The use of the term has grown out of the difficulty in distinguishing between the two conditions using current imaging modalities. It may also be known as hydrosyringomyelia or syringohydromyelia. Diagnosis is made by MRI and electromyography.
In hydromyelia, there is dilatation of the central canal of the spinal cord. In syringomyelia and syringobulbia, there is dissection through the ependymal lining of the central canal and a CSF collection within the cord itself.
Clinically, there is no difference between the two and severity of symptoms is related to the location and size of the syrinx.
Symptoms, which may not occur immediately, include flaccid weakness of the hands and arms as well as "cape-like" distribution of pain and temperature sensory loss with preservation of position, vibration and touch (dissociated sensory loss).
They may be congenital (90%) or acquired.
Congenital causes include:
- Chiari I malformation
- Chiari II malformation
- Dandy-Walker malformation
- Klippel-Feil syndrome
Acquired (secondary) causes include:
- post-traumatic: occurs in ~5% of patients with spinal cord injury usually from a whiplash type injury; symptoms may start many months or years after injury
- cervical canal stenosis
- secondary to a spinal cord tumour
- secondary to a haemorrhage
- due to vascular insufficiency
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