Chapter 44 - Neurotology Flashcards
CPA mass presenting Sx
unilateral SNHL, tinnitus, disequilibrium
Hitzelberger sign
numbness in medial, posterior or superior EAC
Caused by acoustic neuroma compressing VII
Boundaries of cerebellopontine angle
AL: clivus, petrous T bone P: ventral brainstem, cerebellum M: pons, medulla S: cerebellum, middle cerebellar peduncle I: cerebellar tonsil
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
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
Sx from lesion of PICA
Wallenberg/Lateral Medullary Syndrome
dysphagia, dysarthria, vocal cord paralysis, vertigo, facial paralysis, ataxia, ipsilateral Horner’s, hemisensory disturbance
Sx from lesion of AICA
AICA is close to 7/8 nerve roots
Hemiplegia, CN dysfunction (medial injury)
Ataxia (lateral injury)
Internal auditory artery: branch of, and supplies
br of AICA
supplies labyrinth
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
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
Syndromes associated with AN
NF1 (AD)- intra and extracranial neuroma, <5% develop AN. Chrom 17
NF2 (AD)- bilateral AN >90% pts. Chrom 22q12.2
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
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
Signs/Sx of AN
CN VIII dysfunction is how intracanalicular ones present - HL, vertigo, tinnitus
As tumor grows, hearing worse, disequilibrium
Sx of brainstem compression
hydrocephalus (HA, N/V, AMS)
Percentage of AN pts with hearing loss. Percentage with tinnitus, disequilibrium
95% HL
50-60% tinnitus
40-60% disequilibrium
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%)
ABR findings in AN
latency of wave V of >0.2msec
Intensity of AN on MRI
Isointense T1, mildy hyperintense T2, fairly avid enhancement
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
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%
