Minimally Invasive Occipitocervical Decompression Preserving Posterior Muscular-Ligamentous Tension Band for Surgical Management of Type I Chiari Malformation: A Prospective Clinical and Radiological Study

Introduction: Type I Chiari malformation is a frequent neurosurgical entity that presents in most of cases with affection of cerebrospinal fluid circulation and spinal tracts. The therapy of choice is decompression achieved by performing a suboccipital craniectomy and cervical posterior osteotomies with durotomy and duraplasty. Traditional approaches have an increased risk of bleeding and postoperative pain; they also disrupt the posterior cervical muscular-ligamentous tension band, which affects spinal biomechanics. There are no reports about minimally invasive surgery (M.I.S.) for these patients. We sought to describe a new minimally invasive approach through a small suboccipital incision without lesion to the posterior cervical muscles and ligamentum nuchae while obtaining optimal decompression margins, performing adequate repair of the dura mater, and reducing perioperative morbidity. Eleven surgical cases are presented to illustrate the procedure.

Methods: An occipitoatlantal decompression was performed through an incision above the occipital hair insertion line. A muscle-splitting technique was performed by the use of a minimally invasive retractor (MaXcess, NuVasive, Inc.). Craniectomy was performed with Kerrison rongeurs under microscopical guidance. A vertical durotomy was performed and dura repair was made with a synthetic dura mater patch, fixated in six patients with manual suture and in five patients with fibrin sealant; skin closure was performed in standard fashion. Patients were followed prospectively with visits at 1, 3, 6, and 12 months after surgery.

Results: Eleven patients with type I Chiari were included for analysis. Average surgical time was 140.5 minutes with an estimated blood loss of 120.9 cc. All patients were discharged the day after surgery with minimal pain; one patient developed a CSF fistula that required surgical revision; computerized tomography scans showed adequate decompression; no infectious complications were noted.

Conclusions: A minimally invasive approach to the craniocervical junction is feasible to preserve as much normal anatomy as possible to avoid alterations in spinal biomechanics. This work presents a novel procedure that can help to reduce operative morbidity and mortality, as well as promoting earlier recovery in patients with Chiari I malformation.