CerebellopontineAngleTumors.ppt

Cerebellopontine Angle Tumors Introduction 10% of all intracranial tumors Vestibular schwannomas (acoustic neuromas), 78% of CPA tumor Anatomy CPA is an irregularly shaped space in the posterior fossa Ant: temporal bone Post: cerebellum Medial: inf. olive Sup: pons and cerebellar peduncle Inf: cerebellar tonsil CN 5: superiorly CN 9, 10, 11: inferiorly In this space: Foramen of Luschka, lateral aperture of the fourth ventricle Ant. inf. cerebelar artery (AICA) 40 % extends into IAC Labyrinthine a. CN 7 and CN 8, encased in glial tissue throughout intracranial course Schwann cells surround nerves beginning in the IAC, near porus. The glial-schwann junction is also known as the Obersteiner-Redlich zone Scarpa ganglion located the midportion of ICA Internal Acoustic Canal Ant. sup Facial n. Bill bar Post. sup Superior vestibular n. Transverse Crest Ant. Inf Cochlear n. Post. inf Inferior vestibular n. Vestibular Schwannomas Difficult to determine the incidence, clinically silent vestibular schwannomas 7 cases per 10,000 MRI for nonotologic reason 0.7~1.2 of 100,000 Tumor biology Arise from vestibular segment Equal frequency between sup and inf vestibular nerve Japan, 85% from inf. portion From Schwann cells, most within the IAC Most lateral to the Scarpa ganglion Scarpa ganglion with the greatest density of Schwann cells Vestibular schwannomas is not all acoustic neuroma. Misnomer. It is not neuromas. The most appropriate term is vestibular schwannoma. Cochlear schwannomas with propensity for invasion into the cochlea Etiology Sporadic, 95% Bilateral. NF-2, tend to occur in younger patients and associated with other intracranial meningiomas and spinal cord tumors Genetic defect on 22q12 of NF-2 2 subtypes of NF-2 Wishart subtype, more severe Gardner subtype, less severe Biochemical Factors Schwannomas express neureglin, controlling survival and proliferation of schwann cells, and its receptor, erbB2 and erbB3 Vestibular schwannoma may accelerate during pregnancy