A brain tumor is a mass of abnormal tissue growing inside the skull. Some tumors are benign, or non-cancerous; others are malignant, or harmful. When describing brain tumors, the term 'malignant' means not only cancerous tumors, but also any non-cancerous tumors whose size or location makes them dangerous or inoperable. Most people with brain tumors will experience headaches as an early symptom. However, it's important to realize that headaches can have many causes. Some warning signs that may indicate a brain tumor include chronic headaches that are worst in the morning, then improve as the day goes on; visual disturbances; nausea and vomiting; and weakness or loss of feeling in an arm or leg. Other accompanying signs are hearing loss; difficulty speaking; seizures; unusual drowsiness; personality changes; dizziness or loss of balance; and problems with memory or concentration. Again, other disorders can mimic these symptoms, so the best way to confirm or rule out a brain tumor is by the use of tests like a CAT (cat) scan or MRI. These tests show an image of the brain, allowing most tumors to be spotted quickly. If you have severe or recurrent headaches, especially when they occur with other symptoms, it's wise to visit a doctor for a thorough exam.