There is no currently available noninvasive technique to ascertain with certainty the continuity of the cavity of a septated syrinx. A technique is described that allows the confirmation of the continuity before the surgical drainage of a syrinx. This technique may prevent the failure of the drainage because of septations and double cavities. Intraoperative endomyelography is simple to perform and requires no special equipment. Pressure measurements made before the injection of the contrast agent may provide insights into the pathogenesis of the syrinx and may be of prognostic and therapeutic significance.