On the physiological and clinical significance of a trapezius reflex evoked by tapping the spine

On routine clinical examination it was observed that precussion over the thoracic spine occasionally produced reflex contraction of the intermediate and caudal parts of the trapezius muscle. The observation was made in one case of spondylitis and one case of inflammatory connective tissue disorder. Both patients had pain in the thoracolumbar regions. The neurophysiological features of this reflex have been analyzed. The incidence of the phenomenon in a randomly selected normal material was 3%. Electromyographic recording from the trapezius muscle demonstrated that the reflex is present at a subthreshold level in subjects not exhibiting the clinical reflex. The latter is established by pain and/or tension in the thoracolumbar paravertebral region.