A critical appraisal of "terminal ventriculostomy" for the treatment of syringomyelia.

The clinical course of 31 patients who underwent attempted excision of the filum terminale and tip of the conus for syringomyelia is summarized. Of these patients, 17 had had some previous surgical intervention. Eleven patients were continuing to deteriorate at the time of the operation. In three cases, marked postoperative improvement was reported, and objective improvement was thought to result from the conus excision. Eighteen more patients claimed improvement in their preoperative symptoms of loss of pain sensibility, deafness, or reduced motor function, although most of such claims were unverified by objective clinical assessment. Sixteen of the patients who improved have since proceeded to deteriorate. In five of the patients, there was a long-standing improvement of at least subjective phenomena. Thirteen patients were not improved even subjectively and some of these have continued to grow worse. Proof that the greater part of the syrinx was in communication with the conus or filum was difficult to obtain even when the conus was dilated. No correlations have been found to suggest that the operation might be more effective if the central canal was patent at the conus or the filum, nor was there a correlation between a good clinical result and either the age of the patient or the age of the syrinx as judged by the history. The operation did not seem to be more or less beneficial if previous surgery had been performed. The suggestion is made that for syringomyelia with hindbrain abnormalities, other than dense arachnoiditis (particularly if there is evidence of pressure dissociation at the foramen magnum), craniovertebral decompression remains the procedure of choice. In syringomyelia with marked hydrocephalus, drainage by a valved shunt may be the preferred first procedure. If myelotomy is planned it should probably be done where the syrinx is wide, and it is more likely to succeed if the syrinx is drained to a low-pressure area outside the theca, such as the peritoneum or pleura, rather than the subarachnoid space.