A minimally invasive technique for decompression of Chiari malformation type I (DECMI study): study protocol for a randomised controlled trial

Maximum Safety Limits of Laminectomy of the C1 Vertebra for Chiari Malformation Surgery: A Finite Element Analysis

Background

The treatment of Chiari malformations generally consists of posterior fossa decompression. C1 laminectomy is required in selected cases. However, cases of iatrogenic anterior arch fractures at C1 without high-energy trauma have been reported. Developing theoretical models of atlas C1 bones that have undergone a laminectomy can help researchers identify the regions where fractures may occur as a result of sudden loads.

Methods

In this study, we created a detailed three-dimensional solid finite element model of the human atlas bone (C1) using geometric data. The loadings of the laminectomy dimension were evaluated on the basis of three groups. Group I comprised atlas bones that had not undergone a laminectomy. For Group II, the lateral border of the laminectomy was determined as the projection of the lateral mass medial border on the lamina. For Group III, the bilateral sulcus arteriosus was determined as the border for the lateral border of the laminectomy. The analysis results, which are in good agreement with those of previous reports, showed high concentrations of localized stress in the anterior and posterior arches of the atlas bone.

Results

The analysis results showed that the stress increased in the laminectomy models. The maximum stress observed was consistent with the clinical observations of fracture sites in previous studies.

Conclusion

In the treatment of patients with Chiari malformations, C1 laminectomy is often required. The width of this laminectomy can lead to iatrogenic anterior arch fractures. This is the first study to evaluate C1 laminectomy width using finite element modeling.

Minimally invasive posterior fossa decompression with duraplasty in Chiari malformation type I with and without syringomyelia

Background:

Posterior fossa decompression (PFD), with and without duraplasty, represents a valid treatment in Chiari malformation Type I (CM-I) with and without syringomyelia. Despite a large amount of series reported in literature, several controversies exist regarding the optimal surgical approach yet. In this study, we report our experience in the treatment of CM-I, with and without syringomyelia, highlighting how the application of some technical refinements could lead to a good outcome and a lesser rate of complications.

Methods:

Twenty-six patients with CM-I, with and without syringomyelia, underwent PFD through a 3 cm × 3 cm craniectomy with the removal of the most median third of the posterior arch of C1 and duraplasty. Signs and symptoms included sensory deficits, motor deficits, neck pain, paresthesias, headache, dizziness, lower cranial nerve deficits, and urinary incontinence. Postoperative magnetic resonance (MR) was performed in all patients.

Results:

Signs and symptoms improved in 76.9% of cases. Postoperative MR revealed a repositioning of cerebellar tonsils and the restoration of cerebrospinal fluid circulation. In our experience, the rate of complication was 23% (fistula, worsening of symptoms, and respiratory impairment).

Conclusion:

PFD through a 3 cm × 3 cm craniectomy and the removal of the most median third of posterior arch of C1 with duraplasty represents a feasible and valid surgical alternative to treat patients with CM-I, with and without syringomyelia, achieving a good outcome and a low rate of complications.

Technique for Mini-open Decompression of Chiari Type I Malformation in Adults

BACKGROUND: The technique for decompression of Chiari type I malformation relies on open exposure of craniocervical junction for suboccipital craniectomy and upper cervical laminectomy with or without duraplasty. There is no detailed technical report of a minimally invasive approach for Chiari decompression in adults.

OBJECTIVE: To describe a mini-open technique for decompression of Chiari type I malformation (including duraplasty) in adults.

METHODS: Six consecutive adult patients with symptomatic Chiari type I malformation underwent decompression through a 3 to 4 cm midline incision via a speculum retractor. All patients underwent a limited suboccipital craniectomy and C1 laminectomy with an ultrasonic bone scalpel. All patients underwent duraplasty with a synthetic dural substitute. In the 2 patients with syringomyelia, the arachnoid was opened and intradural dissection was carried out. In the remaining 4 patients, the arachnoid was left intact.

RESULTS: All operations were completed successfully through the mini-open exposure. Mean surgery time, blood loss, and length of stay were 114 min, 55 mL, and 1.3 days, respectively. Mean follow-up was 13.2 months (range 9-18). All patients had excellent clinical outcomes as defined by scores of 15 (3 patients) or 16 (3 patients) on Chicago Chiari Outcome Scale. There were no neurological complications or cerebrospinal fluid leaks. Postop computed tomography revealed good boney decompression. In the 2 patients with syringomyelia, MRI at 6 months revealed resolution of the syrinx.

CONCLUSION: Decompression of Chiari type I malformation in adults can be performed safely and effectively through the mini-open exposure described in this report.