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Subependymal Giant Cell Astrocytoma (SEGA)

Last Updated: March 27, 2020

Open Table of Contents: Subependymal Giant Cell Astrocytoma (SEGA)

Figure 1: This subependymal giant-cell astrocytoma (SEGA) is present in its typical location at the foramen of Monro. This lesion is larger than should be seen for other subependymal nodules in tuberous sclerosis. The FLAIR image (left) demonstrates multiple subcortical hyperintense tubers. A hyperintense right posterior periventricular nodule is also visible. Other calcified subependymal nodules are less evident. Postcontrast T1WI (right) demonstrates the avid enhancement typical of SEGAs.

Basic Description

  • Benign tumor of neuroglial origin classically arising in patients with tuberous sclerosis complex (TSC)
  • Slow-growing tumor arising in region of germinal matrix, usually near the foramen of Monro where it may obstruct ventricular outflow resulting in noncommunicating hydrocephalus


  • WHO grade I
  • May arise from subependymal nodules (SEN) near germinal matrix
    • Represents a neuroglial migration abnormality
  • Most common are CNS tumors in TSC patients

    • Uncommonly arises in the absence of TSC
  • Similar histology to SENs with diagnosis of SEGA based on tumor size and growth
  • Autosomal dominant inheritance or de novo mutations of TSC1 and TSC2 genes

Clinical Features

  • Afflicts children and young adults with TSC (mean age 11 years)
  • Presenting symptoms
    • Obstructive hydrocephalus
    • Headache, nausea, vomiting from increased intracranial pressure
    • Rarely, spontaneous tumoral hemorrhage with intraventricular extension
    • Worsening seizures/epilepsy
  • Good prognosis/curable with total surgical resection
  • Treatment: rapamycin and/or surgical resection

Imaging Findings

  • General
    • Slowly enlarging, avidly enhancing mass arising near the lateral ventricles/foramen of Monro in patients with tuberous sclerosis complex (TSC)
    • Well-defined tumor margins, often lobulated or “frond-like”
    • Variable size
    • Additional findings of TSC (cortical tubers/dysplasias, SENs)
  • CT

    • Heterogeneously hypo- to isodense to gray matter
    • May show calcification, hydrocephalus
    • Strong but heterogeneous enhancement on contrast-enhanced CT
  • MRI

    • T1WI: hypo- to isointense to gray matter; areas of calcification may appear hyperintense
    • T2WI: heterogeneously iso- to hyperintense; calcification appearing hypointense
    • FLAIR: heterogeneously hyperintense, periventricular hyperintensity secondary to acute hydrocephalus and transependymal flow of CSF
    • T2*/GRE/SWI: black susceptibility artifact from foci of calcification
    • T1WI+C: avid enhancement
    • DWI: relatively reduced diffusion compared with TSC hamartomas

Imaging Recommendations

  • MRI with contrast, imaging surveillance of enlarging SENs/SEGA

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Rachel Seltman, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.01.38


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Osborn AG, Salzman KL, Jhaveri MD. Diagnostic Imaging (3rd ed). Philadelphia, PA: Elsevier, 2016.

Roth J, et al. Subependymal giant cell astrocytoma: diagnosis, screening, and treatment. Recommendations from the International Tuberous Sclerosis Complex Consensus Conference 2012. Pediatr Neurol. 2013;49:439-444.

Sener RN. Diffusion MR imaging of giant cell tumors in tuberous sclerosis. J Comput Assist Tomogr. 2003;27:431-433.

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