Author

Jennifer Quon

Date of Award

January 2015

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Michael L. Diluna

Subject Area(s)

Medicine, Neurosciences

Abstract

Chiari I malformation is a hindbrain abnormality characterized by tonsillar herniation > 5 mm below the level of the foramen magnum. Extradural decompression is a minimally invasive technique for treating Chiari I that involves a suboccipital craniectomy with removal of the outer dural layer. Other techniques the involve opening of the dura, arachnoid or even manipulation of the cerebellar tonsils have since been the mainstay of treatment, but are associated with a higher complication rate and longer hospital stays. While there is no agreement on which surgical method is optimal, mounting evidence demonstrates that extradural decompression effectively treats clinical symptoms with a minimal reoperation rate. Many of the symptoms associated with Chiari I are now understood to be related to obstructed cerebrospinal fluid (CSF) flow. Therefore, one goal of a successful decompression is improved CSF dynamics. Phase-contrast cine flow MRI provides insight into CSF dynamics before and after surgical decompression. This study describes a surgical series of 18 patients with Chiari I malformation undergoing extradural decompression, for which clinical improvement was correlated with radiologic changes. All 18 patients presented with symptomatic Chiari I malformation, confirmed on imaging to have tonsillar herniation > 5 mm. Two patients had associated syringomyelia. All patients underwent suboccipital decompression and C1-laminectomy with dural splitting. Patients were categorized as having complete, partial, or no resolution of their symptoms. Posterior fossa area (PFA), cisterna magna area (CMA), and tonsillar herniation were assessed on T2-weighted magnetic resonance imaging (MRI). Improvement in CSF flow was evaluated with phase-contrast cine flow MRI. All patients received standard pre- and post-operative MRIs, 8 (44.4%) patients had pre- and post-operative phase-contrast cine, while the rest had only post-operative cine. Patients who had a complete resolution of their symptoms also had a greater relative increase in cisterna magna area compared with those with only partial improvement (p = 0.022). In addition, those with complete improvement had smaller pre-operative cisterna magna area compared with those who had either partial (0.020) or no (0.025) improvement. Ten (91%) of the 11 patients with improved flow also had improvement in their symptoms. There was one post-operative complication of dysphagia and dysphonia. None of the patients have required a second operation. Extradural decompression has the potential to be the first-line treatment for Chiari I malformation, but has since been lacking an objective measure by which to assess surgical success, as well as the need for reoperation. In our study, an increase in the CSF spaces and improved CSF dynamics and were associated with greater resolution of clinical symptoms. Including cine imaging as part of routine pre- and post-operative evaluation can help identify which patients are most likely to benefit from surgery, as well as determine a satisfactory decompression.

Comments

This is an Open Access Thesis.

Share

COinS