Chapter 44 - Neurotology Flashcards by Ben Walters

CPA mass presenting Sx

unilateral SNHL, tinnitus, disequilibrium

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Hitzelberger sign

numbness in medial, posterior or superior EAC

Caused by acoustic neuroma compressing VII

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Boundaries of cerebellopontine angle

AL: clivus, petrous T bone
P: ventral brainstem, cerebellum
M: pons, medulla
S: cerebellum, middle cerebellar peduncle
I: cerebellar tonsil

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CNs travelling through CPA

VII, VIII travel laterally and superiorly from brainstem to IAC
CN V superiorly, travels anteriorly from pons to Meckle’s cave
CN IX, X, XI inferiorly

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Relationship between facial, cochlear and vestibular nerves, from perspective of CPA looking lateral at IAC

facial anterior/superior
cochlear ant/inf
superior vestibular nerve posterior/superior
inferior vestibular nerve posterior/inferior
Facial n and sup vestibular separated by Bill’s bar
Transverse crest separates sup and inf portions of IAC

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Sx from lesion of PICA

Wallenberg/Lateral Medullary Syndrome
dysphagia, dysarthria, vocal cord paralysis, vertigo, facial paralysis, ataxia, ipsilateral Horner’s, hemisensory disturbance

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Sx from lesion of AICA

AICA is close to 7/8 nerve roots
Hemiplegia, CN dysfunction (medial injury)
Ataxia (lateral injury)

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Internal auditory artery: branch of, and supplies

br of AICA

supplies labyrinth

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Differential of CPA mass

Acoustic neuroma 60-90%
Meningioma 3-7%
Epidermoid 2-4%
Other CN Schwannoma (5, 7, 9, 10, 11) 1-4%
Arachnoid cyst 1-2%
Rare: mets, hemangioma, lipoma, chordona, chondrosarcoma, dermoid, neuroepithelial tumors, endolymphatic sac tumor, ependymoma, glioma, astrocytoma, medulloblastoma, choroid plexus papilloma, aneurysm, AVM

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Acoustic Neuroma: what it is, where its located, incidence

arises from schwann cells
lateral to obersteiner-redlich zone (transition of central to peripheral myelin)
Inferior > Superior vestibular nerve
May extend medially to CPA
1 per 100,000

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Syndromes associated with AN

NF1 (AD)- intra and extracranial neuroma, <5% develop AN. Chrom 17
NF2 (AD)- bilateral AN >90% pts. Chrom 22q12.2

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Natural history of AN

Grow 1-2mm/yr, may be as much as 2cm/yr
Possible that they don’t grow after Dx as well
Growth may extend to brainstem, 4th ventricle
May be lethal due to brainstem compression, ICH

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Size criteria of AN. How size affects Tx

small <1.5cm
medium 1.5-2.5cm
large 2.5-4cm
giant >4cm

Smaller lesion- may be able to follow with IMG esp if elderly. Smaller also makes tx less morbid

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Signs/Sx of AN

CN VIII dysfunction is how intracanalicular ones present - HL, vertigo, tinnitus
As tumor grows, hearing worse, disequilibrium

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Sx of brainstem compression

hydrocephalus (HA, N/V, AMS)

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Percentage of AN pts with hearing loss. Percentage with tinnitus, disequilibrium

95% HL
50-60% tinnitus
40-60% disequilibrium

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Tests that indicate AN is likely

Unilateral SNHL with disproportionate loss of speech discrimination
88% have absent reflexes or reflex decay
ABR detects 95% (false neg 18-30%)

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ABR findings in AN

latency of wave V of >0.2msec

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Intensity of AN on MRI

Isointense T1, mildy hyperintense T2, fairly avid enhancement

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How to treat AN

Observe- elderly, small
Stereotactic Rads- cannot tolerate surgery, limited life expectancy
Surgery (may have hearing-preservation approach)
If young, tumor will grow and grow most likely, so they should be treated

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Recurrence after surgery vs regrowth after Rads

Surg: 1-20%
Rads: 5-15%

Benefit of Rads over Surgery

Earlier return to normal activity

Disease free survival and overall tumor control with Rads

10 yr 92-98%

overall rate of tumor control: 93-9%

Modes of delivering rads to AN

SRS (one time) or SRT (fractions)
Gamma Knife (colbalt 60)
CyberKnife (linear accelerator)

Complications after Rads for AN

trigeminal neuropathy (0-27% SRS) facial nerve palsy/paresis (0-23%) HL that worsens over time Second cancer

Translab approach: Indications, Adv/Disadv

Ind: >2cm, small w/o serviceable hearing, facial nerve decomp/vestibular neurectomy and poor hear ADV: exposure, less HA, highest rate CN VII fxn 99% anatomic 75% HB I-IV, ID VII laterally at fundus, may repair nerve, no cerebellar retraction, low recurrence DISADV: hearing loss, short-term vvertigo if poor preop compensation, CSF leak 4-14%, fat graft needed

Size of AN where hearing preservation is unlikely

>2cm

Retrosigmoid approach: Ind, ADV, DISADV

Ind: AN servicable hearing, doesn't extend to lateral IAC, Meningioma with limited IAC involve ADV: exposure, hearing preserve, CN VII preserve DIS: fundus not visualized, more cerebellar retraction, 65% postop HA, limited ventral brainstem view, higher CSF leak than translab

Middle Fossa approach AN: Ind, Adv, Dis

Ind: <1cm AN with CPA extension, superior based meningioma of IAC/petrous bone Adv: hearing preservation 65%, CN VII preserve 91-95% Dis: Not for >65 since dura fragile/adherent, must work around VII, CSF leak equal to translab

Retrolab approach: Ind

Vestibular neurectomy | Posterior craniotomy between sigmoid sinus and otic capsule, exposes posterior fossa

Transcochlear approach: Ind

Anterosigmoid posterior fossa craniotomy View anterior CPA Extends translab craniotomy For meningioma medial to IAC, chordoma, chondrosarcoma, residual AN

Infratemporal fossa approach

for T bone tumors extending inferior to jugular foramen near petrous ICA ALso fro deep lobe parotid tumors with temporal bone involve

Meningioma: what it is, syndromes, malignant potential

Arise form arachnoidal cap cells associated with arachnoid villi Sporadic, but more often in NF2 5% become malignant

Sx of meningioma of CPA

HL, tinnitus, imbalance

Classic imaging for meningioma

enhance postcontrast MRI, dural tail, hyperostosis on CT

Tx of meningioma

Surgery if growing or Sx | SRS or SRT for <3cm or residual post-surg dz may control growth

Postop complications CPA surgery

CSF leak 10-15% - fluid collections near ear (Tx with pressure dress/bed rest, lumbar drain, fat obliteration mastoid) Meningitis VII dysfunction Stroke, edema, air embolus, cerebellar ataxia, death (<1%)

DDx petrous apex lesion

Inflam: cholesterol granuloma, cholesteatoma, mucocele Infectious: apicitis, osteomyelitis Neo: schwannoma, meningioma, paraganglioma, chordoma, sarcoma, nasopharyngeal carcinoma, metastatic lesions (renal cell, lung, breast, prostate) Vascular: carotid artery aneurysm Anatomic: asymmetric pneumatization (up to 35%)

Cholesterol granuloma

Occurs after hemorrhage into petrous apex air cells Punched out bony lesion CT, isodense mass, rim enhancement Drain lesion to other portions of skull if Sx via transsphenoid or infralabyrinthine or infracochlear approach

How to tell cholesterol granuloma vs cholesteatoma/mucocele on imaging

Chol Gloma: hyperintense T1-2 | Cholestea: hypointense T1, hyper T2

Jugular foramen (Vernet) syndrome and tumors that cause it

Paresis of IX, X, XI | Paraganglioma, schwannoma, meningioma, metastatic lesions, jugular vein thrombosis

Sx of glomus tumors in jugular bulb/promontory

pulsatile tinnitus, CHL, aural fullness, CN deficits | Purplish-red mass

Brown's Sign

Paraganglioma blanches when positive pressure is applied

Blood supply to jugular/tympanic paragangliomas

Jug: ascending pharyngeal artery Tymp: inferior tympanic artery (br of ascending pharyngeal)

Names of two staging system for paragangliomas

Fisch

vessel traveling with IX, X, XI in pars nervosa compartment of jugular foramen

inferior petrosal sinus

Relationship between CN IX, X and XI in jugular foramen

IX most anterior, ant to ICA XI most posterior, anterior to IJ X is medial, between ICA, IJ

Most common tumors of EAC

SCCa | basal cell, adenoid cystic

Staging of SCCa EAC

Pitt System T1 limited to EAC T2- limited bony erosion T3- eroding bony EAC full thickness, or involves middle ear/mastoid T4- Eroding cochlea, petrous apex, medial wall carotid, jug

2-year survival rates of T stages of SCCa EAC

T1- 100% T2- 80% T3- 50% T4- 15%