General
- For an incidentally discovered syrinx (i.e., asymptomatic and no neurologic deficit) with no identified etiology, if the size remains stable over 2–3 years of observation, F/U studies at 2–3 year intervals can be done if there are no changes in symptoms.
- For lesions meeting the criteria of a central canal, obtain a contrast MRI to rule out enhancement, and if no enhancement and no symptoms referrable to the lesion are present, a follow-up MRI in 3 months
- If stable, additional routine follow-up MRIs are not indicated, but may be repeated for concerning symptoms.
- Patients may remain asymptomatic for several years even with significant syringes
Surgical treatment
General
- If an underlying cause cannot be determined, it may be very difficult to treat a very small syrinx directly (which is OK since a very small syrinx is unlikely to be causing irreversible symptoms).
- Not all require surgery
- Many syringomyelia cavities enter a state of hydrodynamic equilibrium and these patients require no more than observation.
- Deterioration is usually gradual and obvious to the patient. There is time for follow- up imaging and careful consideration of the role of surgery
- Sudden deterioration is uncommon, usually following an episode of physical straining. It is, however, unnecessary to prohibit physical exercise, on the grounds that Valsalva will likely cause the syrinx to expand.
- Instead, the patient simply needs to be warned to avoid breath- holding during exercise.
Timing of surgery
- Adults
- Surgery seldom needs to be carried out urgently
- Paeds
- Although young children with Chiari may occasionally present in a parlous state, requiring prompt intervention
Indication
- Symptomatic lesions.
- Progressive neurological decline
- Severe pain
Aim
- Primary: halt motor deterioration
- Secondary
- Relief of pain
- Control of sensory disturbances
- Reduction of sweating and spasms
- Restoration of lost function
Options
Option 1: Treatment the underlying pathophysiology to re-establish subarachnoid CSF flow.
- Use syrinx draining procedures as second choice when this is not feasible
- Technique
- For communicating syringomyelia
- FMD
- Procedure of choice when posterior anomalies (e.g. Chiari malformation) are present
- Use tonsillar resection
- Restoration of free CSF flow at the foramen of Magendie, hindbrain decompression, and relief of the “piston-like” action of the tonsils
- This decompression should be small enough to avoid downward migration of the hindbrain into the craniectomy defect.
- Outcome
- Expect syrinx cavities to collapse in at least three- quarters of cases
- Can take up to 6 months
- With Chiari malformations pressure dissociation headaches will usually resolve or lessen in most patients and ocular and motor symptoms tend to improve as well
- Complications
- Chemical meningitis
- CSF leakage
- Bacterial meningitis
- Hydrocephalus
- Acute cerebral swelling
- Dysesthesias
- Due to retractor damage to the greater occipital nerves
- Isolated fourth ventricle and brain slump
- Are particularly difficult complications
- Brain slump may be the result of high pressure from above, rather than lack of support from below
- For non-communicating syringomyelia
- Decompression if a different site of compression, blockage, or tethering is identified
- Laminectomy for untethering of subarachnoid adhesions and expansile duraplasty
- Posttraumatic syringomyelia: Laminectomy + lysis of intradural arachnoid adhesions
- Success rates are poorer than FMD
- The likelihood of any surgery leading to permanent syrinx collapse is inversely proportional to the extent of any intradural arachnoid adhesions.
- Laminectomy and myelotomy/syringotomy with or without syringosubarachnoid/ syringopleural/syringoperitoneal shunt.
Option 2: Drainage of CSF
- Technique
- Subarachnoid-subarachnoid bypass shunts:
- 1 or more silastic drainage tubes placed intradurally with one end above and the other end below the site of CSF flow blockage. Anchored with suture.
- Indicated
- Outcomes (of 20 patients, follow up: 48 months)
- 60% improved
- 20% were stable
- 20% deteriorated
- Transaction of the spinal cord (Cordectomy)
- Indicated
- Posttraumatic syrinx in ASIA A SCI patients with ascending syrinx in whom other measures have failed
- Syrinx shunts
- Indications
- Cases of diffuse arachnoiditis (e.g. following tuberculous or chemical meningitis) &
- Obstruction extends over many levels &
- Syrinx diameter >3–4mm
- Disadvantages
- Complication rate: 16%
- Clinical stabilization rate: 54% at 10 yrs
- May produce traction on spinal cord with potential for further injury
- Obstruction rate high: 50% at 4 years
- Does not correct underlying pathophysiology and so syrinx may recur
- Complications
- Need for myelotomy, causing some loss of dorsal column function.
- Drainage tubes, as with other CSF shunt systems, have a tendency to block with time and long- term efficacy is unlikely to benefit more than half of all cases
- New cavities are prone to form, simply because the underlying filling mechanism has not been disabled.
- Syrinx catheter
- K tube (outflow catheter is angulated relative to the syrinx catheter) or
- T tube (outflow catheter is at a right angle)
- Distal sites
- Peritoneum
- Difficult in cervical region
- Pleural cavity
- If entering from posterior approach, you need to go about 5–6cm lateral to the midline to access the rib and avoid the paraspinal muscles, which usually requires you to tunnel the catheter inferior to the inferior pole of the scapula
- Pleural shunt has negative pressure which is good for syrinx drainage as there is no overdrainage issues.
- Subarachnoid space
- Requires normal CSF flow in subarachnoid space, therefore cannot be used in arachnoiditis.
- A K tube (e.g. Medtronic #23069 or Heyer-Schulte-Pudenz system) is better suited than a T tube
- Available syrinx shunt systems include
- Edwards-Barbaro syringoperitoneal shunt
- T-shaped proximal end ≈ 5FR diameter & 3.5cm total length, supplied with valveless Foltz reservoir, which may be optionally incorporated to permit percutaneous needle access to the system
- Medtronic #44520 T-tube
- The proximal limbs that go into the syrinx total 8cm in length and can be trimmed to desired length
Option 3: ✖ no longer recommended
- For syrinx associated with Chiari malformation: plugging the obex with muscle, teflon, or other material; removing the inferior cerebellar tonsils
- Syringostomy: usually fails to remain patent, therefore using a stent or a shunt (syringosubarachnoid or syringoperitoneal) is recommended
- Percutaneous aspiration of the cyst
Outcomes
- Stabilisation of symptoms following surgery only occurs in 80% of cases at 5- and 10-year follow-up, regardless of degree of radiologic improvement achieved
- Even when a syringomyelia cavity has successfully been induced to collapse, following surgery, by no means will all symptoms settle in all patients.
- Somatic pains and sensory disturbances, be these due to tonsillar pressure on long tracts or arising from a syrinx cavity, tend to persist, in up to half of all patients.
- Neuropathic pain remains a major challenge in the management of syringomyelia in general, often dominating a patient’s life.