Selective Nerve Injection
Each level in the spine has a pair of nerve roots that exit, one to the left and one to the right. The nerve roots can be compressed either in the central canal or as each nerve root exits the spine through the "foramen". Compression or irritation can lead to nerve dysfunction, felt as pain, weakness, numbness, hypersensitivity, etc. These unusual sensations, coupled with diagnostic testing such as MRI, X-Ray, CT Scanning, or electrodiagnostic testing, can help to determine the nerve root that is abnormal. The unusual sensations tend to follow patterns down the arm or leg to the hand or foot, which help to differentiate the source of the problem. The pattern followed by nerve irritation symptoms is called a dermatome (see chart at left).
The channel around the suspected nerve root can then be injected under precise, video X-Ray guidance (fluoroscopy) with local anesthetic, steroid, or a combination of the two, to determine whether the pain is being generated at that level or is from another source. If the symptoms are originating or being transmitted through the nerve root that is blocked, then the patient should have relief of their abnormal sensations. Occasionally, the patient will experience a reproduction of sensations in the same distribution of their typical pattern during the injection, which can help to clarify whether the pain generator or transmitter has been located.
