CHIARI
• These are malformations related to congenital caudal displacement of the brain stem and cerebellum.
• There are 4 types.
Chiari Type 1:
• It is the most common type. It is more common in women than men.
•Unlike other types, it is asymptomatic until adulthood. Symptoms depend on the degree of descent of the tonsils. Over 12 mm is symptomatic.
•Although there are isolated malformations, most malformations may accompany.
•Syrinx in 35%, skeleton in 35%, and hydrocephalus in 30%.
•There is an incompatibility between tonsillar herniation and posterior fossa content and pillar.
•Chiari type 1 tonsillar ectopia should be differentiated. Tonsillar ectopia is detected incidentally and herniation is 3-5 mm.
Radiological Features
•Tonsil herniation that crosses the line between the inner edges of the foramen magnum (opistion-basion) is measured.
•Normal over foramen magnum
•Tonsillar ectopia below 3 mm
•3-6 mm suspicious (sirinx, presence of hydrocephalus is checked
•6mm chiari)
The normal position of the tonsils changes with age. Below the foramen magnum in the newborn. It reaches its lowest point between the ages of 5-15.
Chiari Type 2
Relatively most common of the spine and posterior fossa It is the most common congenital anomaly with brain stem herniation, small posterior fossa, open lumbosacral spina bifida, seen in 1/1000 live births 95% of infants with meningomyelocele have chiari type 2.
