Prevalence and Impact of Underlying Diagnosis and Comorbidities on Chiari 1 Malformation

Abstract

Background: Chiari malformation type 1 affects approximately one in 1,000 people symptomatically, although one in 100 meet radiological criteria, making it a common neurological disorder. The diagnosis of underlying conditions has become more sophisticated, and new radiological markers of disease have been described. We sought to determine the prevalence and impact of additional comorbidities and underlying diagnoses in patients with Chiari malformation type 1 on symptomatology and surgical treatment.

Methods: A retrospective review of 612 pediatric patients with a Chiari malformation type 1 diagnosis and imaging data evaluated between 2008 and 2018 was performed. Because of extensive clinical heterogeneity, patients were separated into four categories based on their primary comorbidities (nonsyndromic, central nervous system, skeletal, and multiple congenital anomalies) to identify associations with age of onset, radiographic measurements, syringomyelia, and surgical treatment.

Results: The largest group had nonsyndromic Chiari malformation type 1 (70%) and the latest age at diagnosis of any group. In the syndromic group, 6% were diagnosed with a known genetic abnormality, with overgrowth syndromes being the most common. Patients with multiple congenital anomalies had the earliest Chiari malformation type 1 onset, the most severe tonsillar ectopia and obex position, and were overrepresented among surgical cases. Although there were no statistically significant differences between groups and rates of syrinx, we observed differences in individual diagnoses.

Conclusion: The underlying diagnoses and presence of comorbidities in patients with Chiari malformation type 1 impacts rates of syringomyelia and surgery. Although most Chiari malformation type 1 cases are nonsyndromic, clinical evaluation of growth parameters, scoliosis, and joint hypermobility should be routine for all patients as they are useful to determine syringomyelia risk and may impact treatment.

Keywords: Chiari 1 malformation; Comorbidities; Epidemiology; Obex; Syringomyelia.

Figure 1.

Distribution of comorbidities of patients in the samples

Figure 2.

Midline sagittal T1-weighted MRI of a CM1 patient showing McRae’s line a.k.a. basion-opisthion line (red) and obex position (blue).^;

Figure 3.. Age at diagnosis is associated with comorbidities and presence of syringomyelia.

Age at diagnosis of CM1 with (red) and without (blue) a syrinx. Patients with CM1 and multiple congenital anomalies are diagnosed earlier, particularly when a syrinx is present. (CNS=Central nervous system, SK=skeletal, MCA=multiple congenital anomalies, NS=non-syndromic)