Posterior fossa decompression in syringomyelia associated with a Chiari malformation: a retrospective analysis of 22 patients

Background: The technique of posterior fossa decompression, nowadays preferred by most neurosurgeons as the first surgical option in the treatment of hindbrain associated syringomyelia, was reintroduced in our center in 1989. We present a retrospective analysis of 22 patients with this pathology who underwent the procedure since then. Methods: In all patients diagnosis was made by MRI of the craniospinal junction. The operation consisted of a suboccipital craniectomy, removal of the posterior arc of C1, laminectomy of C2 or C3 when necessary and a wide duraplasty at the end. The intradural manipulations (opening of the arachnoid membrane, coagulation or resection of the tonsils) were not uniform. Postoperatively short- and long-term clinical outcome and MRI findings were assessed. Results: Sixteen out of 21 patients (76%) experienced an improvement in the early follow-up period. In the late follow-up period 13 out of 19 patients (68%) were improved, whereas five patients (26%) experienced a marked deterioration. There was no unequivocal effect on all symptoms and signs. Postoperative MR images showed a favorable result in 16 out of 20 patients (80%), consisting of syrinx collapse or reduction of the syrinx diameter. Conclusions: We conclude that decompression of the posterior fossa is a safe procedure with a considerable chance of clinical improvement. Although total syrinx collapse is not as frequently seen as in syrinx shunting procedures, the clinical outcome may be better. Moreover, there seemed to be no unequivocal correlation between clinical outcome and postoperative syrinx size in the present study.