Resolution of type I Chiari malformation and associated syringomyelia following intrathecal chemotherapy: case report

Type I Chiari malformation (CM-I) consists of downward herniation of the cerebellar tonsils below the foramen magnum and often requires surgical decompression if symptomatic. Spontaneous resolution of CM-I is rare. We present a case of resolved CM-I without surgery in a 6-year-old boy with B-cell lymphoma who was diagnosed with CM-I during lymphoma staging. Cerebrospinal fluid cytology and brain MRI revealed negative CNS involvement but showed CM-I with tonsillar ectopia 19 mm below the foramen magnum. The patient underwent induction chemotherapy including 5 doses of intrathecal chemotherapy. Follow-up MRI demonstrated marked regression of CM-I to less than 6 mm in 3 months, and complete resolution of CM-I was observed in 2 years. To the best of our knowledge, this is the first case of resolved CM and syringomyelia following chemotherapy. In this case report, the authors summarize all of the clinical characteristics, the radiological appearance, and the potential causes of resolution based on a review of the literature and propose the mechanisms through which intrathecal chemotherapy contributed to the CM-I and syringomyelia resolution in the present case.