Suboccipital decompression for Chiari malformation–associated scoliosis: risk factors and time course of deformity progression

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Chiari malformation Type I (CM-I) is often associated with scoliosis. It remains unclear which subgroups of patients are most likely to experience progression of spinal deformity after cervicomedullary decompression. The authors' goal was to determine the time frame of curvature progression and assess which patient subgroups are at greatest risk for progression of spinal deformity after surgery.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors retrospectively reviewed the records of all pediatric patients with significant scoliosis in whom suboccipital decompression was performed to treat for CM-I during a 10-year period at a single academic institution. Clinical, radiological, and operative variables were assessed as independent factors for failure (worsening of scoliosis) by using a univariate regression analysis.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Twenty-one children (mean age 9 ± 3 years; 4 male) underwent hindbrain decompression for CM-I–associated scoliosis and were followed for a mean of 39 months. All patients harbored a syrinx. Eight patients (38%) experienced improvement in scoliosis curvature, whereas 10 (48%) suffered a progression. Thoracolumbar junction scoliosis (p = 0.04) and failure of the syrinx to improve (p = 0.05) were associated with 5- and 4-fold respective increases in the likelihood of deformity progression. Each increasing degree of preoperative Cobb angle was associated with an 11% increase in the likelihood of scoliotic curve progression (p &lt; 0.05).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Over one third of patients with CM-I–associated scoliosis will improve after cervicomedullary decompression alone. Cervicomedullary decompression is a good first-line option, particularly in children with concordant posterior fossa symptoms. Patients presenting with more severe scoliosis (increasing Cobb angle) or scoliosis that crosses the thoracolumbar junction may benefit from earlier orthopedic involvement and should be monitored regularly for curvature progression after cervicomedullary decompression. In cases in which there is a failure of the syrinx to show improvement after suboccipital decompression, the patients are also more likely to develop curvature progression.</jats:p></jats:sec>

Comparison of clinical and radiological manifestations and surgical outcomes of pediatric Chiari I malformations in different age groups

“…Postoperative changes in syrinx were evaluated with spine MRI obtained during the follow-up period, and they were reported to be resolved (syrinx diameter or extent decreased more than 80 %), improved (syrinx diameter or extent decreased between 20 % and 80 %), static (syrinx diameter or extent changeless to less than 20 %), or aggravated (syrinx increased in diameter or extent more than 20 %) [17,21,22]. A significant change in scoliosis was defined by a criterion of 10°c hange in Cobb's angle on plain spine radiographs during the follow-up evaluation, and the changes were reported as either improved (decrease in Cobb's angle of more than 10°), stabilized (change in Cobb's angle of 10°or less), or aggravated (increase in Cobb's angle of more than 10°) [17,23,24].…”

“…Although it remains a matter of contention, syrinx causes scoliosis, and sustained damage to the motor nuclei of ventral horn has been the proposed mechanism [28,33]. It was generally believed that the young spine before maturation is flexible, and FMD before the adolescent growth spurt could restore the spinal curve in young Chiari I malformation patients with syrinx and scoliotic deformities [20,23,[34][35][36]. However, according to this study, syrinx in Chiari I malformation can appear in a relatively short period of time, approximately 3 years old.…”

Delayed resolution of syrinx after posterior fossa decompression without dural opening in children with Chiari malformation Type I

“…4,11,25,26,32,35,42 High rates of radiographic syrinx improvement have been reported after PFD with dural opening in pediatric CM-I, with symptom resolution often occurring prior to syrinx resolution and scoliosis improvement often occurring after. [1][2][3][4][5][6][7][8][10][11][12][15][16][17]20,26,27,[29][30][31][32][33][34][35]42,44 In part because syrinx improvement has been noted to occur in the majority of 17,19,36,39 At the 2006 American Society of Pediatric Neurosurgeons meeting, for example, a survey of 50% of the membership demonstrated that for children with a symptomatic CM-I and syrinx, only 4% would perform nondural opening surgery and another 4% would use ultrasound to guide whether to add duraplasty, with the vast majority opting for duraplasty with or without tonsillar resection. 36 However, controversy exists over whether the dura must be opened for successful surgery for pediatric CM-I with or without a syrinx, with good clinical outcomes being reported for a variety of methods.…”

Effect of Posterior Fossa Decompression for Chiari Malformation-I on Scoliosis

“…The rates of syrinx reduction is reported to be in the range of 52-100% following PFD for CM-I [18,20,21,23,24,[26][27][28][29]. Similarly, various series have reported successful treatment of scoliosis after neurosurgical management of CM-I with or without syringomyelia [2,[30][31][32][33]. The rate of improvement in scoliosis curve is reported to be in the range of 20-60% [1,10,30,31,33].…”

“…Similarly, various series have reported successful treatment of scoliosis after neurosurgical management of CM-I with or without syringomyelia [2,[30][31][32][33]. The rate of improvement in scoliosis curve is reported to be in the range of 20-60% [1,10,30,31,33]. Overall, there is no consensus on the degree of improvement in scoliosis curve after PFD for CM-I.…”