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Untethering

Reprinted from PN December 2008

Restriction of the cord's movement within the spinal cord can cause neurological changes.

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Over time, many spinal-cord-injury (SCI) survivors experience progressive loss of function, loss of sensation, and a host of other problems. These are often attributed to aging, overuse, and wear and tear. But for a significant number of survivors, these neurological changes are due to spinal-cord tethering, a restriction of the cord’s normal movement within the spinal canal.

For years SCI was thought to be a relatively stable condition; it was assumed that the function, sensation, and strength achieved in rehab would remain intact and any changes would be attributable to normal aging rather than progression of the injury. As medical advances extended the years people survived following injury, more individuals began reporting a variety of neurologic losses, including but not limited to:

- Loss of sensation and strength

- Muscle fatigue with repetitive motion

- Loss of bowel, bladder, or sexual function

- Increased pain and/or spasticity

- Excessive sweating

- Increased extremity edema

This constellation of symptoms was commonly associated with the formation of cysts within the spinal cord at the site of injury. More recently, such symptoms have also been connected to tethering of the cord, which inhibits the natural movement or floating of the cord in the surrounding cerebral spinal fluid.

Tethering is usually the result of formation of scar tissue around the site of injury, and the subsequent anchoring of the cord to the dura, the cord’s protective covering within the canal. It can occur from within months of injury to as long as 40+ years postinjury. Microsurgery offers a way to arrest the damage, as well as hope of some return of lost function—but the price includes significant risks, a long recovery process, and no guarantees. One study places the average surgical intervention at about 12 years postinjury.

Basis for Decisions

Diagnosis can be tricky and is often a process of exclusion, as many of the complaints mimic the symptoms of other problems such as spinal instability or compression, bladder or kidney stones, decreased activity or muscle use, skin sores, or prolonged bed rest. The most telling symptom may be progressive sensory loss, which is not associated with any of the above-mentioned problems. An individual’s description of the symptoms and assessment of sensory and/or motor loss—along with an MRI, the diagnostic tool of choice to determine the degree and location of the tethering—will guide the decision to proceed with surgery.

In one study, more than three quarters of the people sought intervention because of motor and/or sensory loss, more than half did so because of increased spasticity or pain, and over 20% cited autonomic dysreflexia (AD).

The Procedure

The microsurgery is complicated, extensive, and delicate. First, all the shoulder muscles are retracted in order to access the spine. A laminectomy exposes the dura, which is then cut in order to get to the spinal cord. The scar tissue is then dissected in order to release tension on the cord and allow it to once again float freely within the canal. The procedure also serves to improve the flow of spinal fluid.

The entire surgery is monitored for electrical activity up and down the cord to ensure no further damage and to detect any improvement in flow of signals below the surgical site. Once the tethering of the cord has been eliminated to the greatest extent possible, the dura is repaired and the surgical site closed.

Typical untethering surgeries last eight to ten hours, during which patients are positioned face down, with muscles retracted to provide access to the spinal canal. This is an unusually painful surgery, especially for quadriplegics, due to the length and extensiveness of the surgery and the fact that the majority of the shoulder girdle muscles are attached to the neck. As a result, most movements quadriplegics make put stress on the surgical site.

Recovery

The dura requires about 12 weeks to fully heal. Proper healing demands a full week of bed rest after surgery, followed by an additional four to seven days of hospitalization prior to release. Should the dura repair site be compromised, the resulting leak of spinal fluid can cause serious complications. Most people can resume a normal presurgery level of activity within three months, though regaining lost conditioning may take considerably longer.

A study of more than 400 surgical interventions reports a nearly 90% success rate in arresting the progression of symptoms. More than half reported regaining at least one lost activity, and about the same number felt their spasticity and/or pain levels had decreased. Over 80% thought the surgery was worth the pain, time, and effort involved. About 11% said they were not as functional after surgery as before it.

Some words of caution and perspective are in order. Some degree of scarring occurs in virtually all SCIs. As a result, nearly all SCI survivors experience some degree of tethering. One veteran surgeon estimates that about 10% of all SCIs develop tethering to a degree requiring surgery. No hard and fast numbers exist.

Contact: Susie@craighospital.org.

DISCLAIMER

Preparation of this article was funded by the U.S. Department of Education’s National Institute on Disability and Rehabilitation Research (NIDRR). The opinions here are those of the grantee and do not necessarily reflect those of the U.S. Department of Education. None of the procedures mentioned above are specifically endorsed by Craig Hospital or the U.S. Department of Education, and the details are for information purposes only. For more information about this and other research projects at Craig Hospital, contact Susan Charlifue, PhD, 303-789-8306 / susie@craighospital.org.

PVA and PN do not recommend or endorse products or services.

 

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