Chiari malformation

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Chiari malformation

Nervous system


Chiari malformation


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Chiari malformation

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A 2-week-old newborn boy is brought to the emergency department by his parents due to irritability and difficulty feeding over the past few days. Medical history is significant for a red, sac-like lesion noted shortly after birth that was located on the lower back, which presented with flaccid paralysis of the lower limbs and absence of rectal tone. The patient subsequently underwent surgery for the removal of the sac-like lesion. At present, the patient’s temperature is 37.0°C (98.6°F), pulse is 120/min, respirations are 40/min, and blood pressure is 70/40 mmHg. An examination of the eyes is shown below:  

 Retrieved from: Wikimedia Commons    

The other eye reveals similar findings. This infant’s underlying condition is most likely caused by which of the following processes?  

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Chiari malformations p. 506


Chiari malformations are a group of conditions where the cerebellum of the brain extends down into the spinal canal and results in the blockage of the normal flow of cerebrospinal fluid.

The cerebellum, or "little brain", is divided into two hemispheres which are separated by a narrow worm-like structure in the middle called the vermis.

Directly beneath the hemispheres are two smaller lobes called cerebellar tonsils.

Normally, the cerebellum and cerebellar tonsils sit right above the foramen magnum which is the opening at the base of the skull through which the spinal cord passes through.

The cerebellum is contained within the posterior fossa or floor of the back of the skull, which also contains the medulla oblongata.

The cerebellum controls balance, posture, and helps to initiate as well as fine-tune voluntary motor activity - think about the fancy finger work of a piano player or the vocal cords of a singer - that’s the cerebellum in action.

The medulla, on the other hand, controls autonomic functions such as breathing and blood pressure, as well as reflexes such as coughing, vomiting, gagging, and swallowing.

Now, there’s also a set of four interconnected cavities in the brain called ventricles, each of which create and circulate cerebrospinal fluid.

Highest up, are two C-shaped lateral ventricles that lie deep in each cerebral hemisphere.

The two lateral ventricles drain their cerebrospinal fluid into the third ventricle, which is a narrow, funnel-shaped, cavity at the center of the brain.

The third ventricle makes a bit more cerebrospinal fluid and then sends all of the cerebrospinal fluid to the fourth ventricle via the cerebral aqueduct.


Chiari malformation is a structural defect in the brain which occurs when the cerebellum herniates in the foramen magnum due to craniovertebral junction anomalies. This can cause pressure on the spinal cord and other parts of the brain. There are different types of Chiari malformations, but the common ones are type I and II. Type I Chiari malformation occurs when there is the herniation of only the cerebellar tonsils and is associated with syringomyelia. Type II Chiari malformation (also called Arnold Chiari malformation) occurs when there is herniation of both the cerebellar tonsils and the vermis and is associated with myelomeningocele.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Chiari-malformasjon type 1 – diagnostikk og behandling" Tidsskrift for Den norske legeforening (2019)
  6. "Siringomielia no secundaria a Chiari. Actualización en fisiopatología y manejo" Neurología (2019)

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