Myanesin, a specific muscle relaxant of which the chief site of action seems to be the bulbar reticular region, is capable of rapidly dissolving muscle spasm in the "acute discsyndrome". A series of patients with acute low-back and radicular pain were studied before and after the injection of this drug. It was found that pain and limitation of motion of the limb could be altered with gratifying symptomatic relief. In certain instances this response persisted and, when followed by conservative treatment, led to long-term cure. In others there was an abrupt return of pain and limitation of motion as soon as the drug concentration dropped below therapeutic levels. Such patients invariably failed to respond to conservative treatment and eventually came to operation.
The correlation of test response to the drug and prognosis was sufficiently striking in a series of sixty-four patients to warrant discussion as a possible clinical test. In the first group of cases (good response), a high percentage of patients left the hospital symptomatically well after a period of conservative treatment. The group characterized by no response or a rapid return of signs and symptoms immediately after injection quite generally failed to respond to any period of conservative management. Their operative records reveal evidence of root compression of such degree as to make conservative attempts at decompression unfeasible.