Chiari type 1 deformity and syringomyelia

Syringomyelia is associated with pathologies related to the disturbance of cerebralspinal fluid flow found in conditions such as Chiari type 1 deformity, spinal malignancy, tethered cord, trauma, or arachnoid adhesions.

Taylor et al. identifies two subtypes of Chiari type 1 deformity, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation 1).

For patients with syringomyelia and history of prior posterior fossa decompression (PFD), intradural intraarachnoid decompression is required. The prior history of decompression was associated with unfavorable outcomes. The use of duraplasty was associated with longer duration of hospital stay and higher complication rate. Further large cohort prospective study is needed to provide any recommendation on the indication of intra or extradural decompression for a given Chiari malformation I patient 2).

Scoliosis is frequently associated with the presence of a Chiari I malformation (CM), up to 20% of patients, and even more frequently associated with CM in the setting of syringomyelia, with rates as high as 60%. While this clinical entity is not exceedingly rare in practice, there is a relative paucity of published research regarding spinal deformity associated with CM. Thus, the pathophysiology of the spinal deformity, and the effects of the CM with or without syringomyelia, remain poorly understood. Some have proposed that the formation of a syrinx may cause anterior horn cell dysfunction, with scoliosis as a result 3) 4).

Chiari type 1 deformity, with syringomyelia (CIM+SM) is often associated with spinal deformity. Although CIM+SM patients undergoing spine reconstruction can expect similar deformity corrections and outcome scores to adolescent idiopathic scoliosis (AIS) patients, they also experience higher rates of neuromonitoring difficulties and neurological complications related to surgery. Surgeons should be prepared for these difficulties, particularly in children with larger syrinx size 5).

Taylor DG, Mastorakos P, Jane JA Jr, Oldfield EH. Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging. J Neurosurg. 2017 Jun;126(6):1934-1940. doi: 10.3171/2016.6.JNS152998. Epub 2016 Sep 2. PubMed PMID: 27588590.
Chotai S, Medhkour A. Surgical outcomes after posterior fossa decompression with and without duraplasty in Chiari malformation-I. Clin Neurol Neurosurg. 2014 Oct;125:182-8. doi: 10.1016/j.clineuro.2014.07.027. Epub 2014 Aug 12. PubMed PMID: 25171392.
Huebert HT, MacKinnon WB. Syringomyelia and scoliosis. The Journal of bone and joint surgery British volume. 1969;51:338–43.
Isu T, Iwasaki Y, Akino M, Abe H. Hydrosyringomyelia associated with a Chiari I malformation in children and adolescents. Neurosurgery. 1990;26:591–6. discussion 6-7.
Godzik J, Holekamp TF, Limbrick DD, Lenke LG, Park TS, Ray WZ, Bridwell KH, Kelly MP. Risks and outcomes of spinal deformity surgery in Chiari malformation, Type 1, with syringomyelia versus adolescent idiopathic scoliosis. Spine J. 2015 Sep 1;15(9):2002-8. doi: 10.1016/j.spinee.2015.04.048. Epub 2015 May 7. PubMed PMID: 25959792; PubMed Central PMCID: PMC4550545.
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