218. The Management Of Chiari Patients With Worsening Syringomyelia After Posterior Fossa Decompression

Authors: Umberto Tosi; Jacques Lara, MD; John Chae, BA; Mark Souweidane, MD; Jeffrey Greenfield, MD, PhD (New York, NY)


Chiari malformation (CM) is often comorbid with syringomyelia; however, initial treatment of CM via posterior fossa decompression (PFD) may not always improve syringomyelia. Reoperation via PFD or syrinx-subarachnoid shunting are options when clinical symptoms persist. Robust data describing outcomes following failed PFD for syrinx patients are minimal and the lack of correlation between radiographic and clinical symptoms remains difficult to integrate into a surgical algorithm.


Only patients with CM 1 or 1.5 and syringomyelia who underwent PFD without post-operative syringomyelia improvement were retrospectively reviewed. Symptomatology and radiographic measurements including tonsillar herniation, syrinx extent, maximal antero-posterior and lateral diameters, and area, were collected at presentation and on the first and latest available post-operative scans.


43 of 50 (86%) patients who met criteria for PFD, improved radiographically. However, 7 (14.0%) (2 males, 5 females) did not show improvement in syrinx measurements.  In this cohort, average pre-operative syrinx area was 23.9 ± 10.0 mm2. Postoperatively, syrinx area increased to 40.5 ± 9.6 mmand 57.3 ± 12.5 mmon the first and latest post-op scan available (p = 0.02), for an increase of 106.9% ± 94.4% and 186.0% ± 107.4% - the increase in area on the latest scan being greater than immediately post-op (p = 0.04). Initial symptoms included occipital headache, paresthesias, and visual deterioration. On last follow-up (average of 13.9 ± 4.9 months), most symptoms were resolved in a majority of patients, despite persistent syringomyelia.


In a small cohort of patients, syrinx may increase post-operatively. Most of these patients remained asymptomatic and reported overall great control of symptoms supporting a conservative approach. This data does raise questions about syrinx pathophysiology and the importance of strict surgical indications, albeit longer follow-up may alter these early observations.