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myelomeningocele_repair

Myelomeningocele repair

Surgical repair and closure of myelomeningocele (MMC) defects are important and vital, as the mortality rate is as high as 65%-70% in untreated patients. Closure of large MMC defects is challenging for pediatric neurosurgeons and plastic surgeons.

The closure of the skin defect in myelomeningocele (MMC) repair is an essential step that determines the quality of the surgical result. The success of surgical results is related to the decision to use the most suitable techniques, namely flaps or primary closure.

Key concepts

Critical goals:

1) free placode from dura (to avoid tethering)

2) watertight dural closure

3) skin closure (can be accomplished in essentially all cases). Closure does not restore any neurologic function

● timing goal:surgical closure with latex-free setup ideally ≤36 hours after birth.

● helpful tips: start at normal dura, open as wide as the defect, trim placode if necessary to close dura, undermine skin to achieve closure (avoid trapping skin →dermoid tumor).

● post-op CSF leak usually means a shunt is required.

Timing

General principles

Prevent desiccation – keep the exposed neural tissue moist. Use latex-free environment (reduces development of latex allergy, as well as attack by maternal antibodies that may have crossed through the placenta). Do not allow scrub solutions or chemical antimicrobials to contact neural placode. Do not use monopolar cautery. At every point during the closure, avoid plac- ing tension on the neural placode.

Multiple layer closure is advocated, 5 layers should be attempted, although occasionally only 2 or so layers may be closed. There is no evidence that multiple layer closure either improves neurologic function or prevents later tethering, but there is a suggestion that when tethering does occur, it may be easier to release when a previous multilayered closure was performed. Silastic does not prevent adherence in series with long follow-up (>6 yrs), and may even render untethering procedures more difficult.

Begin by dividing the abnormal epithelial covering from the normal skin. The pia-arachnoid may be separated from the neural tissue. The placode is folded into a tube and the pia-arachnoid is then approximated around it with 7–0 suture (absorbable suture, e.g. PDS, may make future re-operation easier). It often helps to start with normal dura above, and then work down. The dura can then be isolated around the periphery and followed deep to the spinal canal superiorly. The dura is then also formed into a tube and approximated in a water-tight closure. If the dura cannot be closed, the placode may be judiciously trimmed. The filum terminale should be divided if it can be located. The skin is then mobilized and closed. Dermoid tumors may result from retained skin during the closure, but alternatively dermoids may also be present congenitally.

If there is a kyphotic deformity, it is repaired at the same sitting as the MM defect closure. The kyphotic bone is rongeured, and 2–0 Vicryl is used to suture the adjacent bones. Some surgeons use a brace post-op, some do not.

Post-op management

1. keep patient off all incisions

2. bladder catheterization regimen

3. daily OFC measurements

4. avoid narcotics (midbrain malformation renders these patient more sensitive to respiratory depression from narcotics)

5. if not shunted

a) regular head U/S (twice weekly to weekly)

b) keep patient flat to ↓ CSF pressure on incision

6. if a kyphectomy was done, use of a brace is optional (surgeon preference)

Issues

Late problems/issues include:

1. hydrocephalus: ALWAYS RULE OUT SHUNT MALFUNCTION when a MM patient deteriorates

2. syringomyelia (and/or syringobulbia)

3. Tethered cord syndrome as many as 70% of MM patients have a tethered cord radiographically (some quote 10–20%), but only a minority are symptomatic. Unfortunately there is no good test to check for symptomatic retethering (SSEPs may deteriorate,15 myelography may help)

a) scoliosis: early untethering of cord may improve scoliosis

b) symptomatic tethering may manifest as delayed neurological deterioration

4. dermoid tumor at the MM site: incidence ≈ 16%

5. medullary compression at foramen magnum, see symptomatic Chiari II malformation

6. use of growth hormone to increase stature is controversial


Some prefer to place the shunt and close the defect in the same procedure, it reduces the risks inherent to exposure to anesthesia, reduces hospital stay, and related costs. If there is a suspicious of infection, they do not place the shunt on the same procedure 1).

Prenatal therapeutic strategies that interrupt progressive pathological processes offer an appealing approach for treatment of MMC. However, a thorough understanding of pathological progression of MMC is mandatory for appropriate treatment to be rendered 2).

Closure of the defect.

MOMS Trial

see MOMS Trial.

References

1)
Bao N, Lazareff J. How I Do It: Management of spina bifida in a hospital in The People's Republic of China. Surg Neurol Int. 2015 Jul 23;6(Suppl 11):S337-45. doi: 10.4103/2152-7806.161410. eCollection 2015. PubMed PMID: 26236554; PubMed Central PMCID: PMC4521313.
2)
Smith GM, Krynska B. Myelomeningocele: How we can improve the assessment of the most severe form of spina bifida. Brain Res. 2014 Dec 9. pii: S0006-8993(14)01659-X. doi: 10.1016/j.brainres.2014.11.053. [Epub ahead of print] PubMed PMID: 25498106.
myelomeningocele_repair.txt · Last modified: 2019/07/16 10:33 by administrador