Long-Term Outcomes of a New Minimally Invasive Approach in Chiari Type 1 and 1.5 Malformations: Technical Note and Preliminary Results.

Background: The treatment options for patients with Chiari malformation type 1 (CM1) and Chiari malformation type 1.5 (CM1.5) have not yet been standardized. In these malformations, the main factors include obstruction at the level of the foramen magnum and dural and ligamentous thickening. Here we present our outcomes of surgery and decompression using a minimally invasive surgery (MIS) technique.

Methods: Sixty-one patients admitted to our clinics between 2009 and 2016 due to CM1 or CM1.5 and who had undergone MIS were investigated retrospectively. All patients were followed up for a mean period of 55 months, both clinically and radiologically, and the outcomes were recorded.

Results: All 61 patients underwent foramen magnum decompression through a 1.5-cm mini-open incision, C1 laminectomy and C2 medial inner side tour, posterior atlanto-occipital membrane removal, external dural delamination, and widening of the internal dura with longitudinal incisions. Fifty-six patients (91.8%) were satisfied with the outcome, 4 patients (6.5%) remained the same, and 1 patient (1.6%) reported a poor outcome. Forty-five percent of the patients with syringomyelia demonstrated resolution within 2 years, and 92% demonstrated resolution in 5 years. Scoliosis was seen in 5 patients (8.1%). The rate of benefit from the surgical procedure was statistically significant (P = 0.0045), and no patient required additional surgery because of poor decompression.

Conclusions: MIS is effective for uncomplicated cases of CM1 and CM1.5 due to its minimal connective and muscular tissue damage, short surgical duration, short recovery time, early mobilization, effective posterior foramen magnum widening, lack of liquor fistula development, and better clinical and radiologic improvement during long-term follow-up.