6 Acoustic Neuroma 1u5l6c

ACOUSTIC NEUROMA DR.AYESHA FAYYAZ TR ENT, SZH

11-1-2018

DEFINITION • ALSO CALLED VESTIBULAR SCHWANNOMA • BENIGN, SLOW GROWING, NERVE SHEATH

TUMOR OF SUPERIOR AND INFERIOR VESTIBULAR NERVE

INTRODUCTION • 78% OF ALL A TUMORS • ARISES IN MEDIAL PART OF THE IAC OR THE LATERAL PART OF THE A

• AGE OF PRESENTATION: SPORADIC: 40-60 YR. NON-SPORADIC < 20-30 YR. • MEAN GROWTH RATE : 1.2 MM / YR. • RARELY MALIGNANT

ANATOMY OF ANGLE • POTENTIAL CSF SPACE IN POSTERIOR CRANIAL FOSSA • ROUGHLY TRIANGULAR IN SHAPE

• ANTERIORLY: TEMPORAL BONE • POSTERIORLY: CEREBELLUM • MEDIALLY: CISTERNS OF THE PONS &

MEDULLA AND OLIVE • SUPERIORLY: INFERIOR BORDER OF PONS & CEREBRAL PEDUNCLE

STRUCTURES CROSSING A • CN V ( SUPERIORLY ) • CN IX,X,XI ( INFERIORLY )

• CENTRE: CN VII AND VIII WITH ARACHNOID SHEATH TO IAC • AICA

ETIOLGY Defective chromosome 22q12

Mutated tumor suppressor “MERLIN”

Somatic mutation in both copies of MERLIN

U/L VS

GROSS ANATOMY • SMOOTH SURFACE • YELLOW TO GRAY COLOR

• USUALLY SOLID WITH OCCASIONAL CYSTIC COMPONENT

HISTOLOGY ANTONI A: • CLOSELY PACKED CELLS

• SMALL SPINDLE-SHAPED AND DENSELY STAINED NUCLEI • WHORLED APPEARANCE • VEROCAY BODY

ANTONI B: • LOOSE CELLULAR AGGREGATION OF VACUOLATED PLEOMORPHIC CELLS

CLASSIFICATION • ACCORDING TO SIZE

Intrameatal tumour

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

>40

SIGNS & SYMPTOMS INTRACANALICULAR: ◦ HEARING LOSS (UL PROGRESSIVE ), TINNITUS, VERTIGO

◦ LOSS OF SPEECH DISCRIMINATION OUT OF PROPORTION TO HL CISTERNAL: ◦ WORSENED HEARING AND DISEQUILIBRIUM

SIGNS & SYMPTOMS COMPRESSIVE: ◦ OCCASIONAL OCCIPITAL HEADACHE

◦ CN V: MIDFACE, CORNEAL HYPOESTHESIA ◦ CN VII : HITZELBERGER’S SIGN, LOSS OF TASTE AND REDUCED LACRIMATION ON SCHIRMER’S TEST , FACIAL WEAKNESS ( LATE) ◦ CN II , IV , VI : DEC. VISUAL ACUITY AND DIPLOPIA

SIGNS & SYMPTOMS HYDROCEPHALIC: ◦ FOURTH VENTRICLE COMPRESSED AND OBSTRUCTED

◦ HEADACHE, VISUAL CHANGES, ALTERED MENTAL STATUS ◦ NAUSEA AND VOMITING ◦ O/E : RAISED I AND PAPILLEDEMA.

COMPRESSION OF CN IX & X ◦ DYSPHAGIA , ASPIRATION AND HOARSENESS ◦ POOR GAG REFLEX AND VC PARALYSIS.

SIGNS & SYMPTOMS CEREBELLAR INVOLVEMENT( LATE ) ◦ INCOORDINATION , WIDELY BASED GAIT , TENDENCY TO FALL

TOWARDS AFFECTED SIDE

BRAINSTEM INVOLVEMENT:

• ATAXIA, WEAKNESS AND NUMBNESS OF ARMS AND LEGS WITH EXAGGERATED TENDON REFLEXES.

INVESTIGATIONS MRI WITH GADOLINIUM CONTRAST • HYPOINTENSE GLOBULAR MASS IN IAC ON T1

• ENHANCEMENT WITH GADOLINIUM • ISO/HYPOINTENSE ON T2

CT SCAN WITH IODINE CONTRAST • OVOID MASS IN IAC WITH NONHOMOGENEOUS ENHANCEMENT.

SPECIAL INVESTIGATIONS

AUDIOLOGY PURETONE AUDIOMETRY: • ASYMMETRIC, DOWNSLOPING, HIGH-FREQUENCY SNHL

WORD RECOGNITION SCORE (WRS): • ROLLOVER PHENOMENON

ACOUSTIC REFLEX THRESHOLDS • ACOUSTIC REFLEX DECAY

VESTIBULAR TESTING ELECTRONYSTAGMOGRAPHY (ENG) • REDUCED CALORIC RESPONSE IN THE PROBLEMATIC EAR

AUDITORY BRAINSTEM RESPONSE • MEASURES YOUR BRAIN'S RESPONSE TO SOUND • FULLY OR PARTIALLY ABSENT

• DELAY IN THE LATENCY OF WAVE V IN THE AFFECTED EAR • INTER AURAL DELAY OF WAVE V LATENCY > 0.2 MS • SENSITIVITY >90%

• SPECIFICITY = 90%

DIFFERENTIAL DIAGNOSIS D/D

S/S

INVESTIGATIONS

MENINGIOMA

LESS PROMINENT HL

NO EXPANSION OF IAC MAY HAVE DURAL TAIL (CT/MRI)

EPIDERMOID

LESS PROMINENT HL

NON-ENHANCHING T1 & T2 IMAGES

FACIAL NERVE SHWANNOMA

EARLY PROMINENT FACIAL WEAKNESS

ENHANCEMENT IN FACIAL CANAL

TRIGEMINAL SCHWANNOMA

LESS PROMINENT HL MORE PROMINENT FACIAL NUMBNESS

DUMBELL SHAPED MASS OVER PETROUS APEX

TREATMENT • SURGICAL REMOVAL • OBSERVATION

• RADIOTHERAPY

SURGICAL REMOVAL • TRANS LABYRINTHINE CRANIOTOMY • RETRO SIGMOIDAL CRANIOTOMY

• MIDDLE FOSSA CRANIOTOMY

TRANSLABYRINTHINE APPROACH • PRIMARY APPROACH • HEARING ABLATING METHOD

• PT SELECTION: POOR HEARING ( HL > 50DB) UNRESECTABLE WITH HEARING PRESERVING METHODS

STEPS

post-auricular incision

Mastoidectomy

Identification of incus, tegmen, sigmoid sinus & facial nerve

Skeletonization of middle and post fossa dura

sigmoid sinus decompressed with a diamond burr

Identification of facial nerve medial to bill’s bar

Tumor removal from lateral to medial side

ADVANTAGES

• ANY SIZE TUMOR CAN BE RESECTED

• MINIMUM BRAIN RETRACTION • FACIAL NERVE PRESERVATION: 97%

DISADVANTAGES

• HEARING LOSS

RETROSIGMOIDAL APPROACH • HEARING PRESERVING METHOD • GOOD VIEW OF A

• PT SELECTION: GOOD HEARING LEVELS TUMOR LIMITED TO MEDIAL IAC

STEPS

Retromastoid curvilinear skin incision

Mastoid & retromastoid bone exposed

Craniotomy performed

dura is opened along the sigmoid sinus

Cerebellum visualized & retracted

A identified

Posterior wall of IAC removed for exposure of canalicular portion

Closure done in layers

ADVANTAGES

• HEARING PRESERVATION

DISADVANTAGES

• PERSISTENT POST-OPERATIVE HEADACHE

• INABILITY TO EXPOSE FACIAL NERVE • PERSISTENT CSF LEAK

MIDDLE FOSSA APPROACH • HEARING PRESERVING APPROACH • INTRACANALICULAR TUMORS WITH <1.5 CM CISTERNAL COMPONENT

• ENTIRE IAC IS ACCESSIBLE WITHOUT VIOLATING THE INNER EAR • POOR SURGICAL POSITION OF THE FACIAL NERVE • TRANSIENT SPEECH AND MEMORY DISTURBANCES AND AUDITORY HALLUCINATIONS

STEPS

inverted U-shaped incision over the ear

Squamous temporal bone exposed

Cranioto my over zygomati c root

Extradura l elevation of temporal lobe

IAC identified and skeletoniz ed

Dura exposed posteriorl y in IAC

Tumor removed

Closure done in layers

OBSERVATION • LIFE EXPECTANCY < DURATION REQUIRED FOR VS GROWTH • RADIOLOGICAL FOLLOW-UP :

AFTER 6 MONTHS THEN YEARLY • TREATMENT: 2-3MM GROWTH / 1ST YEAR

STEREOTACTIC RADIATION • PRECISELY TARGETED HIGH DOSE RADIOTHERAPY • PREVENTS FURTHER GROWTH

• PRESERVE HEARING & FACIAL NERVE • COMPLICATION: HYDROCEPHALUS • PT SELECTION:

• SHORT LIFE EXPECTANCY • HIGH SURGICAL RISK

OPERATIVE COMPLICATIONS • VASCULAR INJURY • AIR EMBOLISMS

• PARENCHYMAL BRAIN INJURY • CRANIAL NERVE INJURY

THANKYOU