Cysts, perineurial, of the sacral roots; another cause, removable, of sciatic pain.

This communication calls attention to a pathologic entity that I described in 1938 1 as a chance encounter at autopsy. Cysts of the posterior sacral nerve roots seem to constitute another cause of the sciatic syndrome, which may be dealt with satisfactorily at operation. Among the manifold causes of sciatica, herniations of the intervertebral disks have emerged as an important entity recently as a result of pathologic studies made by Schmorl and Junghanns, 2 followed by the important clinical work of Mixter and Barr. 3 A group of cases of backache or sciatica or both exist for which an adequate explanation has not been apparent. Moreover, explorations with negative results for protruded intervertebral disks have been carried out in approximately 10 per cent of the patients who presented rather characteristic symptoms and signs of this condition, requiring operation. Such an incorrect diagnosis was made in the present case, in which