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it's not a Tumor!
Surgical approaches
Acoustic neuroma
Radiology
Potpourri
100
what are the most common tumors of the posterior fossa name 5
Acoustic neuroma – 80%, most common adult lesion Meningioma – 5%, 2nd most common adult lesion Epidermoid – 3%, 3rd most common adult lesion Arachnoid cyst – 1% Nonacoustic neuroma - Facial schwannoma most common, 1% Paraganglioma Hemangioma
100
list approaches to the Posterior fossa (4/8)
Translabyrinthine Retrosigmoid (suboccipital)* Retrolabyrinthine* Transcochlear Transotic Middle fossa* Extended middle fossa* Petrosal*
100
discuss Radiographic features of Acoustic Neuroma on mRI
A: MRI – T1 Isointense to brain, Hyperintense to CSF; T2 Hyperintense to brain, Iso/Hypointense to CSF; Gad Intense enhancement
100
Radiographic features of Meningoma on MRI
A: MRI – T1 Isointense to brain, larger lesions may be heterogeneous with central hypointensity; T2 Hyperintense to brain, Hypointense to CSF; Gad Intense enhancement (but less than AN)
100
Define Brown’s sign
A: Seen in Glomus Typmanicum tumors A: Reddish blush seen behind an intact TM which Blanches upon introducing Pneumatic Pressure that exceeds the Systolic BP
200
Seven Uncommon CPA lesions name 4
A: Metastatic malignant tumor A: Lipoma A: Dermoid A: Teratoma A: Chordoma A: Chondrosarcoma A: Giant cell tumor
200
Of the 3 approaches of AN surgery. order then in least to most likely to get a CSF leak
Retrosigmoid craniotomy has the highest CSF leak rate, followed by translabyrinthine craniotomy. Middle fossa craniotomy has the lowest leakage rate. (Bailey’s)
200
Where do Acoustic Neuromas Originate historically?
At Schwann cell-Glial junction (Obersteiner-Redlich zone)
200
Radiographic features of Epidermoid on MRI
A: MRI – T1 Hypointense to brain, Isointense to CSF; T2 Hyperintense to brain, Isointense to CSF;
200
Define Aquino’s sign
A: Seen in Paragangliomas A: Pulsatile Tinnitus of paraganglioma Decreases with Carotid artery Compression
300
Ddx of Petrous Apex lesions (5) name 3
A: Cholesterol granuloma (20x more frequent than epidermoids in the petrous apex) A: Epidermoid A: Asymmetric pneumatization A: Retained mucus/mucocele A: Petrous apicitis +/- Osteomyelitis A: Petrous ICA aneurysm A: Meningioma A: Glomus tumors (Tympanicum, Jugulare) A: Chondrosarcoma
300
Discuss the 4 Advantages & 1 Disadvantage of the Translabyrinthine Approach for Acoustic Neuromas excision
A: Advantages – Safest for CN VII function Preservation; Direct approach to IAC; Wide Exposure not limited by Tumor Size; Minimal cerebellar Retraction A: Disadvantange – Total Hearing Eradication, Increased risk of CSF Leak
300
Audio findings most consistent with AN list 2
A: PTA – 65% will have HF SNHL; 10% present with SSNHL (but only 5% of SSNHL is due to AN); 5% have Normal hearing A: SDS – Poor scores out of proportion to PTA suspicious; Rollover present A: Stapedial Reflex – 88% will have Absent Reflex or Positive Reflex Decay
300
Radiographic features of Arachnoid Cyst on MRI
A: MRI – T1 Isointense, T2 hyperintense to CSF, Homogeneous lesion, DWI suppressed
300
Draw me contents of the IAC
Seven up coch down
400
Ddx of Intraaxial tumors (4) name 2
A: Hemangioblastoma A: Medulloblastoma A: Brainstem Glioma (most common Pediatric CPA lesion) A: Malignant Choroids Plexus Papilloma & Ependymomas
400
Discuss the 2 Advantages & 3 Disadvantages of the Middle Fossa Approach for Acoustic Neuromas excision
A: Advantages – CN VIII nerve preservation possible; Ideal for Small Intracanalicular tumors A: Disadvantages – Contraindicated if >1 cm or extension into CPA; Increased Risk to CN VII, significant Temporal Lobe Retraction, More technically Difficult
400
Average growth rate of AN
0.2 cm/ year
400
Six IAC lesions that light up with Gadolinium name 3
A: Neuromas – Acoustic or Facial nerve A: Meningiomas A: Inflammatory nerve lesions A: AVM’s A: Vascular loops A: Petrous bone metastasis
400
Describe Hitselberger’s sign
A: Numbness of Posterior EAC from Compression of Sensory branches of Facial Nerve
500
From what cells do Meningiomas Arise?
Cap cells, around Tips of Arachnoid Villi
500
Discuss the 50:50 rule or 70:30 rule and how it would guide your surgical management
Hearing preservation 50:50 rule – not recommended if >50db HL, speech discrim <50% Hearing preservation recommended if <30db, >70% speech discrim, normal ABR
500
NF1 and NF2 list the chromosome and % chance of developing AN
NF 1 (17) NF2 (22) <5 vs 96% bilat
500
Eight Radiographic Differences between Meningiomas and Acoustic Neuromas name 4
A: Meningiomas more Dense & Homogenous A: Meningiomas cause More Hyperostosis of surrounding bone A: Meningiomas Sessile, Broad base, Obtuse Angle to Petrous bone A: Meningiomas Eccentric over IAC A: Meningiomas Uncommonly involve the IAC, whereas ANs have Intracanulicular component A: Meningiomas frequently have a Dural Tail A: Meningiomas frequently have Calcifications A: Acoustic Neuroma exhibit Greater, More Homogeneous Gadolinium Enhancement
500
Most common primary lesion of Petrous Apex
Cholesterol Granuloma