Mass-CPA-slides-040602 - Cerebellopontine Cerebellopontine...

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Unformatted text preview: Cerebellopontine Cerebellopontine Angle Masses Alan L. Cowan, MD Arun Gadre, MD University of Texas Medical Branch June 2, 2004 Cerebellopontine Angle Cerebellopontine Angle Area of the lateral (quadrimenal) cistern containing CSF, arachnoid tissue, cranial nerves and their associated vessels. Borders Medial – lateral surface of the brainstem Lateral – petrous bone Superior – middle cerebellar peduncle & cerebellum Inferior – arachnoid tissue of lower cranial nerves Posterior – cerbellar peduncle Definitions Definitions Intra­axial – within the parenchyma of the brain or brainstem Extra­axial – outside of the brainstem parenchyma CPA lesions – lesions arising within the confines of the CPA. Petrous lesions – lesions arising from the petrous portion of the temporal bone. These may extend into the CPA. Differential Differential Acoustic Neuroma Meningioma Epidermoid Rare CPA lesions Petrous Apex masses Vascular malformations Intra­axial masses Acoustic Neuroma Acoustic Neuroma Comprises 60­92% of CPA lesions Majority of cases (95%) are sporatic Occur with equal frequency on the Superior and Inferior vestibular nerves Pathophysiology Composed of Antoni A&B tissue Antoni A – compact tissue with spindle cells in palisades (most common) Antoni B – loose tissue with cyst formation. AN symptoms AN symptoms Cochlear Asymmetric SNHL SSNHL Tinnitus Decreased discrimination Rollover Vestibular Up to 26% of AN may present with SSNHL Only 1­2.5% of SSNHL is due to AN Dysequilibrium (more common) Vertigo (less common) Facial Facial weakness (suspect other tumors ­ epidermoid) Hitselberger’s sign – decreased sensation of EAC due to compression of CN VII sensory roots AN symptoms AN symptoms Cerebellar Brainstem Wide gait Falling to side of lesion Headache Visual Loss Other Cranial nerves V – facial numbness (large tumors, trigeminal schwannoma) VI – lateral rectus palsy (rare) IX – dysphagia (large tumors, jugular foramen syndrome) X – hoarseness, aspiration (large tumors, jugular foramen syndrome) XI – shoulder weakness (large tumors, jugular foramen syndrome) AN ­ Radiology AN ­ Radiology CT Non­contrast: usually isodense to brain, calcification is rare IV Contrast: Over 90% of non­treated tumors enhance homogeneously Gas cisternogram: no longer done MRI T1 – isointense to brain, hyperintense to CSF T2 – hyperintense to brain, iso/hypo­intense to CSF Gadolinium – Intense enhancement of tumor on T1 AN Features •Centered on Porus Acousticus •Acute angles to petrous bone •Often involves the IAC •Homogeneous enhancement •No dural tail •No calcifications Meningioma Meningioma Second most common CPA lesion 3­7 % Arise from cap cells near arachnoid villi which are more prominent near cranial nerve foramina and venous sinuses. Usually arise from posterior surface of the petrous bone and usually do not extend into IAC Symptoms Ataxia Nystagmus Facial hypesthesia Audiologic findings may show retrocochlear pattern or may be normal. Meningioma Meningioma Radiologic features Tumors generally hemispherical with obtuse angles to petrous bone Dural tail often present (50­75%) May herniate into middle fossa (50%) May show calcification (25%) Pial blood vessels with flow voids may be present at the margins. Treatment Surgical removal is treatment of choice XRT may be used to supplement if complete excision not possible Meningioma Features •Arise from surface of petrous bone •Obtuse angles to petrous bone •Uncommonly involves the IAC •Frequently with dural tail •Calcifications common Epidermoid Epidermoid Accounts for 2­6% of CPA masses Physiology May arise within the temporal bone or in the CPA Symptoms Congenital lesions that present in adulthood Rests of ectodermal tissue containing stratified squamous lining and keratin Similar to acoustic neuroma and meningioma Facial nerve paresis and facial twitching may occur Radiologic Features May dumbell into middle fossa or contralateral cistern Highly variable in shape with a cauliflower surface appearance CT usually shows a mass hypodense to CSF MRI – homogeneous lesion T1 – isointense to CSF T2 – isorintense to CSF Differentiation from arachnoid cyst may be difficult Diffusion weighting will show moderate intensity for epidermoid, but low intensity for arachnoid cysts. Arachnoid Cyst Arachnoid Cyst Other Extra­axial Masses Other Extra­axial Masses Primary Secondary Arachnoid Cyst Schwannomas (CN V­XII) Hemangiomas Lipoma Dermoid/Teratoma Paraganglioma Chondroma Chordoma Extension of Petrous bone tumors Schwannomas Schwannomas CN VII Symptoms may be identical to acoustic schwannoma Differentiation from acoustic schwannoma may not be possible by radiography unless lesion extends distal to geniculate ganglion. CN IX – XI Jugular Foramen syndrome Dysphagia Hoarseness Shoulder weakness Enlargement of Jugular Foramen CN XII Hemiatrophy of tongue Enlargement of hypoglossal canal CN V Schwanoma CN V Schwanoma CN VII Schwanoma CN VII Schwanoma CN X CN X Schwanoma Vascular Vascular Vertebrobasilar dolichoectasia AICA loop Enlongation and dilitation of the vertebrobasilar artery. Symptomas ­ Facial spasm, trigeminal neuralgia May loop over, under, or between CN VII & CN VIII. Symptoms ­ vertigo Giant Aneurysms Hemangioma Paragangliomas (may extend to CPA) Glomus Jugulare Glomus Tympanicum Vertebrobasilar Dolichoectasia Vertebrobasilar Dolichoectasia AICA loop AICA loop Giant Aneurysms Giant Aneurysms Glomus Jugulare Glomus Jugulare Petrous Apex Petrous Apex Cholesterol granulomas (most common) Epidermoid cyst Trigeminal schwannoma Carotid artery aneurysm Chondroma Chondrosarcoma Intra­axial Intra­axial Astrocytoma Ependymoma Medulloblastoma Hemangioma / Hemangioblastoma Choroid plexus papilloma Metastasis Imaging Techniques Imaging Techniques XR CT Non­contrasted Iodine based contrast ­ uptake by selected lesions Gas CT cisternogram – no longer performed MRI T1 – Fat density is bright T2 – Water density is bright FLAIR (Fluid Attenuated Inversion Recovery) FSE (Fast Spin Echo) CISS (Constructive Interference Steady State) Gadolinium Treatment Treatment Treatment Treatment Observation Surgery Translabrynthine Retrosigmoid Middle Fossa Radiotherapy Conventional radiation therapy Stereotactic radiosurgery Observation Observation Indications Advanced age (over 65 or 75) Poor health Lack of symptoms Non­progression of symptoms Only hearing ear Isolated IAC tumors in the elderly Contraindications Young patient Healthy patient Symptomatic progression Compression of brainstem structures Trans­labrynthine Trans­labrynthine Indications Extension into CPA > 0.5 ­ 1cm Non­serviceable hearing Adequate contralateral hearing in large tumors Contraindications Serviceable hearing Middle Fossa Middle Fossa Indications Small tumor Intracanallicular tumor Moderate CPA involvement Adequate hearing (SRT<50 db, Disc >50%) Contraindications Large tumors Extensive CPA involvement ( > 0.5 – 1 cm) Older patients ( > 60 yrs. may have higher rate of bleeding or stroke) Retrosigmoid Retrosigmoid Indications Serviceable hearing Large tumors Compression of brainstem Contraindications Functional hearing with extensive IAC involvement Intracanallicular tumors Stereotactic Radiosurgery Stereotactic Radiosurgery Indications Contraindications Tumors > 3 cm Prior radiotherapy Tumor compressing brainstem Outcome Small tumors Funtional hearing Older patients (>75 Hirsch) Medically unstable patients (Hirsch) Previous resection (Hirsch) Local control (non­progression): 94% Hearing preservation: 47 – 77% Complications Facial nerve injury: 5 ­ 17% Trigeminal nereve injury: 2 ­ 11% Hyrodcephalus: 3% Mendenhall, et al. “Management of Acoustic Neuroma” American Journal of Otolaryngology. 2004; 25: 38-47. Bibliography Bibliography Bailey, Byron J. Head and Neck Surgery – Otolaryngology. Lippencott. New York, NY. 2001. Brackmann, Shelton, Arriaga. Otologic Surgery. W.B. Saunders Compant, New York. 2001. Fisch, Mattox. Microsurgery of the Skull Base. Georg Thieme. New York, NY. 1988. Lang, Johannes. Clinical Anatomy of the Posterior Cranial Fossa and its Foramina. Thieme Medical Publishers, Inc. 1991 McElveen, Dorfman. “Petroclival Tumors” Otolaryngology Clinics of North America. 2001, 34: 1219­1230. Mendenhall, et al. “Management of Acoustic Neuroma” American Journal of Otolaryngology. 2004; 25: 38­47. Myers, et. al. Operative Otolaryngology. Head and Neck Surgery . Saunders Company. Philadelphia, PA. 1997. Som, Curtin. Head and Neck Imaging. Mosby. St. Louis, MO. 2003. ...
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