KEY FACTS Terminology Definition: Benign, unencapsulated neoplasm arising from meningothelial arachnoid cells of CPA-IAC dura Imaging 10% occur in posterior fossa When in CPA, asymmetric to IAC porus acusticus NECT Variable; often hyperdense – 25% calcified; 2 types seen □…
KEY FACTS Terminology Benign encapsulated nerve sheath tumor composed of differentiated neoplastic Schwann cells 99% of all schwannomas associated with cranial nerves 95% involve CN8 < 1% of all intracranial schwannomas are intraparenchymal Imaging CT Iso- to slightly hyperdense compared…
KEY FACTS Terminology Vestibular (“acoustic”) schwannoma (VS): Benign tumor from Schwann cells that wrap vestibular CN8 branches in cerebellopontine angle-internal auditory canal (CPA-IAC) Imaging T1WI fat-saturated enhanced MR = gold standard Focal, enhancing mass of CPA-IAC cistern centered on porus…
KEY FACTS Terminology Definition: Vascular loop compressing facial nerve at its root exit zone within cerebellopontine angle (CPA) cistern causing hemifacial spasm Imaging High-resolution T2WI MR or source MRA images show serpentine asymmetric signal void (vessel) in medial CPA Anterior…
KEY FACTS Terminology Trigeminal neuralgia (TN) definition: Vascular loop compressing trigeminal nerve (CN5) at its root entry zone (REZ) or preganglionic segment (PGS) Imaging High-resolution MR: Serpiginous asymmetric signal void (vessel) in cerebellopontine angle (CPA) CN5 REZ or PGS CN5…
KEY FACTS Terminology Bell's palsy (BP): Herpetic peripheral facial nerve paralysis secondary to herpes simplex virus Imaging T1WI C+ fat-saturated MR: Fundal “tuft” and labyrinthine segment CN7 show intense asymmetric enhancement Entire intratemporal CN7 may enhance Imaging note: Classic rapid-onset…
KEY FACTS Terminology Arachnoid cyst (AC): Developmental arachnoid duplication anomaly creating cerebrospinal fluid (CSF)-filled sac Imaging Sharply demarcated ovoid extraaxial cisternal cyst with imperceptible walls with CSF density (CT) or intensity (MR) AC signal parallels (is isointense to) CSF on…
KEY FACTS Terminology Definition: Congenital inclusion of ectodermal epithelial elements during neural tube closure Imaging CPA cisternal insinuating mass with high signal on DWI MR 90% intradural, 10% extradural; margins usually scalloped or irregular; cauliflower-like margins with “fronds” possible TI…
Terminology The contents of the cerebellopontine angle (CPA) and internal auditory canal (IAC) cisterns include the facial nerve (CN7), the vestibulocochlear nerve (CN8), and the anterior inferior cerebellar artery (AICA) loop. The bony IAC, its fundal crests (vertical and horizontal),…
KEY FACTS Terminology Lymphocytic hypophysitis (LH) Synonyms: Adenohypophysitis, primary hypophysitis, stalkitis Idiopathic inflammation of pituitary gland &/or stalk Imaging Thick stalk (> 2 mm + loss of normal “top to bottom” tapering) ± enlarged pituitary gland 75% show loss of…