Evaluation of Brainstem Gliomas in Children

Examination

• Cranial neuropathies and elevated ICP: The evaluation of patients with brainstem tumors should include a detailed history and physical examination. Special attention should be paid to signs and symptoms of hydrocephalus, lower cranial nerve deficits, recurrent respiratory tract infections, changes in quality of voice, and evidence of progressive cervical myelopathy to aid in discrimination between a medullary versus cervical cord syndrome.  Reviewing older photographs of the patient may be useful in revealing the development of subtle cranial neuropathies. 

Laboratory Tests

• Standard preoperative tests: Standard preoperative laboratory studies including CBC, electrolytes, PT/PTT, and blood type and screen are necessary only if the patient is being urgently admitted, surgical intervention is anticipated in the immediate future, or there is concern for metabolic derangements due to prolonged nausea/vomiting or poor oral intake.

Radiologic Tests

CT

• Often the first-line imaging modality: Due to its wide availability, CT is often the first-line modality used by the primary health care provider or emergency room to assess presenting complaints.
• Not the imaging study of choice: CT scans may suggest a lesion in the brainstem. However, due to limited facility in visualizing the posterior fossa and soft tissues of the CNS, its usefulness is greatly limited beyond assessment of bony anatomy and demonstration of obstructive hydrocephalus, if present, from a tumor. MRI is almost always needed to further elucidate tumor details.

MRI

• Image of choice: MRI of the brain with and without gadolinium contrast is the imaging study of choice for brainstem tumors.
• Multi-planar T1 and T2: Both T1- and T2-weighted axial and sagittal sequences should be obtained for the most basic studies.
• Additional useful sequences: Additional sequences including gradient echo (GRE) or susceptibility-weighted imaging (SWI) to evaluate for evidence of hemosiderin deposition, and FLAIR.  Diffusion tensor imaging (DTI) to delineate white matter tracts may help in evaluating a lesion and in operative planning, if appropriate (30).

Characteristic appearance of tumor types

• Midbrain gliomas: The tumors are focal and are typically associated with hydrocephalus. Commonly, the tumor is discovered during imaging evaluation of the hydrocephalus.
• Dorsally exophytic gliomas: Most of the tumor volume is outside the brainstem. These tumors typically erupt through the pia/ependyma early in their growth, so imaging will show the bulk of tumor outside the brainstem.
• Diffuse intrinsic pontine gliomas: Imaging of these tumors will show diffuse involvement of the brainstem (in particular the pons), and there can be infiltration of surrounding structures of the CNS.
• Cervicomedullary gliomas: This group is a mixture of medullary and spinal cord tumors. Imaging of this group of gliomas will show both focal tumors of the medulla growing into the upper spinal cord and spinal cord tumors growing upward to compress the medulla.

Nuclear Medicine Tests

• None: No specific nuclear medicine tests are indicated in the evaluation of children with brainstem tumors.

Electrodiagnostic Tests

• None: There is no role for electrodiagnostic testing in the evaluation of suspected brainstem tumors. Its use is reserved for intraoperative monitoring to guide surgical resection where appropriate.

Neuropsychological Tests

• None: No preoperative neuropsychological testing is indicated.

Correlation of Tests

• Congruency directs treatment: It is expected that the child’s clinical course, examination, and imaging studies will be in agreement. With focal tumors of the brainstem, this congruency (focal symptoms, focal tumor on imaging, and indolent course) should prompt surgical resection of lesions, particularly those located at the cervicomedullary junction or dorsally exophytic in growth.
• Incongruency suggests need for biopsy before definitive treatment: In cases with disagreement between the imaging findings and clinical course (e.g., rapidly progressive course with imaging consistent with a focal or low-grade lesion), frozen sections should be obtained at the time of surgery before progressing to an aggressive resection. These instances may be representative of a more malignant tumor, in which case the potential for iatrogenic injury in the course of resection outweighs the potential benefit of an extensive resection.