Introduction: Foramen magnum stenosis (FMS) and ventriculomegaly are frequent in achondroplasia due to cranial base hypoplasia. While FMS can cause spinal cord compression, the optimal treatment strategy remains debated. We reviewed our single-center experience and explored factors influencing surgical decisions. Methods: We retrospectively analyzed 18 children with achondroplasia evaluated between 2008 and 2024. MRI was used to assess FMS by anterior-posterior diameter and cerebrospinal fluid (CSF) area at the foramen magnum level. Ventriculomegaly was defined as an Evans Index ≥0.30. CT was used to evaluate foramen magnum morphology and synchondrosis fusion. Surgical indications were based on imaging findings of compression and intramedullary changes. Results: The median age at initial imaging was 9.5 months. Thirteen patients underwent foramen magnum decompression (FMD) and 5 were managed conservatively. The surgical group showed significantly smaller craniocervical junction CSF spaces compared with nonsurgical cases (p<0.05). Synchondrosis fusion occurred earlier in achondroplasia than in controls. Ventriculomegaly was present in 66%, but its severity did not correlate with FMD. All surgical cases achieved decompression without major complications. Of the 13 surgical patients, 9 were followed for more than one year (median follow-up: 122 months). Within this subgroup, 4 developed radiological bone regrowth with re-stenosis, but all remained asymptomatic and none required reoperation. Conclusions: FMS in achondroplasia poses major risks, yet its natural history and management remain unclear. Our findings support early imaging-based screening and timely intervention in cases with cord compression. While FMD effectively relieves compression, it does not address underlying ossification abnormalities, requiring continued surveillance. Premature synchondrosis fusion may play a key role, and future studies should consider combined surgical and medical approaches to improve outcomes.
Ando et al. (Sat,) studied this question.