“For example, the diagnostic study (CT scan or MRI) might show a herniated disc at the interspace L4-L5, one of the possible consequences of which might be weakness in the muscles that elevate the foot and the toes. The examination, however, revealed that not only those muscles were weak but so were the ones in the back of the leg, muscles that are not energized by the spinal nerve passing by interspace L4-L5. Then when I found on examination that the buttock muscles in the vicinity of the sciatic nerve were painful to pressure, it was apparent that the nerve disturbance was not coming from the region of the herniated disc but from the sciatic nerve that serves both sets of muscles. (page 120)”