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Chiari Malformation Type I

Background information

The bottom half of the inner skull is split into three areas, the anterior, middle and posterior cavity. Each of these cavities contains specific parts of the brain. The posterior cavity comprises the brainstem and the cerebellum.

In the case of the Chiari Malformation the posterior fossa turns out to be too small and there’s not enough room for the brain structures. Over time, parts of the cerebellum shift gradually towards the Foramen Magnum, which is an opening at the base of the skull, containing the brainstem. Mostly, this developmental disorder develops symptoms not until the 40th year of life and appears a little more often in women than in men.


Usually, patients report 

  • headaches, 
  • neck pain, muscle weakness and sensory disorders in their arms and shoulders,
  • vertigo. 

Because of the described constriction at the level of the Foramen Magnum, an obstruction of CSF (cerebro-spinal fluid) flow is a common occurrence that may lead to hydrocephalus

Apart from that Chiari Malformations are frequently associated with syringomyelia, a cavity within the spinal cord, which may cause senso-motoric deficits of the upper extremities and gait instability.


Once symptoms appear and the diagnosis is confirmed by radiological imaging Chiari malformations should be operated. By enlarging the posterior portion of the Foramen Magnum and by expanding the meninges (dura mater) with a patch, the neural structures are decompressed. 

In the majority of cases the hydrocephalus as well as the syrinx in the spinal cord normalize and the symptoms, including the pain, disappear.

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