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Subependymoma


KEY FACTS

Terminology

  • Rare, benign, well-differentiated, intraventricular ependymal tumor, typically attached to ventricular wall

Imaging

  • Intraventricular, inferior 4th ventricle typical (60%)

  • Other locations: Lateral > 3rd ventricle > spinal cord

  • T2/FLAIR hyperintense intraventricular mass

    • Heterogeneity related to cystic changes; blood products or Ca++ may be seen in larger lesions

  • Variable enhancement, typically none to mild

  • T2WI and FLAIR are often most sensitive sequences

Top Differential Diagnoses

  • Ependymoma

  • Central neurocytoma

  • Subependymal giant cell astrocytoma

  • Choroid plexus papilloma

  • Hemangioblastoma

  • Metastases

Pathology

  • WHO grade I

Clinical Issues

  • 40% become symptomatic, often supratentorial

    • Related to increased intracranial pressure, hydrocephalus

  • Present in middle-aged/elderly adults (typically 5th-6th decades)

  • Treatment: Conservative management with serial imaging if asymptomatic patient

  • Surgical resection is curative in most cases

  • Excellent prognosis for supratentorial lesions

    • Recurrence is extremely rare

Diagnostic Checklist

  • If 4th or lateral ventricular hyperintense mass in elderly man, think subependymoma

Sagittal graphic shows a solid, well-circumscribed mass arising from the floor of the 4th ventricle with mild mass effect
. Note the lack of hydrocephalus, typical of subependymoma.

Sagittal FLAIR MR shows a solid, hyperintense mass along the inferior 4th ventricle
in a 64-year-old man with headaches. Subependymoma was found at resection. These 4th ventricular tumors are often asymptomatic. T2 and FLAIR are typically the most sensitive sequences to identify this WHO grade I tumor.

Axial T2WI MR shows a hyperintense mass
along the inferior 4th ventricle at the level of the medulla (classic imaging of a subependymoma).

Axial T1 C+ MR shows an enhancing mass in the 4th ventricular outflow tract
. The moderate enhancement is uncommon. Subependymomas classically have no or minimal enhancement. They can protrude through the foramen of Magendie. In this case, tumor is also present anterior to the cerebellar hemisphere
through the foramen of Luschka.

TERMINOLOGY

Synonyms

  • Older literature: Subependymal glomerulate astrocytoma, subependymal astrocytoma, subependymal mixed glioma

Definitions

  • Rare, benign, well-differentiated, intraventricular ependymal tumor, often attached to ventricular wall

IMAGING

General Features

  • Best diagnostic clue

    • T2-hyperintense, lobular, nonenhancing, intraventricular mass

  • Location

    • Typical: Intraventricular, inferior 4th ventricle (60%)

      • –

        Often protrudes through foramen of Magendie

    • Other locations: Lateral > 3rd ventricle > spinal cord (cervical or cervicothoracic)

      • –

        Lateral ventricle: Attached to septum pellucidum or lateral wall

    • Rare: Periventricular

  • Size

    • Typically small, 1-2 cm

    • May become large, > 5 cm

      • –

        More commonly symptomatic when large

  • Morphology

    • Well-defined, solid, lobular mass

    • When large, may see cysts, hemorrhage, Ca++

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