ACOUSTIC NEUROMA
Dr. Asha K Joy
15/03/23

Specific learning objectives
• Describe in brief CP angle anatomy and tumours
• Enumerate pathogenesis, clinical features of acoustic neuroma
• Enumerate radiological, audiological and pathological investigations
for acoustic neuromas
• Enumerate treatment guidelines

DEFINITION
• Benign tumor of vestibular nerve
schwann cells

VESTIBULAR SCHWANNOMA
• 6 % of all Intracranial tumors
• 80 - 90% of CPA tumors
• Majority adulthood
• 95% Unilateral
• 5% Neurofibromatosis type 2 (bilateral)
• No known race, gender predilection

ANATOMY OF CPANGLE
• Triangular area
Posterior surface of temporal bone
Edge of pons
Anterior surface of cerebellum
Trigeminal nerve
• Lateral
• Medial
• Posterior
• Superior
• Inferior IX, X, XI cranial nerves

Anatomy of CPA
⚫ AICA is the main artery in the CPA and is the source of the
labrynthine artery .
⚫ The labrynthine artery courses via the IAC & is an end
artery for the hearing and balance organs.

SITE OF ORIGIN
• Schwann cells which envelop distal potion
of VIIIth nerve
• More common from inferior vestibular
nerve
• Arise from schwann cells within the IAC
– lateral to O-R zone in the area of scarpa
ganglion.
• Schwannomas rarely arise from the
cochlear nerve & are rarely malignant .

EFFECTS ON INNER EAR
• Compressive effect on cochlear
nerve
• Vascular occlusion of internal auditory
artery
• Atrophy of organ of Corti
• Vacuolization of stria vascularis

Pathogenesis
• Owing to mutations in the gene for the tumor suppresor protein
MERLIN located on chr 22q12.
• Formation of VS requires mutation of both copies of the merlin gene.
• Somatic mutations in both copies of merlin gene results in sporadic
VSs .
• Familial VS occuring in NF 2 requires only one somatic mutation
event .( inherit one )

• NF2 is autosomal recessive at gene level but inheritance is autosomal
dominant ( pseudodominant )
• A mutation in the normal allele leads to bilateral VS by the age of 20.
• Genetic screens for the NF2 mutation have been developed and are
the basis for genetic counselling for family members of NF2
patients

• Biochemical factors- VS express neuregulin ,which controls survival
and proliferation of schwann cells and its receptors erbB2 & erbB3.
• FGF ,TGF B1 , PDGF & VEGF all these contribute to VS proliferation.
• VS may accelerate during pregnancy.

Pathology
GROSS :
• VS have a smooth surface with a yellow to gray color.
• Tumor is usually solid ,with occasional cystic components and
therefore has a firm to soft texture depending on solid to cystic
components.
MICROSCOPIC :
• Capsule – 3 to 5 micrometer in thickness.
• Two morphological tissue types – Antony A & Antony B areas

GROWTH PATTERN
• Grows medially
• Invested by double
arachnoid layer

1. 2.
3.
4.
INTRACANALICULAR CISTERNAL
COMPRESSIVE HYDROCEPHALIC

STAGES
(< 2 cm)
1 Otological stage (<2cm)
2 Trigeminal nerve involvement (2-2.5 cm)
3 Brain stem and cerebellar compression (2.5-4 cm)
4 Increasing intracranial pressure (>4 cm)
5 Terminal stage

STAGE 1
OTOLOGICAL STAGE
• Deafness
– Unilateral, gradual
• Tinnitus
– Non-pulsatile
• Imbalance
• Trigeminal nerve involvement
• Facial nerve involvement

STAGE 2
TRIGEMINAL NERVE INVOLVEMENT
• Tumor size 2-2.5 cm
• Irritation in eye
• Pain, tingling, numbness on face
• Feeling of cold on face

STAGE 3
BRAIN STEM AND CEREBELLAR
COMPRESSION
• Ataxia
• Gait disturbance
• Tremors
• Nystagmus

STAGE 4
INCREASING INTRACRANIAL PRESSURE
• Headache occipital
• Nausea Vomiting
• Papilloedema

STAGE 5
TERMINAL STAGE
• Failure of vital centres in brain stem

EXAMINATION
• Cutaneous lesions (neurofibromas)
• Otoscopy: Normal
• Tuning fork tests:
– Unilateral senorineural deafness
• Trigeminal Nerve
• Facial nerve
• Eye examination

EXAMINATION
• Finger nose test
• Romberg’s test
• Unterberg’s test

Diagnostic evaluation
• Average patient will require 4 years from the onset of symptoms to
diagnosis.
• Majority will present with complaints of UHL, UT, Vertigo , dysequilibrium,
facial numbness, weakness or spasm.
• Initial step in evaluation includes an audiologic assessment .if it suggests a
retrocochlear lesion , then imaging of the CPA is performed .
• Vestibular testing lacks specificity in diagnosis of VS

INVESTIGATIONS
• Speech test
• Speech audiometry
• PTA
• Stapedial reflex
• Electrocochleography
• ABR
• Caloric test

BERA patterns in AN

RADIOLOGICAL INVESTIGATIONS
• Temporal bone radiology
(contrast))

CT-SCAN WITH CONTRAST

DIFFERENTIAL DIAGNOSIS
• Meningioma
• Primary cholesteatoma
• Arachnoid cysts
• Facial neuromas
• Lipoma
• Choroid plexus papilloma
• Glomus jugulare

TREATMENT
• Surgery
• Observation
• Radiotherapy
– Conventional
– Stereotactic

STEREOTACTIC RADIOSURGERY
Indications
• Patient who is poor surgical risk (age,
medical condition, etc.)
• Tumor < 3 cm
• Younger patients with < 3 cm tumor who
refuse surgery

SURGERY
• Middle fossa approach
• Translabyrinthine approach
• Retrosigmoid approach

Middle Fossa Approach.
Translabyrinthine Approach
SuboccipitalApproach
Surgical Approaches
Factors that influence surgical approach selection
•Age
•Hearing status
•Tumour size
•Surgeon’s preference.

CONSERVATIVE MANAGEMENT
• Advanced age (> 65 )
• Short life expectancy (< 10 years)
• Slow growth rate
• Poor surgical candidate / poor general health
• Minimal symptoms
• Only hearing ear
• Patience preference

Thank you