Chiari malformations - formerly known as Arnold-Chiari malformation - are various problems with the base of the skull and the hole in the base of the skull that the spinal cord exits through into the neck.
There are four types of malformation, with types l and ll, which are discussed here, being more common. Type lll is rare and is associated with a cyst containing some brain at the back/base of the skull with the descent of the cerebellum (area of the brain for co-ordination and balance) into the neck. Type lV is an abnormal development of the cerebellum without it's herniation into the neck.
Types l and ll occur when the cerebellum is found herniated through the foramen magnum.
Type l can be acquired following a lumbo-peritoneal shunt, for example, with type ll being associated with spina bifida.
These types of malformation can present at any age, but the average age seems to be in the late 30's - early 40's. Often the symptoms may have been present for years prior to detection, although as MRI scans become more widely available, diagnosis times will shorten.
Patients may have hydrocephalus, which can cause severe, even life-threatening problems. There can also be syringomyelia - a fluid, cyst-like build-up within the spinal cord itself.
Patients experience symptoms including:
Headaches - usually at the back of the neck causing the patient to extend the neck (look up)
Upper limb weakness
Electric shock-like pains
Visual disturbance with double vision or ‘jumping' eyes
Poor co-ordination when walking
An MRI scan of the brain and whole spine is essential to make the diagnosis, as the brain and spinal cord may have additional abnormalities.
Treatment, in those with symptoms, includes treating the hydrocephalus, which, if successful, may resolve the cerebellar herniation.
If there is no other cause demonstrated then an operation to open up the foramen magnum must be carried out to decompress the cerebellum and to restore the flow of cerebrospinal fluid.
This treatment, if successful, resolves the symptoms. Pain/headaches tend to respond best to the treatment, with weakness and sensory symptoms less likely to respond.
Most surgeons do warn patients that the surgery is to arrest the progression of the condition and any improvement should be considered a bonus.
As this form of Chiari malformation is associated with spina bifida and other brain abnormalities, there is thought to be a general disruption of the development of the brain and spinal cord.
Symptoms can be due to the Chiari malformation itself - as with type l - but can also be secondary to the spine. There can also be some vertebral (base of spine) abnormalities.
Diagnosis and Treatment
Investigation is a MRI scan and treatment includes untethering the spinal cord at the level of the spina bifida, allowing the tension in the cord to be released and the cerebellum to disimpact, or more commonly, a foramen magnum decompression.
Any hydrocephalus may also require treatment.