A brain tumor is any abnormal growth of cells inside the skull. Because the brain controls so many functions, the first clues can show up almost anywhere in the body. Symptoms usually start mild and build over weeks to months, but they can also appear suddenly if the tumor bleeds or blocks fluid flow.

The most common early sign is a new headache that does not feel like your usual headaches. It is often dull, steady, and worse in the morning or when you bend over. Vision may blur or double, and you might find yourself bumping into doorframes because your side vision is fading. Hearing changes, ringing in one ear, or feeling off-balance can happen if the tumor sits near the hearing or balance centers. Many people notice arm or leg weakness, numbness, or trouble finding the right words. Seizures that start out of nowhere—shaking, staring, or blacking out—are another red flag. Mood or memory shifts, such as feeling foggy, irritable, or forgetful, can be subtle early clues. If the tumor grows very large, nausea and vomiting may appear as pressure builds inside the skull.

Because these changes can be blamed on stress, aging, or lack of sleep, many people wait too long to get checked. Any new headache with vision, hearing, strength, or personality changes that linger for weeks should be evaluated with brain imaging.