Use of Minimally Invasive Tubular Retractors for Foramen Magnum Decompression of Chiari Malformation: A Technical Note and Case Series

Abstract

An intraoperative technique for foramen magnum decompression of Chiari malformation is presented. The technique uses minimal exposure tubular retractors attached to a flexible arm to keep the retractor in a fixed position, while allowing flexible angulation under fluoroscopic guidance. Operations were performed between 2009 and 2018 on 22 patients with cerebellar tonsillar descent below the foramen magnum and a diagnosis of type I Chiari malformation. A linear durotomy was necessary, but only the outer layer of the dura was opened for some patients, which is less invasive than the traditional procedure where a durotomy is performed for both the inner and outer layers, and then a duraplasty is performed. The approach allowed access to a wide working area, minimized soft tissue exposure, and optimized extent of decompression. The postoperative imaging demonstrated satisfactory bony removal, and magnetic resonance imaging of the area with cerebrospinal (CSF) flow study showed good CSF flow across the foramen magnum. There was a low incidence of postoperative complications, and the average length of hospital stay was 1 day. For 19 of 22 cases, the symptoms completely resolved or markedly improved, and each of the patients who attended the last follow-up demonstrated syrinx resolution. Based on our experience with this technique, when used to assist in foramen magnum decompression of Chiari malformation I, the minimally invasive tubular retractor is a useful tool, providing the surgeon with enhanced visualization of the operative field, while reducing potential damage to tissue and optimizing surgical outcomes.