Female, 33 years old, with known Chiari malformation. The left cerebellar tonsil herniates approximately 8 mm below the level of the foramen magnum, and the right cerebellar tonsil herniates approximately 6 mm below. Both tonsils maintain a normal round configuration, and there is evidence of patent CSF space both anteriorly and posteriorly through the foramen magnum. On CSF flow imaging, robust biphasic CSF flow is seen anteriorly through the foramen magnum as well as posteriorly along the cerebellar tonsils.Slight reversal of the cervical lordosis is likely positional. Sagittal alignment is otherwise unremarkable. Vertebral body height and morphology are within normal limits. No evidence of concerning marrow replacement or marrow edema is seen.The visualized spinal cord demonstrates normal signal intensity and morphology. No focal lesions are seen. No epidural abnormalities are suspected.Minimal disc osteophyte formation is seen at C5-6. No significant spinal canal or foraminal stenosis is detected level.
The cerebellar tonsils descend below the level of the foramen magnum meeting imaging criteria for a Chiari I malformation. However, the tonsils are round in contour, and there appears to be adequate CSF flow both anteriorly and posteriorly through the foramen magnum. No evidence of spinal cord syrinx or other cord abnormality is seen.