Successful resolution of subdural hygromas following foramen magnum decompression for Chiari malformation type I through therapeutic lumbar puncture alone.

We report a fairly rare case of postoperative acute subdural hygromas without concurrent hydrocephalus complicating foramen magnum decompression (FMD) for Chiari malformation type I (CM-I). Full resolution of subdural hygromas was achieved through therapeutic lumbar puncture releasing bloody cerebrospinal fluid which has been scarcely advocated in managing post-FMD subdural hygromas. This outcome suggests that bloody cerebrospinal fluid may be related to the formation of subdural hygromas after FMD for CM-I and therapeutic lumbar puncture may provide an effective treatment modality in such conditions.