Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Chiari malformation Type I (CM-I) with an associated spinal syrinx is a common pediatric diagnosis. A better understanding of the relative age-related prevalence and MR imaging characteristics of these associated conditions may lead to improved treatment decisions.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors performed a retrospective review of 14,116 consecutive individuals 18 years of age or younger who had undergone brain or cervical spine MR imaging at the University of Michigan between November 1997 and August 2008. In the patients with CM-I, demographic, clinical, and radiographic information was recorded.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Five hundred nine children (3.6%) with CM-I were identified. Among these patients, 23% also had a spinal cord syrinx, and 86% of the syringes were found in the cervical spine. The MR imaging prevalence of CM-I with a syrinx was 1.2% in girls and 0.5% in boys (p &lt; 0.0001). The severity of impaired CSF flow at the foramen magnum was associated with the amount of tonsillar herniation (p &lt; 0.0001) and conformation of the tonsils (p &lt; 0.0001). Patients with CM-I were treated surgically in 35% of cases; these patients exhibited more severe tonsillar herniation (p &lt; 0.0001) and impaired CSF flow (p &lt; 0.0001) as compared with those who did not undergo surgery. On imaging, 32% of all the patients with CM-I were considered symptomatic by the treating physician. Patients were more likely to be considered symptomatic if they were female, had a syrinx, displayed abnormal tonsillar pulsations, or had a greater amount of tonsillar herniation.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>In this study the authors describe the age-related prevalence and MR imaging characteristics of CM-I and its association with a syrinx and other abnormalities in a large group of children who underwent MR imaging for any indication. Syringes are more common in older children, in girls, and in patients with a greater degree of tonsillar descent and CSF flow impairment.</jats:p></jats:sec>

Incidental Findings on Brain and Spine Imaging in Children

“…[135][136][137] The prevalence of syringomyelia in the setting of CM estimated from imaging databases has been reported to be between 12% and 23%. 138,139 Syringes are less likely to be found associated with CM in children younger than 5 years but may develop later in childhood. 139 Lower position of the cerebellar tonsils in CM is associated with a greater likelihood of syringomyelia.…”

“…138,139 Syringes are less likely to be found associated with CM in children younger than 5 years but may develop later in childhood. 139 Lower position of the cerebellar tonsils in CM is associated with a greater likelihood of syringomyelia. [139][140][141] It is probable that Chiari symptoms and the formation of spinal syringes are the result of crowding at the foramen magnum that leads to abnormal movement of CSF at the craniocervical junction.…”

“…149 Conversely, many patients with cerebellar tonsils that are more than 5 mm below the foramen magnum are completely asymptomatic. 139,150,151 Although CM does present with symptoms in many cases, it is also a very common incidental finding in asymptomatic individuals. Unfortunately, the current clinical tendency appears to be unreservedly admitting such patients to a patho-anatomic group we call CM on the basis of tonsil position alone.…”

“…139 Lower position of the cerebellar tonsils in CM is associated with a greater likelihood of syringomyelia. [139][140][141] It is probable that Chiari symptoms and the formation of spinal syringes are the result of crowding at the foramen magnum that leads to abnormal movement of CSF at the craniocervical junction. 134 Children with CM often have a smaller than normal posterior fossa volume, resulting in crowding of the posterior fossa and foramen magnum contents.…”

“…Most often, children are assigned a diagnosis of CM if the cerebellar tonsils are found to be 5 mm or more below the foramen magnum, usually defined as a line between the basion and opisthion in the midsagittal plane. 78,139,[145][146][147][148] This definition of CM resulted from the publication of several clinical studies involving small numbers of patients at the dawn of the MRI era. 145,146 Although cerebellar tonsil measurements that define CM on MRI may be a convenient marker for crowding at the foramen magnum, the correlation is not exact.…”