Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care for a prolonged seizure, repeated seizures without recovery, sudden neurological symptoms, loss of consciousness, or rapidly worsening alertness.
Contact the treatment team promptly for progressive symptoms, fever during treatment, uncontrolled vomiting, or side effects that interfere with eating, drinking, walking, or taking medicines.
Follow-up plans vary by tumor type and treatment.
Visits may include a neurological examination, review of symptoms and medicines, and MRI scans.
Scan timing is based on the diagnosis, previous treatment, stability of earlier images, and current symptoms.
The article also says
Keep appointments even when you feel well.
Bring an updated medicine list and note any new seizures, headaches, weakness, balance problems, thinking changes, or treatment side effects.
Ask who to contact between visits if symptoms change.
Driving and work safety should be discussed, particularly after a seizure or when vision, attention, coordination, or judgment is affected.
Rules about driving after seizures vary by location.
Every sign above is quoted from the sofidex article on Brain tumors in adults. If you are not sure, err upward — it is always reasonable to be checked.