Chiari I malformation associated with syringomyelia: can foramen magnum decompression lead to restore cervical alignment?

Purpose: There are few researches that demonstrate the relationship between the extent of syringomyelia and sagittal alignment of the cervical spine. The purpose of this study is to investigate the correlation between the change of syrinx size and cervical alignment.

Methods: From January 2001 to June 2008, we operated on 207 patients who had syringomyelia. The associated diseases were categorized by Chiari I malformation, tumor, trauma, spinal stenotic lesion, inflammatory disease and idiopathic causes. Thirty patients who had Chiari I malformation associated with syringomyelia and who underwent foramen magnum decompression (FMD), participated in this study. We excluded patients with scoliosis, cervical instrumentation, tumor, trauma, myelomeningocele, hydrocephalus, tethered cord and congenital vertebral anomalies. Lateral radiographs in neutral and magnetic resonance imaging were taken pre- and postoperatively.

Results: Mean follow-up was 6.5 ± 1.5 years (ranged from 4.0 to 9.5 years). The mean pre- and postoperative lordosis angles at C2-C7 were -5.9° ± 1.0° and -10.4° ± 1.0°, respectively (P = 0.001). There was significant correlation between the differences of syrinx width and the cervical lordotic angles before and after surgery (P = 0.016). After FMD, syringomyelia and cervical alignment improved in 28 (93.3%) and 25 (85.18%) of 30 patients, respectively. There was significant correlation between recovery rate by Japanese Orthopaedic Association scores and the difference of the cervical lordotic angles before and after surgery (P = 0.022).

Conclusions: The present results demonstrate that the decrease of syrinx size by FMD may restore the cervical lordosis. We suggest that the postoperative cervical alignment might be a predictive factor for neurological outcome.