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Chiari Malformation and Syringomyelia

Chiari Malformation

Chiari Malformation is usually a congenital condition in which there is an abnormality in the development of the back of the brain and skull. This results in movement or displacement of the back part of the brain, the cerebellum and / or the brainstem from the skull into the spinal space in the neck. When this occurs, it can lead to obstruction to normal flow of cerebrospinal fluid (CSF), which can result in headaches, and development of other neurosurgical conditions, such as hydrocephalus and syringomyelia.

Chiari Malformation are separated into 4 main types. Of these, type 1 is most common and usually is seen in early adulthood. Type 2 (‘Arnold-Chiari Malformation’) is often diagnosed at birth, and is associated with other childbirth diseases, such as spina bifida (myelomeningocoele) and hydrocephalus. Types 3 and 4 are rare, and usually non-survivable beyond pregnancy.


There are no clear causes for Chiari Malformation, but may be associated with…

  • Underdevelopment of the occipital bone in the skull.
  • Cysts or tumours within the posterior fossa (back portion of the skull).
  • Rare abnormalities with development of the upper part of the neck.
  • Leakage of CSF into the spinal canal.


The most common symptom is headache, which can be worse with bending the head backwards or with exertional activities. Other symptoms include weakness, numbness and incoordination.


Syringomyelia (from the Greek ‘syrinx’ meaning pipe, and ‘muelos’ meaning marrow) is a fluid-filled cavity within the spinal cord. It is a disabling condition that causes progressive weakness and numbness in the arms and legs as the spinal cord cavity enlarges.


There are some associated factors with development of syringomyelia…

  • Chiari Malformation (Type 1 and occasionally type 2).
  • After spinal cord injury (‘post-traumatic syringomyelia’).
  • After meningitis or brain haemorrhage.
  • Spinal cord tumours.
  • Arachnoid webs or scarring (‘Arachnoiditis’).
  • Disc protrusions.


Symptoms relating to syringomyelia are variable. They include severe burning pain, which can be located in a distant location from the syrinx cavity. Other symptoms include weakness in the arms or legs, numbness and changes to sensation of temperature (which may affect arms more than legs).

Tests / Diagnosis

Assessment of Chiari Malformation and Syringomyelia involves…

  • Neurological examination – abnormal findings found by medical staff on physical examination.
  • Neuroimaging – either on MRI (magnetic resonance imaging) or CT (computed tomography) scan of the brain and spine. These may be performed with contrast dye injected into the veins. Additional CSF flow studies may determine if there are additional webs or scar tissue in the cranial or spinal fluid spaces impairing CSF flow.


Treatment for Chiari Malformation and Chiari-related syringomyelia usually involves posterior fossa decompression, in which a small portion of the occipital bone at the foramen magnum is removed, and the brain covering (‘dura’) is enlarged with suturing a patch of material (‘duraplasty’).

Treatment for non-Chiari related syringomyelia is targeted at the underlying cause if identified, such as removal of spinal cord tumour, or dividing scarring on the spinal cord. If no causes are identified, a thin plastic tube (‘shunt’) is inserted into the syrinx cavity.

There are no medications available to reverse or treat Chiari Malformation or syringomyelia.

Related Information

Posterior fossa decompression