A complete physical and neurological examination should be performed. Focal deficits may be found depending on location and size of the tumor.
- Infants and head circumference: In the case of infants, the anterior fontanelle and cranial sutures should be examined, and a head circumference measured and compared to previous measurements to determine potential head growth acceleration and rapidity of tumor growth.
- Ophthalmological assessment: Age-appropriate ophthalmological examination, including funduscopic and visual field evaluation, if possible, should be performed. Papilledema may prompt higher doses of corticosteroids or ICU admission.
- Standard preoperative laboratory tests: In anticipation of surgery an assessment of renal function, hematocrit/hemoglobin, platelet count and aggregation if clinically indicated, coagulation studies, and blood typing for cross-matching of blood transfusions should be considered.
- Anticonvulsants: Serum anticonvulsant levels should be documented when appropriate.
- Markers for tumor: No serum marker exists to aid in the diagnosis of HGG.
Access to sophisticated neuro-imaging has led to earlier diagnosis of some of these tumors. Symptoms suggesting intracranial hypertension typically result in a CT or MRI of the brain being performed. Typically, because sedation is rarely required, the CT is the first radiologic test acquired, followed by MRI. Both are helpful in evaluating the child and the tumor, the CT to evaluate calcifications and the calvarium, and the MRI for high-resolution images of the intracranial contents.
- AAs – variable density, surrounding edema and enhancement: CT images typically may show variable attenuation, enhancement, and vasogenic edema. Even in very large lesions there may be little or no edema.
- GBM – variable density and enhancement with surrounding edema: CT images of GBM show variable attenuation and enhancement, which may be ring-enhancing, and associated vasogenic edema contributing substantially to overall mass effect.
- AAs – hypodense to isodense T1-weighted image: Post-contrast T1-weighted images reveal a diffuse lesion with variable enhancement (focal, homogeneous, nodular). Diffuse leptomeningeal spread is not common.
- AAs – hyperintense T2-weighted MRI with variable edema: T2-weighted MRI reveals high intensity with surrounding edema for large lesion, with little edema in smaller tumors.
- AAs bright on axial DWI: DWI shows diffusion restriction (bright area).
- GBM – hypointense T1-weighted MRI with ring enhancement: The T1-weighted images will typically show a hypointense, necrotic center, or a large, heterogeneously tumor with impressive infiltration of surrounding structures. Gadolinium enhancement may be ring shaped or heterogeneous.
- GBM – hyperintense T2-weighted and hypointense Flair imaging with surrounding, hyperintense edema. T2-weighted and Flair sequences will show edema better with Flair differentiating it from solid tumor.
- GBM DWI – bright signal of restriction is typical. The tumor will restrict on DWI and show very bright.
- Decreased NAA, lactate peak, and elevated choline/creatinine ratio: MR spectroscopy provides information about the metabolic and biochemical activity of the tumor (15). When compared to normal brain tissue in the same patient, high-grade tumors reveal a decreased NAA (N-acetylaspartate), a tall lactate peak or doublet, and an increase in the choline/creatinine ratio.
Diffusion Tensor Imaging (DTI)
Nuclear Medicine Tests
- PET used to evaluate hypermetabolism: PET may be helpful in the care of children with high-grade gliomas. It is most often used to evaluate children after surgery when there is a question about whether MRI findings are compatible with tumor, postoperative changes, or radiation necrosis. It may be used preoperatively, however, to delineate areas of increased metabolism.
- Not indicated: Electrodiagnostic tests are not indicated for supratentorial HGGs.
- Neuropsychological tests establish baseline to follow: For children who are cooperative and not significantly impaired, particularly those with specific memory, cognitive, or intellectual symptoms, preoperative neuropsychological testing may be helpful if time permits. Such testing may serve as a baseline for future comparison during and after treatment (16).
Correlation of Tests
- Imaging and pace of symptom evolution: All of the above tests, along with the child’s medical and neurological condition, will help guide the timing and nature of treatment.