Chiari, Part 6 of 6: The Tethered Cord
Tethered Cord is a nearly universal finding after myelomeningocele (MMC) repair. It is the result of normal scarring after surgery, which can bind the spinal cord at the level of the MMC repair and prevent the cord from sliding the way it needs to with normal everyday movement.
It turns out that the tip of spinal cord is at about the level of the L3/4 disk in a newborn. However, because the spinal canal grows (lengthens) rapidly and the spinal cord does not, the normal spinal cord appears to ascend in the canal as the spine lengthens. By the first year, the cord has attained its normal position, with the tip at the level of the L1/2 disk space.
In a MMC patient, the post-op scarring from the initial repair surgery causes the spinal cord to form adhesions to the surrounding tissue, thus tethering it and preventing it from ascending. The spinal cord tolerates such stretching poorly, and the result is generally a reversal or loss of milestones. Patients become incontinent when they had previously been continent, gait changes and deteriorates, child may demonstrate shortening of their heel cords and appear to be walking on tip toes, back pain, headaches (especially when trying to flex neck to look down). In advanced cases, young kids will arch their backs and extend their necks (as if looking up all the time) and refuse to do otherwise. They become fussy and irritable.
Tethered cord tends to make its appearance during growth spurts, such as around puberty. Also commonly seen at four or five years of age.
Surgery involves general anesthetic and re-exploration of the previous repair site. Usually takes about 2 hours. Unfortunately, there is a risk of recurrent tethering. Most kids only need a single detethering, a few will need two surgeries (generally separated by many years). Occasionally an adult will present with a tethered cord.
Results are generally good, though it is better to prevent loss of function than to try to recover it once lost. For this reason, detethering is often undertaken at the first sign of trouble.
The greatest risk of surgery is that of making a patient worse. This is unusual, but not rare. It is more frequent during a revision.
Note that Chiari I is not associated with tethered cord. Also note that if a patient has a vp shunt, its proper function should be verified before operating on the tethered cord. If hydrocephalus is present or the vp shunt is not working, these things should be attended to prior to operating on the tethered cord.
Tethered cord surgery is generally elective and can be scheduled during school vacations.
End of Chiari Postings
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