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Surgical Outcome of Adult Idiopathic Chiari Malformation Type 1
Woon Tak Yuh1, Chi Heon Kim2, Chun Kee Chung3
1Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.
Insights
Chiari malformation type 1.5 in adults does not significantly alter surgical outcomes compared to type 1. Successful surgery depends on restoring cerebrospinal fluid flow and the cisterna magna, not hindbrain herniation extent.
Area of Science:
- Neurosurgery
- Neurology
- Cerebrospinal Fluid Dynamics
Background:
- Idiopathic Chiari malformation (CM) type 1 involves cerebrospinal fluid (CSF) flow disturbance.
- CM type 1.5 includes additional medullary oblongata migration, with unknown significance in adults.
- Surgical restoration of CSF flow is the primary treatment for CM.
Purpose of the Study:
- To compare surgical outcomes of adult idiopathic CM type 1.5 with CM type 1.
- To investigate factors influencing radiological success after surgery for CM.
Main Methods:
- Retrospective review of 38 adult patients with CM type 1 and syringomyelia.
- Patients were categorized into CM type 1 (n=25) and CM type 1.5 (n=13) based on medullary migration.
- Functional status (Modified McCormick Scale) and radiological success (syrinx diameter reduction) were assessed post-surgery.
Main Results:
- Radiological success was achieved in 84% of patients.
- Restoration of the cisterna magna was the sole significant factor for radiological success (p=0.01).
- Medullary oblongata migration (CM type 1.5) did not significantly impact surgical outcomes.
Conclusions:
- Medullary oblongata migration does not affect surgical outcomes in adult CM patients.
- Restoration of the cisterna magna is crucial for successful CM surgery.
- Surgical intervention for CM effectively improves functional status.
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.
