KEY FACTS Imaging Best clue Anterior or central skull base ( SB ) defect on bone CT with positive β2-transferrin test on nasal secretions Anterior SB bone CT findings Bone defect in cribriform plate, lateral lamella of middle turbinate or…
KEY FACTS Terminology Headache caused by ↓ intracranial CSF pressure Imaging Classic imaging Diffuse dural thickening/enhancement – Smooth, not nodular or “lumpy-bumpy” Downward displacement of brain through incisura (“slumping” midbrain) Veins, dural sinuses distended ± subdural hygromas/hematomas Other: Midbrain elongated,…
Overview Understanding the anatomy of the skull, scalp, and meninges is key to formulating a correct imaging diagnosis. Several important differential diagnoses are based on location. However, each of these locations requires a different imaging approach. For example, CT is…
KEY FACTS Terminology Definition: Cerebellopontine angle-internal auditory canal (CPA-IAC) metastases refers to systemic or CNS neoplasia affecting area of CPA-IAC Imaging 4 major sites: Leptomeningeal (pia-arachnoid), dura, flocculus, and choroid plexus T1WI C+ MR Leptomeningeal metastases : Diffuse thickening and…
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…