Clinical diagnosis
Case 207
【Progress】
He came back to the local orthopedic clinic with MRI-CD and MRI findings our radiologist interpreted.
【Discussion】
Syringomyelia is classified into congenital and acquired. The acquired syringomyelia comes out most often following traffic accident. Congenital syringomyelia arise from Chiari syndrome. Chiari syndrome is categorized largely into type 1 and type 2: type1 the lower part of cerebellum descends into cisterna magna, type 2 the lower part of cerebellum and brain stem descends into cisterna magna (1). Syringomyelia associated with Chiari syndrome is thought to arise from the blockade of central spinal fluids (CSF) due to descending of the central nerve system. Namely, the descending central nerve system makes CSF space narrowing and causes the central canal of spinal cord widening, that induces syringomyelia (2-4). Syringomyelia associated with arachnoid adhesion following spinal surgery or arachnoiditis is thought to arise from the similar scenario that CSF space narrowing causes the dilatation of central canal inducing syringomyelia (2-4). But this theory cannot explain our case with idiopathic syringomyelia without Chiari syndrome and arachnoid adhesion.
There is another thesis to cause syringomyelia, Filum traction thesis (5, 6). There is connective filament called terminate filum which extends inferiorly from the apex of conus medullaris. It divides into two parts; internal terminate film, the upper three quarters of the terminate film, which is covered with pia mater, meninge and dura mater: external terminate film, the lower quarter, which is covered with dura mater and reaches to the dorsal coccyx. Spinal cord itself is not growing but the surrounding vertebrae, disk and soft tissue are growing. At the time of being newly born, the position of spinal cord and its branching nerve are the same position as vertebrae. With growing to adult, the position of conus medullaris elevates from L5 level to L1 level.
However, when terminate film is short or when terminate film pull spinal cord forcefully due to growth imbalance, spinal cord itself tears, inducing liquid necrosis and fluid collection from interstitial. The fluid space communicates with central canal of spinal cord and gradually enlarged probably due to check valve mechanism, leading to syringomyelia (2-6). When filum traction is the main cause for syringomyelia, film terminate sectioning is conducted, being just only useful but also minimum invasive and safe. The other spontaneous syringomyelia is reported to be decreased with time in some cases probably because of new formation of fistula to arachnoid space (7). The progress of spontaneous syringomyelia varies.
In our case, lumbar MRI showed the position of conus medullaris situates at L1 level, almost normal which indicates no evidence of filum terminate traction. The mechanism of syringomyelia in our case is still unknown and scheduled to follow-up observation.
【Summary】
We present a twelve-year-old boy for thoracic backache when moving. Thoracic spine MRI showed fluid-accumulation in thoracic spine, indicating syringomyelia. It is borne in mind that acquired syringomyelia is reported to be caused by arachnoiditis, trauma and filum terminate traction. Filum terminate traction induces necrosis of spinal parenchyma, liquid accumulation from interstitial and growing fluid space, becoming syringomyelia. Film terminate section is effective for some cases with lower syringomyelia with tight film terminate. Meanwhile, the other spontaneous syringomyelia reduce or disappearance of syringomyelia without treatment.
【References】
1.Blegvad C, et al. Syringomyelia: a practical, clinical concept for classification. Acta Neurochir 2014; 156:2127–2138
2.Klekamp J. The pathophysiology of syringomyelia—historical overview and current concept. Acta Neurochir 2002; 144:649–664
3.Koyanagi I, et al. Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis. Neurosurg Rev 2010 33:271–284
4.Levine DN. The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis. J Neurol Sci 2004; 220:3–21
5.Kulwin CG, et al. Radiographic and clinical outcome of syringomyelia in patients treated for tethered cord syndrome without other significant imaging abnormalities. J Neurosurg Pediatr 2013; 11(3):307–312
6.Ishisaka, E et al. Surgical outcomes by sectioning a filum terminale in patients with terminal syringomyelia. Childs Nerv Syst (2020). https://doi.org/10.1007/s00381-020-04615-5
7.Kazuhiko Kyoshima, K, et al. Spontaneous Resolution of Syringomyelia: Report of Two Cases and Review of the Literature. Neurosurgery, 2003; 53: 762–769
2020.10.7