Fact-sheet: Schwannoma - Neuroma


Updated on 04/05/2023 at 10:25 AM

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Definition

Schwannoma (formerly Neurinoma): benign tumor arising exclusively from Schwann cells.

"Acoustic neuroma" most often refers to a vestibular nerve schwannoma.

MRI

T1: iso- or hypointense

T1 with gadolinium: intense enhancement after injection

T2: hyperintense +/- heterogeneous. Possible cystic component

T2*: hemosiderin deposits frequently seen in large schwannomas

Target sign: peripheral T2 hyperintensity, central hypointensity

Classification

Eden classification of dumbbell-shaped spinal neurinomas
• type 1: intra- and extradural.
• type 2: intra-, extradural, and paravertebral.
• type 3: extradural and paravertebral.
• type 4: foraminal and paravertebral.
Asazuma classification

In the cerebellopontine angle, to guide treatment decisions (surgery or RT), the Koos classification is the most widely used:

  • grade 1: intracanalicular tumor
  • grade 2: protrusion into the cerebellopontine cistern (CPA); no contact with the brainstem
  • grade 3: tumor filling the cerebellopontine cistern without brainstem displacement
  • grade 4: large tumor exerting a mass effect on the brainstem as well as on the cranial nerves in their cisternal portion

Differential diagnosis

Neurofibroma: Tumor arising from all constituent elements of the nerve

Meningioma

Epidermoid cyst

Secondary lesions, notably carcinomatous leptomeningitis

Ependymoma

For strictly intracanalicular lesions, the differential diagnosis should include:

  • enhancement at the fundus of the acoustic porus related to the venous plexus surrounding the nerve sheath
  • Scarpa's ganglion
  • a low-flow vascular malformation: venous malformation, formerly called cavernous hemangioma.