1. 1. Chiari Malformations ANMC Department of Neurosurgery Jeff Stubblefield, PA-C Rob Lieberson, MD Rev. 11/8/2012
2. 2. The Arnold-Chiari Eponym Hans Chiari (September 4, 1851 May 6, 1916), an Austrian pathologist , described three seemingly related abnormalities at the base of the brain in 1891. Three years later, Julius Arnold (August 19, 1835 February 3, 1915), a German pathologist, described one of the same abnormalities. The term "Arnold-Chiari malformation, which placed Arnolds name first, was coined by two of Arnolds students in 1907.
3. 3. Types of Chiari Malformation Type I Herniation of cerebellar tonsils Sometimes with syringomyelia Type II (Arnold- Chiari) Herniation of cerebellar vermis Usually accompanied by a lumbar myelomeningocele Type III Occipital encephalocele Usually with syringomyelia, a tethered cord and hydrocephalus Type IV Lack of cerebellar development Not compatible with life
4. 4. Type I Herniation of cerebellar tonsils Sometimes with syringomyelia
5. 5. Important Features 1. Small posterior fossa 2. Normally positioned fourth ventricle 3. Obliterated cisterna magna and, 4. Syringomyelia in 25%
6. 6. 1. Syringomyelia ( /srmaili/) , or a syrinx, is a cyst or cavity within the spinal cord. 2. It may cause pain or weakness. a. Sensory complaints are usually in a cape distribution and most often affect pain and temperature sensation out of proportion to light touch. b. Weakness most often involves the hands but may spread. 3. Signs may develop slowly or come on suddenly with coughing, or straining. Syringomyelia
7. 7. Surgery for Chiari I Malforn Tonsil Tonsil Spinal Cord IV Ventricle 1. Craniectomy 2. Dural Opening 3. Separation of Tonsils 4. Opening of IV Ventricle 5. Duroplasty
8. 8. Type II (Arnold- Chiari) Herniation of cerebellar vermis Usually accompanied by a lumbar myelomeningocele 1. Small posterior fossa 2. Cerebellar vermian herniation 3. Extension of medulla below foramen magnum 4. Kinking of medulla (Z- formation) 5. Beaking of the quadrigeminal plate 6. Hydrocephalus 7. Myelomeningocele
9. 9. Type III Occipital encephalocele Usually with syringomyelia, a tethered cord and hydrocephalus 1. Very small posterior fossa 2. High cervical or low occipital encephalocele 3. Varying amounts of brain herniate (cerebellum, occipital lobes, brainstem, etc.) 4. Herniated brain usually non- functional (necrosis, gliosis, heterotropias) 5. Usually, incompatible with life
10. 10. Type IV Lack of cerebellar development Not compatible with life Archaic term 1. Very rare 2. Posterior fossa tiny and funnel shaped 3. Almost complete lack of cerebellum 4. Portions of brainstem may be absent 5. Spinal cord may be absent
11. 11. 1. Enlargement of posterior fossa 2. Agenesis of cerebellar vermis 3. Cystic dilatation of 4th ventricle (ex vacuo) 4. Variable clinical manifestations 5. Hypothesized to result from arrest of cerebellar development prior to the 3rd month of gestation Dandy-Walker Malformation
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