Male, 33 years old, with Chiari malformation. The cerebellar tonsils descend to 5 mm below the level of the foramen magnum which just meets criteria for a Chiari I malformation. However, the tonsils maintain a relatively round morphology, and there is little if any crowding of the brainstem at the foramen magnum. Robust biphasic CSF flow signal is seen through the anterior foramen magnum. Robust biphasic CSF flow signal is seen posterior to the cervical cord. However, minimal if any flow signal is detected around the cerebellar tonsils.Spinal alignment is anatomic. Vertebral body height and morphology are within normal limits. No pathologic marrow replacement or marrow edema is detected. The visualized spinal cord demonstrates normal signal intensity and morphology. No evidence of any spinal cord syrinx or other focal cord lesion is seen.At C3-4, facet hypertrophy, uncovertebral hypertrophy, and a small central disc protrusion are noted. The spinal canal is not compromised, but the left neural foramen is narrowed. No other significant disc degeneration is seen.
Findings are seen compatible with a Chiari I malformation. The cerebellar tonsils descend 5 mm below the level of the foramen magnum. Reduced CSF flow signal is evident around the cerebellar tonsils. However, the tonsils themselves maintain a relatively normal round morphology and there is little if any apparent crowding of the brainstem.