Abstract Background Diffuse intrinsic pontine glioma (DIPG) can cause secondary cerebellar tonsillar descent, resulting in a coexisting Chiari malformation (CM). Because both conditions involve the posterior fossa, their symptom profiles overlap, making it difficult to separate Chiari-related morbidity from tumor effects. The clinical relevance of this dual pathology remains uncertain. This study aimed to define the incidence, clinical impact, management, and evolution of CM in children with DIPG. Methods We performed a retrospective cohort study of pediatric patients with DIPG (2016–2024) to assess the incidence, presentation, and management of associated CM. Results Thirty-six patients with DIPG (median age 4.9 years, range 2.1–19.1) met inclusion criteria. CM was present in 7 patients (19.4%). Radiographic CM appeared a mean of 6 months (range 0–29) after diagnosis, with four cases (57.1%) present at initial imaging. Median tonsillar position was 7 mm (IQR 6.0). Five patients (71.4%) were symptomatic with classic CM symptoms. Six (85.7%) developed hydrocephalus, and one had a syrinx. CM resolved spontaneously in 5 patients (71.4%), remained stable in one, and progressed in one. CM incidence was not associated with age, sex, hydrocephalus, or CSF diversion (p 0.05). Although a smaller dens angle correlated with CM (p = 0.039), the 3-degree median difference was of limited clinical significance. Conclusions Nearly one in five children with DIPG exhibit tonsillar descent meeting criteria for CM. No patient required Chiari-directed surgical decompression; CM usually resolved spontaneously. These findings suggest that DIPG-associated CM rarely merits independent intervention and may not increase hydrocephalus risk.
Weiss et al. (2026) studied this question.