What is Syringomyelia ?
- Length-wise cavities (syrinx = cyst, myelia = spinal cord) may form in the centre of the spinal cord, most often in the cervical region (neck). The cavities may also exist at multiple levels throughout the spinal cord.
- Also known as Hydromyelia, Morvan disease, Spinal cord syrinx, Syringohydromyelia
What causes it ?
- The condition may be caused by spinal cord tumours, spinal cord injuries, and vascular malformations (benign blood vessel tumours).
- It may also be associated with Arnold Chiari Malformation and Spina Bifida (Meningomyelocele).
- May also start after a severe bout of straining or coughing.
- It is also known to occur commonly in King Charles Cavalier dogs.
Tell me more about Arnold Chiari Malformation
- In childhood the spinal cord finishes at the sacral S2/3 level, and because it has a fixed length, it normally ascends during puberty and the growth spurt to the normal adult position of lumbar L2/3.
- In this condition the lower end of the spinal cord is tethered or fixed in the sacral region. The lower part of the brain (cerebellar tonsils) becomes pulled down through the foramen magnum (large exit hole in the base of the skull) by the traction effect of the tethered spinal cord. This has the effect of obstructing the normal flow of CSF (cerbrospinal fluid) from the brain to the spinal cord.
- The CSF obstruction causes syringomyelia and hydrocephalus (raised intra-cranial pressure with headaches).
What are the main features of Syringomyelia ?
- As the condition is most often seen in the cervical part of the spinal cord, it causes Nerve Pain (neuropathy, neuritis, neuralgia), tingling (paraesthesias), numbness, and muscle atrophy in the upper limbs. It needs to be differentiated from a slipped disc in the neck causing brachialgia in the upper limbs.
- Sensory dissociation may occur, where there is loss of temperature perception in the upper limbs but preservation of tactile sense (light touch). This may increase the risk of accidental burns.
- Increased pressure in the cyst may interfere with the long nerve fibres within the spinal cord that supply the legs and bladdder, causing leg spasticity and urinary incontinence.
- When associated with the Arnold Chiari Malformation and hydrocephalus, headaches may be a problem. These are usually worst first thing in the morning, and are aggravated by coughing and straining.
How is Syringomyelia diagnosed ?
- MRI is the investigation of choice . Vascular malformations may show on an MRA (Magnetic Resonance Angiogram).
What happens to Syringomyelia over time ?
- Apart from spinal cord trauma, many of the causes of Syringomyelia are present from birth. Spinal cord tumours can be slowly growing over many years.
- The syrinx (cyst) can form over several decades, only becoming symptomatic / diagnosed in the mid-40's.
- The cyst can enlarge with time causing increasing nerve pain and progressive neurological defcit.
- CSF obstruction associated with the Arnold Chiari Malformation can causes persistent headaches .
- It is therefore very important to make an early diagnosis and have the appropriate treatment to prevent disease progression.
- Nerve pain can be treated in the pain clinic with low dose amitriptyline (10 - 50 mg per day) combined with either carbamazepine (600 - 800 mg per day) or gabapentin (1800 - 2400 mg per day) or pregabalin (150 - 600 mg per day).
- Multiple action drugs e.g. tramadol (Zamadol), tapentadol (Palexia) block morphine, noradrenaline and serotonin receptors
- Diuretics such as acetazolamide (carbonic anhydrase inhibitor) and frusemide can reduce CSF production and help to reduce the syrinx size..
- Oral steroids can also reduce CSF production, but the exact mechanism of action is unknown.
- Foramen Magnum Decompression
- In the presence of the Arnold Chiari Malformation a foramen magnum decompression can reduce the degree of CSF flow obstruction by the herniated cerebellar tonsils.
- Essentially, the size of the hole is enlarged by nibbling away pieces of bone around the edge.
- Ventriculoperitoneal Shunt
- Where hydrocephalus is present (headaches with raised CSF pressure inside the head), a fine tube with a pressure relief valve is inserted into one of the ventricles of the brain, and then tunnelled around to the abdominal cavity, where the excess CSF drains away.
- Syringoperitoneal Shunt
- A fine tube with a pressure relief valve is inserted into the spinal cord syrinx, and then tunnelled around to the abdominal cavity, where the excess CSF drains away. This helps to halt the progression of the condition.