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Arteriovascular Malformation

Arteriovascular Malformation

Brain & skull development begins shortly after conception and continues throughout the growth of a foetus. A complex genetic program coordinates the formation of billions of neurons, or nerve cells and their development into specific brain regions. Interruption of this program, especially early in development, can cause significant structural intracranial defects.


Congenital brain defects may be caused by inherited genetic defects or effects on the embryo or be due to a mother's infection, trauma, medication, drug or alcohol consumption during pregnancy.


One of the more common development abnormalities seen and treated by Neurosurgeons are ‘Type 1 & 11’ Chiari Malformations.


Arnold Chiari Malformation

An Arnold-Chiari malformation is a congenital malformation of the lower part of the brain. It most commonly consists of an abnormal downward displacement of the cerebellar tonsil and the medulla through the foramen magnum, which can cause an obstruction of CSF outflow and hydrocephalus.


There are 4 different levels of severity of this condition, ranging in severity from a moderate extension of the cerebellar tonsils into the foramen magnum, through to an incomplete or underdeveloped cerebellum.


Common symptoms include: severe headache, which is made significantly worse by sneezing coughing or bending down, ringing or buzzing in the ears, hearing loss, impaired swallowing and gag reflex, loss of the breathing reflex, facial paralysis, uncontrolled eye movements (nystagmus), impaired balance and gait. Some Patients may also experience muscle weakness and coordination difficulties, particularly in the upper extremities.


How are Chiari malformations diagnosed?

  • An X-ray can be used to identify bone abnormalities that are often associated with CM.

  • Computed Tomography uses X-rays and a computer to produce two-dimensional pictures to identify hydrocephalus and bone abnormalities associated with CM.

  • Magnetic resonance imaging (MRI) uses radio waves and a powerful magnetic field to produce either a detailed three-dimensional picture or a two-dimensional “slice” of body structures, including tissues, organs, nerves and bone.


How are Chiari Malformations treated?

Surgery is the only treatment available to halt the deterioration this condition can cause to the central nervous system. Most patients who have surgery see a speedy and effective reduction in their symptoms, although some may need more than one surgical procedure to treat their condition completely.


Typically a Posterior Fossa Decompression procedure is performed to create more space for the cerebellum and to relieve pressure on the spinal column. This surgical procedure usually involves making an incision at the back of the head and removing a small portion of the bottom of the skull (and sometimes part of the spinal column) to correct any irregular bony structure. This procedure effectively reduces compression of the brain stem and allows the cerebellar tonsils to move back into their natural position.


In addition, a procedure called electrocautery to shrink the cerebellar tonsils can be used. This surgical technique involves destroying tissue with high-frequency electrical currents.


In addition another related procedure, called a spinal laminectomy, involving the surgical removal of part of the arched, bony roof of the spinal canal (the lamina) to increase the size of the spinal canal and further relieve pressure on the spinal cord and nerve roots can also be performed.


Another consideration may be to also make an incision in the dura (the covering of the brain) and add extra tissue to the dura to create even more space for the flow of CSF.


In cases where Hydrocephalus needs to be treated, a shunt system that drains excess fluid and relieves the resulting build up of pressure inside the skull can also be performed. This procedure involves the insertion of a sturdy tube into the head, connected to a more flexible tube that is then placed under the skin, where it can drain the excess fluid away into either the chest wall or the abdomen. Any excess drainage of CSF fluid can then be naturally absorbed by the body.

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Brain and neurology guide: conditions and treatments