Several of the discs are usually tested, including one disc that appears to be normal that is used as a control, or comparison level. It is anticipated the patient will not be aware of any feeling when the dye is injected into a normal disc.
If the disc is abnormal the patient will begin to feel some discomfort. Based on the patient’s response and the internal pressure of the disc recorded during the procedure, a diagnosis can be made. Once discomfort is felt, the test of that disc is stopped. The concept is to identify an abnormal disc, not to measure pain tolerance. After a brief time of observation, the patient is released from the center. The procedure is considered minimally invasive and done on an out-patient basis. In patients with dye allergies, saline can be substituted for the dye.