A Case Report of an Adverse Outcome: Development of a Dural Arteriovenous Fistula Following Foramen Magnum Decompression for Chiari Malformation.

Chiari malformation is a congenital condition defined by anatomical abnormalities at the craniovertebral junction with downward displacement of cerebellar structures. While some cases are asymptomatic, others present with diverse clinical manifestations, including cerebellar dysfunction, brainstem compression, headaches, hydrocephalus, myelopathy, oropharyngeal dysfunction, sleep-related breathing disorders, scoliosis, and syringomyelia. Surgical intervention is the only treatment option for symptomatic patients, involving foramen magnum decompression (FMD) to decompress the craniovertebral junction and normalize cerebrospinal fluid circulation. Cervical laminectomy and duraplasty may be added depending on the severity of cerebellar tonsil herniation and brainstem compression. Complications of duraplasty include pseudomeningocele formation, cerebrospinal fluid leakage, acute postoperative hydrocephalus, and meningitis. We report a devastating case of a pediatric patient with Chiari malformation who developed cerebellar hemorrhage from a dural arteriovenous fistula (dAVF) after FMD, resulting in death. A 16-year-old female was diagnosed with scoliosis, Chiari malformation, and syringomyelia at age 4. At age 15, due to the progression of scoliosis, corrective fusion surgery was planned, but surgical treatment for Chiari malformation was performed first. The surgery involved FMD, during which a well-developed occipital sinus was observed. When performing duraplasty in addition to FMD and upper cervical laminectomy, the occipital sinus was ligated to reduce bleeding risk. The postoperative course was uneventful with no obvious neurological deficits, and the patient was discharged home. The corrective fusion surgery for scoliosis was also successfully completed, and outpatient follow-up continued. One year and five months after the FMD surgery, the patient presented with a sudden headache and vomiting. Brain MRI revealed cerebellar hemorrhage and suspected dAVF to the occipital sinus. Cerebral angiography showed the occipital artery as the main feeder, the paramedian posterior marginal sinus as the shunt point, and the occipital sinus as the main drainer. Due to deep venous reflux indicating high risk of rebleeding, transarterial and transvenous embolization were performed. However, cerebral edema progressed, hydrocephalus worsened, and cerebellar hemorrhage recurred, resulting in the patient's death. When performing FMD in pediatric cases, thorough preoperative evaluation of venous sinuses is essential. Care should be taken to avoid ligation when a well-developed occipital sinus is observed. In such cases, consider limiting the procedure to bony decompression only.