- Evidence of peripheral neuropathy: Patients with hereditary sensory motor neuropathy are at risk of severe peripheral nerve toxicity if exposed to vincristine.
- CSF cytology: CSF cytology for evaluating the extent of disease most often is performed 10 days after biopsy or resection, as it is usually contraindicated preoperatively and can lead to false positives if performed too early.
- Used when MRI not available: CT scans may be helpful in cases of acute hemorrhage and for identification of tumor if it is more accessible than MRI. It is also helpful as baseline when a germ cell tumor is suspected and the presence of calcification suggests a teratomatous component.
- Standard of care for all brain tumors preoperatively as baseline: MRI of the spine should be obtained in all cases of malignant tumors, with optimal timing preoperatively. If MRI is postoperative, then it must be delayed 3 weeks to avoid false positives. MRI of the spine should be performed in cases of LGGs before chemotherapy or radiation therapy is started to evaluate for the presence of dissemination.
Nuclear Medicine Tests
- Kidney function: The glomerular filtration rate should be assessed before treatment with cisplatin is begun and repeated before each cycle, as dosing may need to be modified according to nephrotoxicity.
- FDG-PET for necrosis vs. recurrence: It may be helpful to perform a FDG-PET study of the brain to differentiate between malignant tumor recurrence and radiation necrosis. FDG-PET may be helpful in identifying malignant transformation in a plexiform neurofibroma.
Evaluation of hearing
- Audiology testing: Audiology testing is required as a baseline before treatment when the use of cisplatin, high-dose carboplatin, and radiation therapy are being considered, and it must be repeated before each cycle of cisplatin as dose adjustment may be required.
- Brainstem auditory evoked potentials: These can be performed in a young patient who is unable to cooperate with audiology testing before platinum therapy.
- Visual evoked potentials: These may be helpful as a baseline and during chemotherapy in a young patient with visual impairment due to a visual pathway tumor, in whom accurate visual testing is difficult.
- Establish baseline and follow treatment impact: Neuropsychological testing is helpful when done before treatment and then periodically during treatment to identify any treatment-related effect on cognition. It is particularly helpful in patients who have developed postoperative mutism syndrome, who are undergoing radiation therapy, or who are receiving neurotoxic agents such as methotrexate. It is also important in patients with learning difficulties or cognitive delays noted before brain tumor diagnosis.
Correlation of Tests
- Age may modify treatment: A young age will alter the use of radiation due to long-term consequences.
- Metastasis on imaging may modify treatment: The presence of metastases will escalate the intensity of chemotherapy in addition to dose and field of radiation.
- Cognitive state may modify treatment: The degree of cognitive dysfunction or brain injury at presentation may alter management, e.g., avoidance of radiation or limitation of the field or dose of radiation.
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