208. Natural History of Pediatric Chiari Type 1 Malformation: A Retrospective Analysis

Authors: Matthew Carey; Matthew Carey; William Fuell; Reem Elwy; Thomas Harkey; Gregory Albert (Maumelle, AR)


Chiari I Malformation (CM-I) is a congenital anomaly where the cerebellar tonsils caudally descend at least 5mm below the foramen magnum into the spinal canal.CM-I is often found incidentally with many patients being asymptomatic. Within the asymptomatic population, longitudinal studies have found that a small cohort can develop symptoms and require surgical intervention long after initial diagnosis. We aim to identify particular characteristics within the asymptomatic population that would indicate the need for later surgical intervention.


311 CM-I patients were divided into three groups: surgery within 6 months post-diagnosis, surgery over 6 months post-diagnosis, and never having surgery. From the database, characteristics such as gender, race, age at diagnosis, signs/symptoms, and MRI imaging results were compared.


30 patients had surgery within 6 months of diagnosis (G1), 18 had surgery after 6 months (G2), and the remaining 263 did not have surgery (G3). For G2, the time post-diagnosis for surgery was approximately 15 months. Between G2 and G3, there was no observable difference in tonsillar descent, tissue density of the foramen magnum, gender, race, or associated conditions like tethered cord, neurofibromatosis, migraines, or seizures. However, G2 demonstrated increased incidence of syringomyelia (33% vs 13%), Valsalva headaches (22% vs 9%), prematurity (11% vs 4%), and developmental delay (28% vs 12%). 


The data show that the prevalence of asymptomatic CM-I is very high. Additionally, there are only a small number of patients that did not initially have surgery that required later intervention. The results indicate that, of initially asymptomatic patients, individuals with Valsalva headaches, a syrinx, a premature birth, or some developmental delay may be at increased risk for eventually developing adverse symptoms that necessitate surgical intervention. Going forward, continuing to analyze when specific symptoms associated with surgery develop in asymptomatic patients.