[Syringomyelia, scoliosis and idiopathic Arnold-Chiari malformations: a common etiology]

The major theories of the pathogenesis of idiopathic syringomyelia (SMI), idiopathic scoliosis (ESCID) and the Arnold-Chiari malformation (ARCH) are reviewed. A new theory involving a common pathology for SMI, ESCID and ARCH is proposed. Its confirmation depends on the presence of an abnormally low position of the conus medullaris (CM) in patients with SMI. Material and method. Of 292 patients with syringomyelia (SM), 231 patients with SMI were selected, and 55 of these were chosen in whom the level of the conus medullaris (NCM) could be determined, together with figures for SMI, ESCID and ARCH by magnetic resonance (RM). The position of the conus medullaris in 50 patients who did not have SM, ESCID nor ARCH on cervical and lumbar RM was determined.

96.54% of patients with SMI showed some descent of the cerebellar tonsils. 72.97% of the SMI patients also had ESCID: 74.07% of the patients in whom the conus medullaris was seen had scoliosis and a low position of the conus medullaris. 6% of the control group had a conus medullaris at the level of the body of L1, whilst 84.21% of the patients with SMI had a partial or complete image of the conus medullaris at this level. In these patients, an unusually low position of the conus medullaris was confirmed.

The unusually low position of the conus medullaris in SMI and its close relationship to ARCH and ESCID make it likely that the same pathogenic mechanism is shared by them all. Abnormal asynchromy of growth of the notochord and the spinal cord gives rise to a distinct disorder which shows as different syndromes.