Vestibular Schwannoma

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 acusticus

  • Small VS: Ovoid-enhancing intracanalicular mass

  • Large VS: “Ice cream on cone” shape in CPA and IAC

  • 15% with intramural cysts (low signal foci)

  • 0.5% with associated arachnoid cyst/“trapped” CSF

• High-resolution T2 space, CISS, or FIESTA: “Filling defect” in hyperintense CSF of CPA-IAC cistern

• FLAIR: ↑ cochlear signal from ↑ protein

• T2* GRE: Microhemorrhages ↓ signal foci (common)

  • Characteristic VS finding when present

  • Not seen in meningioma

Top Differential Diagnoses

• Meningioma in CPA-IAC

• Epidermoid cyst in CPA

• Aneurysm in CPA

• Facial nerve schwannoma in CPA-IAC

• Metastases in CPA-IAC

Pathology

• Benign tumor arising from vestibular portion of CN8 at glial-Schwann cell junction

Clinical Issues

• Demographics and symptoms

  • Adults with unilateral sensorineural hearing loss

  • Other symptoms

    • –

      Unsteady walking

    • –

      Vertiginous sensation

    • –

      Tinnitus

• Surgical approaches

  • Translabyrinthine resection if no hearing

  • Middle cranial fossa approach for IAC VS

  • Retrosigmoid approach when CPA involved

• Treatment: Surgery vs. radiosurgery

TERMINOLOGY

IMAGING