Every word on your report, defined.

265 chiari malformation terms, written for patients and families rather than clinicians. Each entry gives you the one-line answer first, then what it is, why it matters for real decisions, and the questions people actually ask.

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Showing 24 of 265 · 265 in this dictionary

#1 Chiari malformation Core Terms & Classification Chiari malformation is a group of structural conditions in which part of the back of the brain extends down through the opening at the base of the skull toward the spinal canal.
#2 Arnold-Chiari malformation Core Terms & Classification Arnold-Chiari malformation is another name for Chiari malformation, used especially for type II and sometimes for the group as a whole.
#3 Hindbrain herniation Core Terms & Classification Hindbrain herniation is the downward displacement of structures at the back of the brain through the skull's base opening, the central feature of Chiari malformation.
#4 Tonsillar herniation (tonsillar ectopia) Core Terms & Classification Tonsillar herniation is the downward extension of the cerebellar tonsils below the skull's base opening, the hallmark of Chiari malformation type I.
#5 Cerebellar tonsils Core Terms & Classification The cerebellar tonsils are the lower, rounded portions of the cerebellum that descend below the skull's base opening in Chiari malformation type I.
#6 Chiari malformation type I (CM-I) Core Terms & Classification Chiari malformation type I is the most common form, in which only the cerebellar tonsils descend below the skull's base opening, often without symptoms.
#7 Chiari malformation type II (CM-II) Core Terms & Classification Chiari malformation type II is a more severe form, present at birth, in which the cerebellum and brainstem descend, almost always associated with spina bifida.
#8 Chiari malformation type III (CM-III) Core Terms & Classification Chiari malformation type III is a rare, severe form in which hindbrain structures extend into a sac at the back of the skull or upper neck.
#9 Chiari malformation type IV (CM-IV) Core Terms & Classification Chiari malformation type IV is a rare, severe condition involving an underdeveloped cerebellum, now considered by many an outdated or separate term.
#10 Chiari 0 malformation Core Terms & Classification Chiari 0 malformation is a variant in which a person has syringomyelia and CSF flow problems at the skull-spine junction despite little or no tonsillar descent.
#11 Chiari 1.5 malformation Core Terms & Classification Chiari 1.5 malformation is a variant between types I and II, with tonsillar descent plus downward displacement of the brainstem.
#12 Complex Chiari malformation Core Terms & Classification Complex Chiari malformation refers to Chiari with additional craniocervical junction abnormalities, often requiring surgery beyond standard decompression.
#13 Foramen magnum Core Terms & Classification The foramen magnum is the large opening at the base of the skull through which the brainstem and spinal cord connect, the site of herniation in Chiari malformation.
#14 Craniocervical junction (craniovertebral junction) Core Terms & Classification The craniocervical junction is the region where the skull meets the upper spine, the area involved in Chiari malformation and related conditions.
#15 Posterior fossa Core Terms & Classification The posterior fossa is the compartment at the back and base of the skull that holds the cerebellum and brainstem, often small or crowded in Chiari malformation.
#16 Congenital Chiari malformation Core Terms & Classification Congenital Chiari malformation is Chiari that is present from birth, arising from how the skull and brain developed.
#17 Acquired Chiari malformation Core Terms & Classification Acquired Chiari malformation is a less common form that develops after birth due to another condition affecting pressure or space around the brain.
#18 Symptomatic Chiari malformation Core Terms & Classification Symptomatic Chiari malformation is Chiari that is causing symptoms, as opposed to being an incidental, symptom-free finding.
#19 Asymptomatic (incidental) Chiari malformation Core Terms & Classification Asymptomatic Chiari malformation is Chiari that causes no symptoms, often discovered incidentally on imaging done for another reason.
#20 Tonsillar descent (measurement) Core Terms & Classification Tonsillar descent is how far the cerebellar tonsils extend below the skull's base opening, measured on MRI to help define Chiari malformation type I.
#21 Pointed (peg-like) cerebellar tonsils Core Terms & Classification Pointed cerebellar tonsils are tonsils with a peg-like rather than rounded shape, a feature that can support a diagnosis of Chiari malformation type I.
#22 Cerebellar ptosis Core Terms & Classification Cerebellar ptosis is a downward sagging of the cerebellum, a term used both as a feature and as a possible complication after Chiari surgery.
#23 Borderline Chiari (low-lying cerebellar tonsils) Core Terms & Classification Borderline Chiari refers to cerebellar tonsils that sit slightly low but not clearly past the threshold for Chiari malformation type I.
#24 Primary Chiari (small posterior fossa) Core Terms & Classification Primary Chiari refers to Chiari arising from a small or underdeveloped posterior fossa, the most common underlying basis for type I.