To diagnose metastatic brain lesions, or areas of abnormal tissue, doctors usually conduct a neurological examination, including an MRI scan of the brain.
Brain tumors can be difficult to diagnose because they can cause a wide variety of symptoms, all of which might also be caused by other diseases and conditions. To diagnose a brain tumor, a doctor usually takes a complete medical history and conducts a neurological examination, which includes an MRI of the brain.
A technique called contrast-enhanced MRI is particularly useful in making an accurate diagnosis of brain metastases because it provides very detailed images of normal and abnormal brain tissue. Its sensitivity is much greater than that of CT scans, and it is able to detect small tumors, which may be missed on a CT scan. For patients who cannot undergo MRI, such as those with cardiac pacemakers or severe claustrophobia, physicians generally recommend a CT scan.
A biopsy is rarely necessary to diagnose brain metastases, but when appropriate, a small sample of the tumor tissue is removed. In some cases, a lumbar puncture (spinal tap) — removing a sample of spinal fluid for study — is useful particularly in diagnosing neoplastic meningitis, a type of metastasis in which tumor cells invade the cerebrospinal fluid.