J Korean Neurosurg Soc.  2016 Sep;59(5):512-517. 10.3340/jkns.2016.59.5.512.

Surgical Outcome of Adult Idiopathic Chiari Malformation Type 1

• Yuh WT
• Kim CH
• Chung CK
• Kim HJ
• Jahng TA
• Park SB

• KMID: 2351721
• DOI: http://doi.org/10.3340/jkns.2016.59.5.512

Abstract

OBJECTIVE
The pathophysiology of idiopathic Chiari malformation (CM) type 1 is disturbance of free cerebrospinal fluid (CSF) flow and restoration of normal CSF flow is the mainstay of treatment. Additional migration of the medulla oblongata in pediatric patients is referred to as CM type 1.5, but its significance in adult patients is unknown. This study is to compare surgical outcomes of adult idiopathic CM type 1.5 with that of type 1.
METHODS
Thirty-eight consecutive adult patients (M : F=11 : 27; median, 33.5; range, 18-63) with syringomyelia due to idiopathic CM type 1 were reviewed. Migration of the medulla oblongata was noted in 13 patients. The modified McCormick scale (MMS) was used to evaluate functional status before and one year after surgery. All patients underwent foramen magnum decompression and duroplasty. Factors related to radiological success (≥50% decrease in the diameter of the syrinx) were investigated. The follow-up period was 72.7±55.6 months.
RESULTS
Preoperative functional status were MMS I in 11 patients and MMS II in 14 of CM type 1 and MMS I in 8 and II in 5 of CM type 1.5. Of patients with MMS II, 5/14 patients in group A and 3/5 patients in group B showed improvement and there was no case of deterioration. Radiological success was achieved in 32 (84%) patients and restoration of the cisterna magna (p=0.01; OR, 46.5) was the only significant factor.
CONCLUSION
Migration of the medulla oblongata did not make a difference in the surgical outcome when the cisterna magna was restored.

Keyword

Chiari malformation; Hindbrain; Medulla oblongata; Surgery; Syringomyelia; Arachnoid

MeSH Terms

Adult*
Arachnoid
Cerebrospinal Fluid
Cisterna Magna
Decompression
Follow-Up Studies
Foramen Magnum
Humans
Medulla Oblongata
Rhombencephalon
Syringomyelia

Figure

• 

  Fig. 1 The algorithm of the surgical procedures. The surgical procedures for Chiari malformation (CM) type 1 without herniation of the medulla oblongata (A). The numbers in parentheses represent the numbers of patients. Similarly, the surgical procedures for Chiari malformation type 1 with herniation of the medulla oblongata (B). FMD : foramen magnum decompression, C1 ectomy : removal of the posterior C1 ring, C2 ectomy : partial or total laminectomy of C2, SSS : syringo-subarachnoid shunt.

• 

  Fig. 2 Normalization of hindbrain herniation after restoration of the cisterna magna. The T2-weighted sagittal magnetic resonance (MR) image shows syringomyelia in the whole spine. The obex (arrow) and tonsil (double arrow) are located 16.1 mm and 17.2 mm, respectively, below the foramen magnum (A). Tonsillar beaking is observed. Postoperative day 2 : the syringomyelia is slightly reduced, but the retrocerebellar and subtonsillar subarachnoid spaces are not markedly changed (B). Postoperative month 6 : the syringomyelia is reduced by more than 50%, and restoration of the cisterna magna (*) is prominent (C). The length of the dorsal cerebrospinal fluid pathway is 14.5 mm. The tonsil and obex are located above the foramen magnum, and rounding of the tonsil is present.

• 

  Fig. 3 Aggravation of hindbrain herniation after failed restoration of the cisterna magna. The T2-weighted sagittal magnetic resonance (MR) image shows syringomyelia in the cervical and thoracic spine. The tonsil and obex are located 6.5 mm and 5.7 mm, respectively, below the foramen magnum (A). Tonsillar beaking is also present. Postoperative month 3 : the syringomyelia and hindbrain herniation are similar (B). The cisterna magna is not reconstructed. Postoperative month 50 : the obex lies 12.9 mm below the foramen magnum, with persistent syringomyelia (C).

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