Evaluation of Subependymal Giant Cell Astrocytomas in Children

Examination

  • Skin examination: Skin must be examined for the neurocutaneous markers of TSC.
  • Signs of elevated ICP: The examination should look for signs of elevated ICP such as papilledema and sixth nerve palsy.

Laboratory Tests

  • Routine tests: No abnormal findings are expected.

Radiologic Tests

On CT scan and MRI, subependymal nodules appear as small, nonobstructing, subependymal nodular lesions.  They can occur in any ventricle (5). SEGAs, by contrast, appear as moderate to large-sized subependymal or intraventricular masses that are located near the foramen of Monro.  They demonstrate serial growth (5).

CT Scans: SEGAs

  • Isointense: SEGAs appear as an isointense intraventricular mass with peripherally located dense nodular calcifications adjacent to the foramen of Monro.
  • Large: They are usually larger than 1 cm by the time of diagnosis.
  • Enhance: Enhancement is intense and homogeneous (differentiating feature from subependymal nodules) (10, 13, 22).
  • Other lesions seen: Usually, other subependymal nodules, tubers, or parenchymal calcifications are also seen.
  • Hydrocephalus: Accompanying hydrocephalus may be present.

Sagittal reconstructed CT scan of SEGA: The image shows an intraventricular mass located near the foramen of Monro. The mass is causing asymmetric dilatation of the left lateral ventricle.
 
Coronal reconstructed CT scan of SEGA: The image is of the same patient shown to the left

Axial CT scan of a SEGA: This scan is of the child with the Shagreen patch shown on Presentation page
 
Coronal CT scan of a SEGA: The image is of the same child shown to the left

 

MRI

  • T1-weighted images: The lesion will have a mixed hypointense-to-isointense heterogeneous appearance. Intense but nonhomogeneous enhancement may be seen after contrast administration.
  • T2-weighted images:  Besides hyperintense foci, hypointense areas and strongly hypointense zones due to calcifications are seen, giving the tumor an overall heterogeneous appearance.
  • Cortical tubers: Cortical tubers are commonly present in these patients and are better seen with MRI than with CT (28, 22).

Axial T1-weighted MRI of a SEGA: This scans shows no hydrocephalus. The patient was placed under periodic surveillance.
 
Axial T2-weighted MRI of SEGA: There is no evidence of hydrocephalus in this patient either, and thus surveillance was instituted

Coronal T2 MRI of SEGA: The scan shows the tumor occupying the third ventricle, causing obstructive hydrocephalus and midline raised ICP syndrome
Axial T1-weighted MRI of subependymal nodule: A small nodule is seen on the lateral wall of the left lateral ventricle
Axial T1-weighted MRI with gadolinium showing subependymal nodule: Nodule is near the third ventricle, has a diameter of almost 1 cm, and enhances with gadolinium. These features label this subependymal nodule as being at risk for becoming a SEGA.

 

Nuclear Medicine Tests

  • None indicated

Electrodiagnostic Tests

  • None indicated

Neuropsychological Tests

  • Useful for following patient: Neuropsychology can be helpful as a baseline evaluation of memory and intelligence when following small- or moderate-sized lesions. After surgery these tests can be used serially during postoperative follow-up visits and for prognostication.

Correlation of Tests

  • Decline in cognition: A decline in memory, behavior and/or intelligence may indicate involvement of the fornix and the limbic pathways by the tumor. Improvement in these findings would be helpful as markers of recovery in the follow-up period as well as for prognostication.