Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Sudden vision loss, stroke-like symptoms, seizures, severe breathing or swallowing difficulty, or confusion require immediate medical care.
Follow-up generally includes clinical visits and repeat MRI of the skull base.
CT may be added when bone detail is needed.
Chest or other body imaging may be recommended based on the tumor's features, previous findings, and treatment history.
Follow-up may also include eye examinations, hearing tests, pituitary hormone blood tests, and assessments of swallowing, speech, balance, or nerve function.
The article also says
There is no single schedule for everyone.
Timing depends on the extent of surgery, pathology results, radiation, residual disease, and time since treatment.
Because recurrence can occur years later, monitoring usually continues long term.
Contact the care team between appointments about persistent new headaches, double vision, facial numbness, hearing changes, swallowing problems, unexplained changes in weight or energy, increased thirst and urination, or new pain elsewhere.
Every sign above is quoted from the sofidex article on Clival chordoma. If you are not sure, err upward — it is always reasonable to be checked.