Long-term imaging course of Chiari malformation type I due to fibrous dysplasia/McCune-Albright syndrome.

INTRODUCTION: McCune-Albright syndrome (MAS) and fibrous dysplasia (FD) have been reported to cause Chiari type I malformation (CM1) and skull base invagination (BI). CASE: A 6-year-old girl was diagnosed with MAS and FD. She was diagnosed with CM1 at age 8 years, and the syringomyelia had gradually increased by age 20 years. We performed foramen magnum decompression and C1 laminectomy, and the syringomyelia stopped spreading after surgery. DISCUSSION: This patient underwent long-term radiological observation and morphological evaluations, which revealed that the skull thickening was progressing, while the posterior cranial fossa volume (PCFV) remained unchanged for 14 years. Therefore, although PCFV did not decrease, it was considered to be relatively inadequate due to the increase in brain volume with growth, resulting in posterior fossa overcrowding, causing CM1.
CONCLUSION: In patients with FD/MAS, long-term evaluation of bone thickening, odontoid position, and PCFV is necessary.