# Associations of Chiari-1 malformation and syringomyelia with osseous cervical spinal canal diameter in the pediatric spine

## TL;DR

This study finds that children with Chiari malformation and syringomyelia have larger spinal canals, with bigger syrinxes and age/sex factors influencing the extent of dilation.

## Contribution

The study reveals novel associations between syrinx size, Chiari malformation, and spinal canal dilation in pediatric patients, highlighting age- and sex-dependent effects.

## Key findings

- Patients with Chiari malformation and syringomyelia had significantly larger spinal canal diameters compared to controls.
- Syrinxes ≥ 3 mm were associated with greater spinal canal dilation than smaller syrinxes.
- Spinal canal dilation was more pronounced in females and younger patients with Chiari malformation and syringomyelia.

## Abstract

To examine the associations between cerebellar tonsillar ectopia and syrinx size on bony spinal canal diameter in pediatric patients to explore the impact of CM with or without SM on the developing spine.

Cohorts of patients with CM + SM, CM-only, and neither condition were compared. Anteroposterior (AP) syrinx diameter was measured at C2 (SX2) and C7 (SX7) for patients with syringomyelia. Tonsillar ectopia was measured for all patients in the CM + SM and CM-only cohorts. AP diameter of the bony spinal canal at C2 (SC2) and C7 (SC7) was measured for all patients. Patients were stratified by age and sex in secondary analyses.

357 patients had CM + SM and 217 patients had CM-only. Both cohorts had larger SC2 (p < 0.0001) and SC7 (p < 0.0001) compared to controls. CM + SM had larger SC7 (p < 0.0001) but not SC2 (p = 0.10) compared to CM-only. Increased SX2 was associated with increased SC2 (p < 0.0001); both SX2 and SX7 were significantly associated with increases in SC7 (p < 0.0001). Syringes ≥ 3 mm were associated with larger SC2 and SC7 compared to syringes < 3 mm (p ≤ 0.002). SC2 and SC7 for syringes < 3 mm were not significantly different from CM-only. Children with CM + SM in early childhood/adolescence experienced the greatest percentage spinal canal dilation. Females experienced greater spinal canal dilation than similarly-aged males.

Patients with CM ± SM experience significant increases in bony cervical spinal canal diameter during development. Syringes ≥ 3 mm with CM are associated with further canal dilation of the spinal canal at syrinx level. The degree of spinal canal dilation appears to be age- and sex-dependent.

The online version contains supplementary material available at 10.1007/s00381-026-07233-9.