Characterization of additional MRI findings in patients with Chiari spectrum disorders: focus on Chiari 0-1.5...

To evaluate the prevalence, distribution, and clinical significance of additional MRI findings in Chiari types 0-1.5 and their association with Chiari subtypes.

In this study, 147 patients who underwent comprehensive brain and whole-spine MRI for suspected Chiari deformity were categorized as Chiari 0, 0.5, 1, or 1.5 based on tonsillar descent and obex localization. Imaging review included assessment of syringomyelia (location, diameter, length, number), conus level, lumbosacral transitional vertebrae (LSTV), partial empty sella (PES), basilar invagination, block vertebrae, and hydrocephalus.

Subtype distribution was Chiari 0 (16.3 %), 0.5 (6.8 %), 1 (40.1 %), and 1.5 (36.7 %). Syrinx morphology did not differ significantly among subtypes. A subforaminal obex was associated with higher syrinx prevalence (p = 0.04), whereas LSTV was more common when the obex was at or above the foramen magnum (p = 0.003). Additional findings included PES (13.6 %), basilar invagination (10.8 %), block vertebra (2.7 %), and paraspinal lipoma (0.7 %). PES was enriched in Chiari 1 (p = 0.02), and basilar invagination was enriched in Chiari 1.5 (p = 0.02). Syringomyelia occurred in 30.6 % overall and was positively correlated with hydrocephalus (5.4 % overall; p = 0.01; r = 0.23).

Additional craniospinal anomalies show subtype-specific patterns within the Chiari 0-1.5 spectrum: LSTV associates with a normal/high obex, PES with Chiari 1, and basilar invagination with Chiari 1.5. A significant syringomyelia-hydrocephalus association supports shared CSF dynamic disturbances. It is also thought that case-specific practices, such as hormonal screening in Chiari cases presenting with PES and dynamic flexion-extension screenings in Chiari 1.5 cases with basilar invagination, improve disease management.