Association of Cerebellar Tonsil Dynamic Motion and Outcomes in Pediatric Chiari I Malformation.

Abstract

Chiari I malformation (CM-1), traditionally defined as a descent of the cerebellar tonsils by 5 mm or more, is surgically managed via posterior fossa decompression. However, there is currently no clear radiologic or symptomatic selection criteria for surgical intervention to indicate which patients may see the most improvement following decompression. This retrospective pilot study included 22 patients who had symptomatic CM-1 managed via surgical decompression and 22 patients who had nonoperative management of CM-1. Tonsillar motion was assessed using phase-contrast magnetic resonance imaging and 2-dimensional fast imaging employing steady-state acquisition. Both quantitative and qualitative results that best described the CM-1 anatomy, radiologic measurements, and tonsillar motion were obtained and analyzed. Statistical analysis suggested that clinical symptoms differ based on tonsillar motion (P = 0.0044). Surgical patients had significantly more tonsillar motion than nonsurgical patients (P = 0.0010). Among the patients who underwent suboccipital decompression, the presurgery to postsurgery change in clinical symptoms was statistically significant (P < 0.0001), with all clinical symptoms showing decreased prevalence postsurgery. Anterior flow (P = 0.0004) and posterior flow (P < 0.0001) had significant negative associations with tonsillar motion. Tonsillar motion correlated positively with increased clinical symptoms of CM-1. Furthermore, tonsillar motion was associated with impaired cerebrospinal fluid flow that manifested in increased clinical symptoms. We recommend use of 2-dimensional fast imaging employing steady-state acquisition and assessment of cerebrospinal fluid flow as an adjunct to both clinical judgement and magnetic resonance imaging when selecting patients with CM-1 who would best benefit from surgical decompression.