Suboccipital craniectomy (SOC) for the treatment of syringomyelia associated with Chiari I malformation has been routinely performed to improve clinical symptoms. A retrospective study was conducted of eight patients who underwent SOC followed by cranioplasty with hydroxyapatite (HA) implants. Neurological impairments and radiological findings based on magnetic resonance imaging (MRI) were assessed preoperatively and at a mean 13.3-month follow-up. The six female and two male patients ranged in age from 9 to 66 years (mean, 41.4 years). Each patient exhibited varying degrees of sensory discomfort of the extremities. Computed tomography study in one case with an intramedullary lesion revealed a cerebrospinal fluid (CSF) density, and the patient was diagnosed with syringomyelia. Operations were performed through SOC and upper cervical laminectomies. Duraplasty using Gore-Tex or resection of the outer layer of the dura was selected under intraoperative ultrasound echography. Subsequently, the decompressed foramen magnum was covered with a curved plate of HA and tenting sutures of the dura were added. Neurological impairments improved in five of eight patients and persisted in three cases. Postoperative MRI showed diminution in the size of the syrinx and the ascent of the cerebellar tonsils in seven of eight cases. Three-dimensional computed tomography (3D-CT) in some patients revealed bone fusion of HA with the adjacent occipital bone within 6 months after surgery. In conclusion, the findings in this study showed HA cranioplasty has the advantage of early securement of the retrotonsillar subarachnoid space and preclusion of epidural CSF retention.
