of the tumor
• Extensive resorption extends to
• Inferiorly as far as the cochlear aqueduct
• Superiorly to the middle fossa dura
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22. Cystic Vestibular Schwannoma
• Cyst formation is seen regularly and easily detected with MRI
• It may be due to cystic degeneration or coalescence of microcysts.
• Cystic element expands causing displacement of brainstem and
compression of fourth ventricle result in brainstem herniation and
hydrocephalus respectively.
• Surgical outcomes of cystic VS is less favorable than solid tumor of
comparable size
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23. • The large size of tumor at the time of diagnosis with the cysts which
can expand dramatically have been consider to contraindication to
either radiotherapy or conservative treatment (wait and scan).
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24. CLASSIFICATION OF VESTIBULAR SCHWANNOMA
• Based on the largest diameter of extra-meatal portion
• Further recommended to note whether the fundus is empty or filled
with tumor and whether VS is cystic.
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26. 26

27. 27

28. 28

29. CLINICAL FEATURES
• Hearing loss of sensorineural
type (CN VIII)
• Tinnitus (CN VIII)
• Vertigo / Unsteadiness (CN VIII)
• Ipsilateral ataxia (cerebellum)
• Absent caloric response (CN VIII)
• Headache
• Facial numbness (CN V sensory)
• Facial weakness (CN VII)
• Facial or ear pain (CN V / VII)
• Diplopia (CN VI) usually affected
late
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30. DIAGNOSIS
• Audiometric testing
• Electrophysiologic testing
• Vestibular testing
• CT & MRI
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31. Audiometric testing
• Pure tone audiometry (PTA)
• SNHL most commonly high frequency
• Normal hearing (5%)
• Speech discrimination
• Scores out of proportion with pure-tone thresholds
• Some may score well
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32. Electrophysiologic testing
• Auditory Brainstem Response (ABR)
• Most sensitive & specific audiologic test
• Interaural difference in latency of wave V with delay of more than 0.2msec
(40-60%)
• No identifiable wave forms in 20-30%
• Wave I present but all remaining waves are absent in 10-20%
• Normal in 10-15%
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33. Vestibular Testing
• ENG
• Abnormal in 70-90%
• Unilateral weakness in caloric testing
• Spontaneous nystagmus
• No abnormality for small tumors
• Computerized dynamic
posturography
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34. Imaging technique
• CT
• Non-contrast: usually isodense to
brain, calcification is rare.
• IV contrast: over 90% of non-
treated tumors enhance
homogeneously
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35. • MRI
• T1 W – isointense to brain,
hyperintense to CSF
• T2 W – hyperintense to brain,
iso/hypointense to CSF
• Gadolinium – intense
enhancement of tumor on T1 W
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36. MANAGEMENT
• Conservative management
• Active management
Surgery
Radiotherapy
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37. • Tumor size (extra-meatal diameter)
• <15-20mm – conservative
• >15-20mm – active management
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38. Conservative management
Indications
• Advanced age
• Poor health
• Lack of symptoms
• Non-progressive of symptoms
• Only hearing ear
• Isolated IAC tumor in elderly
Contraindications
• Young patient
• Symptomatic progression
• Compression of brainstem
structure
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39. Conservative management (wait & scan)
• Yearly MRI for 5years
• MRI alternate year for 4 years
• MRI after 5year
After which observation is terminated if no further growth of tumor.
If significant growth occurs, active management is recommended.
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40. According to rigid data interpretation, there is no reason to follow a
patient for more than 5years because the tumor growth only occurred
within the first 5years after diagnosis.
But we follow this protocol because only a limited number of tumor
have been followed more than a decade, and to be on the safe side.
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41. Active management
• Primary treatment is recommended for Tumor >15-20mm as further
growth extends the tumor diameter into range associated with a
considerable increase in treatment co-morbidity (eg. Damage to facial
nerve function)
• Cystic tumors are not eligible to radiotherapy and need primary surgery is
recommended as these tumors display sudden and dramatic growth.
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42. Surgery
• Trans-labyrinthine approach
• Middle fossa approach
• Retrosigmoid approach
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43. Trans-labyrinthine approach
• Indications
• Extension into CPA . 0.5-1cm
• Non-serviceable hearing
• Adequate contralateral hearing in large tumors
• Contraindications
• Serviceable hearing
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44. • Advantages
• Wide CPA exposure
• Extradural bone drilling (possibly limiting post-op headache)
• Consistent and early facial N identification
• Less cerebellar retraction
• Only approach that can address the intra-labyrinthine and intracochlear
tumor which can be difficult to diagnose at MRI if they are small
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45. Middle Fossa Approach
Indications
• Small tumor
• Intracanallicular tumor
• Moderate CPA involvement
• Adequate hearing
Contraindications
• Large tumors
• Extensive CPA involvement (>0.5-
1cm)
• Older patients (may have higher
rates of bleeding or stroke)
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46. • Advantages
• Hearing preservation
• Superior exposure of IAC fundus
• Disadvantages
• Limited exposure of CPA
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47. Retrosigmoid Approach
• Indications
• Serviceable hearing
• Large tumors
• Compression of brainstem
• Contraindications
• Extensive IAC involvement
• Intracanallicular tumors
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48. • Advantages
• No tumor size limitation
• Wide exposure of CPA
• Possibility of hearing preservation
• Disadvantages
• Inability to expose the most lateral IAC
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49. Comparison of Surgical Approaches
Approach Overview Advantages Limitations
Trans-labyrinthine Postauricular incision
Complete mastoidectomy
Labyrinthectomy
Triangular mastoid fat graft
Wide CPA exposure
Lowest recurrence rate
Address tumor in cochlea or
labyrinth
Hearing eliminated
Cerebellar atrophy
Fat graft harvesting
complications
Middle Cranial fossa Preauricular incision
Temporal craniotomy
IAC roof removed
Fat or fascia graft over IAC
Hearing preservation
Full IAC exposure
Poor CPA exposure
increased prevalence of facial
nerve palsy
Retrosigmoid Postauricular incision
Subcoccipital craniotomy
Posterior IAC wall removed
Hearing preservation
Wide CPA exposure
No tumor size limitation
Limitation of lateral IAC
exposure
Increased prevalence of CSF
leakage
Cerebellar atrophy
Higher prevalence of aseptic49

50. Radiotherapy
• Sterotactic RadioSurgery (SRS) firstly introduced in 1980.
• Gamma knife is one of the well known SRS
• It uses specialized equipment to focus about 200 tiny beams of
radiation on the tumor with sub-milimeter accuracy.
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51. • Although each beam has very little effect on the brain tissue it passes
through, a strong dose of radiation is delivered to the place where all
the beams meet.
• So the precision of GKRS results in minimal damage to healthy tissues
surrounding the target.
• GKRS is usually one-time therapy completed in a single day.
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52. Indications
• Small tumors
• Functional hearing
• Older patients
• Medically unstable patients
• Patient’s choice
Contraindications
• Tumor > 3cm
• Tumor compressing brainstem
structure
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53. Complications of GKRS
• There is no potential complication associated with anaesthesia,
bleeding and infections
• 1. Fatigue –tiredness and fatigue may occur tor the first few weeks
after GKRS
• 2. Swelling – swelling in the brain at or near the treatment site can
occur. But regress after 6 months.
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54. THANKS FOR YOUR KIND ATTENTION
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