- Only use Chiari 1 and 2, other Chiari types listed here is just for completeness.
- While the different types of Chiari refers to a recognisable radiological entity, the use of this terminology is seen by some as "regrettable".
- This is because introducing these specific "grades" or subtypes tends to propagate the incorrect notion that the Chiari series is a spectrum of anomaly.
- In actuality, Chiari types I, II, III, and IV are often considered distinct pathological conditions.
Type | Structures herniated through the Foramen magnum | Other findings | Notes |
Chiari 0 | None (<5 mm tonsillar descent) | Syringomyelia | Clinical feature similar to Chiari I |
Chiari I | Cerebellar tonsils (>5 mm descent of tonsils but this is not diagnostic) | May have syringomyelia | Young adult, cervical pain, suboccipital tussive headache |
Chiari 1.5 | Cerebellar tonsils, medulla, 4th ventricle | Persistent syringomyelia, bone anomalies | ㅤ |
Chiari II | Cerebellar vermis and tonsils, medulla, 4th ventricle | Myelomeningocele | Spina bifida/myelomeningocele (rarely absent), hydrocephalus (rarely absent), medullary kink in 55%, cephalad cervical nerves Infancy, progressive hydrocephalus, respiratory distress |
Chiari III | Medulla, 4th ventricle, cerebellum | Herniation into occipitocervical encephalocele (brainstem, occipital lobes, parietal lobes, dural venous sinuses, and subarachnoid spaces.) | Severe and rare |
Chiari IV | None | Primary cerebellar aplasia/hypoplasia, no hindbrain herniation | Extremely rare, sometimes considered obsolete |
Made with Bullet