Computerized Cranial Tomography
This technique (called CCT or CAT scan) utilizes a computer to analyze the absorption of small quantities of x-ray by the brain. X-rays are best used to view bone. The result is a photograph of the contents of the skull showing any major abnormalities. The first part of the test involves stabilizing the head while the x-ray beam scans the skull. There is no pain or other sensation during the scanning. A second picture is then made while an iodine-containing dye is run into an arm vein. Abnormalities within the skull will appear different than the normal brain tissue.
Small abnormalities, particularly within the inner ear, may not be detected on these scans. In that case, a small quantity of air is inserted into the lower part of the back (spinal tap) and the patient is positioned so that the air rises to the area of the inner ear. If the inner ear is normal, the air will enter the inner ear canal. Even a small tumor will prevent filling of the inner ear canal and be seen by this technique. In rare cases, the air will not fill the canal, but yet the diagnosis of a tumor is in doubt. In this case, a small quantity of iodine-containing dye is inserted into the back and x-rays are taken at a later time to exclude the possibility of a small tumor.
Magnetic Resonance Imaging
This technique (MRI) utilizes a computer to analyze the magnetic field in the skull created when one lies within a magnet. The result is a photograph of the contents of the skull showing any abnormalities. During the test, the patient lies quietly within a large tube containing a magnet. There is no pain or other sensation during the procedure. There is no exposure to x-rays during the test. At times, a material is injected into an arm vein to enhance the MRI image. MRI is used best to view soft tissue (brain). It cannot be used in patients who are using a cochlear implant.